EP4164886A1

EP4164886A1 - Additively manufactured article and method for producing an additively manufactured article

Info

Publication number: EP4164886A1
Application number: EP20750231.1A
Authority: EP
Inventors: Lars Frederik PEISS
Original assignee: Volkswagen AG
Current assignee: Volkswagen AG
Priority date: 2020-06-12
Filing date: 2020-07-30
Publication date: 2023-04-19
Also published as: WO2021249659A1

Abstract

An additively manufactured article is produced by a 3D printing process, in which the article is built up by depositing material on the basis of a digital 3D model. The article comprises a 3D printed part (1) and at least one support structure (3). The support structure supports the 3D printed part (1) during the 3D printing process of the 3D printed part in order to avoid a deformation of the 3D printed part and is configured to provide an integrated grasping aid (4, 5) for a robot (9) or other automated machine after the 3D printing process.

Description

Additively manufactured article and method for producing an additively manufactured article

Field:

The present invention relates generally to an additively manufactured article produced by a 3D printing process, in which the article is built up by depositing material on the basis of a digital 3D model, and to a method for producing an article comprising a 3D printed part and at least one support structure by a 3D printing process.

Background:

Additive manufacturing (AM), for instance 3D printing, is based on the deposition / solidification of material, typically a liquid or powder, on a build platform in a layer-by-layer fashion. Thanks to the flexibility to deposit layers of material on top of each other, many different object shapes can be 3D printed. Every new print can produce a different shape and nearly unlimited shape complexity of the produced objects is possible. This is a stark contrast to traditional means of manufacturing like injection molding, casting, or CNC machining, where the tools have to be adapted to the features of the produced object. Thus, it is said that AM gives “complexity for free”, whereas complexity is very costly for the traditional manufacturing processes.

However, AM processes still have to handle gravity as the opposing force to the material deposition / solidification on the build platform or on top of other layers. Material can generally not be 3D printed freely in the air, which makes especially overhangs of parts hard to produce. In order to solve or mitigate this problem, most AM processes rely on support structures. For the most processes, such support structures are printed sections underneath a part that serve as support structures (e.g. pillars) for overhangs. Without support structure, such overhangs would bend under the load of the gravity and the print of the part would fail. Being sacrificial structures, the supports are removed after the print. Thus, they are not attached to the part with a strong connection but rather loosely connected, so that an AM technician can pull them off by hand rather easily during the post-processing steps.

Support structures have a certain geometrical shape and are made out of support material which itself has no specially designed and locally varying shape or structure of its own. While some AM processes can deposit raw material (such as some powder bed processes) as support material, most processes have to cure the support material in the same manner as the other sections of the printed part. This means that nowadays energy is wasted for the production of supports. In addition, the production of support structures ultimately becomes waste, as the support structures become useless after the print and are usually tossed, and thus using such disposable support structures has an undesirable environmental impact. Furthermore, the work of removing support structures from printed parts after the printing process and the subsequent cleaning step is an extra effort in money and time that ideally would not be needed for 3D printing. There are no ways to avoid support material for all additive manufacturing processes at all times, but only under certain circumstances, e.g. by rotating the build platform in multiple axes through a robot arm. However, these relatively recent multi-axis setups are very costly, as they require a robot arm or similar hardware for the full duration of the print, and potentially decrease the printing accuracies. Also, for very intricate, complex parts to be printed the multi-axis approach might not suffice and some support structures are still needed. Consequently, these multi-axis machines are not established on the mass market yet.

Furthermore, AM processes are generally not automated so far. If they are deployed in commercial setups, usually AM technicians load the 3D printers, unload the printed parts and perform the post-processing steps such as support removal in a manual fashion. This under automation has some technical reasons.

As described above, additive manufacturing processes typically mean ever-changing shapes from part to part that is being produced. The infinite possible number of part geometries and part layouts on the platform make robotic task planning very hard since robots have to be reprogrammed or retaught for every new shape or layout. Furthermore, after the printing, the fresh parts are often fragile. Any rough handling can damage the part, especially for the complex structures that additively manufactured parts are typically produced in. This can mean that they are still hot and quite flexible/vulnerable after the print or in any other “green state”, characterized by brittleness or other types of insufficient material behavior. When parts are cooling down rapidly, their material behavior may also change quite quickly during the handling after the printing phase. Often, a post-curing step is then required to turn the parts into their final characteristics and thus to change the properties notable. However, depending on the type of printed material, the parts may remain even compliant / elastic in their final state. Moreover, process remnants stick to the part or build platform. They may influence the handling of the part negatively and are generally hard to predict in their spread and distributions over the surfaces. When being squeezed onto the part’s surface by the robot, they might even damage the surface. These circumstances do not allow for stable process planning with the robot and they require it to be outfitted with advanced machine vision tools to localize the process remnants. These issues are appearing all together during the support removal and cleaning step, when the part is freed from the support structures or other remnants that are not needed for the part any more. Here, the robot has to interact with the part and pull off material with gentle force. Such manipulation tasks are still subject to research and not stable since robots do not understand or appropriately react to material behavior. Due to the complicated structure, AM support removal steps are neither known to be automated in a larger scale today, nor with good surface quality.

The subsequent steps of the supply chain (life cycle) are neither ready for the ever-changing shapes that AM processes produce. It is difficult to plan for storage, containers and shipment of parts that look differently from lot to lot.

As a result of these difficulties, only the printing process itself in the 3D printer is automated. All subsequent handling and post-processing is manual labor, which is very costly and sometimes even hazardous due to the chemicals involved. Also, the labor outcome, i.e. the surface quality of the printed part with support being removed, might differ between different workers and different working stages.

The lack of automation is not only the case for the additive manufacturing post-processing steps, but also for many other steps in the supply chain (life cycle) of industrial production, especially the assembly. Thus, for example in automotive assembly 3D printed parts are still assembled manually by human workers today because the assembly tasks have proven to be too complex for robots, especially if cables, compliant parts or other little pieces are involved. Also, computer vision for industrial robot arms is still not widespread, so that robots have problems to localize assembly objects if their location is not well-defined in all process steps. It even happened that some assembly steps have been taken back from robots to human workers in order to increase the process stability. This under-automation is very costly because of humans involved. Some assembly steps are even ergonomically dangerous to human assembly workers when they perform them over many years.

Some approaches have tried to improve the automation potential by integrating grasping aids into traditionally manufactured final parts as part of a “Design for (automated) assembly”. However, these measures are limited since the grasping aids would be visible in the final state of the product, which is not accepted by the customer.

A method for powder bed-based additive manufacturing of a component together with a support structure for supporting the component is disclosed in DE 102017 101 835 A1. The component, the support structure and the construction platform build a structure with a cavity through which an active medium is routed to remove the powder located therein.

US 2019/0143665 A1 discloses for articles prepared using a three-dimensional printing method to form an auxiliary structure beyond an extension of one or more printed components such as a frame surrounding the components and connected to the components by strips. This makes it possible to use automated removal of 3D-printed objects from loose particulate material by a robot and to supply them to a post-processing process such as cleaning.

Summary:

The following presents a simplified summary in order to provide a basic understanding of some aspects of various invention embodiments. The summary is not an extensive overview of the invention. It is neither intended to identify key or critical elements of the invention nor to delineate the scope of the invention. The following summary merely presents some concepts of the invention in a simplified form as a prelude to the more detailed description below.

According to the present disclosure, additively manufactured articles comprising a 3D printed part and at least one support structure are provided that add beyond classical, only printing process-related supports extra functionality in later life cycle phases of the 3D printed parts, therefore also called functional supports in the following. Furthermore, also a method for producing such a part by a 3D printing process and a computer program product containing computer readable instructions that, when executed by a computer, cause it to perform such method is provided.

Accordingly, the present disclosure looks at additive manufacturing support material from a totally new perspective. Additive manufacturing supports are no longer used and considered as short-temporal waste, but purposely deployed even after the pure printing process in order to fulfill more functions than just facilitating the printing. This justifies their existence much more than in the prior art of short-temporal waste, where various efforts have been made to try to eliminate classical additive manufacturing supports as much as possible.

