Collision detection device and collision detection method for apparatus for additive manufacturing of articles

Abstract

The present invention provides a collision detection device for apparatus for additive manufacturing of articles, such apparatus, and a method for avoiding collisions with objects in a powder coating machine in apparatus for additive manufacturing of articles. [Solution] The collision detection device 1 comprises bushings 3a and 3b connected to the powder coating machine drive unit, bolts 2, 2a and 2b movably mounted within the bushings and connected to the powder coating machine, and an elastic element 4 that biases the bushings together with the bolts 2 and detects collisions between the powder coating machine and objects based on changes in the biasing force of the elastic element 4.

Description

Technical Field

[0001] The present invention relates to a collision detection device for an apparatus for additive manufacturing of articles, such an apparatus, and a method for avoiding collision of a powder coating machine with an object in an apparatus for additive manufacturing of articles.

Background Art

[0002] Additive manufacturing is a manufacturing process in which an article (such as a workpiece) is built layer by layer. In a powder bed-based additive manufacturing process, a powdery substance is applied layer by layer by a powder coating machine and then fused by an optical interaction such as a laser or an electron beam. The powder bed-based additive manufacturing process includes, for example, selective laser melting (SLM) in which a metallic powder substance is particularly used to preferentially remelt layer by layer by a focused laser beam to form a continuously solidified portion. Machine parts, tools, prostheses, gemstones, etc. can be manufactured in this way.

[0003] The manufacturing process includes three iterative steps: applying a layer of raw material powder on a build plate with a powder coating machine, melting the powder layer according to the geometric shape of the article to be manufactured, and lowering the build plate by one layer thickness. Due to thermal interactions in the process, thermal stresses are generated, and parts of the article to be manufactured may appear from the surface of the powder layer. Such objects can be an obstacle to the powder coating machine when the next layer is applied. If these obstacles / objects are not detected, the powder coating machine or its drive unit may be damaged.

Summary of the Invention

Problems to be Solved by the Invention

[0004] Therefore, an object of the present invention is to detect an obstacle / object in front of the powder coating machine during additive manufacturing (especially during powder coating), and to switch off the powder coating machine in a timely manner to avoid damage to the powder coating machine or the powder coating machine drive unit, for example. [Means for solving the problem]

[0005] This objective is addressed by the features of the independent claim. Advantageous embodiments are found in the dependent claims.

[0006] A collision detection device for an additive manufacturing apparatus for articles, and a method for avoiding collisions between a painting machine and objects in an additive manufacturing apparatus for articles are proposed. Furthermore, an additive manufacturing apparatus for articles is proposed, including a painting machine, a painting machine drive unit, and a collision detection device, as described below.

[0007] In this specification, additive manufacturing of articles is understood to mean the layer-by-layer construction of an article from a powdered material by optical interaction.

[0008] In particular, a powder coating machine can extend over the floor area of ​​a process chamber of an additive manufacturing apparatus, and within the process chamber, there may be a build plate on which an article can be constructed. The build plate can be lowered vertically for the construction of the article. For example, the powder coating machine can apply a predetermined amount of raw material powder to the build plate while moving linearly through the process chamber in a horizontal direction, and then distribute it on the build plate. For example, the powder coating machine can apply the raw material powder while moving in a first direction and distribute it in layers, for example, by a scraper lip. Subsequently, the powder coating machine can move in a second reverse direction to remove excess raw material powder with the scraper lip. Alternatively, the scraping of excess raw material powder can be performed in a single operation that involves applying and distributing the powder on the build plate. In this case, the powder coating machine performs the same function in the first and second directions of movement, and provides a new layer of raw material powder on the build plate in both directions of movement.

[0009] The powder coating machine drive unit may, in particular, be a linear drive unit having two drive units, each comprising a drive spindle, for example, a ball screw spindle, driven by an electric motor. The powder coating machine may be positioned between the drive units and connected to them. Alternatively, the powder coating machine drive unit may comprise only one drive unit positioned on one side of the powder coating machine. Instead of at least one drive spindle, which converts the rotational motion of an electric motor into linear motion, at least one linear motor may be used to drive the powder coating machine. At least one electric motor may be equipped with a control system that allows its current consumption to be determined.

[0010] The collision detection device according to the present invention comprises a bushing connected to a powder coating machine drive unit, and a bolt movably mounted within the bushing and connected to the powder coating machine. The bolt may be axially or rotationally movable within the bushing. The bushing may be connected to the powder coating machine drive unit, for example, by a corresponding holder. For this purpose, the bushing may be screwed, bonded, or welded to the holder, for example. The bushing may include a sliding bearing for holding the bolt. The bolt may also be connected to the powder coating machine by a holder, which may be screwed, bonded, or welded to the powder coating machine.

