Method for the treatment of residual thermoplastic powders

Abstract

A method for the treatment of residual thermoplastic powder from an additive manufacturing process includes, in one step of the process, a powder that includes the residual powder is provided and compressed into granules as raw material for a primary shaping process. A pressing apparatus with two roller elements rotating in opposite directions and having lateral surfaces adjacent to one another in a pressing area is used to compress the powder into the granules. The lateral surfaces each having a plurality of molding elements assigned to one another in pairs such that the powder is compressed into granules in the pressing area. A cam mechanism positioned within one of the roller elements and configured to deflect the plurality of molding elements radially as a function of an angle of rotation of the roller element can be included.

Claims

1. A method for treatment of residual thermoplastic powder from an additive manufacturing process, the method comprising: providing a powder that consists of a residual thermoplastic powder; and compressing the powder into granules as raw material for a primary shaping process.

2. The method according to claim 1, wherein the residual thermoplastic powder is kept in a solid state during compressing of the powder.

3. The method according to claim 1, wherein the residual thermoplastic powder is provided from a selective laser sintering process.

4. The method according to claim 1 further comprising using the granules as raw material for an injection-molding process.

5. The method according to claim 1 further comprising separating a portion of bulk residual thermoplastic powder that is reusable in the additive manufacturing process from the residual thermoplastic powder included in the powder before compressing the powder into granules using a first separating operation.

6. The method according to claim 5 further comprising separating non-compressed powder from the granules using a second separating operation.

7. The method according to claim 6 further comprising compressing the non-compressed powder into granules.

8. The method according to claim 1, wherein the powder is compressed into the granules with a pressing apparatus comprising two roller elements rotating in opposite directions and having lateral surfaces adjacent to one another in a pressing area, the lateral surfaces each having a plurality of molding elements assigned to one another in pairs such that powder is compressed into granules in the pressing area.

9. The method according to claim 8, wherein the two roller elements are drivable in opposite directions.

10. The method according to claim 9, wherein the pressing apparatus comprises a cam mechanism configured to deflect the plurality of molding elements of one of the two roller elements radially as a function of an angle of rotation of the one of the two roller elements and the powder is compressed into the granules by the plurality of molding elements assigned to one another in pairs.

11. The method according to claim 10, wherein the powder is compressed into the granules by the radial deflection of the plurality of molding elements of the one of the two roller elements.

12. The method according to claim 10 further comprising deflecting the plurality of molding elements of the one of the two roller elements radially outward in the pressing area using the cam mechanism such that the powder is compressed by the plurality of molding elements of the one of the two roller elements.

13. The method according to claim 10, wherein the two roller elements comprise a first roller element and a second roller element, and the cam mechanism has a cam element that is off-center with respect to a first axis of rotation of the first roller element and is arranged within the first roller element, wherein the plurality of molding elements of the first roller element are radially deflected by the cam element.

14. The method according to claim 13, wherein the first roller element has guide channels that extend radially inward with respect to the lateral surface of the first roller element and the plurality of molding elements of the first roller element are guided within the guide channels.

15. A method for treatment of a residual thermoplastic powder from an additive manufacturing process, the method comprising: feeding a powder to a pressing area of an apparatus, wherein the powder consists of the residual thermoplastic powder and the apparatus comprises: two roller elements, wherein the two roller elements are drivable in opposite directions and have lateral surfaces adjacent to one another in the pressing area, the lateral surfaces each having a plurality of molding elements assigned to one another in pairs; and a cam mechanism configured to deflect the plurality of molding elements of one of the two roller elements radially as a function of an angle of rotation of the one of the two roller elements; and rotating the two roller elements in opposite directions such that the powder fed into the pressing area is compressed in granules by the plurality of molding elements assigned to one another in pairs.

16. The method according to claim 15 further comprising deflecting the plurality of molding elements of one of the two roller elements radially outward in the pressing area using the cam mechanism such that the powder is compressed by the plurality of molding elements of the one of the two roller elements.

17. The method according to claim 15, wherein the two roller elements comprise a first roller element and a second roller element, and the cam mechanism has a cam element arranged within the first roller element and arranged off-center with respect to a first axis of rotation of the first roller element, wherein the plurality of molding elements of the first roller element are radially deflected by the cam element.

18. The method according to claim 15 further comprising deflecting the plurality of molding elements of the first roller element radially outward after leaving the pressing area using the cam mechanism such that the granules are ejected from the first roller element.

Description

DRAWINGS

(1) In order that the disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings, in which:

(2) FIG. 1 shows a block diagram of a process according to the teachings of the present disclosure;

(3) FIG. 2 shows a schematic illustration of a device that can be used in the process according to the teachings of the present disclosure; and

(4) FIG. 3 shows an enlarged detail view of FIG. 2.

(5) In the different figures, identical parts are always provided with the same reference signs, for which reason these parts are generally also described only once.

DETAILED DESCRIPTION

(6) The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

(7) FIG. 1 shows a block diagram of a process according to one form of the present disclosure. For example, a workpiece (not shown) is manufactured by selective laser sintering (SLS) in an SLS plant 1. To this end, a thermoplastic powder is used, which may be for example a polyamide filled with glass fibers. Residual powder R that remains after manufacture (i.e., a bulk residual powder) is fed to a first screen 2, where a share R1 of the residual powder R is separated off that can be reused in SLS and is returned. This first separating operation is optional.