According to a general aspect of at least one embodiment, an additively manufactured article which is produced by a 3D printing process, in which the article is built up by depositing material on the basis of a digital 3D model, comprises: a 3D printed part; and at least one support structure, which supports the 3D printed part during the 3D printing process of the 3D printed part in order to avoid a deformation of the 3D printed part and is configured to provide an integrated grasping aid for a robot or other automated machine after the 3D printing process.

In one preferred embodiment, the at least one support structure supports automated handling steps of the 3D printed part after the 3D printing process.

Advantageously, the grasping aid is formed by one or more holes, pins, bars, rings or handles located on the outer surface of the support structure, each surrounded by a reinforced support structure area.

In a further preferred embodiment, the support structure supports the 3D printed part at support points during the 3D printing process of the 3D printed part, which are configured to provide predetermined break points to facilitate removal of the 3D printed part from the support structure after the 3D printing process.

In a further preferred embodiment, the integrated grasping aid is designed in such a way that the robot or other automated machine can pull off a whole block or zigzag parts of the support structure; or peel off layer by layer the support structure starting from the outside of the support structure and going inwards by moving in circles around the part or by staying still and rotating the part.

In a further preferred embodiment, the support structure is configured to provide at least one integrated cleaning channel which allows a cleaning medium to flow through at least a part of the 3D printed part and/or the support structure in order to remove excess material.

In a further preferred embodiment, the support structure is configured to provide a fixation to prevent or deliberately force bending during part post-curing after the 3D printing process. ln a further preferred embodiment, the support structure is configured to provide one or more location aids at standardized positions for fixtures of the robot or other automated machine.

In a further preferred embodiment, the support structure is configured to provide one or more protectors surrounding at least one surface of the 3D printed part.

In a further preferred embodiment, the support structure is configured to provide packaging functionalities.

In a further preferred embodiment, the support structure is configured to provide a pattern on the surface of the 3D printed part after the detachments of the support structure from the 3D printed part.

According to another general aspect of at least one embodiment, a method for producing an article comprising a 3D printed part and at least one support structure by a 3D printing process, comprises the steps: receiving a digital 3D model for the 3D printed part; generating a digital 3D model for at least one support structure such that the at least one support structure supports the 3D printed part during the 3D printing process of the 3D printed part in order to avoid a deformation of the 3D printed part; modifying the digital 3D model for the at least one support structure to adapt the at least one support structure to provide an integrated grasping aid for a robot or other automated machine after the 3D printing process; generating 3D printing control data for the 3D printed part and the adapted at least one support structure; and

3D printing the part comprising the 3D printed part and the at least one support structure based on the generated 3D printing control data.

In one preferred embodiment, the modifying step further comprises: cutting the generated 3D model for at least one support structure into sections; determining the usage and removal order of the sections of the at least one support structure; placing gripping points in the sections and/or planning grasps and/or handling or support removal motions; generating 3D printing control data for the 3D printed part and the adapted at least one support structure to be printed; and determining separation interfaces between the sections of the at least one support structure and the 3D printed part.

According to an especially preferred embodiment, the method further comprises: modifying the 3D model for at least one support structure by increasing the volume of the generated 3D model for the at least one support structure in case not all planed functional support functions could be integrated within the initial volume of the generated 3D model.

According to another general aspect of at least one embodiment, a computer program product containing computer readable instructions is provided that, when executed by a computer, cause it to perform such a method.

Brief Description of Figures:

The present disclosure may be better understood by consideration of the detailed description below in conjunction with the accompanying figures, in which:

Fig. 1 shows grasping aids integrated in the volume of classical support structures under a 3D printed part on a build platform (a) right side view, b) front view, c) left side view, d) top view);

Fig. 2 shows a possible robot grasp on the grasping aids of figure 1 and, indicated by arrows, a possible robot motion to detach the part from the build platform;

Fig. 3 is an illustration showing a functional support to ease the automated removal of a 3D printed part from the build platform by creating a sacrificial structure sticking to the platform;

Fig. 4 shows a robot gripper using a rectangular functional support structure to pull off a block of the support structure;

Fig. 5 shows a robot peeling off layer by layer of support by moving in circles around the 3D printed part;

Fig. 6 shows a robot pulling a zigzag support off a 3D printed part by a linear motion; Fig. 7 shows robot handling of a 3D printed part by means of functional supports;

Fig. 8 shows a block-shaped 3D printed part (a) with an internal cavity filled with functional support material (b), wherein the functional support structure exhibits two functional support wash channels meandering through the cavity (c);

Fig. 9 shows a fanned out 3D printed part with functional support for preventing warping in post-curing;

Fig. 10 shows a 2D view of functional supports on the sides of a 3D printed part as location aids;

Fig. 11 shows a 2D view of functional supports on the sides of a 3D printed part as protectors of surfaces of the 3D printed part;

Fig. 12 shows functional supports integrated into classical, process-related supports of a 3D printed plug (a) with holders for further plugs of cables as packaging and how the cables are fixed using these holders (b) during transportation;

Fig. 13 shows a 2D view of a 3D printed part that is hard to stack in packaging (a) and the 3D printed part being extended by functional supports for easy stacking (b);

Fig. 14 shows a 3D printed part with traditional supports that produce by removal support marks on a surface of the 3D printed part (a) and the usage of purposely positioned functional supports that do leave support marks after removal that match to the surface (b);

Fig. 15 shows a functional support as break-off aid for a destructive disassembly of a 3D printed part by a robot before (a) and during (b) partial removal of the 3D printed part;

Fig. 16 shows a flowchart for a method for producing an article comprising a 3D printed part and a functional support structure;

Fig. 17 shows a fictive 3D printed part and the backwards carrier structure for the fictive 3D printed part; Fig. 18 shows for the fictive 3D printed part the defined printing orientation and acceptable support volume (a), a generated classical support (b), and a first sequencing of the classical support for functional supports (c); and

Fig. 19 adding support volume (a), a second sequencing of the classical support for the functional supports, and a grasping aid located in a support section (c).

It should be understood that the figures are for purposes of illustrating examples of various aspects and embodiments and are not necessarily the only possible configurations. Furthermore, the figures and descriptions provided herein may have been simplified to illustrate aspects that are relevant for a clear understanding of the herein described devices, systems, and methods, while eliminating, for the purpose of clarity, other aspects that may be found in typical devices, systems, and methods. Those of ordinary skill may recognize that other elements and/or operations may be desirable and/or necessary to implement the devices, systems, and methods described herein. Because such elements and operations are well known in the art, and because they do not facilitate a better understanding of the present disclosure, a discussion of such elements and operations may not be provided herein. However, the present disclosure is deemed to inherently include all such elements, variations, and modifications to the described aspects that would be known to those of ordinary skill in the art.

Detailed Description:

In the following various embodiments and variants for functional supports for additive manufacturing are provided. Functional supports means in the present disclosure that support material is kept on the 3D printed part also after the 3D printing process in order to be able to add extra functionality in later life cycle phases. Furthermore, also a process of generating such functional supports is described.

In general, the primary purpose of functional supports in the manufacturing phase is to provide semi-standardized interface shapes to other process tools in the manufacturing process. This helps to tackle the technological challenge that 3D printers can produce parts, which have very complex shapes that change from print to print. While this flexibility poses a huge advantage from a pure production perspective, it makes the process much more difficult to automate because robots handling the 3D printed parts have to be reprogrammed for every new shape. Furthermore, other auxiliary process tools such as part holders and/or robot gripper extensions have even to be reproduced for every new shape, which creates extra costs and wastes material. With the inventive functional support structures, the adaption efforts can be reduced, while at the same time keeping the shape flexibility of the actual 3D printed parts. All necessary adaptation / planning complexity is transferred to the generative design phase of the functional supports. The functional supports are a physical interface or connection between the flexible shape of the 3D printed part and the shape of the standardized, inflexible automation tool. In contrast, the classical, printing process-related supports of prior art have only connected the flexible shape of the part to the 3D printer during the 3D printing process, but not to other tools and not in any later steps of the life cycle.

