Method and device for producing three-dimensional models with a temperature-controllable print head

Abstract

The present invention relates to a method for producing three-dimensional models by a layering technique, particulate build material being applied to a build space, and binder material subsequently being selectively applied to the build material with the aid of a printer, the binder material containing a moderating agent and subsequently being sintered with the aid of a heat lamp, the print head being protected against overheating by active and/or passive cooling.

Claims

1. A device for producing three-dimensional models by a layering technique, particulate build material being applied to a build space in a process chamber, a moderating agent subsequently being selectively applied with the aid of an ink-jet print head, and the printed areas being solidified by supplying energy that controls a temperature of the build space, characterized in that the print head is protected against overheating by active and/or passive cooling by a cooling component that independently regulates a temperature of the print head relative to the temperature of the process chamber, wherein the cooling component acts to cool the temperature of the print head lower than the temperature of the build space; wherein the cooling takes place with the aid of the print medium to be printed; or the cooling takes place with the aid of cooling air which is flushed around sensitive parts in the interior of the print head; or the cooling of the print head takes place by dissipating heat with the aid of an additional fluid medium; or the cooling takes place with the aid of Peltier elements.

2. The device according to claim 1, characterized in that the device has a temperature sensor, a temperature controller and a cooling and heating unit including the cooling component.

3. The device according to claim 1, characterized in that the print head is protected against the residual energy of the build space and the particulate material and active energy supply on the build space by partitioning.

4. The device according to claim 3, wherein the device is characterized by one or any combination of the following: i) the print head is moved behind a flexible or fixed wall in the build space; or ii) a collision with the wall is detected by sensors in the print head or the wall; or iii) the partitioning takes place using a movable wall; or iv) an air curtain partitions off the print head.

5. The device according to claim 1, characterized in that the print head is protected by an external cooling means.

6. The device according to claim 5, wherein the external cooling means includes: actively moving cooling air to flow around the print head; or the print head is brought into contact with a cool object or a fluid from the outside; or the print head is passively cooled in a cooled chamber.

7. The device according to claim 1 characterized in that the condensate formation on the print head is prevented by temperature control and by controlling the humidity.

8. The device according to claim 7, wherein the device includes metal cooling plates positioned at reversing points in the build space for cooling the print head by passing the print head over the metal cooling plates.

9. The device according to claim 1, wherein an evaporator is disposed in the print head.

10. The device according to claim 1, wherein the device has a cooling system including a temperature sensor, a temperature controller and the cooling component for cooling the print head; and the print head is protected against the residual energy of the build space and the particulate material and active energy supply on the build space by partitioning.

11. The device of claim 1, wherein the device includes an insulated build cylinder to reduce heat loss.

12. The device of claim 1, wherein the process chamber is insulated.

13. The device of claim 1, wherein the print head is characterized by a drop size of about 20 to 200 μm.

14. The device of claim 1, wherein the print head moves at a distance of about 1-5 mm above the particulate material in the build space, and the print head is maintained at a temperature of 40 to 60° C.

15. The device of claim 1, wherein the device provides a control a temperature of the print head of +/−2° C.

16. The device of claim 1, wherein a lamp is used to supply energy which emits an essentially linearly distributed radiation and which is guided over the build space in such a way that the radiation essentially evenly covers the entire build space, wherein the build space is in an insulated process chamber.

17. The device according to claim 16, characterized in that the power of the lamp is controlled in segments and may thus also be regulated.

18. The device according to claim 17, wherein the lamp essentially emits IR radiation in the wavelength range of 1 μm to 4 μm.

19. The device according to claim 18, wherein the lamp is separated from the print head by partitioning in its idle position or the lamp is spatially located at a distance from the print head in its idle position.

20. The device of according to claim 19, wherein the partitioning is included and the partitioning takes place with the aid of a flexible or fixed wall; or the partitioning takes place with the aid of an air curtain; or the partitioning takes place with the aid of a movable wall.

