UNPACKING STATION AND ITS OPERATING PROCEDURES

Description

[0001] The invention relates to an unpacking station with a build plate holder that can be pivoted about two axes for unpacking components produced by means of an additive manufacturing process, with a closable work space through which a gas flow can flow, and to a method for operating such an unpacking station with a workpiece mounted on a build plate.

[0002] From DE 10 2014 010 501 A1, an unpacking station through which a gas flow flows is known, in which the construction plate with the workpiece mounted on it is inserted into a work space.

[0003] Document EP 3 533 538 A1 discloses a cleaning device that cleans three-dimensional objects produced by layer-by-layer application and selective solidification of a powdered building material from unsolidified powdered building material surrounding the objects and / or remaining in openings or channels of the objects. During the cleaning process, an object to be cleaned can be releasably clamped in a clamping device on a rotary plate of the cleaning device. The rotary plate can, for example, be driven to rotate about a first axis of rotation by means of a first motor, in particular at an angle of 0 to 360 degrees. Furthermore, the rotary plate can be mounted on a rotary arm, which in turn is driven to rotate about a second axis of rotation by means of a second motor.

[0004] The present invention is based on the problem of increasing the occupational safety of the unpacking station and enabling automation of workpiece handling.

[0005] This problem is solved by the features of independent claims 1 and 10. For this purpose, the working chamber is integrated into a closed gas flow circuit supplied by a circulation pump. A dust measuring device is arranged between the working chamber and the circulation pump, at least in a partial gas flow. Furthermore, a separation device is connected upstream of the circulation pump.

[0006] During operation, the build plate with the workpiece is secured to the build plate holder. The work chamber is sealed. The circulation pump circulates gas in a closed circuit through the work chamber, the dust measuring device, and the separation device. The dust load is continuously measured using the dust measuring device. If the dust load falls below a preset threshold, an enable signal is issued.

[0007] The invention terminates the unpacking of additively manufactured workpieces when the pollutant content in a gas circuit flowing through the work chamber falls below a critical limit. Opening the work chamber to remove the machined workpiece after this point significantly reduces the health risk for the operator. The pollutant content signal can also be used in an automated process sequence to trigger subsequent process steps.

[0008] Further details of the invention emerge from the subclaims and the following description of schematically illustrated embodiments. Figure 1: Unpacking station; Figure 2: Cross section of the unpacking station from Figure 1 ; Figure 3: Hood; Figure 4: Base part; Figure 5: Workpiece clamping system; Figure 6: Section of the tool holder unit; Figure 7: Gas flow diagram.

[0009] The Figures 1 and 2show an unpacking station (10) for components manufactured using an additive manufacturing process. Such manufacturing processes include, for example, laser melting processes or laser sintering processes. In these manufacturing processes, the individual workpiece is built up layer by layer from a powder-like material on a build plate, with the individual layers being fused together. The material used can be metallic or plastic. The powder used has, for example, a grain size of 15 micrometers to 70 micrometers. A laser is used to heat the areas to be fused. The build plate used has, for example, a square base with an edge length of 120 millimeters or 300 millimeters.

[0010] The unpacking station (10) has a support frame (11), which in the illustrations has four adjustable feet (12). The unpacking station (10) can also be designed to be movable. In this case, it stands on four casters, for example. A lifting device (13) is arranged on the support frame (11). In the exemplary embodiment, this is a chain hoist (13) with which individual components of the unpacking station (10) can be lifted. The total height of the unpacking station (10) is, for example, 2.4 meters. The unpacking station (10) illustrated has a base area of, for example, 1.5 meters by 1.4 meters.

[0011] The support frame (11) can be covered. For example, it has a door providing access to an unpacking unit (20) located in the support frame (11). A screen, operating elements, media supply connections, etc., can also be integrated into the cover. An access opening to a powder collection container (14), see Fig. Figure 7 , should be provided.

[0012] The unpacking unit (20) has a base part (21) and a cover (91). In the illustrations of the Figures 1 and 2 , which show the unpacking station (10) in a loading position, the hood (91) is spaced from the base part (21). The base part (21) is mounted in the support frame (11), for example so that it can swing. However, it can also be fastened in the support frame (11). In the open state, the hood (91) is raised by, for example, 700 millimeters relative to the base part (21). Two linear lifting devices (92) arranged on both sides of the unpacking unit (20) are used for lifting. In the exemplary embodiment, the parting line between the base part (21) and the hood (91) lies in an inclined plane. As a result, the edge of the base part (21) lies, for example, 800 millimeters above the hall floor when the workpiece is being loaded.