The process of additive manufacturing comprises not only the very first 3D printing step, but also some post-processing steps. So far, the post-processing steps require a lot of human labor. In order to automate these post-processing steps the challenge of shape diversity of the various 3D printed parts has to be tackled, as mentioned above. Due to the shape flexibility and the limited space in the build volumes of 3D printers, typically one or several industrial robot arms are expected to be required to take over part removal, handling, and post-processing tasks from a human worker. Due to the shape flexibility of the printed part, the shift to a robot process chain comes along with high programming efforts. With current methods, the robots would have to be physically re-taught by hand-guiding or re programmed again for every single type of 3D printed shape and for every step of the manufacturing phase.

Also, industrial robot arms are typically equipped with end effectors in the shape of jaw grippers, three finger grippers or other types of simple technical hands. Since their technical end effectors are not as versatile as the human hand, the robot programming for ever- changing additive manufacturing parts becomes even harder of a task. During the post processing phase of many additive manufacturing processes, the 3D printed parts are often in a green state that does not possess the full mechanical strength the parts will have after post-processing. Typically, 3D printed parts are then prone to bending / breaking in case of just very low forces. Since robot grippers have only limited adaptive force control of their motions, extra programming effort is required to make sure that the robot does not deform or destroy the green 3D printed part. However, the inventive functional supports can ease the adoption of industrial robot arms by providing grasping aids. Grasping aids are meant as pre-defined grasping points for the handling and support removal tasks that are integrated into the support structures. In order to mitigate the above described problems, the grasping aids must be reachable for simple jaw grippers or technical hands during the different process steps of the manufacturing phase. The specific requirements to the grasping aid vary depending on the process step, while the basic task, the support of the robot gripper to find the right position in the part, is always the same.

One varying requirement between different kinds of grasping aids for the different process steps is the increased mechanical strength that the functional support must provide in comparison to the classical, printing process-related supports. Typical increases can be chosen as (+ low increase, ++ medium increase, +++high increase): grasping aids for unloading step: + grasping aids for detaching step: +++ grasping aids for cleaning step: ++ grasping aids for support removal step: +++ grasping aids for post-curing step: + grasping aids for all handling steps in between: ++

The specific reasons for the increase levels will be explained below. Generally, the grasping aids in the functional support structures must be physically strong enough to be held by the insufficiently sensitive robot without bending or braking the connected 3D printed part in its green or final state. Current classical, printing process-related supports do not always provide the mentioned accessibility or the physical strength. Often, these support structures are only strong in the Z direction, i.e. the actual printing direction. The human technician handling them nowadays can account for the weaknesses in the X and Y direction and grasp the parts with extreme care. The functional support structures providing grasping aids, however, need to be strong in the X and Y direction as well to allow for robust robot grasping and handling in the future. As shown in the list, the additional strength of the grasping aid depends on the process step in the manufacturing process it is meant for.

To achieve such strength and accessibility for grasping aids, physically denser grasping features have to be integrated into the support. For example, a circular/rectangular hole, pin, bar, ring or handle can be integrated into the support structures. The exact selected shape depends on the type of available gripper and the part’s shape and material. The rule for the grasping aid’s shape is that it has to bridge the shape difference between gripper and part/other support while enabling a safe automated grasp. The requirement of a stable grasp means that the position of the grasping aids should usually be on the outer perimeter of the part-support-structure. Depending on the gripper design, two or three grasping points should allow for grasping around them, i.e. sit on different sides of the part.

As an example, the use of circular and rectangular holes surrounded by reinforced supports as one type of grasping aid is shown in figure 1, wherein the partial figures depict a right side view (a), front view (b), left side view (c), and top view(d). An additively manufactured article comprising a 3D printed part 1 and at least one support structure 3 has been produced by a 3D printing process on a build platform 2, the printing direction being indicated by the arrow. The support structure 3 is located under an overhanging section of the 3D printed part 1 in order to make 3D printing of this overhanging section possible at all and avoid a deformation of the 3D printed part. In the volume of support structure 3 circular and rectangular holes are integrated as grasping aids. As indicated in the figure, the classical supports 3 consist of many printed “pillars” that are interconnected, but somewhat flexible. In comparison, the functional supports 4, 5 are printed as a denser lattice or cell structure or even as a fully dense solid to be able to rigidly withstand higher grasping forces by a robot without failure or negative impact on the actual part. The positioning of the grasping aids is only exemplarily. The grasping aid might be purposely dislocated from the direct line of force to the parts center of mass, so that grasping it automatically produces a torque that helps to detach the part-functional support compound from the build platform. For example, in the right side view shown in figure 1(a) the grasping aid can be positioned more to the left border of the support volume, or in the top view shown in figure 1(d) the grasping aid locations between the left side and right side can be tilt to facilitate a rotating removal.

A resulting robot grasp could be like shown in figure 2. A robot gripper 6 grasps the additively manufactured article 1 using the grasping aids 4, 5 of figure 1, which due to their center hole can fit into the robot gripper 6 equipped with conical tips, as a key-lock-pair.

A possible robot motion to detach the additively manufactured article 1 from the build platform 2 is indicated by arrows, however, this is only exemplary, other movements of the robot gripper 6 for the detachment of the additively manufactured article 1 are possible as well.

Another aspect for the grasping aid positioning is related to the planning scheme since the support functionalities have to be planned along the life cycle phases of an additively manufactured article. This means that certain sections of the functional support volume will be removed in a later life cycle phase than others. For example, functional supports serving as a surface protection and grasping aid during logistics and assembly phases will be kept longer on the part than the only printing process-related supports for the manufacturing phase. Therefore, the grasping aids of the functional supports for later phases may be located behind the grasping aids of the supports for earlier phases. For instance, in the previous example of figures 1 and 2, the grasping aids might be pulled off in perpendicular direction after part detachment to open up some wash channels for the cleaning step.

As mentioned, the design of the functional supports for grasping aids is dependent on the required mechanical connection strength, which in turn depends on the specific manufacturing phase process step that is targeted with the grasping aid. The requirements for the different steps are as follows:

In the unloading step, the build platform of the 3D printer with the printed part and support structures attached to it will be removed from the 3D printer. Usually, the 3D printer has a locking mechanism that needs to be opened to release the build platform, which can then be taken out by a human or robot. Some parts with expansive lengths or thin cross sections are prone to bending or breaking during that removal procedure, especially if they are printed in weak material such as silicone. Nowadays, in these special cases the human technician has to grasp both the build platform and the part cautiously to keep all sections together. In order to automate this step, the robot may need grasping points on the part it can reliably touch in parallel to the build platform to fulfill the same handling support that the technician has provided so far. The grasping points may look similar to those of figures 1 and 2.

If multiple parts on the build platform have to be kept in place, the robot could make use of a holder that attaches to the standardized grasping aids in the parts. In any case, the necessary forces are low. Thus, grasping aids for the unloading step from the 3D printer typically do not need much increased strength because the part is still supported by all other supports structures attached to the build platform, which are not removed in the printer.

Since the unloading phase does not exert more forces than the printing process itself beforehand, all printing process-related support structures together should be sufficient.

However, once all types of supports including the grasping aids are generated, the influence of the robot and its motion on the freshly printed or fully cured part(s) through the functional support structures are examined using a finite element analysis (FEA) simulation. If the FEA simulations yield any risk of damage on the part(s) in their green or final state, the functional supports are reinforced.

In contrast, for the detaching step the grasping aids as functional support have to withstand high forces. In this step, the robot has to separate the printed part from the build platform.

The printed part can either have been attached directly to the build platform through the print or can be printed on top of support structures that connect it to the build platform. In both cases the direct or indirect connection between part and build platform is quite strong as it had to carry the weight of the part during its printing process. To detach the part, the robot needs to exert a correspondingly high force. This force can potentially bend or break vulnerable sections of the part or at least the sections around the gripping points that have to bear the highest forces directly. Thus, the grasping aid has to be reinforced by dense support material, for instance by strong lattice or cell structures. Also, detaching a part that is connected through supports to the build platform may lead to breaks in the support-part connection points so that some support structures stick to the platform while the part is removed from it. Then the build platform needs its own support removal and cleaning step.

Also, support breaking off in this manner is a highly unstable effect, so that it is not always the same amount of support, which sticks to the platform or is detached together with the part. Thus, an inspection step for the part and platform, e.g. by a depth camera or laser scanner, is used prior to any automated support removal and cleaning of platform and part.

