ADDITIVE MANUFACTURING PROCESS WITH CONVEYED GOODS CONVEYANCE BY MEANS OF POSITIVE PRESSURE

Abstract

Conveyed goods of grains are fed from a pressure vessel into a conveyor line at a feed point for conveyance to a discharge point for supply to an extrusion head. The goods are plasticized in the extrusion head and extruded in a punctiform manner via a nozzle of the extrusion head. The extrusion head is moved dynamically by a manipulator during extrusion of the plasticized goods. Conveyor gas is force into the conveyor line by a gas compressor and allowed to escape the conveyor line at a separation point in a region of the discharge point. A gas positive pressure is temporarily applied by the gas compressor to the pressure vessel as the goods are fed from the pressure vessel into the conveyor line while bypassing the conveyor line via a first valve and closing a second valve in the conveyor line between the feed point and the gas compressor.

Claims

1.-15. (canceled)

16. A method for operating a production machine, said method comprising: feeding conveyed goods in the form of grains with an average grain size from a pressure vessel into a conveyor line at a feed point for subsequent discharge of the goods at a discharge point and supply to an extrusion head; plasticizing the conveyed goods in the extrusion head; extruding the conveyed goods in a punctiform manner via a nozzle of the extrusion head, while moving the extrusion head dynamically by a manipulator; forcing a conveyor gas by a gas compressor in a region of the feed point into the conveyor line; allowing the conveyor gas to leak out the conveyor line at a separation point in a region of the discharge point; and temporarily applying by the gas compressor a gas positive pressure to the pressure vessel as the conveyed goods are fed from the pressure vessel into the conveyor line while bypassing the conveyor line via a first valve and closing a second valve in the conveyor line between the feed point and the gas compressor,

17. The method of claim 16, wherein the discharge point forms a last part of the conveyor line and is designed as a hose which is permeable to the conveyor gas.

18. The method of claim 16, wherein a dense phase conveying takes place in the conveyor line, in particular a plug conveying,

19. The method of claim 16, wherein a ratio between a conveyed mass of conveyed goods and a conveyed mass of conveyor gas is 100:1 or above.

20. The method of claim 16, wherein the gas positive pressure is above 1 bar.

21. The method of claim 16, wherein the average grain size is at least 0.5 mm.

22. The method of claim 16, wherein the grains are spherical,

23. The method of claim 16, wherein the average grain size has a statistical variance of 20% maximum.

24. The method of claim 16, further comprising: detecting by a sensor a conveying state in the conveyor line; comparing by a control device the conveying state with a target conveying state; and controlling by the control device a feeding of the conveyed goods into the conveyor line and/or a conveying of the conveyed goods in the conveyor line.

25. A production machine, comprising: a pressure vessel containing conveyed goods in the form of grains with an average grain size; a manipulator; an extrusion head configured for plasticizing the conveyed goods and including a nozzle for extruding plasticized conveyed goods, said extrusion head being arranged on the manipulator for dynamic movement during extrusion of the plasticized conveyed goods; a conveyor line including a feed point for receiving conveyed goods from the pressure vessel for subsequent conveyance and discharge of the conveyed goods at a discharge point to the extrusion head; a gas compressor connected to the conveyor line to force a conveyor gas into the conveyor line hi a region of the feed point, with the conveyor gas being allowed to leak out the conveyor line at a separation point in a region of the discharge point, said gas compressor being connected to the pressure vessel; a first valve allowing conveyor gas to flow from the gas compressor to the pressure vessel while bypassing the conveyor line so as to temporarily apply a gas positive pressure to the pressure vessel, as the conveyed goods is fed into the conveyor line and the first valve is open; and a second valve configured to control a flow of conveyor gas from the gas compressor to the conveyor line, said second valve being dosed, when the gas positive pressure is temporarily applied to the pressure vessel.

26. The production machine of claim 25, wherein the discharge point forms a last part of the conveyor line and is designed as a hose which is permeable to the conveyor gas.