21. A device for producing three-dimensional models by a layering technique, particulate build material being applied to a build space in a process chamber, a moderating agent subsequently being selectively applied with the aid of an ink-jet print head, and the printed areas being solidified by supplying energy, characterized in that the print head is protected against overheating by active or passive cooling, wherein the cooling takes place with the aid of the print medium to be printed, wherein an excess of the print medium is applied from a reservoir to the print head.

Description

(1) This may result in component distortion. For the purpose of more detailed explanation, the invention is described in greater detail below on the basis of preferred exemplary embodiments with reference to the drawing.

(2) In the drawing:

(3) FIG. 1 shows a method known from the prior art.

(4) FIG. 2 shows a diagram of the process sequence of a 3D printer which operates according to the HSS principle;

(5) FIG. 3 shows a graphic representation of the dwell times of the print head above the heated build space in a process according to FIG. 2;

(6) FIG. 4 shows a representation of the structure of the print head according to the prior art;

(7) FIG. 5 shows a diagram of the control of the temperature of a print head according to the prior art;

(8) FIG. 6 shows an expanded diagram of the control of the temperature of a print head according to the prior art, including internal or external print head cooling;

(9) FIG. 7 shows a diagram of the cooling process by means of flushing or nozzle actuation;

(10) FIG. 8 shows an isometric view and a side view of a print module, with an indication of the flaw lines of the cooling air,

(11) FIG. 9 shows a sectional view of the coolant channels for cooling the modules and the cover plate;

(12) FIG. 10 shows a sectional view of the Peltier elements for actively cooling the print head with the aid of massive cooling lines;

(13) FIG. 11 shows a sectional view of a print head, including surfaces for cooling through evaporation;

(14) FIG. 12 shows a top view of a preferred device having partitioning in a block diagram;

(15) FIG. 13 shows side view one preferred embodiment, including a partition wall;

(16) FIG. 14 shows a top view of one preferred embodiment, including different partitioning means;

(17) FIG. 15 shows a side view of one preferred embodiment, including an air curtain;

(18) FIG. 16 shows a side view of one preferred embodiment, including a print head air cooling means;

(19) FIG. 17 shows a side view of a device for active contacting with a fluid-cooled cleaning device and a cooling block;

(20) FIG. 18 shows a top view of a device according to the invention, including cooled build space edges;

(21) FIG. 19 shows a top view of one preferred embodiment, including a linear lamp, segmented activation and a diagram for the movement speed.

(22) FIG. 1 shows a known device according to the prior art. It is used to produce bodies such as object 103. Body 103 may have a nearly arbitrary complexity. The device is referred to below as a 3D printer.

(23) The process of constructing a body 103 begins in that movable building platform 102 is moved to its highest position in device 104. At least one layer thickness is also present between building platform 102 and the lower edge of coater 101. The coater is moved to a position in front of build space 111 with the aid of an axis system, which is not illustrated. In this position, coater 101, including its stock 113 of particulate material, is caused to vibrate. The particulate material flows out of gap 112. Outflowing material 110 fills the still empty layer due to a forward movement 106 of coater 101.

(24) Subsequently or even during the movement of coater 101, print head 100 is set in motion by an axis system, which is also not illustrated. The latter follows a meandering path 105, which passes over the build space. According to the sectional diagrams of body 103 to be produced, the print head dispenses drops of binder 109 and solidifies these areas. This basic principle remains the same regardless of print head 100 used. Depending on the size, in extreme cases, meandering path 105 is reduced to a simple forward and backward movement.

(25) After printing, building platform 102 is moved in direction 108. A new layer 107 for coater 101 is generated thereby. The layer cycle begins all over again when coater 101 returns to its starting position. Repeatedly carrying out this cycle produces component [sic; body] 103 in the end. After the building process, component [sic: body] 103 may be removed from the loose powder still surrounding it.

(26) The solidification process described above, in which the particles of the particulate material are sintered, is one variant of this process. FIG. 2 shows the sequence of a method of this type. It is an expansion of the 3D printer described above.

