WO2025214922A1

WO2025214922A1 - Method for additive manufacturing of a 3d item by means of fused deposition modeling and additive manufacturing apparatus

Info

Publication number: WO2025214922A1
Application number: PCT/EP2025/059389
Authority: WO
Inventors: Markus Weigandt; Simon Geissler; Malte Bogdahn; Ulf Mueller; Tilmann SPITZ; Fabian LOOSE; Niklas KALHOFF; Sebastian ZABLOCKI
Original assignee: Merck Patent GmbH
Current assignee: Merck Patent GmbH
Priority date: 2024-04-09
Filing date: 2025-04-07
Publication date: 2025-10-16
Anticipated expiration: 2026-10-09

Abstract

The invention relates to a method and an additive manufacturing apparatus (1) for additive manufacturing of a 3D item by means of fused deposition modeling of a composite material. The composite material is fed through a heated printer extruder head (4) and deposited on a printer bed (5) as a layer arrangement (7) that forms the 3D item. A weighing step comprises a weighing preparation step during which the printer bed (5) is moved from a manufacturing position without any weight transmitting contact between the printer bed (5) and a weighing device (14) into a weighing position in which the printer bed (5) is in a weight transmitting contact with the weighing device (14) that is arranged below the printer bed (5). The weighing step further comprises a weighing execution step during which the weight of the layer arrangement (7) on top of the printer bed (5) is determined with the weighing device (14) by determining the weight of the printer bed (5) together with the layer arrangement (7) with the weighing device (14) and by deducting the previously determined weight of the printer bed (5).

Description

Method for additive manufacturing of a 3D item by means of fused deposition modeling and additive manufacturing apparatus

Technical Field

The present invention relates to a method for additive manufacturing of a 3D item by means of fused deposition modeling of a composite material, whereby the composite material is fed through a heated printer extruder head and deposited on a printer bed as a layer arrangement that forms the 3D item, whereby during or after the additive manufacturing of the 3D item a weighing step is performed for determining the weight of the layer arrangement that has been deposited on the printer bed. The present invention also relates to an additive manufacturing apparatus for additive manufacturing of a 3D item by means of fused deposition modeling of a composite material, the additive manufacturing apparatus comprising a printer bed mounted at a printer bed support structure and a printer extruder head for discharging and depositing the heated composite material as a layer arrangement on a printer bed to generate the 3D item out of the composite material, whereby the discharging and depositing of the heated composite material can be controlled by a control device, the additive manufacturing apparatus further comprising a heating device for heating the composite material prior to discharging the heated composite material out of the printer extruder head, the additive manufacturing apparatus further comprising a weighing means for measuring a total weight of the layer arrangement that has been deposited on the printer bed during or after manufacturing of the 3D item.

State of the Art

Additive manufacturing of 3D items allows for almost instantaneous manufacture of 3D items of almost any shape or composition of material. Furthermore, additive manufacturing does not require the preceding production of a tool form, which is costly and time consuming, but allows for cheap manufacture of a large number of 3D items. However, some shapes of 3D items cannot be manufactured by using tool forms, e.g. due to undercuts or internal formations that cannot be created by a tool form. Thus, additive manufacturing is very attractive for the manufacture of individual 3D items or of small batches of 3D items with either different or complex shape or composition. Furthermore, additive manufacturing allows for the manufacture of 3D items with shapes that cannot be manufactured by other means or methods, e.g. by injection molding or cutting.

There are several different methods of additive manufacturing known in prior art. Powder molding or selective laser sintering is performed by selectively heating a small spot of powder particles that melt and fuse to form a part of the 3D item. By consecutively fusing a number of such small spots into a layer of the desired shape and a layer arrangement into a large object, a 3D item can be manufactured. However, for each layer a powder bed must be provided, which usually limits this method to making use of the same composition of powder for each layer. Furthermore, the precision of manufacture is limited by the precision that can be achieved for the selective heating and melting of a small spot of powder.

Another method that can be used for additive manufacturing is fused deposition modeling. Usually, a thermoplastic filament is fed into a heated printer extruder head, the filament is heated and melted within the printer extruder head, and then extruded layer-wise from the printer extruder head on a printer bed. Many parameters like e.g. flow geometry of the extruder, heating method and the melt flow behavior of the heated and viscous composite material affect the deposition of layers and the manufacture of the 3D item as a layer arrangement of composite material extruded by the printer extruder head. By changing the thermoplastic filament during manufacture of a single 3D item it is possible to generate a 3D item that comprises two or more regions of different materials. However, the precision of the manufactured 3D item is limited by the flow characteristics of the heated and viscous composite material that will be affected by many parameters like e.g. the temperature of the printer extruder head or the printer bed, the conveyance of composite material through the printer extruder head or even ambient temperature and alignment of the printer bed with respect to the printer extruder head.

According to known prior art, it is possible to perform a weighing step during or after the manufacture of the 3D item to determine the weight of the layer arrangement or of the finished 3D item in order to determine the manufacturing quality. Performing the weighing step usually requires the 3D item or the layer arrangement to be removed from the printer bed and to be placed onto the weighing device for measuring the weight of the 3D item or the layer arrangement. However, after performing the weight measurement it is rarely possible to continue with additive manufacturing of the same layer arrangement or 3D item with high precision, as the removal and the replacement will affect the layer arrangement or the 3D item and it is also very difficult to replace the layer arrangement or the 3D item in the same position as before on printer bed.

Thus, there is a need for a method that allows for easy weight control during or after the manufacturing of a 3D item and that allows for rapid and precise manufacturing of a 3D item, especially from materials usually considered problematic for fused deposition molding.