There are two strategies for functional supports facing this problem. One the one hand, the support structures can be totally reinforced and bound to the part with many strong connection points so that it will not tear off the part and not stick to the platform. In this case, the connection between (functional) supports and part(s) will be stronger than the connection between part(s) / supports and build platform. One the other hand, printing process-related supports sticking to the build platform may be easier to clean and to remove than if they adhered to the part being removed from the platform. If this is the case and the respective supports are not needed as grasping aids or other for other functionalities, weak sections can be integrated into this support as sacrificial points and reinforce the support’s connection to the build platform. The weak sections can be located within a block of support or at the connection interface between support material and the actual part. Through this design, the support gains the functionality of adhering always to the platform, while the part can be torn off it like a hook and loop fastener. An example for this solution is shown in figure 3. The classical supports 3 consist of tapered printed “pillars”, i.e. the support’s connection 7 towards the printed part 1 is much thinner than towards the build platform 2. This makes the support remain on the build platform after the part has been pulled off. Additionally, some grasping aids can be integrated into the support structure remaining on the platform, so it can be removed from it later more easily.

In the cleaning step, the detached part and all remaining support sections on it will be freed from process remnants of the printing process like liquid resin, powder or short plastic filament pieces. This happens by means of cleaning agents such as gases (like compressed air), liquids (like water jet, alcohol, or other solvents) or granulate. The part may be located in fixture in a cleaning machine, may be freely floating in a liquid or may be held into the cleaning machine by the grasping robot. Consequently, the functional supports need to withstand medium forces from the cleaning agents and maybe the grasp force of the robot or fixture. Thus, the required mechanical strength can be lower than for the detaching step, but higher than for the build platform removal.

Depending on the cleaning process, it may be desired that the cleaning agents remove some of the printed support structures along with the uncured material. In this case, the cleaning step is combined with the support removal step. Then, those sections of the functional support that are to be removed, should be intentionally designed with low mechanical strength so that the cleaning agent has enough strength to remove them. All sections that are meant to survive this cleaning and support removal procedure have to be mechanically stronger in order not to be detached by the weak support sections.

In the support removal step, mechanical force is used to remove printed support material. As described beforehand, this step can be connected with the cleaning step in case the cleaning agents are able exert sufficiently high forces on the support material. Alternatively, the support removal step is separated from the cleaning and follows afterwards. In this case, the robot arm has to make use of its grippers to pull off the desired support sections that are meant to be removed, mimicking the workflow of a human post-processing the part. The part and the remaining supports need to be hold firmly in place when the other support structures are being removed. This can be accomplished via a second robot gripper, e.g. by using a second robot arm or a dual-arm solution, or by means of some fixtures. In both cases, some type of grasping aids are required to connect the part and the remaining supports firmly to the gripper or fixture. The shape of the grasping aids for support removal could be similar to the suggestions above. In the end, the shape is not only dependent on the type of gripper but also on the motions the robot uses to remove the supports. Three examples are depicted in the following.

If the robot pulls off thicker blocks of support right away from the part, little cylindrical or rectangular holes in the sides of these blocks will be useful, as shown in figure 4. In that case a rectangular functional support 5 is used by a robot 9 with gripper 6 to pull off a whole block of the support structure 3 held together by the functional support. The 3D printed part 1 is held in place by flexible fixtures 8, clamping the rectangular shape without further grasping aids.

In a variant, a handle 10 instead of holes is used in order to allow the robot to peel off layers of support starting from the outside and going inwards. Two versions of handles as functional supports are shown in figures 5 and 6.

In figure 5 a robot (depicted schematically and miniaturized) is peeling off parts of the support structure 3, which exhibits holes in this variant, layer by layer by moving in circles around the 3D printed part 1. In an alternative, the robot is still and the part is rotating. The fixture of the part is not depicted in the figure, but is holding the part from the bottom, e.g. by fitting into a rectangular hole. In case the 3D printed part 1 is meant to rotate for support removal, the fixture includes a rotary plate.

Figure 6 shows a robot which is pulling zigzag supports 3 off the 3D printed part 1 by a backwards motion out of the paper plane, potentially by utilizing vibration during the motion. The robot is piercing one or more layers of support with aid of functional support 11 , in the shape of elliptic holes with reinforced edges. The accordingly aligned robot tool then rotates by 90° against the support to form a bayonet-like fastener to pull. If the robot has pulled off some layer of support, it can pierce more layers of support, rotate to fasten, and pull again. In the back, functional supports 12 are shown as grasping aids for fixtures 8 with holes for localization.

As for the grasping aid for the detaching step, FEA simulations can be used to dimension this grasping aid. Also, the explanations about the mechanical strength parameters from the detaching step generally hold for the support removal step: the mechanical strength must be very high at the grasping aid for the support removal step. Especially, the connection force at the grasping aid must be stronger than the connection force between the support section to be removed and other support sections or the part. Otherwise, the robot would rip the grasping aid off the part or off the other supports instead of removing whole sections of support. Again, as for the detaching step, there is an opportunity to purposefully decrease the mechanical strength of certain support sections in order to cause them to break off during the support removal step as sacrificial points. FEA simulations can be used for the process design here, too. Another cleaning step may follow after the support removal. The requirements for the support withstanding this procedure are described above.

The final step of the manufacturing phase is the post-curing step. Here the printed part as well as all remaining functional supports will be cured in some kind of oven to their final strength. Because all functional supports will leave their green state, their connection strength will be increased and their get harder to remove in the later steps. Consequently, the remaining grasping aids will be reinforced as well so that they do not need high mechanical strength from the start on, if they are only meant for grasping processes after the post-curing.

In (between) the described process steps of the manufacturing phase, there is a lot of robot handling involved such as the robot 9 handling a 3D printed part 1 by means of functional supports 12 shown in Figure 7. While the robot moves a part and its supports through the air, the grasping aids need to prevent deformation and break, which requires medium mechanical strength and ideally verification by FEA simulations. This is important because of the high handling speeds that today’s robots are capable of.

As described above, in the cleaning step a cleaning agents flows through the part and the surrounding support structures to remove excess uncured material, e.g. liquid resin. In the case of soluble supports, even the support material itself can be washed away. The highest cleaning priority is for the part, while excess uncured material may remain on the support sections that are removed afterwards anyway. However, it can happen especially for automated cleaning machines and very thick support structures that the cleaning agent only reaches the outer perimeters of the printed part-support-structure and not intricate inner sections, which are typically the actual part, i.e. the cleaning target. The solution to this problem are functional supports that contain open channels to bring the cleaning agent to the part at the innermost sections. The channels can have different layouts.

One example for wash channels based on a functional support structure is shown in figure 8. A block-shaped part 1 with a geometry as shown in figure 8(a) is 3D printed with complex internal cavities 13 that are filled with functional support material 3 as shown in figure 8(b) and 8(c). A functional support inflow hole 14 at the outer perimeter of the support splits up into two functional support wash channels 15 that meander at the upper and lower cavity surface until they merge into a single functional support outflow hole 16 again. Two exemplary section views at different depths show the different positions of the two wash channels at these depths. Washing agent, symbolized by arrows, is flowing through the channel and also distributes in the support lattice area around the channels to wash away even more remaining print material.

The layout of the cleaning channels is optimized depending on the cleaning process using a FEA and fluid dynamics simulations so that the cleaning medium can flow through all relevant sections. Especially if the cleaning agent is meant to remove some of the cured, printed support as well, it has to be made sure that these support leftovers can drain off freely in order not to clog the cleaning channels.

During the post-curing step, UV light, direct heat or other media/radiation types are used to increase the mechanical strength of the printed part(s) and the remaining supports. These media / radiation types typically directly or indirectly heat up the part quite quickly through energy absorption. The temperature changes can cause the part, which has been in its green state, to warp or bend. Slight warping or bending is usually an unintended process instability, unless the part requires some significant bending to reach its final shape. The problem of bending and warping is especially the case for thin sections or sharp angles in the part.