(27) The representation under I shows the printing process, which takes place in a manner similar to the above description. Print head 100 undergoes a meandering movement and deposits drops, including moderating agent 109, in the area of component [sic: body] 103. In terms of many of its parts, device 104 is structured like a 3D printer. The drop generation is preferably based on the piezoelectric principle, since print heads having maximum lifespans may be built hereby. This effect may be used only up to a certain limit temperature TLimit. Above this temperature, the drop generation is disturbed, or the drop generator sustains irreversible damage.

(28) Step II deviates from the above description. A heat lamp, which generates radiation 201 adapted to the moderating agent, is guided over the build space. When it reaches the printed sites, the heat is effectively coupled into the particulate material and causes it to be sintered. The rest of the build space also absorbs not inconsiderable amounts of heat.

(29) Process steps III and IV are again entirely similar to the description of 3D printing. Building platform 102 is first lowered into device 104 in direction 108. Coater 101 then fills layer 110 with new particulate material.

(30) FIG. 3 shows a top view of a preferred device according to the invention. Print head 100 is omitted for the purpose of better illustrating meandering print head path 105. It is apparent that the print head executes large sections of its movement over build space 111. Simplified, the build space has a fixed temperature T111. At the beginning of the process, the print head has temperature T100=TBegin. FIG. 3 also shows a schematic representation of the dwell time of print head 100 over build space 111. The diagram shows the process steps from FIG. 2.

(31) Assuming that the build space has temperature T111, the following conditions arise, which are illustrated in the other diagrams in FIG. 3. The print head heats up over the build space. Afterwards, it may again transfer heat to the surroundings in its idle position. Depending on the heat absorption over the build space and the heat dissipation in the idle position, a stationary temperature between start temperature TStart and build space temperature T111 sets in. It is demonstrated that, if a higher printing capacity is desired, the print head must be protected against overheating above TLimit with the aid of active and/or passive cooling. To ensure uniform dispensing capacities, the print head must also be maintained within a very narrow temperature range. Temperatures of 40-60° C. are particularly preferred in this case. According to experience, a control of ±2° C. delivers good print results.

(32) FIG. 4 shows the structure of a print head 100 according to the prior art. Various assemblies are integrated into housing 212. Print modules 400 are essential for drop generation 109. These print modules contain the nozzles, the piezoelectric drives and the fluid system for distributing the fluid. A heater is usually also integrated for temperature regulation. These modules 400 are frequently purchased from print head manufacturers such as Dimatix, Xaar, Seico, Epson, Konica or Kyocera. Intervention into the inner structure is not possible. Modules 400 are connected to a storage tank 401, which contains print fluid 408, by hoses, a valve 406 and a filter 407. Electrical connections exist to heating controller 413 and data electronics 414. The connections are run to the outside (415, 416). The storage tank is connected to underpressure, overpressure and the refill line by additional lines switched by valves (409, 410 and 411). These lines are again run to the outside (417, 418 and 419).

(33) On the underside, the print head is protected against the penetration of fluids or contaminants by a cover plate 402. The modules and the cover plate absorb heat 404 in the form of radiation and convection during the travel over build space 111. If the temperature exceeds the setpoint of the heating controller, the temperature may no longer be held at a constant level.

(34) FIG. 5 shows the heating controller of existing print heads as a block diagram. Heating system 501 itself is controlled by a power controller 503. It receives its control signals from a controller 504, which, together with a sensor 500, detects the temperature directly in module 400 and thus implements a closed control circuit. The heat losses due to heat conduction to the surrounding parts, the convection in the housing and the thermal radiation losses are identified by 502. Energy is also transferred along with heated fluid drops 109 if the temperature of the drops is higher than the temperature of the refilled fluid. All losses must be compensated for by the heating system. The temperature at the lower end of the module is relevant for drop formation.