Summary of the Invention

The present invention discloses a method for additive manufacturing of a 3D item by means of fused deposition modeling and additive manufacturing apparatus, characterized in that the weighing step comprises a weighing preparation step during which the printer bed is moved from a manufacturing position without any weight transmitting contact between the printer bed and a weighing device into a weighing position in which the printer bed is in a weight transmitting contact with the weighing device that is arranged below the printer bed, in that the weighing step further comprises a weighing execution step during which the weight of the layer arrangement on top of the printer bed is determined with the weighing device by determining the weight of the printer bed together with the layer arrangement with the weighing device and by deducting the previously determined weight of the printer bed. It is considered a very favorable aspect of this invention that the arrangement and mounting of the printer bed can be switched between two different positions, namely a manufacturing position and a weighing position. The manufacturing position results in a fixture of the printer bed that allows for a precise manufacturing process, i.e. that fixes the printer bed reliably at a precise position and that prevents any displacement during the discharge of the heated composite material out of the printer extruder head onto the printer bed. In the weighing position, the printer bed is placed on top of a weighing device and is brought into a weight transmitting contact with the weighing device, i.e. the printer bed needs to be movable in such a manner as to allow for a precise weighing performance, whereby the determination of the weight of the printer bed is not significantly affected by a mounting of the printer bed that provides for a force bypass that interferes with the measurement of gravitational forces acting on the printer bed with the layer arrangement on top of the printer bed.

In order to be able to precisely determine the weight of the layer arrangement, the printer bed should be mounted freely movable in a vertical direction. Furthermore, the mounting should be in such a manner as to reduce or avoid any force bypass that affects the determination of gravitational forces, i.e. that restricts or affects any vertical movement of the printer bed. Contrary thereto, during the manufacturing process and the discharge of the extruded composite material, the printer bed should be mounted as reliably and precisely as possible in a predetermined position to which the printer bed can be repeatedly relocated during a manufacturing process of a single 3D item.

The weighing preparation step and the weighing execution step can be performed automatically and without any manual interference. There is no need for manual interaction, which allows for the implementation of the weighing step within a fully controlled environment and without any risk of unwanted contamination of the 3D item during the manufacturing process. This allows for making use of the fused deposition molding for manufacturing pharmaceutical solid administration forms that must be carefully monitored and controlled in order to minimize any health risks due to deviations of the manufactured pharmaceutical solid administration form from the manufacturing specifications like, e.g. any deviation of the content of the pharmaceutical ingredient or some unwanted cross contamination with residual pharmaceutical ingredients from a preceding manufacturing process. As the method described above allows for a very precise and contamination free manufacturing and controlling of a 3D item, this method can be used particularly advantageously for the precise production of individualized pharmaceutical solid administration forms.

According to a very favorable aspect of the invention, the weighing step further comprises a weighing termination step during which the printer bed is relocated into a manufacturing position in which the weight transmitting contact of the printer bed with the weighing device is disconnected, and in which the printer bed is in a positive locking contact with a printer bed support structure that retains the printer bed in a fixed position during the additive manufacturing of the layer arrangement on the printer bed. Thus, the weighing device is only in a weight transmitting contact with the printer bed for the duration that is required for performing the weighing execution step, i.e. that is required for the determination of the weight of the printer bed, but decoupled from the printer bed in times that are not related to any such determination of the weight of the printer bed. Apart from the duration of the weighing execution step, the weighing device is not in a weight transmitting contact and preferably not in any contact with the printer bed during the discharge of the heated composition material out of the printer extruder head, which helps to increase the precision of the weight measurement, which protects the weighing device from any unwanted force transmitting contact and which also increases the precision of the manufacture of the 3D item as there is no unwanted feedback with the weighing device that might affect the position of the printer bed during the discharge of the composite material from the printer extruder head onto the printer bed. Furthermore, the disengagement of the weighing device from the printer bed also enables and at least simplifies the positioning and fixation of the printer bed during the discharge of the heated composition material out of the printer extruder head during manufacturing of the 3D item, which in turn enhances the precision of the manufacturing process. According to a favorable aspect of the invention, during the relocation of the printer bed during the weighing termination step the printer bed is brought into a predetermined alignment of the printer bed with respect to the printer bed support structure. Such an alignment can be predetermined by positive guide elements that provide for guidance and, if deemed appropriate or needed, also for a form-fitting fixing of the printer bed with respect to the printer bed support structure.

The alignment and the fixing of the printer bed with respect to the printer bed support structure can be facilitated or fully provided by magnetic guidance elements that provide for a magnetic force between the printer bed and the printer bed support structure. Preferably, the magnetic guidance elements comprise at least one electromagnet for which the magnetic force that acts between the magnetic guidance elements can be easily controlled and manipulated in such a way as e.g. to apply an attractive force during the additive manufacturing of the 3D item and to not apply any magnetic force during the performance of the weighing execution step which might affect the precision of the weight determination.