[0013] The Figure 3shows the hood (91). It has a cylindrical shell-shaped base body (93) and a conical shell-shaped upper section (94). The base body (93) has a circumferential double seal (95) on its outside. This inflatable double seal (95) comes into contact with the inner wall (22) of the base section (21) when the unpacking unit (20) is closed. This virtually hermetically seals the internal working space (15) of the unpacking station (10) from the environment (1). When the hood (91) is lifted, the upper of the double seals (95) is first exposed and cleaned using a gas stream. Then, as it is lifted further, the lower of the double seals (95) is also cleaned. This means that no powder residue remains on the double seal (95), ensuring that the working space (15) is hermetically sealed the next time the hood is closed.

[0014] A gas supply connection (96) is located in the upper part (94). This connection penetrates the wall of the hood (91), so that when the unpacking station (10) is in operation, gas is pumped into the working chamber (15) through this gas supply connection (96). The nominal diameter of the gas supply connection in this example is 50 millimeters.

[0015] The hood (91) carries two recirculating ball bearings (97) on each side. These recirculating ball bearings (97) guide the hood (91) vertically, for example, in the support frame (11). Additionally, the hood (91) is supported in the support frame (11) by a support roller (98) located on its rear side.

[0016] In the Figures 2 and 4the base part (21) is shown in two mutually orthogonal sectional planes. The base part (21) has a cylindrical shell (24) defined by an edge (23), to which a downwardly tapering conical funnel (25) is connected in these illustrations. At the lower end of the funnel (25) there is an extraction connection (26) which penetrates the wall of the funnel (25). In the exemplary embodiment, the nominal diameter of the extraction connection (26) corresponds to the nominal diameter of the gas supply connection (96). Furthermore, a media flange for additional operating media can be provided on the base part (21). Several flushing connections (27) are provided along a circumferential line of the funnel (25). These can be used, for example, to clean the double seal (95) and / or the funnel (25).

[0017] A workpiece holding unit (31) is pivotally mounted in the base part (21). For this purpose, the workpiece holding unit (31) has a pivot shaft (32) with a horizontal pivot axis (33). The pivot shaft (32) is mounted on both sides in the base part (21) by means of roller bearings (34). By means of a pivot drive (not shown here), which is arranged, for example, on the outside of the base part (21), the workpiece holding unit (31) can be pivoted in both pivot directions through an angle of, for example, 240 degrees. To transmit torque from the pivot drive, the pivot shaft (32) of the workpiece holding unit (31) has a keyway (35). The pivot drive has an electrically driven servo motor and a position and / or angle measuring system. This allows the respective pivot angle of the workpiece holding unit (31) about the aforementioned first pivot axis (33) to be adjusted, for example, with an accuracy of one tenth of a degree.The maximum swivel speed of the swivel drive is, for example, one revolution per minute.

[0018] The workpiece holding unit (31), see Figure 6, has a central support body (36) in which a workpiece pivoting unit (41) is pivotally mounted. Rolling bearings (42), for example, are used for mounting. The pivot axis (43) of the workpiece pivoting unit (41) is oriented in the vertical direction. This pivot axis (43) is referred to below as the second pivot axis (43). The workpiece pivot drive (44) has an electric motor (45) arranged in the support body (36) in the form of a servomotor with a downstream gear (46). The gear (46) is, for example, a bevel gear whose output shaft forms an angle of 90 degrees with the input shaft. The use of a worm gear is also conceivable. The output shaft of the gear (46) drives a pulley (49), which, by means of a belt drive (48), drives a pulley (48) of the workpiece pivoting unit (41). The belt drive (48) can be designed as a flat belt, a V-belt, a toothed belt, etc.The electrical control and monitoring of the workpiece swivel drive (44) is carried out in the same way as the control of the swivel drive of the workpiece holding unit (31) described above. The swivel angle of the workpiece swivel unit (31) is, for example, 360 degrees. The angular velocity of the workpiece swivel unit (41) corresponds to the angular velocity of the workpiece holding unit (31).

[0019] The workpiece swivel unit (41) has a bearing body (51), a workpiece clamping system (61) and a building plate holder (52), see. Figure 5The building board holder (52) is, for example, a flat, e.g., square plate with a central opening (53). In the exemplary embodiment, the building board holder (52) has chamfered corners. The size of the building board holder (52) is, for example, matched to the particular building board used. The building board holder (52) is, for example, designed to be replaceable. For replacement, fastening screws (54) can be loosened, for example. Two centering bolts (55), for example, for centering the building board, are arranged outside the opening (53).