27. The production machine of claim 25, wherein in the conveyor line a dense phase conveying, in particular plug conveying, is performed.

28. The production machine of claim 25, wherein a ratio between a conveyed mass of conveyed goods and a conveyed mass of conveyor gas is adjustable at 100:1 or above.

29. The production machine of claim 25, wherein the gas positive pressure is above 1 bar.

30. The production machine of claim 25, further comprising: a sensor configured to detect a conveying state in the conveyor one; and a control device configured to compare the conveying state with a target conveying state and to control a feeding of the conveyed goods into the conveyor line and/or conveyance of the conveyed goods in the conveyor line in response to the comparison between the conveying state with a target conveying state.

Description

[0043] The properties, features and advantages of this invention described above and the manner in which these are achieved will become dearer and more readily comprehensible in connection with the following description of the exemplary embodiments which are explained in more detail in connection with the drawings. In a schematic representation, the drawings show in:

[0044] FIG. 1 a production machine,

[0045] FIG. 2 a time diagram,

[0046] FIG. 3 an end section of a conveyor one,

[0047] FIG. 4 a section of a conveyor line,

[0048] FIG. 5 a grain of conveyed goods,

[0049] FIG. 6 a statistical evaluation of a grain size,

[0050] FIG. 7 a statistical evaluation of an average grain size and

[0051] FIG. 8 a control structure.

[0052] According to FIG. 1, a production machine for additive manufacturefor example the so-called FDM methodhas an extrusion head 1. The extrusion head 1 is arranged on a manipulator 2 of the production machine. The manipulator 2 can be movedcontrolled by an automation device 3in automated fashion. With the movement of the manipulator 2, the extrusion head 1 is also moved at the same time. The manipulator 2 is moved in at least three translational directions. This is indicated in FIG. 1 by three straight double arrows. Often a swiveling of the manipulator 2 (and with it, of the extrusion head 1) by up to three rotational orientations is also possible. This is indicated in FIG. 1 by three curved double arrows.

[0053] In the framework of the operation of the production machine, initially a pressure vessel 4, for example an autoclave, is filled from a reservoir 5, for example a silo, with a conveyed material 6. As a rule, the pressure vessel 4 is arranged in a fixed position. As a rule, the conveyed goods 6 are a plastic material. Alternatively, in individual cases it can be a metal. The conveyed goods 6 consist of a plurality of grains 7. After filling the pressure vessel 4, the pressure vessel 4 and the reservoir 5 are shut off. Furthermore, a positive pressure p is applied to the pressure vessel 4. The pressurization of the pressure vessel 4 with the positive pressure p takes place via a gas compressor 8 of the production machine which applies positive pressure p to a conveyor gas 9. As a rule, positive pressure p is above 1 bar, for example, between 1.5 bar and 10 bar. As a rule, the conveyor gas 9 is air. However, it may alternatively be another gas, for example a protective gas. The gas compressor 8 should have as steep a characteristic curve as possible (high increase in the pressure loss as a function of the velocity of the conveyed gas 9 emerging from the gas compressor 8). For example, the gas compressor 8 can be designed as a rotary blower or as a de Laval nozzle fed from a conventional compressed air network,

[0054] The conveyed goods 6 are fed from the pressure vessel 4 into a conveyor line 11 of the production machine at a feed point 10. The feed point 10 is located in the vicinity of the pressure vessel 4. The feeding of the conveyed goods 6 into the conveyor line 11 takes place in that the positive pressure p is temporarily applied to the conveyed goods 6see FIG. 2 in additionby the gas compressor 8 via a first valve 12 while bypassing the conveyor line 11 during first periods T1. During second periods T2 complementary thereto, in this case the positive pressure p is not applied to the pressure vessel 4. The gas compressor 8 is connected to the pressure vessel 4 in order to apply the positive pressure p to the pressure vessel 4 via the first valve 12, while bypassing the conveyor line 11. To apply the positive pressure p, the first valve 12 is temporarily opened, for the remainder of the time it is kept closed. The control of the first valve 12 is likewise carried out by the automation device 3.