It is also possible that the alignment and the fixing of the printer bed with respect to the printer bed support structure can be facilitated or fully provided by guiding and/or fixing elements that have a form-fitting or force-fitting mechanism of action. Furthermore, it is also possible to combine magnetic guidance elements with formfitting or force-fitting elements. Preferably, the alignment and the fixing of the printer bed can be automatically controlled and any movement of the printer bed in order to be aligned and positioned with respect to the printer bed support structure can be either automatically performed or reliably prevented as needed when performing the weighing preparation step or when performing the weighing termination step. According to a favorable embodiment of the invention, the printer bed comprises a printer bed plate with a top side, on which the layer arrangement is deposited, and with an underside opposite to the top side, whereby the printer bed further comprises a guide rod that projects from the underside of the printer bed plate towards the weighing device. For such an embodiment of the printer bed, it is considered advantageous if during the weighing preparation step the guide rod is moved towards the weighing device until the guide rod is in a weight transmitting contact with the weighing device. The weight transmitting contact between the weighing device and the guide rod can be easily designed and supported in such a manner as to reduce or completely avoid any unwanted transfer of momentum from the printer bed plate towards or onto the weighing device, which enhances the precision of the weight determination during the weighing execution step. Furthermore, the guide rod can be mounted and guided in a forced guidance device that only allows for a longitudinal displacement of the guide rod along a guide rod longitudinal axis and that prevents any unwanted tilting of the guide rod and thus of the printer bed during the weighing preparation step or during a weighing termination step.

According to a very favorable aspect of the invention, during the weighing termination step the guide rod is brought into positive engagement with a guide rod displacement device that displaces the guide rod from the weighing position into the manufacturing position. Thus, the guide rod and the printer bed plate that is inextricably linked or detachably connected with the guide rod can be guided and displaced by the guide rod displacement device. The forced guidance and the displacement of the guide rod along a longitudinal axis of the guide rod can be easily performed and precisely controlled. An appropriate design of a suitable guide rod displacement device does not require much space and can easily be mounted on or at the printer bed support structure. The linear movement of the guide rod can be driven by e.g. one or more linear actors or an electric motor with a gearbox that comprises a gear meshing with the guide rod. Thus, providing for a guide rod displacement device allows for a precise displacement as well as of a precise fixing of the printer bed that can be easily controlled and does not require much space.

In yet another embodiment of the invention, the method further comprises a precise manufacturing step, whereby during the precise manufacturing step an additional non-gravitational force is exerted on the printer bed that holds the printer bed in a manufacturing position on or at a printer bed support structure. The non- gravitational force can be provided by a positive locking mechanism that provides for a form-fitting engagement of the printer bed with the printer bed support structure during the precise manufacturing step, and that can be disengaged e.g. before, during or after the weighing execution step. The form-fitting engagement of the printer bed with the printer bed support structure may comprise form-fitting latches, locking bolts or clamping tongues that can be moved back and forth between a locking position and an unlocking position that releases the printer bed from the printer bed support structure.

According to a very advantageous embodiment of the invention, during the precise manufacturing step the printer bed is pulled or pushed with at least one electromagnet into the manufacturing position. The additional non-gravitational force can be a magnetic force that acts between the printer bed and the printer bed support structure. The magnetic force can be provided by one or more electromagnet devices that can be operated in order to push or pull the printer bed into the manufacturing position. By making use of a magnetic force that securely locks the printer bed within the manufacturing position, no additional movable form-fitting elements with a physical contact with the printer bed are required, which facilitates the cleaning of the additive manufacturing apparatus or the removal and replacement of the printer bed during or after the manufacturing of a batch of 3D items.

The present invention also relates to an additive manufacturing apparatus for additive manufacturing of a 3D item by means of fused deposition modeling of a composite material, the additive manufacturing apparatus comprising a printer bed mounted at a printer bed support structure and a printer extruder head for discharging and depositing the heated composite material as a layer arrangement on a printer bed to generate the 3D item out of the composite material, whereby the discharging and depositing of the heated composite material can be controlled by a control device, the additive manufacturing apparatus further comprising a weighing means for measuring a total weight of the layer arrangement that has been deposited on the printer bed during or after manufacturing of the 3D item. Even though many different embodiments of such additive manufacturing apparatus are known and widely used, most embodiments do not allow for a rapid and precise measurement of the weight of the layer arrangement that has been deposited during or after the manufacture of the 3D item. Usually, the weight of the 3D item can only be determined after removal of the 3D item from the printer bed. Even after returning a non-finished 3D item back to the printer bed, it requires much efforts to continue with a precise manufacture of the repositioned 3D item. So, for many applications it is considered best practice and more efficient to finish with the manufacture of a 3D item and to perform a checking of the essential properties like e.g. the weight of the finished 3D item afterwards, resulting in either further use of a properly manufactured 3D item or in rejection and discarding a 3D item that does not meet the manufacturing criteria. However, with very strict specifications e.g. defined or recommended by standards like the Good Manufacturing Practices that apply for the manufacturing of pharmaceutical solid administration forms with active pharmaceutical ingredients, such a verification of essential properties after finishing the manufacture of the 3D item might result in the rejection of many 3D items which increases the time and costs for the manufacturing of a given batch of 3D items.

Thus, the present invention is also directed to an additive manufacturing apparatus for additive manufacturing of a 3D item by means of fused deposition modeling of a composite material configured to carry out the method as described herein. Thus, it is considered a further object of this invention to provide for an additive manufacturing apparatus that allows for a very precise manufacturing of a 3D item and in particular of a pharmaceutical solid administration form comprising at least one active pharmaceutical ingredient.

The present invention discloses an additive manufacturing apparatus as described above, whereby the printer bed support structure comprises a printer bed displacement means with which the printer bed can be moved back and forth between a manufacturing position in which there is no weight transmitting contact between the printer bed and a weighing device and a weighing position in which the printer bed is in a weight transmitting contact with the weighing device. As already described above with respect to the inventive method for determining the weight of the layer arrangement, it is considered a very advantageous aspect of such an additive manufacturing apparatus that the weighing device can either be brought into weight transmitting contact or completely detached from the printer bed. Thus, the weighing device does not affect the manufacturing process, i.e. the precise discharge of the heated composition material as one or more layers of composite material onto the printer bed. Also, the manufacturing process and the deposition of heated composite material onto the printer bed does not affect the weighing device, e.g. by transmitting forces or moments onto the weighing device. Both method steps, the complete manufacturing of the 3D item and a weighing execution step for determining the weight of the layer arrangement that has already been deposited onto the printer bed can be performed without any risk of interference, resulting in an increased precision for both method steps.