[0011] Furthermore, the collision detection device includes an elastic element that clamps the bushing to a bolt. The elastic element may be shaped to transmit a driving force for the linear movement of the powder coating machine during normal operation. Normal operation of the powder coating machine should be understood as operation in which there are no obstacles / objects in front of the powder coating machine during its movement and the powder coating machine can move smoothly over the process chamber floor surface.

[0012] For the transmission of driving force during normal operation, a predetermined stiffness of the elastic element may be selected, for example, so that the accelerating force during the startup of the powder coating machine does not cause a change in the biasing force of the elastic element; that is, the elastic element is not compressed or stretched by process-related acceleration processes. Similarly, process-related temperature dependence of friction in the drive unit of a powder coating machine that requires higher driving force during normal operation may be taken into consideration, for example, when selecting the stiffness of the elastic element.

[0013] According to one embodiment, the bolt of the collision detection device may extend in the direction of movement of the powder coating machine. An elastic element may be positioned between the bushing and the bolt and may be biased in the axial direction of the bolt. A predetermined biasing force of the elastic element may be selected such that the driving force for moving the powder coating machine during normal operation can be transmitted without compressing or stretching the elastic element. However, if, for example, due to thermal stress during an additive manufacturing process, a part of the article to be manufactured or its supporting structure (object) appears vertically upward from the existing powder layer, preventing the powder coating machine from applying the next powder layer or exerting a reaction force on the coating machine, the bolt may be pushed by the object in the opposite direction to the current direction of movement of the coating machine within the bushing, against the biasing force of the elastic element.

[0014] Alternatively, the bolt itself may be formed as an elastic element, particularly as a torsion bar spring, extending perpendicular to the direction of movement of the powder coating machine. In this case, the reaction force applied to the powder coating machine by the object may result in torsion of the torsion bar spring within the bushing.

[0015] In either case, the collision detection device detects a collision between the powder coating machine and an object based on a change in the biasing force of an elastic element caused by the movement of a bolt in the bushing or the twisting of a torsion bar spring. Therefore, the change in the biasing force of the elastic element is first determined by the collision detection device. When the change in biasing force exceeds a predetermined threshold, a collision between the powder coating machine and the object is detected. The change in the biasing force of the elastic element can be detected, for example, by an increase in the current consumption of the electric motor in the powder coating machine drive unit. In this case, the threshold may be, for example, a predetermined offset from the maximum current required to drive the powder coating machine during normal operation.

[0016] In response to a detected collision, the collision detection device may, for example, reverse the direction of movement of the powder coating machine and move it in the opposite direction by a predetermined distance. The collision detection device may then move the powder coating machine toward the object at a reduced speed in an attempt to override it. This procedure may be repeated a predetermined number of times before the powder coating machine drive unit is switched off by the collision detection device. In this case, the powder coating machine may move again in the opposite direction by a predetermined distance, for example, after the last attempt to override it, to allow a view of the process field on the build plate, before the powder coating machine drive unit is switched off. The latter may also be the sole response to the detected collision.

[0017] In addition, if a collision between the powder coating machine and an object is detected, an action recommendation may be issued to the operator of the equipment for additive manufacturing of articles, for example, on the equipment's display unit. For example, the operator may receive instructions on the display unit to check for any protruding objects on the powder bed and / or to check the connections and / or design of any protruding or damaged support structures.

[0018] According to one embodiment, a bolt within a bushing can move against the biasing force of an elastic element in a first and a second direction, the second direction being opposite to the first direction. In other words, the bolt can move against the biasing force of an elastic element in both directions of movement of the powder coating machine. For example, an object interfering with the powder coating machine when it is moving in a first direction can cause the bolt to move in a second direction, and vice versa. In this way, both an object appearing in front of the coating machine during movement in the first direction and an object appearing in front of the coating machine during movement in the second direction can be detected by the collision detection device.