[0020] In the exemplary embodiment, the workpiece clamping system (61) is designed as a zero-point clamping system, see DE 10 2018 009 226 A1.

[0021] The Figure 5 The workpiece clamping system (61) shown has a central plunger (62) which is actuated by means of a spring energy store (63) designed as a compression spring (63) in the illustration of the Figure 5is loaded upwards. The plunger (62) has a sealed annular piston (64) which is guided on a cylinder wall (65). When the spring energy accumulators (63) are relaxed, the plunger (62) loads a ball wedge system (66) so that the outer balls (67) are displaced outwards. When the build plate is inserted, these balls (67) engage behind a complementary engagement pin in the build plate. The plunger (62) is hollow and has an internal pneumatic channel (68). In its upper area, the plunger (62), which is constructed in several parts, for example, has radial openings (69). These radial openings (69) connect the pneumatic channel (68) to a pressure chamber (71). The pressure chamber (71) is delimited by means of the annular piston (64) and a sealing ring (72). The plunger (62) is connected to the media connection of the base part (21), for example by means of a pneumatic tube (73) and an upstream flexible hose.The penetration of contamination into the workpiece clamping system (61) is prevented by means of several sealing elements (74).

[0022] Before clamping the construction plate, the pressure chamber (71) is pressurised with pneumatic pressure so that the plunger (62) is moved under load of the compression springs (63) in the representation of the Figure 5 is displaced downward. The balls (67) are displaced inward, so that the build plate with its engagement pin can be easily inserted into an engagement recess (75). The pneumatic pressure in the pressure chamber (71) is then reduced, e.g., to ambient pressure. The relieving compression springs (63) move the plunger (62) upward, so that the engagement pin of the build plate is fixed. The build plate is released in a similar manner.

[0023] In this exemplary embodiment, the unpacking station (10) has a vibration module (16). This can, for example, impart pulses or vibrations to the base part (21). Vibration excitation of the build plate holder (52) is also conceivable.

[0024] The Figure 7shows a diagram of the gas flow. A gas pump (101) is connected to the unpacking station (10). This is designed, for example, as a suction pump and pumps gas, e.g. inert gas, nitrogen, etc. through the gas supply connection (96) into the working space (15) of the unpacking station (10). A gas flow is sucked out of the base part (21) of the unpacking station (10) through the suction connection (26). In the exemplary embodiment, the sucked-out volume flow is divided into a first partial flow, which is passed through a dust measuring device (102), and a second partial flow, which is passed through a bypass (103). The ratio of the two partial flows can be fixed or adjustable. It is also conceivable to design the circuit without a bypass (103). A separation device (104) is connected downstream of the dust measuring device (102).This separation device (104) has, for example, a coarse separator (105), a medium-fine filter (106), and a fine filter (107), which are connected in series. The coarse separator (105) is connected to the powder collection container (14) via a closable powder discharge channel (108). The suction pump (101) draws the filtered gas through the unpacking station (10), the dust measuring device (102), and the separation device (104), so that the suction pump (101) forms a circulation pump (101) of a closed circuit.

[0025] A flushing line (109) branches off from the pressure side of the circulation pump (101). This line opens into the dust measuring device (102).

[0026] The purge air is used here, for example, to clean the optical sensors of the dust measuring device (102).

[0027] In this example, the dust measuring device (102) has a light source and an optical sensor. This receives a wavelength of, for example, 880 nanometers. The light intensity detected by the sensor is proportional to the dust load of the measured gas. For example, the sensor outputs an analog signal between 4 milliamperes and 20 milliamperes to a central control unit of the unpacking station (10).

[0028] In the illustrated example, the coarse separator (105) is a cyclone separator (105). It has one inlet and two outlets. The first outlet is the powder discharge channel (108). The second outlet opens into the medium-fine filter (106).

[0029] The medium-fine filter (106), for example, has a filter cartridge with airflow from the outside to the inside. It has a filter surface of 48,000 square centimeters. The filter fleece is made of cellulose and has a dust capacity of 4,000 grams. Its pressure resistance at the beginning of use is, for example, 24 millibars, and its resistance at the end of use is, for example, 65 millibars. The maximum air flow is, for example, 8 cubic meters per minute. The filter fineness is 99.9% for particles larger than 3 micrometers.