Furthermore, it is not necessary to remove the layer arrangement from the printer bed or to remove the printer bed together with the already deposited layer arrangement from the additive manufacturing apparatus to perform a weight execution step for determination of the weight of the layer arrangement. It is solely required to provide for a weight transmitting contact between the printer bed and the weighing device, which can be quickly and automatically established or disconnected. This allows not only for a very quick performance of the weighing execution step, but also for the performance of the weighing execution step once or at intervals during the manufacturing of the 3D item, i.e. before the 3D item is finalized. In case that the determination of the weight of the layer arrangement that is performed during such a weighing execution step reveals a discrepancy between the expected weight at that time and the weight actually determined for the layer arrangement, it is possible to make appropriate corrections during the continued manufacturing and finalization of the 3D item. Thus, in case that e.g. the determined weight after performing half of the 3D item manufacturing process is less than expected, additional composite material can be discharged through the printer extruder head or the second half of the 3D item manufacturing process can be extended to manufacture a 3D item for which the actual weight equals the expected total weight. In a same manner, it is possible to reduce the amount of composite material that will be discharged during the second half of the 3D item manufacturing process in case that after the first half of the manufacturing process the determined weight is larger than the expected weight of the layer arrangement that has already been deposited onto the printer bed. As it is not necessary to remove the printer bed or the layer arrangement from the printer bed in order to perform the weighing execution step, performing one or more weighing execution steps during the manufacture of a single 3D item does not adversely affect the precision of manufacture of the 3D item, but on the contrary reduces the number of finished 3D items that do not meet the criteria for essential properties like e.g. the weight of the finished 3D item or the ratio of two or more different composite materials that have been used to manufacture the 3D item.

According to a favorable embodiment of the invention, the printer bed support structure comprises means for a positive locking of the printer bed with the printer bed support structure that retains the printer bed in a fixed position during the additive manufacturing of the layer arrangement on the printer bed. A positive locking of the printer bed with the printer bed support structure can be provided by e.g. form-fitting latches, locking bolts or clamping tongues that can be moved back and forth between a locking position that locks the printer bed with the printer bed support structure, and an open position that releases the printer bed from the printer bed support structure. By providing for a positive locking mechanism that positive locks the printer bed with the printer bed support structure, the position of the printer bed can be precisely preset and maintained during the manufacturing of a 3D item, which facilitates and enables a very precise manufacturing of the 3D item that is deposited as a layer arrangement onto the printer bed.

In yet another embodiment of the invention, the printer bed support structure comprises means for positioning the printer bed in a predetermined alignment of the printer bed with respect to the printer bed support structure. Such means for positioning the printer bed may comprise guide elements or forced guidance elements that support or effect an alignment of the printer bed relative to the printer bed support structure during any relative movement of the printer bed with respect to the printer bed support structure. It is also possible to make use of magnetic guidance elements that push or pull the printer bed into a preset alignment with respect to the printer bed support structure. Furthermore, such means for positioning the printer bed may also comprise one or more spring- loaded guide elements, whereby the spring-loaded guide elements act on the printer bed during any movement or within a preset range of movement of the printer bed with respect to the printer bed support structure.

According to a favorable aspect of the invention, the printer bed comprises a printer bed plate with a top side, on which the layer arrangement is deposited, and with an underside opposite to the top side, whereby the printer bed further comprises a guide rod that projects from the underside of the printer bed plate towards the weighing device, and in that the printer bed support structure comprises a guide rod displacement device with which the guide rod can be displaced back and forth between the weighing position and the manufacturing position. The guide rod can be designed as integral part of the printer bed and can be inextricably linked with the printer bed plate.

It is also possible and considered a favorable embodiment of the invention that the printer bed plate is removably attached to the guide rod. Thus, it is possible e.g. to provide for a form-fitting contact between the guide rod and the printer bed plate that allows for a detachment of the printer bed plate from the guide rod to facilitate a cleaning operation of the printer bed before or after the additive manufacturing of a 3D item, or to remove or replace a printer bed plate. According to yet another embodiment, the printer bed plate can be attached to the guide rod by e.g. magnetic force or by clamping catch elements. Means for positioning the printer bed may provide for one or more forced guidance elements that provide for a linear displacement of the guide rod. Furthermore, the means for positioning the printer bed may also provide for a positive locking of the guide rod either in the manufacturing position or in a weighing position.

A printer bed plate that is removably attached to the guide rod significantly simplifies the cleaning of the additive manufacturing apparatus before or after the manufacturing of a 3D item, or even after a change of composite material that is discharged during the process of manufacturing a 3D item made of at least two different composite materials.