In order to prevent or deliberately force bending during part curing functional supports can be used as baking fixtures, i.e. as fixations. An example is shown in figure 9. In this case for a fanned out 3D printed part 1, the “arms” are prevented from warping by functional support 4. For comparison, also contours 17 are indicated in the figure, showing how the arms would warp in the post-curing if the functional supports were missing.

Using functional supports in the post-curing step, however, also means that these supports will be post-cured together with the part. Thus, the supports get mechanically stronger as well, i.e. become harder to separate from the part. Therefore, the anti-warp aid supports should be located only on class B surfaces, i.e. surfaces not visible to the customer. Also, the connection strength of these supports to the part needs to be extremely low, e.g. by designing the connection points with necks, so they can be pulled off later, as shown already in figure 3. As described previously, the automated post-processing steps require a robot or other tools to work precisely with the printed part and the supports. The robot can typically only make use of one gripper, whereas a human 3D printing technician has two hands to work on the part. The typical solution in automation setups for such problems is to deploy fixtures that the robot puts the part in to be held firmly in place. Similar fixtures can also be used in the cleaning and baking machines. As the shape of additively manufactured articles may change from print to print, these fixtures would have to be reproduced for every new shape.

However, with functional supports of the invention, standardized fixtures can be introduced that fit the location aids of these functional supports for many different part shapes. The requirement on the functional supports for location aid is consequently that they are located on standardized positions, even for different part shapes. For instance, on functional supports, there could be printed little pins or cones that stand out every inch/centimeter and fit into a shape negative in the fixture or a kind of clamp like shown in the previous figures 4 or 6. Another embodiment of functional supports as location aid is depicted in figure 10, which shows a 2D view of functional supports 4 on the sides of a 3D printed part 1 being supported by a classical support structure 3. The functional supports 4 are implemented as location aids with conical pins 18, which e.g. have a distance of one centimeter, and that fit into deepenings 20 in the surface of a fixture 19.

During the processing the involved process tools can potentially collide with the printed part in its green or final state and cause scratches or even worse damage. Other sources of damage or imperfections on the part could be a little piece of cured 3DP material, dust, wind, water or UV light. The inventive functional support structures can serve as protectors against these influences. To protect the part, the support needs to surround the exposed surfaces of the part, especially the surfaces visible to the customer, so-called class A surfaces. However, class A surfaces should not have support marks visible to the customer. Thus, the functional support material needs to be fixated to the non-visible class B surfaces or other support sections.

Figure 11 shows a 2D view of functional supports 4 on the sides of a 3D printed part 1 as protectors of class A surfaces 21. The supports at the bottom are reinforced to be able to withstand handling forces at the outside without bending and touching the class A surfaces

After the parts and all remaining supports have been post-cured in the end of the additive manufacturing phase, they will be transported from the 3D printing shop to the assembly line. This logistics phase can span different companies or even different continents, if the supply chains are longer. Also in this life cycle phase, functional supports according to the invention can take over particular functions, mainly to ease automation and to protect the part during its journey as mentioned above.

In addition, dedicated functional supports in this logistics phase can facilitate the packaging. Nowadays, a lot of cardboard waste is being produced because smaller cardboard boxes sit inside of bigger cardboard boxes inside of bigger cardboard boxes inside of containers to keep the parts in place and protected. Inside of the smaller cardboard boxes, some cardboard strips hold cables and various components of a product set in position. With the inventive functional supports though, these support structures can be used to take over some packaging abilities, e.g. around plugs and cables, as exemplarily shown in figure 12.

In this example, the functional supports 4 are integrated into the classical, process-related supports of a 3D printed plug 1 and include holders for plugs 23 of cables 22, as shown in figure 12 (a). The plugs 23 can be clipped into the holders to be fixed in place as some kind of packaging for a transportation phase, as shown in figure 12 (b).

Another example of functional supports for packaging is depicted in figure 13. In this case a relatively round 3DP part 1 shown in figure 13 (a) is hard to stack in packaging and in addition may have a sensitive class A surface. Adding the functional supports 4 around the 3DP part results in a shape that is easy to stack as shown in figure 13 (b), indicating on top of the wrapped 3DP part 1 the functional supports 4 of a next 3DP part being stacked above it.

After the parts and their remaining functional supports have been brought to the assembly line of the final factory, they are assembled with other parts to form a product that can be handed over to a customer. In addition to functionalities as described above, another inventive functional support application during the usage phase is a support pattern as described in the following.

The background of this functional support is the problem that the detachments of supports from a part’s surface usually leave support marks behind - little bumps or holes that show where support material had been physically attached and has been broken off. These support marks are usually not acceptable on surfaces visible to the customer. However, if the surface structures show a support mark pattern that is appealing to the customer from a design standpoint, they might get acceptable. In order to generate an appealing surface pattern, all support marks should have the same look and should be overall regularly spread over a surface, with some random irregularity being acceptable. They might be combined with a surface design on the part that is not influenced by the supports. Thus, in the generation of the functional supports, the positioning of the connection points between support and part has to be purposefully designed if an appealing surface pattern should be generated in order to “hide” the remnants of previous support structures from the customer.

This is depicted in figure 14. As shown in figure 14 (a), with traditional supports 4, support marks 24 would be produced by the support removal on a class A surface 21 of a 3DP part 1. Shown in figure 14 (b) is the usage of purposely positioned functional supports 4 that do also leave support marks after removal, but these are matched to the surface, e.g., here a snake-like pattern 25, integrate into it, and in this way become invisible.

Examples of 3DP parts where surface pattern make sense are a 3D printed automotive door handle or a 3D printed roof grab handle. Since almost the whole surface of these parts is touchable / touched by the user and thus are class A surfaces, there is not much space to place classical supports on class B surfaces to facilitate the printing process, if these parts are 3D printed. Thus, using functional support surface patterns can relieve the support position problem quite a lot. In addition, the user might feel the texture of the surface pattern with the support marks and consider it as a haptic benefit, which may also reduce slipping.

After a product has been used, it will be dumped or recycled. In the future, even the automated disassembly of products is likely to become established. A future product producer will plan these disassembly processes together with the introduction of a new product.

On the one hand, if the part is planned to be re-used in another product it has to be carefully disassembled and brought to the re-assembly factory. Here, no damage on the part can be accepted. All previous assembly and logistic steps have to be executed in reverse order, thus the invented functional supports from the assembly and logistics phase described above can be useful for this reverse process if they are still in place on the part. However, most functional supports must have been removed in prior life cycle phases after they had served their function. Just by exception, one or another type of functional support has “survived” the usage phase and can aid the disassembly and re-use phase.

On the other hand, if the part is not planned for reuse, it can be disassembled even destructively and recycled. Since damage or even destruction is not a problem, functional supports can be used as sacrificial points to ease the part removal by destructive disassembly or the crushing for recycling.

In the disassembly step, the targeted part could, for example, be partially covered by other assembly parts from subsequent assembly steps so that a normal disassembly is not possible. Here, the robot could break the part into halves by removing some functional supports in the part’s middle section as depicted in figure 15. As shown in figure 15 (a),, a robot 9 is not able to remove the full 3DP part 1 , because it is partially hidden behind the main assembly body 26 and the sidewise access is still obstructed by other parts. The use of functional supports 4 as break-off aids, however, allows for partial removal of the 3DP part as shown in figure 15 (b). This opens up motion space for the robot to remove also the remaining parts, i.e. in the shown example the robot can remove two smaller pieces without problems.

Figure 16 illustrates an exemplary method according to a general aspect of the method for producing an article comprising a 3D printed part and at least one functional support structure by a 3D printing process.

In step 31, the 3D printed part’s initial 3D shape is received as a digital 3D model, e.g. by importing a CAD file. Further parameters for the 3D printing process can be included in the file or can be defined once the file is imported. Such parameters may comprise the orientation of the 3DP part in the build volume of the 3D printer, the amount of parts being printed per print and their layout on the build platform and where around the 3DP part supports are acceptable.

Another parameter are surface quality requirements, wherein the surface of the 3DP part is divided into “class A surfaces” and “class B surfaces” (or similar classifications). “Class A surfaces” are visible to the customer or serve a special mechanical function, so no classical, printing process-related supports would be allowed to be attached to this surface because they usually leave support marks such as small bumps or surface inequalities, even after they have been removed. As these support marks would influence the aesthetics or the mechanical function, all classical, printing process-related support structures would have to be attached solely to the non-visible or not mechanically functioning “class B surfaces”.