[0019] According to one embodiment, the collision detection device may include a sensor capable of detecting the movement of a bolt within a bushing. This may be particularly useful when it is not possible to sufficiently accurately detect changes in the biasing force of an elastic element by measuring the current consumption of an electric motor in the powder coating machine drive, in order to avoid damage to the powder coating machine or the powder coating machine drive. The sensor may be connected to or attached to the bolt so as to be able to determine the relative movement of the bolt with respect to the bushing. The sensor may be, for example, an inductive or potentiometric displacement sensor. A Hall sensor may also be used. Based on the measured displacement of the bolt, a change in the biasing force of the elastic element can be calculated if the biasing force exceeds a predetermined threshold. It is also possible to directly define a threshold for the allowable displacement of the bolt such that, when it exceeds that threshold, the powder coating machine drive may be activated and, in particular, subsequently switched off. In particular, the powder coating machine drive may always be switched off when the bolt moves its maximum possible displacement within the bushing, and therefore the spring biasing force reaches its maximum value. Another criterion for activating or switching off the powder coating machine drive may be the rate of change of the biasing force (e.g., instantaneous).

[0020] According to one embodiment, the bushing and the bolt may each have circumferential recesses facing each other, in which an elastic element may be disposed. In other words, the outer diameter / circumferential circumference of the bolt may be reduced by the circumferential recesses, and the opposing inner diameter / circumferential circumference of the bushing may be increased by the corresponding circumferential recesses, thereby enabling the two recesses to form an annular space between the bushing and the bolt. In particular, the two recesses of the bushing and the bolt may have equal lengths in the axial direction.

[0021] The elastic element may include at least one spring, in particular a coil spring, which may be positioned or clamped within an annular space. For this purpose, the coil spring may be pushed into the recess of the bolt beyond its reduced outer circumference. The outer circumference of the coil spring may be surrounded by the enlarged inner circumference of the recess of the bushing. In this way, at least one spring can be positioned between the bushing and the bolt in a space-saving manner, thereby allowing the collision detection device to be formed in a very compact manner.

[0022] According to one embodiment, the elastic element may comprise a first spring, a second spring, and a washer. The first and second springs may be coil springs in particular. In this case, the first spring may have a smaller diameter than, for example, the second spring. In particular, in this case, the first spring may be pressed into the recess of the bolt via a reduced outer circumference, so that the inner circumference of the first spring surrounds the reduced outer circumference within the recess of the bolt. The second spring may have a larger inner diameter than the outer diameter of the first spring, so that the second spring surrounds the first spring. The outer circumference of the second spring may be surrounded by the enlarged inner circumference of the recess of the bushing. As a result, the first and second springs can form a parallel circuit, and the spring stiffness of the individual springs may be selected such that their sum is sufficient to transmit a driving force to move the powder coating machine during normal operation in the spring-biased state.

[0023] According to one embodiment, the first end of the first spring and the first end of the second spring may each be adjacent to the first surface of the washer of the elastic element. In other words, the washer of the elastic element can receive the two springs by the first surface at one end in both cases in order to clamp the two springs within the annular space formed by the recesses of the bushing and the bolt.

[0024] In particular, the washer can have circumferential protrusions on the first surface (attachment surface), and the protrusions separate the first end of the first spring from the first end of the second spring. This enables the washer to hold the two springs separately, so that as a result, they can be tensioned / released separately without interfering with each other.

[0025] According to one embodiment, the washer of the elastic element having a second surface opposite the first surface may be adjacent to the first end face of the circumferential recess of the bolt and the first end face of the circumferential recess of the bushing. In other words, the washer contacts the entire front surface of the annular space between the bushing and the bolt through the surface opposite to the pressure-receiving surfaces of the two springs, thereby forming a connection between the recess of the bolt and the recess of the bushing.

[0026] According to one embodiment, the first spring may be adjacent with its second end on the second end side of the circumferential recess of the bolt, and the second spring may be adjacent with its second end on the second end side of the circumferential recess of the bushing. This means that the first spring can be clamped within the recess of the bolt and the second spring can be clamped within the recess of the bush.

[0027] Moving the bolt towards the second end face of the recess of the bushing may cause a change in the biasing force of the second spring within the recess of the bushing. This is because in this case, the second spring is pressed towards the second end face of the recess of the bushing by the washer connecting the recess of the bushing and the recess of the bolt, while the first spring moves with the bolt without changing its biasing force.

[0028] However, moving the bolt towards the first end face of the recess of the bushing may cause a change in the biasing force of the first spring within the recess of the bolt. This is because, in this case, the first spring is pressed from the second end face of the bolt recess towards the washer on the first end face of the bolt recess, while the second spring remains in its initial position without changing its biasing force.

[0029] By using two springs as described above, it becomes possible to apply a sufficient preload for the transmission of the driving force during the normal operation of the powder coating machine, and at the same time, it is possible to detect even the slightest force applied to the powder coating machine by an object. For example, when two springs with the same spring stiffness are used, only half the force is required for the same displacement of the bolt compared to when only one spring is used. In this way, the described elastic element reacts very sensitively to the forces acting on the powder coating machine, and damage to the powder coating machine can be reliably avoided. Furthermore, it is possible to use springs with different spring characteristics, whereby different forces acting on the powder coating machine depending on its direction of movement can be taken into account.