For many applications and in particular for the manufacturing of a pharmaceutical solid administration form comprising at least one active pharmaceutical ingredient, reliable cleanliness of all sections and parts of the additive manufacturing apparatus that might come into contact with the 3D item or that might contaminate the 3D item during manufacture is of utmost importance, and thorough cleaning at intervals or after performing some or specified tasks with the additive manufacturing apparatus is required. Thus, it is possible to have all inner surfaces of the additive manufacturing apparatus that face the printer bed plate covered with an easy to clean coating or with a removable cover that can be replaced by a new or cleaned cover. The guide rod and other movable parts that protrude towards the printer bed can be covered or shielded by a removable or easy to clean textile or elastic cover that allows for the movement but provides for a sealing off of the printer bed plate from surrounding parts of the additive manufacturing apparatus. According to a favorable embodiment of the invention, the guide rod displacement device comprises a linear displaceable slider and engaging means for a positive engagement of the guide rod with the slider. A linear displaceable slider allows for a precise control of the movement of the slider and thus of the guide rod that is itself slidable and detachably mounted to the linear displaceable slider. The linear displaceable slider can be used to perform the movement of the printer bed back and forth between the manufacturing position in which there is no weight transmitting contact between the printer bed and a weighing device and the weighing position in which the printer bed is in a weight transmitting contact with the weighing device. Making use of the linear displaceable slider as printer bed displacement means that only allows for a linear displacement to perform the required movement allows for a very quick movement and a precise control of the required as well as the actually performed movement in an easy and cost-effective manner. Furthermore, making use of the linear displaceable slider also reduces unwanted interference of non-linear forces and moments that might act upon the printer bed during or after any movement of the printer bed.

According to yet another embodiment of the invention, the guide rod comprises at least one radially outwardly projecting engagement element and the guide rod displacement device comprises at least one receiving element for a positive engagement with a corresponding engagement element of the guide rod. Thus, the guide rod can be easily brought into positive engagement with the guide rod displacement device or released from it by establishing or separating the positive engagement between the radially outwardly projecting engagement element of the guide rod and the receiving element of the guide rod displacement device. The design and arrangement of the receiving element of the guide rod displacement device can be preset to provide for or interrupt the positive engagement with the radially outwardly projecting engagement during a respective linear displacement of the guide rod displacement device. Thus, no further actors, means or separate movement of the guide rod displacement device is required in order to establish or interrupt the positive engagement between the guide rod and the guide rod displacement device. The receiving element can comprise for each radially outwardly projecting engagement element a suitably designed groove or slit into which the radially outwardly projecting engagement element can be inserted for the positive engagement between the guide rod and the guide rod displacement device. Thus, such an embodiment also provides for an anti-rotation lock that determines the alignment of the printer bed and in particular of the printer bed plate.

It is considered a favorable aspect of the invention that the guide rod comprises a cone section that widens radially with decreasing distance from the printer bed plate and in that the guide rod displacement device comprises a cone support adapted to receiving the cone section of the guide rod in a positive fit. The cone support of the guide rod displacement device may be designed and arranged to define the manufacturing position and to provide for a radially projecting support of the printer bed plate within the manufacturing position of the printer bed. A matching cone shape of the cone section of the guide rod and of the guide rod displacement device provides for a self-centering effect during a movement of the guide rod displacement device with respect to the guide rod.

According to a very favorable option of the invention, the printer bed support structure comprises means for exerting an additional non-gravitational force on the printer bed that holds the printer bed in a manufacturing position on or at the printer bed support structure. The means for exerting a non-gravitational force can comprise a positive locking mechanism that provides for a form-fitting engagement of the printer bed with the printer bed support structure during the precise manufacturing step, and that can be disengaged e.g. before, during or after the weighing execution step. The form-fitting engagement of the printer bed with the printer bed support structure can also comprise form-fitting latches, locking bolts or clamping tongues that can be moved back and forth between a locking position and an unlocking position that releases the printer bed from the printer bed support structure. By fixing the printer bed in a manufacturing position, any unwanted movement of the printer bed during the discharge of the heated composition material out of the printer extruder head onto the printer bed, which helps to increase the precision of the manufacturing of each layer of the layer arrangement resulting in an increase of the precision of the 3D item that is manufactured with the additive manufacturing apparatus.

According to a very advantageous embodiment of the invention, the means for exerting an additional non-gravitational force comprises at least one electromagnet for pulling the printer bed into the manufacturing position on or at the printer bed support structure. The magnetic force that is exerted by an electromagnet can be easily controlled and adapted during the use of the additive manufacturing apparatus. Thus, the non-gravitational force can be exerted as long as the printer bed is positioned within the manufacturing position, but the non-gravitational force can be interrupted during the performance of the weighing execution step in such a manner as to not interfere with the weight determination during the weighing execution step. Furthermore, switching on or switching off the non-gravitational force does not require any movement of a part of the additional manufacturing apparatus.

As apparent from the description above and as illustrated by the embodiment depicted in Figure 1 below, the printer bed moving back and forth between a manufacturing position in which there is no weight transmitting contact between the printer bed and a weighing device and a weighing position in which the printer bed is in a weight transmitting contact with the weighing device may mean the printer bed moves upwards and downwards between the manufacturing position and the weighing position.

Brief description of the drawings

The present invention will be more fully understood, and further features will become apparent, when reference is made to the following detailed description and the accompanying drawings. The drawings are merely representative and are not intended to limit the scope of the claims. In fact, those of ordinary skill in the art may appreciate upon reading the following specification and viewing the present drawings that various modifications and variations can be made thereto without deviating from the innovative concepts of the invention. Like parts depicted in the drawings are referred to by the same reference numerals.