Once these parameters are defined, in the next step 32 support structures are generated which serve as a planning baseline for the integration of functional supports because they show where (classical) supports are definitely necessary to succeed in the pure printing process. This step works with geometrical features like the part geometry such as thickness changes, inclination angles and overhang sizes as well as specific material and process parameters of the chosen AM process to distribute support material.

In the following step 33, the algorithm attempts to fit all desired functional support structures into the (classical) support structures that have been generated in the previous step. For this purpose, the digital 3D model for the support structures is modified such that the support structures provide the functionality of an integrated grasping aid and possibly further additional functionality after the 3D printing process.

The algorithm takes into account information about the additive manufacturing process as well as other later following life cycle phases. For the additive manufacturing, this concerns for instance which material is printed by which 3D printing process using which physical effect and process parameter. Using these details allows to plan the spatial distribution of functional support material and especially the connection strengths between functional support material and the 3D printed part. For the later steps, it can also be taken into account how the 3D printed part is post-processed, how mechanically vulnerable it is in its green state and as a finished product. Furthermore, it is crucial to know which robots and other automation equipment are available in which phases and how their gripping devices look like. Similarly, any other equipment, tools, and process interfaces in the later steps of logistics, (dis)assembly, and recycling can be considered.

Ideally, the integration of all desired functional support structures is possible without adding any extra support. Otherwise, a minimum of extra functional supports is added on top of the (classical) supports in order to keep material costs and waste low. Also, the algorithm may optimize the automation steps and in particular the support removal. This step comprises several sub-steps such as creating support sections, bringing them into an order, producing robot grasps and robot motions for these sections, and lastly defining the connection interfaces between the sections. Details of these sub-steps are described further below.

In the following step 34, the algorithm generates 3D printing control data for the 3DP part and the functional support structures. The format of these 3D printing control data depends on the way layers are deposited to create parts and in the materials that are used by the chosen 3D printing process.

Finally, in step 35 an article comprising the 3DP part and the functional support structures is 3D printed based on the generated 3D printing control data. The 3D printing process builds the article in a layer-by-layer fashion, e.g. by pulling it gradually out of a reservoir of 3D printing resin, where it is photo-polymerized, i.e. solidified by shining a laser on the resin sections that shall become rigid.

In an ideal case, step 33 has integrated all relevant sections of functional support within the volume of the generated classical, only printing process-related supports. However, if this could not have been achieved, additional support material is added. If this material addition has not helped to integrate all targeted functional supports, the initial 3D shape or orientation of the part is modified. Several iterations may be required to define the final shape of the article comprising the functional supports.

As mentioned, the generation of the functional support structures within the classical support structures according to step 33 comprises several sub-steps. First, the volume of the generated classical supports from step 32 needs to be partitioned into sections based on the different types of targeted functional supports. These sections are representing the different life cycle phases that the supports are used in. For example, some of the (classical) supports will be removed immediately after the print, whereas other (functional) supports are kept on the part for the cleaning phase to house washing channels and others even for the assembly phase to serve as grasping aids. Thus, there needs to be a clear separation between these supports. While both functional support sections might have been a unified body within the build volume of the classical, printing process-specific support, they have to be split up and even a connection interface has to be defined.

This sub-step could be software-assisted or interactive, if the user specifies the different sections only roughly (e.g. by their center point) and a planning algorithm, based on FEA simulations, decides where exactly to put the section borders that weaken the mechanical strength by a minimal amount.

Furthermore, sections could be generated in an unsupervised fashion by an algorithm based on geometrical features, e.g. the algorithm detects an undercut or a hole that needs its own section of support to be removed. Such detections can be driven by machine learning- processes on 3D data or by hard-coded feature detection of shape primitives.

Also, it is defined which operation on which section will happen at which point in time. For example, it is decided which section will be grasped when from which direction by the robot.

It has to be figured out if the corresponding support section will be accessible at all or if a different support section has to be removed first to make space to be able to tear off the next one. Furthermore, the influence of the build platform’s print layout on the accessibility and the feasible robotic movements or other support functions is to be examined, like other printed parts being in front of the respective functional support. This also includes the position of non-grasping functional support types like wash channels or protectors. The geometric reasoning in this step helps to clear any conflicting functional supports, so that the interaction of the supports with robots or other process tools can be planned in the next step.

Facilitating process automation, such as the interaction of the involved robots or fixtures with the functional support sections, is a major purpose of functional supports. Thus, gripping points or features are placed on the surface sections. The positioning of these gripping points has to ensure that the robot can grasp in a stable manner or that the part can be hold by a fixture firmly. The computation of grasps and fixtures may start with the sections’ shape that is inherited from the classical, only printing process-related supports from step 32 and modifies the sections to improve the grasps or fixtures.

The positioning of the grasping aids depends on which support sections have been defined in the volume of the classical support structures (or in the specifically added functional support areas in minimal added support volume). Only where support is present in one section, a grasping aid can be placed on it. In most cases, a grasping aid cannot be positioned on two sections at the same time, unless the usage and removal order is identical with respect to the phase of when the grasping aid is used. The functional support sectioning is planned after selection of the targeted functional support cases and after the decision about the orientation of the part in the build volume of the 3D printer as well as about the amount of parts being printed per print and their layout on the build platform and the decision where around the part supports are acceptable. The layout, orientation and acceptable support volume are the initial constraints on the position of grasping aids.

With respect to the life cycle, the positioning of the grasping aid depends on the usage and removal order of the single defined section. For instance, if a functional support section A is in front of a section B up to the life cycle phase of e.g. assembly, a grasping aid cannot be positioned on B for the post-processing phase as it is still covered by A at this earlier point in time. Correspondingly, it is crucial here when a robot will place a grasp on it. If, on the other hand, a grasping aid is needed for assembly, it has to be placed on a functional support section that remains long enough on the part to not be removed prior to assembly. The presence of other functional support sections in the proximity of the grasping aid also constraints the planning of the robot grasp motion: the robot can only move around and grasp where no other material from other support sections is in the way. I.e., free workspace to close the robot grippers around the grasping aid is needed. In case the grasping aid is used to facilitate support removal, workspace must also accommodate the removal motion,

Furthermore, the available connection strengths of the separation interfaces between the defined sections determines the grasping aid position. E.g., if the grasping aid has to withstand high forces when the robot grasps the 3D printed part through it, it needs to be positioned on a section that has a high connection strength to the part. Regarding the robot gripper, the grasping aid should be positioned so that the robot gripper can exert a stable grasp. In the case of functional supports, the grasp stability analysis is complex as the shape of the part changes during the phases and the part-functional-support compound cannot be considered as rigid.

As mentioned above, the requirement of a stable grasp means that the position of the grasping aids should usually be on the outer perimeter of the part-support-structure. Depending on the gripper design, two or three grasping points should allow for grasping around them, i.e. sit on different sides of the part. However, the 3D structure is not truly given as a static object. The support sections could still be changed in their physical shape to improve the grasping process, as they are not part of the final part. A mutual optimization of gripping position and gripping feature shape can be conducted, starting with the sections’ shape that is inherited from the classical, only printing process-related supports and modifying the sections to improve the grasps or fixtures.

In addition, it also needs to be known how the 3D printed part is post- processed, how mechanically vulnerable it is in its green state and as a finished product. In the simplest case, it can be assumed that the functional support section with the grasping aid is stiff enough to be grasped like a tea cup handle and the connection strength between this section and the part is high enough so that moving around the part with a grasp around the grasping aid handle does not break apart the functional support section(s) from the part. Then, the position can be derived:

1. A grasping aid meant for handling should be positioned on the part, so that the forces and torques that are transmitted from the gripper through the grasping aid onto the functional support section and part are minimized. The forces/torques can be determined by means of FEA analysis or in a simple case by mechanical calculations.