[0030] According to one embodiment, the bolt can consist of two parts, the first end face of the circumferential recess can be arranged on the first part of the bolt, and the second end face of the circumferential recess can be arranged on the second part of the bolt. Thereby, for example, during the assembly of the collision detection device, it becomes possible to simply press the first spring against the reduced outer circumference of the bolt recess and then connect the two parts in order to adjust the preload of the first spring. The first and second bolt parts can be screwed together, for example.

[0031] In particular, to simplify the manufacturing of the bolt, the reduced outer circumference of the circumferential recess may be present on only one of the two bolt portions. For example, only the second bolt portion may have the reduced outer circumference on a second end face on which both the first spring and washer can be pressed. In this case, one outer end of the first bolt portion can be adjacent to the second surface of the washer, forming the first end face of the bolt recess. In particular, the bushing may also be formed in two parts to make it easier to assemble the second spring.

[0032] The apparatus for additive manufacturing of articles according to the present invention includes, as described above, a powder coating machine, a powder coating machine drive unit, and at least one collision detection device. In particular, the powder coating machine drive unit may comprise at least one drive unit, particularly two drive units, and each drive unit of the powder coating machine drive unit may include a collision detection device. In other words, a collision detection device may be provided between each drive unit and the powder coating machine, thereby transmitting the driving force of each drive unit to the powder coating machine.

[0033] In the method for detecting collisions between a powder coating machine and an object according to the present invention, a collision detection device as described above is used to determine a change in the biasing force of the elastic element of the collision detection device. When the change in biasing force exceeds a predetermined threshold, a collision between the powder coating machine and an object is detected. The change in the biasing force of the elastic element can be detected, for example, by an increase in the current consumption of the electric motor in the powder coating machine drive unit. In this case, the threshold may be, for example, a predetermined offset from the maximum current required to drive the powder coating machine during normal operation of the powder coating machine.

[0034] According to one embodiment, the change in the biasing force of the elastic element can be determined from the movement of the bolt of the impact device relative to the biasing force of the elastic element, which can be measured, for example, by a displacement sensor. In this case, the change in the biasing force of the elastic element may also be calculated from the measured displacement of the bolt, and the paint machine drive unit may be switched off, for example, when it exceeds a predetermined threshold. It is also possible to directly define a threshold for the allowable displacement of the bolt, and when this threshold is exceeded, the paint machine drive unit can be activated, and in particular, switched off. In particular, the paint machine drive unit may always be switched off when the bolt moves the maximum possible distance within the bushing, and as a result the spring biasing force reaches its maximum value. [Brief explanation of the drawing]

[0035] [Figure 1] A schematic and illustrative cross-section is shown through an apparatus for additive manufacturing of articles according to one embodiment of the present invention. [Figure 2] Figure 1 shows a schematic and illustrative longitudinal section of the device, where the elements of the collision detection device are visible. [Figure 3] The elements of the collision detection device shown in Figure 2 are shown in an enlarged cross-sectional view. [Figure 4a] Figure 3 shows cross-sections of the collision detection device at different locations. [Figure 4b] Figure 3 shows cross-sections of the collision detection device at different locations. [Figure 4c] Figure 3 shows cross-sections of the collision detection device at different locations. [Figure 5] Figure 1 shows a schematic and illustrative cross-sectional view of the device, where the sensors of the collision detection device are visible. [Figure 6] Figure 5 shows a schematic and illustrative example of the details of the collision detection device's sensors. [Figure 7a] A collision detection device according to a further embodiment of the present invention is shown schematically and illustratively. [Figure 7b] A collision detection device according to a further embodiment of the present invention is shown schematically and illustratively. [Figure 8a]The collision detection devices shown in Figures 7a and 7b are shown in different positions. [Figure 8b] The collision detection devices shown in Figures 7a and 7b are shown in different positions. [Modes for carrying out the invention]

[0036] In the following, design examples of the present invention will be described in detail with reference to illustrative drawings. The features of the design examples can be combined in whole or in part, and the present invention is not limited to the design examples described. In the drawings, identical elements are denoted by the same reference numerals, and redundant descriptions of elements are omitted unless necessary.