Fig. 1 illustrates a schematic cross-sectional representation of an additive manufacturing apparatus for additive manufacturing of a 3D item by means of fused deposition modeling, whereby a printer bed with a printer bed plate with some layers of a layer arrangement of composite material that already have been deposited onto the printer bed plate is mounted on a linear displaceable slider and positioned without any weight transmitting contact with a weighing device that is arranged below the printer bed,

Fig. 2 illustrates a schematic cross-sectional representation of the additive manufacturing apparatus shown in Fig. 1 , whereby the printer bed is in a weight transmitting contact with the weighing device that is arranged below the printer bed,

Fig. 3 illustrates a perspective view of a printer bed support structure with a printer bed plate and a guide rod mounted at a guide rod displacement device that is linearly displaceable with respect to the weighing device that is arranged below the printer bed, whereby the guide rod is in a positive locking contact with the guide rod displacement device and positioned at a distance from the weighing device,

Fig. 4 illustrates a perspective view of the printer bed support structure shown in Fig. 3, whereby the guide rod is linearly displaceable with respect to the guide rod displacement device, but in a weight transmitting contact with the weighing device, and

Fig. 5 illustrates a partial cross-sectional representation of a part of the printer bed support structure shown in Figs. 3 and 4. Main components of an additive manufacturing apparatus 1 are schematically illustrated in Fig. 1 . The additive manufacturing apparatus 1 comprises a printer extruder head 2 with a discharge nozzle 3 for discharging heated and melted composite material onto a printer bed plate 4 of a printer bed 5, thereby depositing one or more layers 6 of subsequently solidified composite material into a layer arrangement 7 that forms a 3D item. The printer extruder head 2 and the printer bed plate 4 can be displaced with respect to each other during a manufacturing process by either moving the printer extruder head 2 or by moving the printer bed plate 4, or even by moving both, the printer extruder head 2 and the printer bed plate 4 at intervals or simultaneously. Preferably, the additive manufacturing apparatus 1 allows for a displacement of the printer extruder head 2 relative to the printer bed plate 4 in all spatial directions. The relative displacement of the printer extruder head 2 and the printer bed plate 4 as well as the heating and discharging of the composite material through the discharge nozzle 3 can be controlled by a control device that is not shown in Fig. 1 .

The printer bed 5 comprises the printer bed plate 4 and a guide rod 8 that projects from an underside 9 of the printer bed plate 4 that opposes the top side 10 of the printer bed plate 4 onto which the layer arrangement 7 is deposited during manufacture of a 3D item. The guide rod 8 is linearly displaceable mounted in a linear displaceable slider 11 that is part of a guide rod displacement device 12. The linear displaceable slider 11 is itself linearly displaceable mounted with respect to a printer bed support structure 13 of the additive manufacturing apparatus 1 . By moving the linear displaceable slider 11 , the guide rod 8 that is mounted at and supported by the linear displaceable slider 11 will be shifted and positioned either upwards in the direction of the printer extruder head 2, or downwards in the direction of a weighing device 14 that is arranged in a fixed position below the printer bed 5.

By a linear movement of the linear displaceable slider 11 , the guide rod 8 and the guide rod displacement device 12, i.e. the linear displaceable slider 11 can either be brought into a positive locking connection or be released from the positive locking connection. As illustrated within Figs. 3 to 5 in more detail, the guide rod 8 comprises a cone section 15 that widens radially with decreasing distance from the printer bed plate 4. The guide rod displacement device 12 comprises a cone support 16 that is formed by the linear displaceable slider 11 and that is adapted to receive the cone section 15 of the guide rod 8 in a positive locking connection. Furthermore, the guide rod 8 comprises two radially outwardly projecting engagement elements 17 that are formed by a pin 18 that is mounted perpendicular to a longitudinal direction of the guide rod 8 and extends laterally beyond the guide rod 8. The linear displaceable slider 11 comprises a receiving element 19 that is mounted at the linear displaceable slider 11 and that comprises two slits 20 that are designed to either receive or release the respective radially outwardly projecting engagement element 17 of the guide rod 8.

Thus, in case that during a weighing termination step the linear displaceable slider 11 of the guide rod displacement device 12 is displaced upwards towards the printer extruder head 2 into a manufacturing position, the radially outwardly projecting engagement elements 17 of the guide rod 8 will slide into the respective slit 20 of the receiving element 19 of the linear displaceable slider 11 until a positive locking connection between the linear displaceable slider 11 and the guide rod 8 is formed. At the same time, the cone section 15 shifts into the cone support 16, resulting in another positive locking connection between the linear displaceable slider 11 and the guide rod 8. The position of the guide rod 8 can be fixed with respect to the linear displaceable slider 11 not only by a gravitational force that pushes the cone section 15 into the cone support 16, but in addition thereto also by an additional non-gravitational force that is exerted e.g. by at least one electromagnet that can exert a magnetic force between the guide rod 8 and the linear displaceable slider 11 during a precise manufacturing step in order to ensure a reliably defined arrangement and a secure hold of the guide rod 8 with respect to the linear displaceable slider 11 and to avoid any unwanted movement of the printer bed plate 4 during the deposition of a layer 6 of composite material from the discharge nozzle 3 of the printer extruder head 2 onto the printer bed plate 4. During a weighing preparation step the linear displaceable slider 11 and the guide rod 8 are displaced downwards towards the weighing device 14 until a tip 21 of the guide rod 8 facing away from the printer bed plate 4 touches a contact element 22 of the weighing device 14 which brings the guide rod 8 and the printer bed plate 4 into a weight transmitting contact with the weighing device 14. However, the linear displaceable slider 11 is further displaced downwards until the cone section 15 disengages from the cone support 16 of the linear displaceable slider 11 and until the radially outwardly projecting engagement elements 17 of the guide rod 8 are released from the respective slits 20 of the receiving element 19 of the linear displaceable slider 11 . In this position, there is no longer a positive locking connection between the linear displaceable slider 11 and the guide rod 8, and the linear displaceable slider 11 does no longer affect or adversely interfere with any weight transmitting contact between on the one hand the guide rod 8 and the printer bed plate 4 with the layer arrangement 7 of composite material on the top side 10 of the printer bed plate 4 and on the other hand the contact element 22 of the weighing device 14.

