SE545644C2

SE545644C2 - Additive manufacturing device and method for controlling an additive manufacturing device

Info

Publication number: SE545644C2
Application number: SE2100060A
Authority: SE
Inventors: Daniel Wedlund; Magnus Boström
Original assignee: Sandvik Machining Solutions Ab
Priority date: 2021-04-22
Filing date: 2021-04-22
Publication date: 2023-11-21
Also published as: SE2100060A1; WO2022223744A1

Abstract

Disclosed is a method for controlling an additive manufacturing device. The method comprises depositing (202) a layer of loose powder composition and adding (204) binder to a part of the layer of loose powder composition. The method further comprises heating (206) the powder composition and obtaining (208) temperature information of the layer of powder composition. The method further comprises analyzing (210) the temperature information by clustering the temperature information into a plurality of clusters and discarding all but the two largest clusters, in order to obtain at least one of a first lower temperature and a second higher temperature, and controlling (212) a temperature in the additive manufacturing device based on the at least one temperature.

Description

Technical field

[0001] The present disclosure relates generally to methods and systems for controlling the temperature of an additive manufacturing device, particularly when the additive manufacturing device employs binderjetting.

Background

[0002] Additive manufacturing, also known as 3D printing, generally involves manufacturing, or printing, one layer at a time using specialized systems. ln particular, a layer of powder material may be deposited on the working surface of a build chamber and bonded with another layer of the same or of a different material. Additive manufacturing may be used to manufacture articles from computer-aided design models using techniques such as binderjetting.

[0003] ln binderjetting, after a layer of powder has been deposited, a step of dispensing binder to the powder bed follows. This dispensing step forms a green body in the powder bed. The dispensing is performed by a print head which supplies the binder to the powder bed in droplets. The dispensed binder soaks into the powder bed and the solvent in the binder starts to evaporate, often using a radiation source such as a heat lamp or the like to enhance the evaporation. Each powder layer comprises at least one closed shape with dispensed binder. These closed shapes are stacked on each other and form the green body in the powder bed of the build chamber during the subsequent steps of layer formations. Here the term “printed area" is used interchangeable for the closed shapes of dispensed binder in the powder bed.

[0004] The heating of the powder bed is controlled with the bed temperature as input data. However, in the current art, it is usually not known whether the measurement of the temperature is a measurement of a printed area, i.e. combination of powder and binder, an unprinted area, i.e. an area with only loose powder, or a combination thereof.

[0005] However, since the properties of the loose powder and the powder with binder added to it differ, it would be beneficial if a bettertemperature control could be achieved.

[0006] Consequently, there exists a need for improvement when it comes to controlling the temperature in additive manufacturing processes comprising both printed and unprinted areas.

Summary

[0007] lt is an object of the invention to address at least some of the problems and issues outlined above. An object of embodiments of the invention is to provide a method for controlling an additive manufacturing device, in which a better and more accurate temperature control of the build box, particularly of the powder bed, may be achieved, such that the combination of binder and powder composition does not become too dry or too wet. lt is further an object to provide an additive manufacturing device for the same purpose.

[0008] According to one aspect, a method for controlling an additive manufacturing device is provided. The method comprises depositing a layer of loose powder composition and adding binder to a part of the layer of loose powder composition. The method further comprises heating the powder composition and obtaining temperature information of the layer of powder composition. The method further comprises analyzing the temperature information in order to obtain at least one of a first lower temperature and a second higher temperature, and controlling a temperature in the additive manufacturing device based on the at least one temperature.

[0009] According to another aspect, an additive manufacturing device is provided. The additive manufacturing device comprises a build box comprising a powder bed, a powder supply for supplying the powder bed with powder, and means for dispensing binder to the powder bed. The additive manufacturing device further comprises means for obtaining temperature information of the powder bed and means for controlling the temperature in the powder bed. The additive manufacturing device further comprises processing means comprising processing circuitry, and a memory, the memory containing instructions executable by said processing circuitry. The additive manufacturing device is operative for depositing a layer of loose powder composition, adding binder to a part of the layer of loose powder composition and heating the powder composition.

The additive manufacturing device is further operative for obtaining temperature information of the layer of powder composition and analyzing the temperature information in order to obtain at least one of a first lower temperature and a second higher temperature. The additive manufacturing device is further operative for controlling a temperature in the additive manufacturing device based on the at least one temperature.