2. In contrast, a grasping aid meant as a connection point for support removal or detaching, has the purpose of producing/transmitting high forces and torques when being grasped. Then, the grasp must be more stable and the grasping aid must be positioned differently so that it is able to endure or to produce these forces internally in the part. For example, the grasping aid might be purposely dislocated from the direct line of force to the parts center of mass, so that grasping it automatically produces a torque that helps to detach the part-functional support compound from the build platform.

Depending on where the biggest weaknesses are located in the part-functional support compound the grasping aid has to be repositioned to either increase mechanical strength (as in 1.) or to purposely decrease it (as in 2.).

Furthermore, also the robot capabilities of the robot planned to be used influences the grasping point placement. Examples of possible types of capabilities can be:

1. Position capabilities: not all robots have 6 or 7 degrees of freedom or arms long enough to reach any point on a 3D printed part. Especially intricate features are hard to reach, like holes in the part or the space in between two parts that are placed “back to back” on the build platform (“JL”-shape). Thus, the set of all grasping aid position candidates that has resulted from the aforementioned part-specific planning constraints can be further restricted to only robot capability-specific reachable points on the surface.

2. Force capabilities: Most robot arms of today are still only controlled by position in their movements, not by the forces that their movements create. Unlike humans, they do not “feel” resistance when pushing something. Only few modern robots are fully force/torque controllable, e.g. the KUKA LWR Light Weight Robot. If a robot without force sensing is moved by slightly inaccurate position commands, it might produce high forces when trying to drive through the part or the functional support sections. This is in stark conflict with the vulnerability of 3D printed parts in their green state and the potentially low connection strengths between the part and the functional support sections. If the robot is thus unable to grasp a grasping aid with gentle force, it has to be repositioned so that it withstands higher process forces without failure. This limits the possible grasping aid locations to those with a high stiffness (enough support material or support material largely connected to the part).

Similar tasks are to be done for the other non-grasping related types of functional support supports such as wash channels, protectors, surface patterns or break off aids. The shape optimization within the given volume from step 32 also holds for these types of functional supports. For instance, the position of wash channels within the volume from step 32 has to be defined in order to improve the cleaning process, i.e. by letting the cleaning agent flow to all relevant surfaces of the final part.

Based on the grasps and fixtures, the motions of the robot gripper and the support section or support with part have to be defined such that the motion produces no damage on the printed part, especially in its green state and when supports are pulled off. Once the movements of robots and other process tools are specified, their influence on the functional support sections is finally defined. The supports sections are connected to the part and to each other via contact surfaces where support material is attached to other support material or to the part. For any motion of the part-support conglomerate or the detachment of single support sections, the strength that these contact interfaces build up is defined.

In the following, the design process of functional supports will be exemplified by a fictive 3DP part, such as a future in-car VR goggle holder, which is planned to be additively manufactured. It is neglected here that multiple of the fictive 3DP parts could be potentially printed on a single build platform.

In the car interior the fictive 3DP part is held by a backwards carrier structure. The fictive 3DP part 40 and the backwards carrier structure 41 are schematically shown in figure 17. In this example, the fictive 3DP part is visible to the customer from the outside, and fixed to the assembly from the inside. Thus, the outside surfaces 42 have to be considered as “class A” surfaces where no functional support can ever be attached to during the life cycle, unless its remnants will be hidden by the “surface pattern” functional support mentioned above. All inner surfaces 43, however, are considered as “class B” surfaces that are acceptable for support placement.

In the design process, initially the additive manufacturing and other life cycle processes are defined, the available automation equipment is specified and the optimal part orientation and acceptable volume for functional support structures is defined. The resulting printing orientation and acceptable support volume 44 underneath the 3DP part 40 as well as the acceptable support volume 45 around the 3DP part 40 is shown in figure 18(a). Any support 44 underneath the lower side of the part can be considered as acceptable functional support volume. Furthermore, there is extra available volume around the part to accommodate functional supports for use cases that do not directly touch the part’s surface, such as packaging or protector. Based on this, classical, printing process-related (classical) support structures are generated as planning baseline which leads for the exemplary 3DP part to the supports 3 being unavoidable in order to facilitate a successful print, as shown in figure 18 (b).

In the following step the algorithm tries to accommodate all targeted functional supports in the classical, printing process-related supports 3. For this example, the sequence and types of the targeted functional supports are:

As a consequence, an ideal grasping aid combines the applications ® and ®, i.e. stays on the part from the printing process until the assembly phase. This means that it must not be in the way of removal of any other functional supports being removed earlier, like the removal aid ©. The removal aid will be removed together with the printing process- related support that is pulled off in the post-processing phase.

The anti-warp aid © has to stay until the part has been successfully baked in the heat oven, i.e. until the end of the manufacturing phase. I.e., it must not be in the way of removal for the removal aid ©. The functional support protector for the assembly phase has to stay on the part until the end of the assembly phase ©. If automated assembly processes are executed in proximity to the 3DP part after its assembly, this can even mean that it stays longer on the 3DP part, essentially until these neighboring processes are finished as well .

This first attempt of sequencing the classical support for the targeted functional supports without touching the class A surfaces is shown in figure 18(c). Support 3 is split up into four functional support sections 46 - 49. However, as can be seen, this attempt was not totally successful since the protection © for the class A surfaces in the assembly phase could not have been integrated and grasping aids ®® in block 48 would provide only very limited grasping ease for a robot.

Therefore, the support generation algorithm is (re-)deployed to fix the issue of lacking functional supports by adding more support volume which enables to accommodate all targeted functional supports. For this purpose the algorithm makes use of some part of the enlarged support volume 45 of figure 18(a). Since there is no chance to create more reasonable functional support without touching the class A surfaces, the above mentioned functional support surface patterns are deployed by adding support volume 50 to the planning process, as shown in figure 19(a).

With that, the sequencing and robot planning are revisited, resulting in a new sectioning including these newly added supports which is able to accommodate all targeted types of functional supports, as shown in figure 19(b).

By adding a block of supports on the left side, attached to some class A surface with a surface pattern, more functional support space is created to accommodate all use cases at minimal extra material cost. The added block 51 is meant to stay on the part until assembly is finished, so that it can serve as a protector. Furthermore, it can serve as a grasping aid throughout all pre-usage life cycle phases because it stays long enough on the part at an advantageous position. To hold this support block 51, there is a block 52 added underneath, which can serve as a grasping aid during the post-processing phase. In addition, there are slight angles between the different support sections to create clear separations between them, so that they can be torn apart easily and consistently by a robot.

Furthermore, gripping points are placed in the sections as shown in figure 19(c). Since the part is quite block-shaped and thus stable in itself, no safety grasp on the part is required while unloading the build platform with the part attached from the printer. The robot can grasp the build platform directly and carry it around. However, for the subsequent part detaching step, high grasping forces have to be exerted on the 3DP part. Thus, the robot should grasp at a very stable section of the functional support. In order to allow pulling the part upwards, a circular grasping aid 4 is located at block 53, similar to those presented in figure 1. On the back side of the part, an identical grasping aid is to be placed so that the robot can wrap its jaw grippers around the part from both sides and lift it up.

It is also possible to add another similar grasping aid for detaching on block 52. However, this section tolerates less grasping force since it is not located fully underneath the part. I.e., there the part / support can be grasped and lifted up for detachment only with gentle force. Otherwise, the support would break off and potentially even damage the class A surface above. Therefore, having grasped with gentle force, after block 52 and block 53 start to peel off a bit, the robot has to re-grasp to the main grasping aid to be able to pull the part off completely with much higher force. If even that second-step pull-off should not succeed in a single motion, another similar grasping aid in the right block 46 can be integrated. This allows for a second re-grasp to that right grasping aid and another uplifting motion to finally detach the part / support completely from the build platform, especially the very right part section that is directly attached to the build platform.

For the support removal, the grasping aids are used in blocks 46, 52 and 53. The support blocks are peeled off the 3DP part one by one from left to right while using one the remaining functional supports as a fixture point. I.e., for the start, the gripper removes section 52 as a whole block first, while the part is clamped into a fixture holding section 53, e.g. by its grasping aid. Afterwards, for removing block 53 by the grippers, the part will be clamped into the grasping aid of block 46. For finally removing functional support section 46, the part could be clamped around the block-shaped lower section of its right half, which is all class B surface, invisible to the customer later. Additionally or alternatively, the fixture could clamp on section 51. This section is also meant for the further robot grasping, in the handling for cleaning, and baking, and later for assembly. Into the upper and the lower surface of section 51, circular or rectangular grasping aids could be integrated.