During a manufacturing step, the linear displaceable slider 11 and the guide rod 8 are within a manufacturing position, whereby the guide rod 8 and thus the printer bed plate 4 are securely fixed within the manufacturing position. The arrangement of the printer bed plate 4 in the manufacturing position is shown in Fig. 1 . At intervals at any time during or after the manufacturing of a 3D item, a weighing step for determining the weight of the layer arrangement 7 that has been deposited onto the printer bed plate 4 can be performed. Such a weighing step comprises a weighing preparation step, a weighing execution step and a weighing termination step.

During a weighing preparation step the guide rod 8 and the printer bed plate 4 are moved from the manufacturing position without any weight transmitting contact between the printer bed 5 and the weighing device 14 into a weighing position in which the printer bed 5, i.e. the guide rod 8 is in a weight transmitting contact with the weighing device 14 that is arranged below the printer bed 5. The arrangement of the guide rod 8 and the printer bed plate 4 in the weighing position is shown in Fig. 2.

The weighing step further comprises the weighing execution step during which the weight of the layer arrangement 7 on top of the printer bed plate 4 is determined with the weighing device 14 by determining the weight of the printer bed 5 together with the layer arrangement 7 with the weighing device 14 and by deducting the previously determined weight of the printer bed 5. Afterwards, during the weighing termination step the printer bed is relocated back into the manufacturing position in which the weight transmitting contact of the printer bed 5 with the weighing device 14 is disconnected, and in which the printer bed 5 is again in a positive locking contact with the printer bed support structure 13 that retains the printer bed 5 in a fixed position during the additive manufacturing of the layer arrangement 7 on the printer bed plate 4.

Figs. 3 to 5 illustrate by way of example a working embodiment of such an additive manufacturing apparatus 1 , whereby only a part of the printer bed support structure 13 with the printer bed plate 4 and the weighing device 14 is shown. All components of the additive manufacturing apparatus 1 that are not explicitly mentioned below equal the components that have been shown in Figs. 1 and 2 and that have already been described above, whereby the respective reference numerals are identical.

In the embodiment as shown in Figs. 3 to 5, the additive manufacturing apparatus 1 comprises a printer bed support structure 13 with an XY table mechanism 23 and the guide rod displacement device 12 mounted to the XY table mechanism in such a manner that the guide rod displacement device 12 can be positioned at any given X and Y position within the range of the XY table. Thus, the printer extruder head 2 can be mounted stationary with respect to the printer bed support structure 13. In Fig. 3, the linear displaceable slider 11 of the guide rod displacement device 12 is shifted into the manufacturing position, i.e. at a distance from the weighing device 14 below the guide rod 8 that is mounted to the linear displaceable slider 11 of the guide rod displacement device 12. The radially outwardly projecting engagement elements 17 of the guide rod 8 are within a positive locking connection with the receiving element 18 of the linear displaceable slider 11 (receiving element 18 depicted in Figure 5). At the same time, the cone section 15 is within a positive locking connection with the cone support 16 of the linear displaceable slider 11 . Due to the positive locking connection between the radially outwardly projecting engagement elements 17 within the respective slits 20 of the receiving element 18, this also provides for a torsion-proof connection between the linear displaceable slider 11 and the guide rod 8, resulting in a very precise orientation of the printer bed plate 4 with respect to the printer bed support structure 13. Furthermore, there are two electromagnets 24 which can be activated and controlled in such a manner as to pulling the printer bed 5 into the manufacturing position, i.e. the guide rod 8 into the positive fit with the linear displaceable slider 11 of the guide rod displacement device 12. The two electromagnets 24 form a means for exerting an additional non-gravitational force on the printer bed 5 that holds the printer bed 5 in the manufacturing position with respect to the printer bed support structure 13.

Fig. 4 illustrates the additive manufacturing apparatus 1 shown in Fig. 3, but with the guide rod 8 in the weighing position in which the guide rod 8 is in a weight transmitting contact with the weighing device 14 that is arranged below the printer bed 5. The electromagnets 24 are deactivated, and the guide rod 8 is not in a positive locking connection with the linear displaceable slider 11 which only provides for a forced guidance that allows for an unrestricted movement with respect to the Z-axis, but prevents the guide rod 8 together with the printer bed plate 4 from unwanted tilting during the performance of the weighing step. For illustrative purpose only, Fig. 5 illustrates a partial cross-sectional view of the additive manufacturing apparatus 1 with the guide rod 8 in the weighing position as shown in Fig. 4.

Claims

C L A I M S

1 . Method for additive manufacturing of a 3D item by means of fused deposition modeling of a composite material, whereby the composite material is fed through a heated printer extruder head (4) and deposited on a printer bed (5) as a layer arrangement (7) that forms the 3D item, whereby during or after the additive manufacturing of the 3D item a weighing step is performed for determining the weight of the layer arrangement (7) that has been deposited on the printer bed (5), characterized in that the weighing step comprises a weighing preparation step during which the printer bed (5) is moved from a manufacturing position without any weight transmitting contact between the printer bed (5) and a weighing device (14) into a weighing position in which the printer bed (5) is in a weight transmitting contact with the weighing device (14) that is arranged below the printer bed (5), in that the weighing step further comprises a weighing execution step during which the weight of the layer arrangement (7) on top of the printer bed (5) is determined with the weighing device (14) by determining the weight of the printer bed (5) together with the layer arrangement (7) with the weighing device (14) and by deducting the previously determined weight of the printer bed (5).