[0030] The fine filter (107) in the example shown has a cylindrical shape. Its diameter is, for example, 160 millimeters and its length 190 millimeters. The filter surface is, for example, 0.7 square meters. The filter material is, for example, glass fiber paper. The fine filter (107) used here is a class H14 HEPA filter according to

[0031] EN 1822-1:2009. This fine filter (107) further separates the particles contained in the gas stream.

[0032] The workpiece, manufactured using the additive manufacturing process and mounted on the build plate, is embedded in a powder bed after production. The build plate, together with the workpiece and the powder, is removed from the production machine and placed in the unpacking station (10). The unpacking station (10) is in the open position, as shown in the Figures 1 and 2 The assembled build plate can be handled manually or using a handling device. During manual handling, the operator wears both skin protection, e.g., gloves, and respiratory protection.

[0033] In the unpacking station (10), the build plate is placed, for example, on the build plate holder (52) such that its engagement pin protrudes into the engagement recess (75) of the workpiece clamping device (61), and the centering pins (55) protrude into the centering pin receptacles of the build plate. The pressure chamber (71) is pneumatically loaded, so that the plunger (62) compresses the compression springs (63). After the build plate is inserted, it is secured to the build plate holder (52) by means of the combined mechanical-pneumatic workpiece clamping system (61). Another design of the workpiece clamping system (61) is also conceivable.

[0034] The hood (91) is then lowered onto the base part (21). This hermetically seals the work space (15) from the environment (1). The command to close the work space (15) can be given manually, e.g. using a button. However, it is also conceivable that feedback that the workpiece has been secured triggers the closing of the work unit (20). For this purpose, for example, the movement of the ram (62) relative to the bearing body (51) is monitored by means of a position measuring system or a switch. A collision protection switch arranged on the hood (91) prevents the hood (91) from closing if there are still objects in the opening area of ​​the hood (91).

[0035] After the work station (10) has been closed, gas, for example from a gas reservoir (not shown here), is pumped into the work chamber (15) by means of the circulation pump (101). The gas used can be, for example, argon, nitrogen, etc. This reduces the oxygen content in the gas mixture in the work chamber to a value of, for example, 5%. When the gas is pumped, an overpressure of, for example, 20 millibars is created in the work chamber (15). This not only reduces the risk of explosion, but also prevents a reaction between the oxygen and the workpiece material.

[0036] In the workspace (15), the workpiece is moved by means of the two driven pivot axes (33, 43). The movement of the two pivot axes (33, 43) depends on the geometry of the workpiece such that every surface, every hole, and every recess faces downward at least once. With this workpiece-specific control of the pivot axes (33, 43), the loose powder falls into the hopper (25), assisted by the volume flow of the gas. Powder adhering to the workpiece is additionally loosened, for example, by the vibration module (16).

[0037] The released powder is extracted from the work chamber (15) by the circulation pump (101) through the extraction connection (26). The extracted volume flow is divided, for example, into the partial flow through the dust measuring device (102) and the partial flow through the bypass (103). These two partial flows have, for example, the same pneumatic resistance, so that the ratio of the partial flows remains constant even when the volume flow changes. The two partial flows are recombined downstream of the dust measuring device (102).

[0038] The signal emitted by the dust measuring device (102) is displayed to the operator, for example, visually as a binary signal. If the dust load in the gas stream exceeds a specified threshold, a red bar is displayed, for example. As soon as the dust load falls below the threshold, a green bar can be displayed, for example. The threshold is derived, for example, from the maximum dust load in work spaces specified by occupational health and safety regulations.

[0039] In the separation device (104), coarse particles are first separated in the coarse separator (105). These particles are conveyed to the powder collection container (14). A filled powder collection container (14) can be replaced, for example, after closing the shut-off valve (111). The gas flow is then conveyed through the two filter stages (106, 107), where additional particles are separated.

[0040] The gas continues to circulate, progressively cleaning the workpiece of powder and the separation device (104) continues to separate particles. As circulation continues, the dust load in the gas stream decreases. The dust load value checked or measured by the dust measuring device (102) falls below the threshold value.

[0041] Falling below the threshold value is the signal that the workpiece has been successfully unpacked. The unpacking process can be terminated. The drives of the swivel axes (33, 43) are stopped and the circulation pump (101) is stopped. For example, a lock of the hood (91) relative to the base part (21) can be released. The work space (15) can now be opened. After releasing the build plate fixation, the workpiece can be removed with the build plate. This process can also be carried out manually or using a handling device. When the workpiece is removed manually, there is a very low risk for the operator of inhaling dust or coming into contact with residual powder due to the cleaning process.