[0037] Figure 1 schematically and illustratively shows a cross-section through an apparatus 100 for additive manufacturing of articles according to one embodiment of the present invention. The apparatus 100 comprises two drive units (powder coating machine drive units, not shown) which may be located on either side of a process chamber 30. Each drive unit comprises a holder 15c for connecting the respective drive unit to the powder coating machine 10 via a collision detection device 1. The collision detection device 1 is located between each of the two drive units and the powder coating machine 10. The two drive units may be driven by, for example, an electric motor (not shown).

[0038] The powder coating machine 10 and the two collision detection devices 1 are mounted inside the process chamber 30 of the apparatus 100 for additive manufacturing of articles, inside which a build plate 20 for constructing articles is further integrated into the bottom surface 30a of the process chamber 30. A bracket 15c connecting the drive unit to the powder coating machine 10 and the collision detection devices 1 positioned between them is guided through the side wall 30b of the process chamber 30.

[0039] The powder coating machine 10 extends above the build plate 20 across the entire width of the process chamber 30 to coat and distribute raw material powder (not shown) in layers on the build plate 20 while moving in a first direction, and to remove excess raw material powder from the process chamber floor 30a while moving in a second direction opposite to the first direction. For example, during the melting of the layered raw material powder by a laser (not shown), the powder coating machine 10 may be positioned behind a partition wall 30c located at one end face of the process chamber 30 so as not to disturb the inert gas flow necessary for laser melting.

[0040] The collision detection devices 1 on both sides of the coating machine 10 move together with the powder coating machine 20 in a predetermined direction by the drive unit during normal operation. However, if an obstacle / object arises in front of the powder coating machine 10 that may collide with it, for example, by emerging from the buildup on the build plate 20 due to thermal stress, the two collision detection devices 1 can move relative to each other against the biasing force of the elastic elements located within them, thereby allowing the powder coating machine 10 to move briefly in the opposite direction to the drive direction. This changes the biasing force of the elastic elements within the collision detection devices 1, and this change can be used to detect the collision that has occurred in order to control and switch off the drive unit in a timely manner, for example, before the powder coating machine 10 is damaged. In response to a detected collision, the collision detection device 1 can, for example, reverse the direction of movement of the powder coating machine 10 and move it in the opposite direction by a predetermined distance. Subsequently, the collision detection device 1 can move the powder coating machine 10 toward the object at a reduced speed in an attempt to override the powder coating machine 10. This procedure may be repeated a predetermined number of times before the powder coating machine drive unit is switched off by the collision detection device. In this case, the powder coating machine 10 may move again a predetermined distance in the reverse direction, for example, after the last attempt to drive over an object, in order to allow a view of the process field on the build plate 20, before the powder coating machine drive unit is switched off. The latter may also be the sole response to a detected collision.

[0041] Figure 2 schematically and illustratively shows a longitudinal section of the apparatus 100 shown in Figure 1, where the elements of the collision detection device 1 are visible. The longitudinal section is created along the plane C drawn in Figure 1, passing through the corresponding collision detection device 1 and powder coating machine 10.

[0042] The diagram shows a cross-section CC of a powder coating machine 10, which essentially has a channel 10b inside for supplying raw material powder. A scraper lip 10c for distributing the raw material powder and removing excess raw material powder is mounted on the powder coating machine 10 on the side opposite the bottom surface 30a of the process chamber. On the upper side of the powder coating machine 10, a bracket 10a connects the collision detection device 1 to the powder coating machine 10 on both sides in its longitudinal direction. Inside the illustrated collision detection device 1, which is connected to the drive unit (see Figure 1) by a bracket 15c, a bolt 2 and a bushing 3 are visible.

[0043] To illustrate the individual elements of the collision detection device 1 shown in Figure 2 in more detail, an enlarged cross-section is shown in Figure 3. The field of view of the cross-section has been rotated 180° compared to Figure 2.

[0044] The illustrated collision detection device 1 comprises a bushing 3, 3a, and 3b consisting of two parts, and a bolt 2, 2a, and 2b consisting of two parts, mounted within the bushing 3 by a sliding bearing 3c. The two bolt parts 2a and 2b are screwed together by a screw 2c. The two bushings 3a and 3b are also screwed together by two further screws (not shown). The two bolt parts 2a and 2b are each connected to a bracket 10a that connects the bolt 2 to a powder coating machine (see Figure 2). The bushing 3 is then connected to a drive unit by a bracket 15c (see Figure 1).