[00010] According to other aspects, computer programs and carriers are also provided, the details of which will be described in the claims and the detailed description.

[00011] Further possible features and benefits of this solution will become apparent from the detailed description below.

Brief description of drawinqs

[00012] The solution will now be described in more detail by means of exemplary embodiments and with reference to the accompanying drawings, in which:

[00013] Fig. 1 shows a flow chart of a method for controlling an additive manufacturing device according to an embodiment.

[00014] Fig. 2 shows a block schematic of parts of an additive manufacturing device according to an embodiment.

Detailed description

[00015] Briefly described, the present disclosure relates to a method for controlling an additive manufacturing device, also referred to as a 3d printer, particularly for controlling the temperature of the additive manufacturing device. The method comprises the general steps of depositing powder, adding binder to part of the powder, and heating the powder. The method further comprises obtaining temperature information of the layer of powder composition, and analyzing the temperature information in order to obtain at least one of a ﬁrst lower temperature and a second higher temperature, and then controlling a subsequent temperature application in the printer based on either the first temperature or the second temperature.

[00016] The present disclosure provides a method for controlling the temperature based on more detailed temperature information, which differentiates between printed and unprinted areas, and which may be agnostic to the location of the printed and unprinted areas. An unprinted area is an area comprising only loose powder with no binder added, and a printed area is an area comprising both powder and binder.

[00017] An insight which is relevant for the present disclosure is that the temperature of unprinted areas, i.e. areas with loose powder, and printed areas, i.e. areas with powder to which binder has been added, differ to a relevant degree. Further, a key part when controlling the temperature is to ensure that the printed areas are heated to the correct degree, not too much and not too little. However, present technologies usually employ temperature sensors which measure a temperature for the entire powder bed, and do not differentiate between printed and unprinted areas. This results in that the temperature control is not as accurate as it can be, and that an optimal temperature is rarely achieved, which entails that printed areas are often too wet or too dry.

[00018] Another insight which is relevant for the present disclosure is that there will only be two different larger clusters of temperature information in a powder bed of an additive manufacturing device, one representing printed areas and one representing the unprinted area. Based on this, it is possible to achieve a method which is agnostic to where the printed and unprinted areas are located, but still different between them from a temperature perspective.

[00019] An example of an additive manufacturing device used for performing methods according to the present disclosure will now be described. ln some embodiments, the additive manufacturing device is a binderjet printer.

[00020] The additive manufacturing device comprises a build box with a powder bed, and a powder supply for supplying the powder bed with powder. The binder jet further comprises means for dispensing binder to the powder bed, such as a print head. The additive manufacturing device further comprises means for obtaining temperature information of the powder bed, such as a temperature detector. The temperature detector may be a thermal imaging device. The additive manufacturing device further comprises means for controlling the temperature in the powder bed, such as a heat source. The printer may further comprise a levelling device configured to |eve| the powder in the build box. The binderjet may further comprise processing means comprising processing circuitry, and a memory, the memory containing instructions executable by said processing circuitry.

[00021] Looking now at Fig. 1, a method for controlling the temperature of an additive manufacturing device according to an embodiment will now be described.

[00022] The method comprises depositing 202 a layer of powder composition, on a powder bed of an additive manufacturing device. The additive manufacturing device may for example be one which employs binderjetting technology, but is suitable for any additive manufacturing device where an agent is combined with loose powder and going through a temperature change, either by itself, or by an external heat source.

[00023] The method further comprises adding 204 binder to a part of the layer of powder composition. The binder is preferably added such that at least one closed shaped is formed by the area to which binder is added.

[00024] The method further comprises heating 206 the powder composition. The heating may be performed by any suitable method, for example by moving an irradiation device over the layer of powder composition, or by heating the entire space in which the powder composition is contained.

[00025] The method further comprises obtaining 208 temperature information of the layer of powder composition. The temperature information should preferably be detailed enough to contain information for all parts of the powder composition, including both the printed and unprinted areas. The area which is to considered to be one point in the temperature information is between 0.1 mm2 - 4cm2, and preferably around 4 mm

[00026] The method further comprises analyzing 210 the temperature information in order to obtain at least one of a first and a second temperature. As previously mentioned, there will generally be only two larger clusters of temperature in a powder composition where some parts have binder added to it, one representing the printed area, i.e. powder with binder added, and one representing the unprinted area, i.e. loose powder without binder added. The purpose of the analyzing step is to obtain at least one of these two temperatures, in order to use that as input for subsequent temperature control of the method.