[0055] From the feed point 9, the conveyed goods 6 are fed via the conveyor line 10 to a discharge point 13. For this purpose, the conveyor gas 9 can be compressed into the conveyor line 11 by means of the gas compressor 8 in the region of the feed point 10. At the discharge point 13, the conveyed goods 6 are discharged out of the conveyor line 11 and supplied to the extrusion head 1. Before feeding and supplying, however, the conveyor gas 9 leaks out of the conveyor line 11 at a separation point 14. As a result, the conveyed goods 6 are fed to the extrusion head 1 virtually free of conveyor gas 9. The leaking takes place automatically because of the positive pressure p. Active suction of the conveyed gas 9 is not necessary,

[0056] The separation point 14 can, for example, in accordance with the representation in FIG. 3, form the last part of the conveyor line 11 and be designed as a hose which is permeable to the conveyor gas 9. Alternatively, the separation point 14 can, for example, be designed as a membrane with a suitable permeability. Regardless of its structural design, however, the separation point 14 is designed in such a way that on the one hand it only permits the passage of the conveyor gas 9 but not also the grains 7 of the conveyed goods 6, while on the other hand, only offering the lowest possible flow resistance to the conveyor gas 9.

[0057] Depending on the embodiment of the production machine and arrangement of its individual components, the conveyor line 11 can be relatively short in individual cases (length of only a few meters). It is also possible, however, for the conveyor line 11 to be of a considerable length, for example several 100 m or even more than 1000 m.

[0058] In accordance with the representation in FIG. 1, a second valve 15 is arranged between the gas compressor 8 and the conveyor line 11. As a result, the gas compressor 8 is connected to the conveyor line 11 via the second valve 15. The second valve 15 is controlled by the automation device 3. The control can take place in particular in accordance with the representation shown in FIG. 2 in such a way that the second valve 15 is opened during third time periods T3 and is closed during complementary fourth periods T4. In accordance with the representation in FIG. 2, in this case the actuation of the first and second valve 12, 15 takes place essentially in a push-pull manner. In particular, during the application of the positive pressure p to the pressure vessel 4, the second valve 15 is thus closed. Actuation in push-pull need not correspond directly 1:1 with each other. It may be sufficient for some overlap to exist.

[0059] The conveyed goods 6 are plasticized in the extrusion head 1. For example, they can be melted by means of a heating device (not shown). The extrusion head 1 also has a nozzle 16. After plasticization, the conveyed goods 6 (which now no longer comprise grains 7 but are a plasticized mass) are extruded via the nozzle 16 in a punctiform manner. The plasticized mass is applied to a substrate 17 (which may in principle be of any nature). During the extrusion of the plasticized conveyed goods 6 (or the plasticized mass), the extrusion head 1 is moved dynamically by means of the manipulator 2. As a result, the desired structure is built up gradually. Due to the dynamic method of the extrusion head 1, even during the conveying of the conveyed goods 6, the conveyor line 11 is designed as a flexible hose at least in certain sections. Alternatively, or in addition, an embodiment may be possible with pipe sections which are connected to one another by means of joints.

[0060] In accordance with the representation in FIG. 4, dense phase conveying, in particular, plug conveying, is preferably carried out in the conveyor line 11. Loading can be 100:1 or above. If a different type of operation is desired in individual cases, however, this can easily be setincluding in an automated manner,

[0061] In accordance with the representation in FIG. 5, the grains 7 of the conveyed goods 6 are preferably in the shape of a sphere. They havesee also FIG. 6an average grain size d0 of at least 0.5 mm. Within the respective grain 7, however, slight fluctuations of the grain size d are possible as a function of the orientation under which the grain size d is determined. As a rule, fluctuation is at most within the limits of 10%. Furthermore, from grain 7 to grain 7, the grains 7 display the most uniform possible average grain size d0. In particular, seen across a sufficiently large plurality of grains 7, the statistical variance of the average grain size d0 should be 20% maximum in accordance with the representation in FIG. 7, These embodiments facilitate the setting of a stable conveying state.