2. Method according to claim 1 , characterized in that the weighing step further comprises a weighing termination step during which the printer bed (5) is relocated into a manufacturing position in which the weight transmitting contact of the printer bed (5) with the weighing device (14) is disconnected, and in which the printer bed (5) is in a positive locking contact with a printer bed support structure (13) that retains the printer bed (5) in a fixed position during the additive manufacturing of the layer arrangement (7) on the printer bed (5).

3. Method according to claim 2, characterized in that during the relocation of the printer bed (5) during the weighing termination step the printer bed (5) is brought into a predetermined alignment of the printer bed (5) with respect to the printer bed support structure (13).

4. Method according to any of the preceding claims, characterized in that the printer bed (5) comprises a printer bed plate (4) with a top side (10), on which the layer arrangement (7) is deposited, and with an underside (9) opposite to the top side (10), whereby the printer bed (5) further comprises a guide rod (8) that projects from the underside (9) of the printer bed plate (4) towards the weighing device (14), and in that during the weighing preparation step the guide rod (8) is moved towards the weighing device (14) until the guide rod (8) is in a weight transmitting contact with the weighing device (14).

5. Method according to claim 4, characterized in that during the weighing termination step the guide rod (8) is brought into positive engagement with a guide rod displacement device (12) that displaces the guide rod (8) from the weighing position into the manufacturing position.

6. Method according to any of the preceding claims, characterized in that the method further comprises a precise manufacturing step, whereby during the precise manufacturing step an additional non-gravitational force is exerted on the printer bed (5) that holds the printer bed (5) in a manufacturing position on or at a printer bed support structure (13).

7. Method according to claim 6, characterized in that during the precise manufacturing step the printer bed (5) is pulled or pushed with at least one electromagnet (24) into the manufacturing position.

8. Additive manufacturing apparatus (1) for additive manufacturing of a 3D item (2) by means of fused deposition modeling of a composite material, the additive manufacturing apparatus (1) comprising a printer bed (5) mounted at a printer bed support structure (13) and a printer extruder head (2) for discharging and depositing the heated composite material as a layer arrangement (7) on a printer bed (5) to generate the 3D item out of the composite material, whereby the discharging and depositing of the heated composite material can be controlled by a control device, the additive manufacturing apparatus (1 ) further comprising a weighing means for measuring a total weight of the layer arrangement (7) that has been deposited on the printer bed (5) during or after manufacturing of the 3D item, characterized in that the printer bed support structure (13) comprises a printer bed displacement means with which the printer bed (5) can be moved back and forth between a manufacturing position in which there is no weight transmitting contact between the printer bed (5) and a weighing device (14) and a weighing position in which the printer bed (5) is in a weight transmitting contact with the weighing device (14).

9. Additive manufacturing apparatus (1 ) according to claim 8, characterized in that the printer bed support structure (13) comprises means for a positive fit of the printer bed (5) with the printer bed support structure (13) that retains the printer bed (5) in a fixed position during the additive manufacturing of the layer arrangement (7) on the printer bed (5).

10. Additive manufacturing apparatus (1) according to claim 8 or claim 9, characterized in that the printer bed support structure (13) comprises means for positioning the printer bed (5) in a predetermined alignment of the printer bed (5) with respect to the printer bed support structure (13).

11 . Additive manufacturing apparatus (1 ) according to any of the preceding claims 8 to 10, characterized in that the printer bed (5) comprises a printer bed plate (4) with a top side (10), on which the layer arrangement (7) is deposited, and with an underside (9) opposite to the top side (10), whereby the printer bed (5) further comprises a guide rod (8) that projects from the underside (9) of the printer bed plate (4) towards the weighing device (14), and in that the printer bed support structure (13) comprises a guide rod displacement device (12) with which the guide rod (8) can be displaced back and forth between the weighing position and the manufacturing position.

12. Additive manufacturing apparatus (1 ) according to claim 11 , characterized in that the printer bed plate (4) is removably attached to the guide rod (8).

13. Additive manufacturing apparatus (1 ) according to claim 11 or claim 12, characterized in that the guide rod displacement device (12) comprises a linear displaceable slider (11 ) and engaging means for a positive engagement of the guide rod (8) with the slider (11 ).

14. Additive manufacturing apparatus (1 ) according to claim 11 to claim 13, characterized in that the guide rod (8) comprises at least one radially outwardly projecting engagement element (17) and in that the guide rod displacement device (12) comprises at least one receiving element (19) for a positive engagement with a corresponding engagement element (17) of the guide rod (8).

15. Additive manufacturing apparatus (1) according to any of the preceding claims 8 to 14, characterized in that the guide rod (8) comprises a cone section (15) that widens radially with decreasing distance from the printer bed plate (4) and in that the guide rod displacement device (12) comprises a cone support (16) adapted to receiving the cone section (15) of the guide rod (8) in a positive fit, optionally further characterized in that the printer bed support structure (13) comprises means for exerting an additional non-gravitational force on the printer bed (5) that holds the printer bed (5) in a manufacturing position on or at the printer bed support structure (13); wherein the means for exerting an additional non-gravitational force optionally comprises at least one electromagnet (24) for pulling the printer bed (5) into the manufacturing position on or at the printer bed support structure (13).

16. Method for additive manufacturing according to any of claims 1 to 7, wherein the 3D item is a pharmaceutical solid administration form comprising at least one active pharmaceutical ingredient.