[00027] The method further comprises controlling 212 a temperature of the powder composition, based on the at least one temperature, i.e. the first or second temperature, representing either the printed or unprinted area.

[00028] The step of controlling 212 the temperature preferably comprises controlling the subsequent heating step 206 for the next layer of powder composition, it does not necessarily comprise controlling the temperature immediately after the analyzing step. ln other words, the controlling step 212 may be seen as performing steps 202, 204 and 206, wherein step 206 is controlled based on the at least one of the first and second temperature.

[00029] The temperature which is most relevant for deciding which temperature to use in subsequent operations is generally the part representing the printed area, since the purpose of the temperature control is to control the processes occurring in printed areas. One example of such a process is the evaporation of solvent in the a deposited binder lf the solvent in the binder evaporates too quickly due to too much heating, the structural integrity of the green body might be compromised, e.g. lose strength and/or delaminate. On the other hand, if the temperature is too low, binder might bleed through a subsequently deposited layer and cause powder to stick to the roller, which leads to defects in the build bed surface.

[00030] However, the relationship between the temperature of printed and unprinted area will usually be constant, and thus, if the relationship is known beforehand, the method may just as well be performed by controlling the temperature based on the unprinted area, adapted based on the relationship between the two temperatures. For example, if the unprinted areas are generally two degrees warmer than the printed areas, the method could be controlled based on the unprinted area, with an offset of two degrees.

[00031] The method is generally performed for a plurality of layers of powder composition, wherein the steps are performed for each layer of powder composition.

[00032] However, in some embodiments, the controlling 212 may comprise adjusting a temperature of the additive manufacturing device directly after the analyzing 210, for example if the temperature information indicates that there is still binder left which has not been evaporated. ln some embodiments, when the controlling 212 comprises directly adjusting a temperature, the method may further comprise analyzing again, and then possibly controlling 212 the temperature again, and depending on the results, the method may comprise continuing to loop the controlling 212 and the analyzing 210 steps, until a desired temperature has been obtained.

[00033] ln some embodiments, the step of analyzing 210 the temperature information comprises clustering the temperature information into two clusters, based on the temperature information. As described previously, the reason for doing this is that there is usually only two relevant different temperatures to consider, one representing the printed area and one representing the unprinted area.

[00034] ln some embodiments, clustering the temperature information into two clusters comprises clustering the temperature information into a plurality of clusters and discarding all but the two largest clusters. There may be small differences between different parts of the printed area, as well as between different parts of the unprinted area, that may result into more than two clusters, depending on the method used for clustering.

[00035] ln some embodiments, the first temperature is an average value of a ﬁrst temperature cluster, and the second temperature is an average value of a second temperature cluster. A reason for using the average temperature rather than a highest or lowest temperature, is that the average temperature is more stable and represent a larger amount of data, and may thus be more accurate and less susceptible to noise.

[00036] ln some embodiments, controlling 212 the temperature comprises controlling the temperature based on the lower temperature, i.e. the ﬁrst temperature, which represents the printed area.

[00037] ln some embodiments, obtaining 208 temperature information comprises obtaining a thermal image of the powder composition. A thermal image may be obtained e.g. by using a pixel based temperature detector, such as an IR camera. ln such embodiments, one pixel may be regarded as one data point for temperature. The size of each pixel will depend on the properties of the sensor, as well as the distance from which the thermal image is captured.

[00038] ln some embodiments, analyzing 210 the temperature information further comprises analyzing spatial information of the temperature information. By using spatial information about the location of different temperature, a better analysis may be obtained, where outliers, noise, and similar sources of errors can be more easily detected. lt should be noted that using spatial temperature information is different form using spatial information regarding the powder composition itself, even though it represents a similar set of underlying data. ln the present method, there is generally no need to match the spatial powder information with the spatial temperature information.

[00039] Thus, in some embodiments, the method may comprise not obtaining any spatial information about the powder itself or any other information about the physical layout in the build box. ln some embodiments, the method comprises only using the temperature information and no other information for performing the analyzing 210 and the subsequent controlling 212 of the temperature.