[0045] A circumferential recess 5 is provided on the outer circumference of the bolt 2, and a circumferential recess 6 is provided on the inner circumference of the bushing 3, which are positioned opposite each other, forming annular spaces 5, 6 between the bushing 3 and the bolt 2. An elastic element 4 is clamped within these annular spaces 5, 6, comprising a first spring 4a, a second spring 4b, and a washer 4c. The washer 4c extends across the first end faces 5a, 6a of both the circumferential recesses 5, 6 of the bushing 2 and the bolt 3, i.e., it is adjacent to or rests on these two end faces 5a, 6a, which have a second surface 4cb. A circumferential projection 4cc is formed on the first surface 4ca of the washer 4c, opposite the second surface 4cb. The first ends of the first spring 4a and the second spring 4b are housed on either side of the projection 4cc. Therefore, the circumferential projection 4cc separates the two first ends of the two springs 4a and 4b, thus preventing them from interfering with each other in the event of compression, for example, due to the movement of the bolt 2. The second end of the first spring 4a is supported by the second end face 5b of the circumferential recess 5 of the bolt 2, and the second end of the second spring 4b is supported by the second end face 6b of the circumferential recess 6 of the bushing 3. Thus, the two springs 4a and 4b are clamped by the washer 4c within the annular spaces 5 and 6 between the bushing 3 and the bolt 2. In particular, at the illustrated central position of the bolt 2 within the bushing 3, the two springs 4a and 4b can be in a predetermined preloaded state, which allows force to be transmitted from the drive unit to the powder coating machine 10, provided that the powder coating machine 10 does not collide with an object.

[0046] The circumferential recess 5 of bolt 2 is provided only on the outer circumference of the second bolt portion 2b, and the first bolt portion 2a is pressed against the two bolt portions 2a and 2b, connecting them. Similarly, the circumferential recess 6 of bushing 3 is provided only on the inner circumference of the second bushing portion 3b, and the first bushing portion 3a is inserted into it. Therefore, the outer ends of the first bolt portion 2a and the first bushing portion 3b form the first end faces 5a and 6a of the circumferential recesses 5 and 6 of bolt 2 and bushing 3, respectively.

[0047] One operating mode of the collision detection device 1 shown in Figure 3 is shown in Figures 4a-4c. These figures show a cross-section of the collision detection device 1 shown in Figure 3 at a different position. In particular, the bolt 2 is in a different position in Figures 4a-4c. The position of the bolt in Figure 4b corresponds to the position already shown in Figure 3, in which the two springs 4a and 4b are in a resting position and are clamped by a washer 4c with a predetermined preload within the annular spaces 5 and 6 between the bushing 3 and the bolt 2. The bolt 2 of the collision detection device 1 is in this position when the powder coating machine 10 moves smoothly over the process area floor surface 30a and does not collide with any obstacles / objects.

[0048] As shown in Figure 4a, when the powder coating machine 10 collides with object 50 (indicated by a white square with a thick outline to the left of the left holder 10a) as it moves in a first direction (indicated by a long arrow pointing to the lower left of the collision detection device 1), the bolt 2 moves in the opposite direction to the first direction of movement (indicated by a short arrow pointing to the right inside the bolt 2) against the biasing force of the second spring 4b. This compresses the second spring 4b through the washer 4c within the circumferential recess 6 of the bushing 3, thereby changing the biasing force of the latter. In this case, the first spring 4a moves with the bolt 2 without changing its biasing force.

[0049] As shown in Figure 4c, when the powder coating machine 10 collides with object 50 (indicated by a white square with a thick outline to the right of the right holder 10a) as it moves in the second direction (indicated by a long arrow pointing to the lower right of the collision detection device 1), the bolt 2 moves in the opposite direction to the second direction of movement (a short arrow pointing to the left inside the bolt 2) against the biasing force of the first spring 4a. This causes the first spring 4a to be pressed against the first surface 4ca of the washer by the second end surface 5b of the circumferential recess 5 of the bolt 2, which is then supported by the first end surface 6a of the bushing 3. Thus, in this case, the biasing force of the first spring changes, while the second spring 4b remains in its resting position.

[0050] As described above, by using the two springs 4a and 4b, sufficient initial tension can be provided to transmit the driving force of the powder coating machine 10 and at the same time to detect even slight forces acting on the powder coating machine 10 by the interfering object 50. By using the two springs 4a and 4b connected in parallel, the spring stiffness is added during the normal operation of the powder coating machine 10, and as a result, the required driving force can be reliably transmitted. When the powder coating machine 10 collides with the object 50 while moving in the first or second direction, only one of the two springs 4a and 4b is compressed, and as a result, only the spring stiffness of the affected spring 4a or 4b is effective.

[0051] In this way, the elastic element 4 described above responds very sensitively to the forces acting on the powder coating machine 1.