(35) FIG. 6 shows the design of a print head according to the invention. A massive heat flow 404 is added to the aforementioned variables in this case. In the HSS process described above, this heat flow is greater than the dissipated amounts of heat. The control by the print head-internal heating system may be facilitated only by introducing additional cooling 600. Cooling system 600 may include all preferred embodiments according to the invention.

(36) The form of heat dissipation illustrated in FIG. 7 is also covered by 600. In principle, two options exist. On the one hand, cold print fluid may be pressed through the print head. For this purpose, an overpressure 700 is applied to module 400 or to storage tank 401 (FIG. 4). A large amount of fluid is dispensed, and colder fluid enters module 400. In one preferred embodiment of the invention, the fluid enters print head 100 or print module 400 from a reservoir outside the build space at room temperature via insulated lines. This form of cooling may likewise take place via the drop generator of the print head. As in standard operation, an overpressure 702 is present at the tank.

(37) The intensity of this form of cooling must be ascertained by controller 504 of print head heating system 501. If the temperature leaves the control range in the upward direction, more intensive cooling is required. This scenario may be detected by the switching times of heating system 501.

(38) The cooling of module 400 may also be achieved via its housing. For this purpose, compressed air 800 may flow to the housing to compensate for heat absorption 404 from below. The compressed air nozzles may also be disposed in such a way that the flow rises vertically on the print module. In both embodiments of the invention, cover plate 402 (FIG. 4) must seal the modules toward the build space so that no particulate material is swirled up.

(39) FIG. 9 shows another preferred embodiment of the invention. In this case, heat 404 to be dissipated is transferred from module 400 to a fluid by heat conduction. For this purpose, contact blocks 900 on module 400 and cover plate 402 are disposed in a way that facilitates good heat transfer. Contact blocks 900 have bores 903, in which cooling fluid 901 may flow. Connections 902 connect the contact blocks to a hose system, which passes out of the print head and the warm build space. The hose system has an insulated design. Depending on the accumulating heat, cooling fluid 901 is then cooled passively or actively.

(40) FIG. 10 shows a likewise preferred device. In this case, excess heat 404 at module 400 is also dissipated via contact blocks 1000. In this case, the latter are in contact with Peltier elements 1002 via massive copper connections 1001. The Peltier elements pump the heat out of print head housing 412 when a voltage is applied to contacts 1004.

(41) The evaporation of a liquid may also be used for cooling. FIG. 11 shows an arrangement of this type. Heat 404 at module 400 is dissipated to cover plate 402 by heat conduction. A fluid 1102, which has a suitable evaporation point, is continuously redispensed thereto. The energy is taken from steam 1100 and guided out of the print head using a discharge system 1101 to avoid harmful condensation. For example, if water is selected as the fluid, temperatures around 100° C. may be controlled.

(42) FIG. 12 shows one preferred embodiment in the form of a block diagram. Print head 100 is separated from the build space by a partition 1200. In the phase of sintering, lowering and coating (FIG. 3, II, III, IV), print head 100 may thus cool without absorbing any more radiation from build space 111. The convection is also reduced. In the same manner, another partition 1201 may ensure that no additional heat reaches print head 100 due to the still warm lamp 200 during the passage of print head 105.

(43) FIG. 13 shows a side view of one preferred embodiment of the invention. Partition 1300 for print head 100 is rotatably supported. Print head 100 may thus strike the partition and reach build space 111. An energy exchange takes place only when it passes through. Partition 1300 forms a chamber for the print head in which it may cool. Likewise, partition 1301 may be designed for coater 101 and lamp 200.

(44) The partitions illustrated in FIG. 13 may also be designed to be active, as shown in FIG. 14. Once again, one partition 1400 may be provided for print head 100, and one partition 1401 may be provided for coater 101 and lamp 200. Compared to the rotatably supported partition, this has the advantage of lesser restrictions in the movement of the units in build space 111. The opening times may also be designed to be very short. For example, pneumatic actuators or electrically driven spindles are suitable as drives.