[00040] ln some embodiments, analyzing the thermal image comprises analyzing temperature data points in an area of interest. lt may not be necessary or optimal to use the entire thermal image, and instead an area of interest is chosen. ln some embodiments, such an area of interest comprises both printed and unprinted GFGGS.

[00041] ln some embodiments, the heating 206 may be achieved by other means than a heat source, such as a chemical reaction between components in the powder and/or binder. ln such embodiments, the heating may be controlled by controlling the amount of chemicals added for causing such a reaction. ln such embodiments, the means for controlling the temperature of the additive manufacturing device, may be means for controlling the amount of chemicals added.

[00042] ln some embodiments, the method further comprises performing steps 208, 210 and 212 prior to step 206. lt should be noted that the method still comprises performing steps 208, 210 and 212 after step 206 as well. Performing steps 208, 210 and 212 both before and after step 206 may be relevant for obtaining information about how the temperature of an unprinted area is affected by the addition of binder, and based on this information, a more detailed analysis may be possible.

[00043] ln some embodiments, the method further comprises performing steps 202, 204, 208, 210 and 212, prior to performing step 202. ln other words, the method may comprise depositing a layer, or a plurality of layers, without adding binder, but still perform the temperature analysis and subsequent temperature control based on the temperature analysis. This is generally performed in order to have a stable temperature between subsequent powder layers before starting the actual print process.

[00044] ln some embodiments, the clustering may comprise clustering the temperature information into more than two clusters, and the controlling may be based on at least one of the clusters. This may be relevant e.g. if there are different areas with different concentrations of binders, which could result in more than two distinct temperature clusters.

[00045] Fig. 2, shows parts an additive manufacturing device 600, operable for performing an additive manufacturing process. The additive manufacturing device 600 comprises processing circuitry 603 and a memory 604. The processing circuitry 603 may comprise one or more programmable processor, application- specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The memory contains instructions executable by said processing circuitry, whereby the device/system 600 is operative for depositing a layer of loose powder composition, adding binder to a part of the layer of loose powder composition and heating the powder composition. The additive manufacturing device is further operative for obtaining temperature information of the layer of powder composition and analyzing the temperature information in order to obtain at least one of a first lower temperature and a second higher temperature. The additive manufacturing device is further operative for controlling a temperature in the additive manufacturing device based on the at least one temperature. The additive manufacturing device may further comprise the components described earlier herein.

[00046] ln some embodiments, the additive manufacturing device 600 for which the method is performed may be a group of devices, wherein functionality for performing the method are spread out over different physical, or virtual, devices of the system. ln other words, the additive manufacturing device 600 may comprise a cloud-solution, i.e. parts of the additive manufacturing device 600 may be deployed as cloud computing resources that may be distributed in the system.

[00047] According to an embodiment, the additive manufacturing device 600 is operative for performing any of the method steps described herein.[00048] According to other embodiments, the additive manufacturing device 600 may further comprise a communication unit 602, which may be considered to comprise conventional means for communicating with other parts of an additive manufacturing system. The instructions executable by the processing circuitry 603 may be arranged as a computer program stored e.g. in a memory 604. The processing circuitry 603 and the memory 604 may be arranged in a sub- arrangement 601. The sub-arrangement 601 may be a micro-processor and adequate software and storage therefore, a Programmable Logic Device, PLD, or other electronic component(s)/processing circuit(s) configured to perform the methods mentioned above.

[00049] The computer program may comprise computer readable code means, which when run in an additive manufacturing device 600 causes the additive manufacturing device 600 to perform the steps described in any of the described embodiments of the additive manufacturing device 600 or the method for controlling an additive manufacturing device 600. The computer program may be carried by a computer program product connectable to the processing circuitry 603. The computer program product may be the memory 604. The memory 604 may be realized as for example a RAM (Random-access memory), ROM (Read- Only Memory) or an EEPROM (Electrical Erasable Programmable ROM). Further, the computer program may be carried by a separate computer-readable medium, such as a CD, DVD or flash memory, from which the program could be downloaded into the memory 604. Alternatively, the computer program may be stored on a server or any other entity connected to the additive manufacturing device 600, to which the additive manufacturing device 600 has access via the communication unit 602. The computer program may then be downloaded from the server into the memory