[0052] Changes in the biasing force of the first or second springs 4a and 4b can be detected, for example, by an increase in the current consumption of the electric motor of the drive unit required to compress each spring 4a and 4b. If this current exceeds a predetermined threshold, for example, the two drive units may be switched off. However, in particular, to reliably detect even smaller changes in biasing force as described above, the movement of the bolt 2 can be measured by a displacement sensor 7. Such a displacement sensor 7 will be described below with reference to Figures 5 and 6.

[0053] Figure 5 schematically and illustratively shows a further longitudinal section of the device 100 shown in Figure 1, where the displacement sensor 7 of the collision detection device 1 is visible. The displacement sensor 7 is located in the collision detection device on the opposite side from the drive unit. In this design example, each of the two collision detection devices 1 is equipped with a displacement sensor 7. However, if two collision detection devices are used, it is also possible that only one of the two has a displacement sensor. The illustrated displacement sensor 7 is a potentiometric displacement sensor with a probe 7a at its tip (see Figure 6). During the movement of the bolt 2 in the first or second direction, the displacement sensor 7 moves along the ramp 7b, thereby pushing the probe into the sensor housing 7c. This changes the resistance of the displacement sensor, which is proportional to the position of the potentiometer mounted inside the sensor 7, and thus proportional to the displacement of the bolt 2, and therefore also proportional to the spring displacement of the first or second springs 4a, 4b. In this way, the change in the biasing force of the first or second springs 4a, 4b can be determined. It is also possible to directly set a threshold for the allowable displacement of bolt 2, such that when it exceeds a certain value, the drive unit is activated and, in particular, can be switched off thereafter. Specifically, the drive unit can be switched off whenever bolt 2 moves its maximum possible displacement within bushing 3, thereby causing the biasing force of the first or second springs 4a, 4b to reach its maximum value.

[0054] Figure 6 schematically shows a detailed example of the displacement sensor 7 of the collision detection device 1 shown in Figure 5. In this case, the field of view of the displacement sensor 7 is rotated by 90° compared to Figure 6.

[0055] In this figure, the button 7a, housing 7c, and screw connection 7d, to which the displacement sensor 7 is attached to the collision detection device 1, are clearly visible. The displacement sensor 7 may also have an electrical connection (not shown) that can be connected to the control unit of the drive unit, for example, to detect changes in the resistance of the displacement sensor 7, calculate the displacement of a bolt from the displacement sensor 7, and compare this to a predetermined threshold for switching off the drive unit if it is exceeded.

[0056] In the illustrated view, a holder 10a is shown in the front view, which connects the collision detection device 1 to the powder coating machine 10. This connection is formed by four unspecified screws, two of which are screwed into the collision detection device 1 and two of which are screwed into the powder coating machine 10 (not shown). Furthermore, a bracket 15c that connects the drive unit to the collision detection device 1 can be seen on the side of the collision detection device opposite the displacement sensor 7. The bracket 15c comprises a first screw 15ca, by which the collision detection device 1 is screwed, and a second screw 15cb, by which the bracket 15c is attached to the drive unit 15 (not shown). It is clear that the design of the position sensor 7 and its placement on the collision detection device 1, as shown here as an example, provides a simple and robust method for detecting collisions between the powder coating machine 10 and objects 50.

[0057] Figures 7a and 7b schematically and illustratively show a collision detection device 1' according to a further embodiment of the present invention. In this embodiment, the bolt 2' itself is formed as an elastic element 4', in particular as a torsion bar spring 2', 4', and can extend perpendicular to the direction of movement of the powder coating machine 10.

[0058] Figure 7a schematically shows a cross-section of the collision detection device 1', and shows a bushing 3' that is mounted inside the collision detection device 1' and receives a bolt 2'. In this case, the displacement sensor 7 is positioned above the bushing 3' and interacts with the ramp 7b'. The bolt 2' is formed as a torsion bar spring 2', 4', which can be screwed into the bushing 3' as seen in Figure 7b.

[0059] Figure 7b schematically shows a longitudinal section of the collision detection device 1' in section AA depicted in Figure 7a. Torsion bar springs 2' and 4' are connected at their centers to a holder 10a via serrations 8, which then connects the collision device 1' to the powder coating machine 10. The torsion bars 2' and 4' are rotatably mounted at their two outer ends within two sliding bearings 3c'. In this way, the reaction force applied to the powder coating machine 10 by the object 50 can be used to twist the torsion bars 2' and 4', which can be detected by the sensor 7.

[0060] Figures 8a and 8b show the collision detection device 1' illustrated in Figures 7a and 7b from different positions. Here again, the cross-section of the collision detection device 1' is shown corresponding to the illustration in Figure 7a.