[0062] In accordance with the representation in FIG. 8, a conveying state F of the conveyor line 11 is preferably detected by means of the at least one sensor 18 (for example, a pressure sensor).

[0063] The conveying state F is supplied to a control device 19. The control device 19 can, for example, be realized as a software block within the automation device 3. In the control device 19, the conveying state F is compared to a target conveying state P. Depending on the comparison, the feeding of the conveyed goods 6 into the conveyor line 11 and/or the conveying of the conveyed goods 6 in the conveyor line 11 is regulated by the control device 19.

[0064] For example, the control device 19 can vary the periods at which feeding takes placethat is to say, the total of the periods T1 and T2. Variation can take place alternatively with or without variation of the ratio of the periods T1 and T2 in relation to one another. To the extent necessary and appropriate, the control device 19 can alternatively or in addition also vary the periods T3 and T4. Alternatively, or in addition, it is possible in addition to inject conveyor gas 9 into the conveyor line 11 at predetermined points. A gas line 20 is preferably laid parallel to the conveyor line 11 for this purpose. Only conveyor gas 9 is conveyed in the gas line 20, but not conveyed goods 6. The gas line 20 and the conveyor line 11 are connected to one another at predetermined points via valves 21. The additional conveyed gas 9 is injected by means of corresponding actuation of the valves 21 by the control device 19. Alternatively, or in addition, it is possible to vary the positive pressure p by means of appropriate actuation of the gas compressor 8.

[0065] If, in the context of the embodiments explained above the conveyed goods 6 are completely fed out of the pressure vessel 4 into the conveyor line 11 and conveyed to the extrusion head 1, the conveying of the conveyed goods 6 is briefly interrupted. After the positive pressure p has been reduced, the pressure vessel 4 is opened, refilled from the reservoir 5 and dosed again. Conveying of the conveyed goods 6 is then recommenced. Alternatively, it is possible to provide several pressure vessels 4 which can be connected in parallel or in series. By means of these embodiments it is possible to carry out conveying of the conveyed goods 6 almost continuously.

[0066] In summary, the present invention thus relates to the following facts:

[0067] Conveyed goods 6 consisting of grains 7 are fed from a pressure vessel 4 into a conveyor line 11 at a feed point 10, conveyed from there to a discharge point 13 via the conveyor line 11, discharged out of the conveyor line 11 and supplied to an extrusion head 1. The conveyed goods 6 are plasticized in the extrusion head 1 and then extruded in a punctiform manner via a nozzle 16 of the extrusion head 1. The extrusion head 1 is moved dynamically by means of a manipulator 2 during the extrusion of the plasticized conveyed goods 6. A conveyor gas 9 is compressed into the conveyor line 11 in the region of the feed point 10 by means of a gas compressor 8. It leaks out of the conveyor line 11 at a separation point 14 in the region of the discharge point 13.

[0068] The present invention has many advantages. By conveying the conveyed goods 6 through the conveyor line 11 by means of compression (as opposed to suction), simple conveying of the conveyed material 6 is made possible without adversely affecting the operation of the extrusion head 1 (in particular its dynamic positioning including the static and/or dynamic positioning accuracy). As a result of dense phase conveying, energy-efficient, low-wear operation of the conveyor line is obtained. This applies, in particular, in the case of plug conveying. Very high loads (as a rule, of at least 100:1, in extreme cases up to 400:1) can be conveyed over long conveyor lines (in some cases up to several km). In particular, in an application in a printer park with a plurality of production machines, longer conveyor lines 11 can be used as a result which are fed with conveyed goods 6, for example, from a common pressure vessel 4. Under certain circumstances, additional treatments of the conveyed goods 6 can take place within the conveying section, for example drying or preheating. It may even be possible to feed different conveyed goods 6 from a plurality of pressure vessels 4 sequentially into the conveyor line 11 in a controlled manner and thereby supply the extrusion head 1 with a premixed mixture of conveyed goods 6 which need only be melted in the extrusion head 1 but need no longer be further mixed.