(45) FIG. 15 shows one preferred embodiment of the partitioning means. Moving parts are dispensed with, Nozzles 1501, 1500, 1502 allow air having different temperatures to flow in the direction of build space 111 as a curtain. If a laminar flow is set, only a limited mixing of the air masses 1503, 1505 and 1504 takes piece. The temperature may be controlled and also regulated in segments via corresponding heating and cooling units.

(46) According to the invention, it is not only possible to cool print head 100 by partitioning or from the inside, but the print head may also be cooled from the outside. FIG. 16 shows a design of this type. Print head 100 is flushed with cooling air 1601 and 1603. This air is discharged from nozzles 1600 and 1602. The flow of cooling air should not interact with the particulate material. It is therefore particularly preferred to combine the cooling with a partitioning.

(47) FIG. 17 shows another means of cooling the print head from the outside. Print head 100 is brought directly into contact with a heat-dissipating material. This may be a fluid which absorbs the heat. This may be combined with a cleaning device for the print head. A counter-rotating roller 1700 may be brought into contact with print head 100 moving in direction 105. The roller, which has been moistened by a shower 1702 or a fluid-filled basin 1703, absorbs heat from the print head. A good thermally conductive body 1701 may also be pressed onto cover plate 102 of print head 100. This body, in turn, is passively or actively cooled, for example using a cooling fluid 1704.

(48) Print head 100 may cool not only in its idle position but also on its path 105 on the edge of build space 111. For this purpose, build space edges 1800 must be colder than the build space. This may be achieved by the fact that edges 1800 of build space 111 are designed as pipes through which cooling air 1801 flows.

(49) FIGS. 19 and 20 show of one particularly preferred embodiment of the invention FIG. 19 shows the design of lamp 200 in an essentially linear embodiment. A homogeneous illumination of build space 111 is achieved. Due to the control, the direct influence of the print head may be minimized. Since cooler areas may occur on the edge of the build space, despite a uniform radiation power, due to the air circulation, additional segments 2000 may be mounted here, or a lamp with segmented control of the power may be used.

(50) FIG. 19 also shows a diagram for a particularly preferred control of the lamp movement of a linearly designed lamp. Due to the convection on build space 111, it is sensible to irradiate the edges at a slower movement speed while maintaining a constant power. It is likewise possible to adjust the power. The inertia of the lamp imposes limits on the method.

LIST OF REFERENCE NUMERALS

(51) 100 Print head 101 Coater 102 Building platform 103 Body 104 Device 105 Print head path 106 Coater path 107 Built layers 108 Direction of building platform 109 Microdrops 110 Particulate material roll 111 Build space 112 Coater gap 113 Powder stock 200 Heat lamp 400 Print module 401 Storage tank 402 Cover plate 403 Heated surface 404 Heat transfer 406 Valve 407 Filter 408 Printing fluid 409 Valve for underpressure 410 Valve for overpressure 411 Valve for refilling 412 Print head housing 413 Heating controller 414 Data electronics 415 Feed-through for data electronics 416 Feed-through for heating controller 417 Feed-through for underpressure line 418 Feed-through for overpressure line 419 Feed-through for refilling line 500 Temperature sensor 501 Heating 502 Heat dissipation 503 Power controller 504 Controller 600 Cooling 700 Overpressure 701 Overpressure jet 702 Underpressure 800 Flow, horizontal 801 Flow, vertical 802 Air nozzles 900 Contact block 901 Cooling fluid 902 Cooling line* 903 Cooling pipe 1000 Contact block 1001 Massive heat conductors 1002 Peltier element 1003 Pumped-off heat 1004 Electrical contacting 1100 Steam 1102 Fluid 1101 Steam guidance 1200 Print head partition 1201 Coater partition 1300 Rotatable print head partition 1301 Rotatable coater partition 1400 Movable print head partition 1401 Movable coater partition 1500 Air nozzles for build space flow 1501 Air nozzle for print head flow 1502 Air nozzle for coater flow 1503 Print head flow 1504 Coater flow 1505 Build space flow 1800 Build space edge 1801 Cooling air for build space edge 2000 Additional lamps