Method for the treatment of cake resulting from additive manufacturing processes

Abstract

A machine and a method for treating cakes from additive manufacturing processes, wherein the cake contains residual powders and sintered pieces is disclosed. The machine includes a cylindrical vibrating body which is placed in a position above a vibratory finishing or tumbling or vibro-blasting machine and is separated from the vibratory finishing or tumbling or vibro-blasting machine by a remotely operable door and the cylindrical vibrating body obtains its vibration from the machine below. The machine includes means for destructuring the cake in order to obtain the separation of the non-sintered powder from the sintered pieces present in the cake and means for recovering the powder resulting from the destructuring of the cake.

Claims

1. A machine for treating cakes resulting from additive manufacturing processes, wherein said cake contains residual powders and sintered pieces, said machine comprising: a cylindrical vibrating body placed in a superior position with respect to a vibratory finishing, tumbling, or vibro-blasting machine, wherein said cylindrical vibrating body is separated from the vibratory finishing, tumbling, or vibro-blasting machine by a remotely operable hatch and wherein said cylindrical vibrating body is configured to vibrate as a consequence of the vibration of the vibratory finishing, tumbling, or vibro-blasting machine below, wherein said machine includes means for destructuring the cake in order to obtain separation of the unsintered powder from the sintered pieces present in the cake and means for recovering the powder resulting from the destructuring of the cake.

2. A method of treating cake using a machine of claim 1, wherein a cake destructuring step is provided to separate the unsintered powder from the sintered pieces present in the cake, which takes place within the vibrating cylindrical body.

3. The method of claim 2, wherein the step of destructuring the cake occurs by interference of the cake with elastic elements placed at different heights or with different configurations within said vibrating cylindrical body against which said cake is made to collide in such a way that the process of separating the powders of the cake from the pieces is progressively carried out.

4. The method of claim 3, wherein the cake destructuring step is performed by means of groups of nozzles, placed inside said cylindrical vibrating body, said nozzles being configured to inject compressed air against the cake, wherein the jets of compressed air emitted by the groups of nozzles and their activation is adjustable to provide for periods in which the jets are active, alternating with periods in which the jets are not active.

5. The method of claim 4, wherein each group of nozzles is associated with at least one antistatic bulb capable of effectively attenuating the electrostatic charge inside the cylindrical body, to provide cleaning between one change of the treated material and the next.

6. The method of claim 2, further comprising a step of recovering the powder resulting from the cake destructuring step, said step of recovering being performed by means of a vibrating screen, equipped with a separation plane, and configured to separate the powder thereby obtaining a powder of materials to be subsequently recovered and mixed with powders that have not undergone sintering treatments.

7. The method of claim 2, wherein an action of a vibrating screen separation table is assisted by an ultrasonic generator.

8. The method of claim 2, further comprising a step of automatically transferring the sintered pieces to the vibratory finishing, tumbling, or vibro-blasting machine, said step of automatically transferring being performed by means of a pneumatic cylinder-piston assembly which opens a hatch on which said pneumatic cylinder-piston assembly acts to transfer the powder separated sintered pieces to a lower section.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) Further features and advantages of the invention will be apparent from reading the following description provided by way of non limitative example, with the aid of the figures illustrated in the appended tables, wherein:

(2) FIG. 1 shows an axonometric view of a machine for de-structuring cake from additive manufacturing processes, according to an embodiment of the invention;

(3) FIG. 2 shows a further axonometric view of the machine in FIG. 1; and

(4) FIGS. 3-5 show different method steps for de-structuring cake from additive manufacturing processes, according to an embodiment of the present invention.

DETAILED DESCRIPTION OF CERTAIN FORMS OF EMBODIMENT OF THE PRESENT INVENTION

(5) With initial reference to FIG. 1, it shows a side view of a machine for de-structuring cakes resulting from additive manufacturing processes, according to an embodiment of the invention and globally indicated by numerical reference 10.

(6) The machine 10 comprises a cylindrical body 21 equipped with a loading door 22 and an unloading door 26.

(7) A feed table 24 or other means of feeding a cake 20 to be handled by the machine 10 may be placed at the loading door 22.

(8) A grid 30 is also provided in the lower part of the cylindrical body 21. The cylindrical body 21 is in turn mounted on a vibratory finishing or vibro-blasting (vibroblast) machine 100, for example a machine of the type described in the cited Italian patent application IT 10201900007052.

(9) The machine 10 also visible in FIG. 2 is also equipped with a circular vibrating screen for dust selection and recovery 50.

(10) The cylindrical body 21 may be set in vibration by the same means that set the vibratory finishing machine 100 below said cylindrical body 21 in vibration.

(11) The purpose of the machine 10 is to destructure the cakes 20 coming from particular additive manufacturing processes of the SLS, SIM, DMLS, etc. type, where the expression destructure means here to automatically separate the sintered pieces 25 (FIGS. 3, 4, and 5), obtained by additive manufacturing from the non-sintered powders that are in excess on said cake 20 (FIG. 1).