Thus, the robot uses a grasp around to put the part into the heat oven for post-curing. The functional support section 49, the anti-warp aid in manufacturing, is still attached to the part when it goes into the oven. Its purpose is to avoid heat deflection at the sharp angle in the part that section 49 fills up. After the curing, the robot gripper can pull off this support from the left or right side. Since the cured support is much more rigid and firmly attached to the cured part than before baking, the support-part-connection must be very weak. It is therefore suggested that the functional support section 49 is designed as a zigzag support like in figure 6.

After removal of section 49, the part can be packaged and shipped to the assembly line. At assembly, the robot arm will grasp the part at section 51 to assembly it into the main assembly body. The section 51 may include a thin protector at its upper end to protect the part from scratches through other adjacent processes. After all of these assembly processes are finished, this last support can be removed.

While only a single 3DP part was considered above, further embodiments of functional supports result in case of simultaneously printing two or more 3DP parts on the build platform. For example, if two identical L-shaped clips are printed on a build platform, they can the positioned “back to back” on the build platform, i.e. as a shape of “JL”. Then, functional support structures can be placed in between their “backs” as a grasping aid for detaching and further handling. It should be understood that the operations explained herein may be implemented in conjunction with, or under the control of, one or more general purpose computers running software algorithms to provide the presently disclosed functionality and turning those computers into specific purpose computers.

Moreover, those skilled in the art will recognize, upon consideration of the above teachings, that the above exemplary embodiments may be based upon use of one or more programmed processors programmed with a suitable computer program. However, the disclosed embodiments could be implemented using hardware component equivalents such as special purpose hardware and/or dedicated processors. Similarly, general purpose computers, microprocessor based computers, micro-controllers, optical computers, analog computers, dedicated processors, application specific circuits and/or dedicated hard wired logic may be used to construct alternative equivalent embodiments.

Moreover, it should be understood that control and cooperation of the above-described components may be provided using software instructions that may be stored in a tangible, non-transitory storage device such as a non-transitory computer readable storage device storing instructions which, when executed on one or more programmed processors, carry out the above-described method operations and resulting functionality. In this case, the term non-transitory is intended to preclude transmitted signals and propagating waves, but not storage devices that are erasable or dependent upon power sources to retain information.

Those skilled in the art will appreciate, upon consideration of the above teachings, that the program operations and processes and associated data used to implement certain of the embodiments described above can be implemented using disc storage as well as other forms of storage devices including, but not limited to non-transitory storage media (where non-transitory is intended only to preclude propagating signals and not signals which are transitory in that they are erased by removal of power or explicit acts of erasure) such as for example Read Only Memory (ROM) devices, Random Access Memory (RAM) devices, network memory devices, optical storage elements, magnetic storage elements, magneto optical storage elements, flash memory, core memory and/or other equivalent volatile and non-volatile storage technologies without departing from certain embodiments. Such alternative storage devices should be considered equivalents.

While certain illustrative embodiments have been described, it is evident that many alternatives, modifications, permutations and variations will become apparent to those skilled in the art in light of the foregoing description. Accordingly, the various embodiments of, as set forth above, are intended to be illustrative, not limiting.

Reference Signs List

3D printed part Build platform Support structure , 5, 11, 12 Functional supports Robot gripper

Connection towards printed part

Flexible fixtures

Robot 0 Handle 3 Internal cavities 4 Inflow hole 5 Wash channels 6 Outflow hole 7 Contours of fanned out 3D printed part without functional supports at post-curing 8 Conical pins as location aid 9 Fixture 0 Deepenings in the surface of fixture 1 Class A surface of 3DP part 2 Cables 3 Plugs 4 Support marks produced by support removal 5 Surface pattern 6 Main assembly body 1 - 35 Method steps 0 Fictive automotive 3DP part 1 Backwards carrier structure 2 Outside surface of fictive automotive 3DP part 3 Inner surface of fictive automotive 3DP part 4 Acceptable support volume underneath the 3DP part5 Acceptable support volume around the 3DP part6 - 49, 51 - 53 Functional support sections 0 Added support volume

Claims

Patent Claims

1. An additively manufactured article produced by a 3D printing process, in which the article is built up by depositing material on the basis of a digital 3D model, comprising: a 3D printed part (1); and at least one support structure (3), which supports the 3D printed part (1) during the 3D printing process of the 3D printed part in order to avoid a deformation of the 3D printed part and is configured to provide an integrated grasping aid (4, 5) for a robot (9) or other automated machine after the 3D printing process.

2. The additively manufactured article of claim 1 , wherein the at least one support structure (3) supports automated handling steps of the 3D printed part (1) after the 3D printing process.

3. The additively manufactured article of claim 1 or 2, wherein the grasping aid (4, 5) is formed by one or more holes, pins, bars, rings or handles located on the outer surface of the support structure, each surrounded by a reinforced support structure area.

4. The additively manufactured article of any of the preceding claims, wherein the support structure supports the 3D printed part (1) at support points during the 3D printing process of the 3D printed part which are configured to provide predetermined break points (7) to facilitate removal of the 3D printed part from the support structure after the 3D printing process.

5. The additively manufactured article of any of the preceding claims, wherein the integrated grasping aid is designed in such a way that the robot or other automated machine can pull off a whole block or zigzag parts of the support structure; or peel off layer by layer the support structure starting from the outside of the support structure and going inwards by moving in circles around the part or by staying still and rotating the part.

6. The additively manufactured article of any of the preceding claims, wherein the support structure is configured to provide at least one integrated cleaning channel (15) which allows a cleaning medium to flow through at least a part of the 3D printed part and/or the support structure in order to remove excess material.

7. The additively manufactured article of any of the preceding claims, wherein the support structure is configured to provide a fixation to prevent or deliberately force bending during part post-curing after the 3D printing process.

8. The additively manufactured article of any of the preceding claims, wherein the support structure is configured to provide one or more location aids at standardized positions for fixtures of the robot or other automated machine.

9. The additively manufactured article of any of the preceding claims, wherein the support structure is configured to provide one or more protectors surrounding at least one surface of the 3D printed part.

10. The additively manufactured article of any of the preceding claims, wherein the support structure is configured to provide packaging functionalities.

11. The additively manufactured article of any of the preceding claims, wherein the support structure is configured to provide a pattern (25) on the surface of the 3D printed part after the detachments of the support structure from the 3D printed part.

12. Method for producing an article comprising a 3D printed part and at least one support structure by a 3D printing process, comprising the steps: receiving (31) a digital 3D model for the 3D printed part (1); generating (32) a digital 3D model for at least one support structure (3) such that the at least one support structure supports the 3D printed part (1) during the 3D printing process of the 3D printed part in order to avoid a deformation of the 3D printed part; modifying (33) the digital 3D model for the at least one support structure to adapt the at least one support structure to provide an integrated grasping aid (4, 5) for a robot (9) or other automated machine after the 3D printing process; generating (34) 3D printing control data for the 3D printed part (1) and the adapted at least one support structure; and

3D printing (35) the article comprising the 3D printed part and the adapted at least one support structure (3) based on the generated 3D printing control data.

13. Method of claim 12, further comprising: cutting the generated 3D model for at least one support structure (3) into sections (46 - 49, 51 - 53); determining the usage and removal order of the sections (46 - 49, 51 - 53) of the at least one support structure; placing gripping points in the sections (46 - 49, 51 - 53) and/or planning grasps and/or handling or support removal motions; generating 3D printing control data for the 3D printed part and the adapted at least one support structure to be printed; and determining separation interfaces between the sections (46 - 49, 51 - 53) of the at least one support structure and the 3D printed part.

14. Method of claim 13, further comprising: modifying the 3D model for at least one support structure by increasing the volume of the generated 3D model for the at least one support structure in case not all planed functional support functions could be integrated within the initial volume of the generated 3D model.

15. A computer program product containing computer readable instructions that, when executed by a computer, cause it to perform a method according to any one of claims 12 to 14.