[00050] Although the description above contains a plurality of specificities, these should not be construed as limiting the scope of the concept described herein but as merely providing illustrations of some exemplifying embodiments of the described concept. lt will be appreciated that the scope of the presently described concept fully encompasses other embodiments which may become obvious tothose skilled in the art, and that the scope of the presently described concept is accordingly not to be limited. Reference to an element in the singular is not intended to mean "one and only one" unless explicitly so stated, but rather "one or more." All structural and functional equivalents to the elements of the above- described embodiments that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed hereby. Moreover, it is not necessary for an apparatus or method to address each and every problem sought to be solved by the presently described concept, for it to be encompassed hereby. ln the exemplary figures, a broken line generally signifies that the feature within the broken line is optional.

Claims

1. A method for controlling an additive manufacturing device, comprising: a) depositing (202) a layer of loose powder composition: b) adding (204) binder to a part of the layer of loose powder composition; c) heating (206) the powder composition; d) obtaining (208) temperature information of the layer of powder composition; UR _ ._ . á V11/ .Qsaxs-xss šš: mxëx. *rf/a å f e) analyzing (210) the temperature information by clustering the temperature information into a plurality of clusters and discarding all but the two largest clusters, in order to obtain at least one of a first lower temperature and a second higher temperature; and f) controlling (212) a temperature in the additive manufacturing device based on the at least one temperature, wherein the analyzing (210) and the controlling (212) comprises only using the temperature information and no other information.

2. The method according to any one of the previous claims, wherein the first temperature is an average value of a first temperature cluster, and the second temperature is an average value of a second temperature cluster.

3. The method according to any one of the previous claims, wherein controlling (212) a temperature in the additive manufacturing device comprises controlling a temperature based on the lower temperature.

4. The method according to any one of the previous claims, wherein obtaining (208) temperature information comprises obtaining a thermal image of the layer of powder composition

5. The method according to any one of the previous claims, further comprising performing steps d-f before step c.

6. The method according to any one of the previous claims, wherein contro||ing (212) a temperature in the additive manufacturing device comprises performing steps a-c, wherein the heating is based on the at least one temperature.

7. The method according to any one of the previous claims, wherein the temperature information is obtained using a pixel based temperature detector.

8. The method according to any one of the previous claims, further comprising, prior to step a): depositing a layer of loose powder composition: heating the powder composition; obtaining temperature information of the layer of powder composition; analyzing the temperature information in order to obtain a temperature; and contro||ing a temperature in the additive manufacturing device based on the obtained temperature.

9. An additive manufacturing device (600) comprising: a build box comprising a powder bed; a powder supply for supplying the powder bed with powder; means for dispensing binder to the powder bed; means for obtaining temperature information of the powder bed; means for contro||ing the temperature in the powder bed; processing means comprising processing circuitry (603), and a memory (604), the memory (604) containing instructions executable by said processing circuitry (603), whereby the additive manufacturing device (600) is operative for: depositing a layer of loose powder composition: adding binder to a part of the layer of loose powder composition; heating the powder composition; obtaining temperature information of the layer of powder composition; analyzing the temperature information by clustering the temperature information into a plurality of clusters and discarding all but the two largest clusters, in order to obtain at least one of a first lower temperature and a second higher temperature; and controlling a temperature in the additive manufacturing device based on the at least one temperature_._

10. The additive manufacturing device (600) according to claim 9, further operative for performing the steps of a method according to any one of claims

11. A computer program (605) comprising computer readable code means to be run in _*j___additive manufacturing device (600), which computer readable code means when run in the additive manufacturing device (600) causes the additive manufacturing device (600) to perform the following steps: depositing a layer of loose powder composition: adding binder to a part of the layer of loose powder composition; heating the powder composition; obtaining temperature information of the layer of powder composition; \' \ i ' _ .\\.\,\<.-. _ \\ - Iwsmš» t t\§\- analyzing the temperature information by clustering the temperature information into a plurality of clusters and discarding all but the two largest clusters, in order to obtain at least one of a first lower temperature and a second higher temperature; and controlling a temperature in the additive manufacturing device based on the at least one temperature,

12. A carrier containing the computer program (605) according to claim 11, wherein the carrier is one of an electronic signal, optical signal, radio signal or computer readable storage medium.