(12) To destructure the cake 20 (FIG. 1), an operator need only place the cake 20 itself on the external platform or feeding table 24 designed to load the machine 10 ergonomically.

(13) After the operator closes the loading door 22, all he has to do is select the recipe corresponding to the loaded item and press a cycle start button on a touch-screen control panel.

(14) From now on, the machine 10 is programmed to perform all subsequent operations in fully automatic mode.

(15) In particular, the de-structuring of cake 20 can be achieved automatically with the help of a method illustrated schematically in FIGS. 3-5.

(16) FIG. 3 illustrates a first phase of the above method, in which the cake 20 has been schematically represented at the top left of said FIG. 3 with the numerical reference 20a, so as to indicate that the pieces 25 to be obtained from the cake 20 are still almost completely covered or enveloped in the powders.

(17) As the process of the invention proceeds, the cake 20 is progressively deconstructed and the pieces 25 become progressively more prominent, as symbolically indicated in the succession of FIGS. 20a, 20b and 20c.

(18) When the machine 10 is set to vibrate, the cake 20 tends to move in an anti-clockwise direction when viewed from above as shown in FIGS. 3, 4 and 5, and progressively encounters elastic 80 and 82 placed at different heights and/or with different configurations against which it is made to collide in such a way that the process of separating the powders of the cake 20 from the pieces 25 is progressively initiated.

(19) In addition to this, groups of nozzles 90 are provided at several points to deliver compressed air against the cake 20, these nozzles being preferably arranged in groups of three.

(20) The compressed air jets emitted by the various nozzle groups 90 and their time sequence can be adjusted via PLC, e.g. by stop-and-go sequences, i.e. periods when the jets are active, alternating with periods when the jets are not active.

(21) The number of nozzle assemblies and their positioning within the cylindrical body 21 depends on the machine model and its capacity.

(22) In some versions of machines, each group of nozzles 90 may be associated with an optional antistatic bulb 91 (or group of antistatic bulbs 91), capable of effectively attenuating the electrostatic charge inside the cylindrical body 21, so as to optimize cleaning between one material change and the next.

(23) The destructuring phase or cycle depends on the machine model and can last for a predefined time T1, generally a few minutes, e.g. 2-3 minutes, or longer in the case of medium-large machines.

(24) As soon as the growth plate or cake 20 is destructured by losing volume, size and part of the sintered components is gradually released, the decomposed mass proceeds, according to the programmed vibration, to the next areas in a counterclockwise direction in a short time, where for a certain period T2, other compressed air nozzles continue the dust removal action (FIG. 4).

(25) When no more dust remains, a hatch 70 over which a pneumatic cylinder-piston unit 72 acts opens for transferring to the lower section of the workpieces 25, or for transferring to the lower section of the workpieces 25 to the vibratory finishing or vibratory blasting (vibroblast) machine 100 below.

(26) In particular, it is noted that the vibratory finishing or vibro-blasting (vibroblast) machine 100 is separated from the machine 10 for de-structuring cakes from additive manufacturing processes of the invention, in order to avoid pollution of the dust to be recovered.

(27) Therefore, as the vibratory finishing or vibratory sandblasting machine (vibroblast) 100 is completely separate from the cake de-structuring machine 10, it can operate with the required action on the workpieces 25.

(28) In any case, even the drive of the vibratory finishing machine 100 and its timing and processing programs can be managed by executing recipes stored in the system software and, of course, everything can be managed on the basis of tailor-made programs that the operator can change whenever he wishes.

(29) For example, the cycle can be short (10-15 minutes) if only a little residual dust attached to the parts needs to be removed, or they can continue to be finished without sanding, just with vibratory finishing media, for another 45 minutes, for example to sand and refine the surface finish as required.

(30) The dust that falls from the cake 20 as a result of these destructuring processes on the one hand progressively releases the parts 25, and on the other hand said dust, falling through the grid 30, is conveyed through a pipe 61 into a vibrating screen 60.

(31) In turn, vibrating screen 60 is configured to separate the powder and obtain a first type which is collected in bucket 64. This is a powder of materials such as polyamide or nylon that can be subsequently recovered.

(32) The recovered powders can be mixed with new powders at a later stage, i.e. with powders that have never been subjected to laser sintering processes to recover a part of the material, up to half of the total quantity, so as to reduce the overall costs of the products obtained by SLS, SIM, EVILS etc.

(33) Finally, larger components are recovered in the bucket 68, e.g. in the form of granules, abnormally agglomerated dust clusters and the like, which were left on the grid 30 because they were too large to fall through.

(34) In some embodiments, the separation table or screen mesh of the vibrating screen 60 can be assisted by ultrasound 66 which makes the process very efficient and reduces maintenance and screen cleaning intervals almost to zero.

(35) In embodiments where antistatic bulbs 91 were already present, in synergy with ultrasound 66, a very high level of efficiency in the recovery of polymeric additive powders would be achieved.

(36) Obviously, modifications or improvements may be made to the invention as described, dictated by contingent or particular motives, without going beyond the scope of the invention as claimed below.