[0061] The position of the collision device in Figure 8a corresponds to the position already shown in Figure 7a, where the torsion bar springs 2' and 4' are unloaded. However, as shown in Figure 8b, when the powder coating machine 10 collides with object 50 (indicated by a white square with a thick outline to the left of the holder 10a) as it moves in the first direction (indicated by a long arrow pointing to the lower left of the collision detection device 1'), the torsion bar springs 2' and 4' are twisted, causing the holder 10a to rotate around the pivot point D. This rotation can be detected by the displacement sensor 7 because the rotation results in the movement of the displacement sensor probe 7a along the ramp 7b. In this way, in this embodiment as well, the collision of the powder coating machine 10 with object 50 can be reliably detected by the change in the biasing force of the elastic element.

Claims

1. A collision detection device (1) for an apparatus (100) for the additive manufacturing of an object, including a powder coating machine (10) and a powder coating machine drive unit, wherein the collision detection device (1) is The bushing (3) connected to the powder coating machine drive unit, A bolt (2) is movably supported within the bushing (3) and connected to the powder coating machine (10), An elastic element (4) for biasing the bushing (3) together with the bolt (2), Equipped with, The collision detection device (1) is configured to detect a collision between the powder coating machine (10) and an object (50) based on a change in the biasing force of the elastic element (4).

2. The collision detection device (1) according to claim 1, wherein the bolt (2) extends in the direction of movement of the powder coating machine (10), and the elastic element (4) is positioned between the bushing (3) and the bolt (2) and is biased in the axial direction of the bolt.

3. The collision detection device (1) according to claim 1 or 2, wherein the bolt (2) is movable within the bushing (3) against the biasing force of the elastic element (4), the second direction being opposite to the first direction.

4. The collision detection device (1) according to claim 1 or 2, wherein the bushing (3) and the bolt (2) each have circumferential recesses (5, 6), the recesses (5, 6) face each other and the elastic element (4) is disposed inside them.

5. The collision detection device (1) according to claim 1, wherein the bolt (2) is formed as an elastic element, particularly as a torsion bar spring, and extends perpendicular to the direction of movement of the powder coating machine (1).

6. The collision detection device (1) according to claim 1 or 2, further comprising a sensor (7) configured to detect the movement of the bolt (2) within the bushing (3).

7. The collision detection device (1) according to claim 1 or 2, wherein the elastic element (4) comprises a first spring (4a), a second spring (4b), and a washer (4c).

8. The collision detection device (1) according to claim 7, wherein the first end of the first spring (4a) and the first end of the second spring (4b) are adjacent to the first surface (4ca) of the washer (4c) of the elastic element (4).

9. The collision detection device (1) according to claim 7, wherein the washer (4c) has a circumferential projection (4cc) on the first surface (4ca), and the projection (4cc) separates the first end of the first spring (4a) from the first end of the second spring (4b).

10. The collision detection device (1) according to claim 8, wherein the washer (4c) of the elastic element (4) is adjacent to the first end face (5a) of the circumferential recess (5) of the bolt (2) and / or the first end face (6a) of the circumferential recess (6) of the bushing (3) by a second face (4cb) opposite to the first face (4ca).

11. The collision detection device (1) according to claim 7, wherein the first spring (4a) is adjacent to the second end face (5b) of the circumferential recess (5) of the bolt (2) by its second end, and the second spring (4b) is adjacent to the second end face (6b) of the circumferential recess (6) of the bushing (3) by its second end.

12. The collision detection device (1) according to claim 11, wherein the bolt (2) consists of two parts, the first end face (5a) of the circumferential recess (5) is located on the first part (2a) of the bolt (2), and the second end face (5b) of the circumferential recess (5) is located on the second part (2b) of the bolt (2).

13. An apparatus (100) for additive manufacturing of an object, comprising a powder coating machine (10) and a powder coating machine drive unit (15) according to claim 1 or 2, and at least one collision detection device (1).

14. A method for detecting a collision between a powder coating machine (10) and an object (50) within an apparatus (100) for the additive manufacturing of an object, using a collision detection device (1) according to claim 1 or 2, A step of determining the change in biasing force of the elastic element (4) of the collision detection device (1); and The step of detecting a collision between the powder coating machine (10) and an object (50) when the change in the biasing force exceeds a predetermined threshold. A method for providing this.

15. The method according to claim 14, wherein the change in the biasing force of the elastic element (4) is determined from the movement of the bolt (2) of the collision detection device (1) against the biasing force of the elastic element (4).

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