[0042] The control of these functions can be integrated into a common control system. This means that if the threshold value is exceeded, the rotary actuators and the circulation pump (101) can be automatically stopped. As a follow-up function, after the hood lock is released, the hood (91) can be opened. The opened hood (91) can issue the release signal for a handling device that removes the machined workpiece from the work area.

[0043] It is also conceivable to display the remaining running time of the cleaning process based on the measured dust load. This could be based, for example, on empirical values ​​from the cleaning process stored in a database. For example, the remaining running time is shown in seconds on an operating display.

[0044] In the event of a process interruption, for example, during an emergency stop, the lock of the work area (15) can be unlocked manually. The hood (91) can also be raised manually or using the chain hoist (13). Further processing of the workpiece can then be carried out at another unpacking station (10) or manually. List of reference symbols:

[0045] 1Environment 10Unpacking station 11Support frame 12Adjustable feet 13Lifting device, chain hoist 14Powder collection container 15Working area 16Vibration module 20Unpacking unit 21Base part 22Inner wall 23Rim 24Cylinder jacket 25Funnel 26Suction connection 27Rinsing connections 31Workpiece holder unit 32Pivoting shaft 33Pivoting axis, first pivoting axis 34Rolling bearing 35Keyway 36Support body 41Workpiece swivel unit 42Rolling bearing 43Swivel axis, second swivel axis 44Workpiece swivel drive 45Electric motor 46Gearbox 47Pulley 48Belt drive 49Pulley 51Bearing body 52Building panel holder 53Breakthrough 54Fastening screws 55Centering bolt 61Workpiece clamping system 62Push 63Spring energy storage, compression spring 64Annular piston 65Cylinder wall 66Ball wedge system 67Balls 68Pneumatic channel in (62) 69Radial openings 71Pressure chamber 72Sealing ring 73Pneumatic tube 74Sealing elements 75Engagement recess of (61) 91 Hood 92 Linear lifting devices 93 Base body 94 Upper section 95 Double seal 96 Gas supply connection 97 Recirculating ball bearings 98 Support roller 101 Gas pump, suction pump, circulation pump 102 Dust measuring device, dust measuring device 103 Bypass 104 Separation device 105 Coarse separator, cyclone separator 106 Filter stage, medium-fine filter 107 Filter stage, fine filter 108 Powder discharge channel 109 Flushing line 111Shut-off valve

Claims

1. Unpacking station (10) having a building board receptacle (52) which can be pivoted about two pivot axes (33, 43) for unpacking components produced by means of an additive manufacturing method, having a closable working space (15) through which a gas stream can flow, characterized in that: the working space (15) is incorporated in a closed circuit of the gas stream which is acted on by means of a circulating pump (101), a dust measuring device (102) is arranged between the working space (15) and the circulating pump (101) at least in a partial gas stream, and a separating device (104) is connected upstream of the circulating pump (101).

2. Unpacking station (10) according to Claim 1, characterized in that a bypass (103) is connected parallel to the dust measuring device (102).

3. Unpacking station (10) according to Claim 1, characterized in that the separating device (104) has a coarse separator (105), at least one medium-fine filter (106) and at least one fine filter (107) which are connected in series with one another.

4. Unpacking station (10) according to Claim 1, characterized in that the circulating pump (101) is a suction pump (101), the suction side of which faces the separating device (104).

5. Unpacking station (10) according to Claim 1, characterized in that a flushing line (109) is arranged between the circulating pump (101) and the dust measuring device (102).

6. Unpacking station (10) according to Claim 3, characterized in that the coarse separator (105) is connected to a powder collection container (14) by means of a closable powder discharge channel (108).

7. Unpacking station (10) according to Claim 1, characterized in that the building board receptacle (52) has a combined mechanical-pneumatic workpiece clamping system (61).

8. Unpacking station (10) according to Claim 1, characterized in that the dust measuring device (102) is coupled to a lock of the working space (15), with the result that the lock is released when the dust load falls below a predefined threshold value.

9. Unpacking station (10) according to Claim 1, characterized in that the movements of the pivot axes (33, 43) of the building board receptacle (52) are controlled in a workpiece-specific manner.

10. Method for operating an unpacking station (10) according to Claim 1 with a workpiece built up on a building board, wherein the building board with the workpiece is fixed on the building board receptacle (52), the working space (15) is closed, gas is conveyed in a closed circuit through the working space (15), the dust measuring device (102) and the separating device (104) by means of the circulating pump (101), the dust load of the gas stream is determined continuously by means of the dust measuring device (102), a release signal is output when the dust load falls below a preset threshold value.