(8) That residual powder R that cannot be reused is fed, together with at least one additive Z (for example a further thermoplastic powder, a pigment, a filler or the like), to a mixer 3, where a powder P is mixed that is used in the further process steps. This process step is likewise optional and the powder P subsequently used can also consist exclusively of residual powder R. Otherwise, the powder P can have for example a weight proportion of at least 95% residual powder R, although other weight proportions are also possible. The powder P is filled into a storage container 12 of a feed apparatus 11, which is part of the apparatus 10 illustrated in FIG. 2. The feed apparatus 11 is arranged above a pressing apparatus 20, which has a first roller element 21 and a second roller element 22. The roller elements 21, 22 are rotatable about a first and second axis of rotation A, B, which extend horizontally and parallel to one another, wherein a drive (not illustrated here) provides synchronous rotation in opposite directions. The feed apparatus 11 feeds the powder P to a pressing area 29 by allowing it to trickle or fall into the pressing area 29 under gravity.

(9) Lateral surfaces 21.1, 22.1 (FIG. 3) of the roller elements 21, 22, respectively, roll in contact with one another in the pressing area 29. The two roller elements 21, 22 have a plurality of molding elements 23, 24 in the region of their lateral surfaces 21.1, 22.1 (FIG. 3). First molding elements 23 of the first roller element 21 are accommodated in a guide frame 25, within which they are displaceable radially with respect to the first axis of rotation A. Each first molding element 23 is in this case arranged in a radially extending guide channel 26 within the guide frame 25, the cross section of which is coordinated with the cross section of the molding element 23. The guide frame 25 also forms the first lateral surface 21.1 (FIG. 3) of the first roller element 21. In each case one first molding element 23 is assigned to a second molding element 24 of the second roller element 22 and cooperates therewith in the pressing area 29 in order to compress powder P into granules G. The second molding elements 24 are arranged in a fixed position on the second roller element 22 and project radially somewhat beyond the second lateral surface 22.1 (FIG. 3) of the second roller element 22.

(10) Arranged within the first roller element 21 is a roller-like cam element 28, which is formed or positioned in an off-center manner with respect to the first axis of rotation A but in a rotationally symmetric manner with respect to a cam axis C parallel to the first axis of rotation A. The cam element 28, which belongs to a cam mechanism 27, cooperates with the first molding elements 23 and deflects the first molding elements 23 radially depending on the angle of rotation of the first roller element 21. In this case, the first molding elements 21 can be preloaded radially inward for example by spring elements that are not illustrated here. During their movement, they therefore follow the external contour 28.1 of the cam element 28. Before and upon reaching the pressing area 29, each particular first molding element 23 is retracted into the guide channel 26.

(11) As can be seen in FIG. 3, the guide channel 26 in the process also receives powder P. During the further rotary movement of the roller elements 21, 22, the respectively assigned second molding element 24 engages in the guide channel 26 and thus closes the guide channel 26 toward or from the outside. The powder P contained in the guide channel 26 is compressed into granules G between the first molding element 23 and the second molding element 24, wherein the pressure desired for this purpose is applied both by the mutual approaching of the molding elements 23, 24 in accordance with the rotary movement of the roller elements 21, 22 and by the first molding element 23 being deflected radially outward by the cam element 28 in the pressing area 29. The compression takes place without active heating up of the powder P. If heating up occurs as a side effect of friction and compression, the heating does not result in melting the powder P and/or the residual powder R.

(12) After leaving the pressing area 29, the first and second molding elements 23, 24 move apart, with the result that the granules G are released. In some variations, the granules G can be released from the guide channel 26 and drop out under gravity during the further rotation of the first roller element 21. In the alternative, or in addition to, the first molding elements 23 are deflected further radially outward by the cam element 28 after the pressing area 29 has been left, with the result that the first molding elements 23 eject the granules G in a dispensing area 30. The granules G drop downward together with non-compressed powder P under gravity to a separating apparatus 31, which has a second screen 32 in the example illustrated. The grains of the granules G are retained by the screen 32 and, on account of the inclined position of the screen 32, pass into a container 33, while the particles of the powder P fall through the screen 32. The particles of the powder P are guided back to the storage container 12 by a return apparatus 40 and are subsequently compressed into granules G. The return apparatus 40 is illustrated only schematically here and can have for example a system of pipes in which the powder P is sucked to the storage container 12 by a negative pressure.

(13) The finished granules G can subsequently be used as raw material for various primary shaping processes in plastics processing. In the example in FIG. 1, they are used in an injection-molding apparatus 4.

LIST OF REFERENCE SIGNS

(14) 1 SLS plant 2, 32 Screen 3 Mixer 4 Injection-molding apparatus 10 Apparatus 11 Feed apparatus 12 Storage container 20 Pressing apparatus 21, 22 Roller element 21.1, 22.1 Lateral surfaces 23, 24 Molding element 25 Guide frame 26 Guide channel 27 Cam mechanism 28 Cam element 28.1 External contour 29 Pressing area 30 Dispensing area 31 Separating apparatus 33 Container 40 Return apparatus A, B Axis of rotation C Cam axis G Granules P Powder R Residual powder R1 Share Z Additive

(15) Unless otherwise expressly indicated herein, all numerical values indicating mechanical/thermal properties, compositional percentages, dimensions and/or tolerances, or other characteristics are to be understood as modified by the word “about” or “approximately” in describing the scope of the present disclosure. This modification is desired for various reasons including industrial practice, material, manufacturing, and assembly tolerances, and testing capability.

(16) Although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections, should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer and/or section, from another element, component, region, layer and/or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section, could be termed a second element, component, region, layer or section without departing from the teachings of the example forms. Furthermore, an element, component, region, layer or section may be termed a “second” element, component, region, layer or section, without the need for an element, component, region, layer or section termed a “first” element, component, region, layer or section.

(17) Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above or below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

(18) As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A OR B OR C), using a non-exclusive logical OR, and should not be construed to mean “at least one of A, at least one of B, and at least one of C.”

(19) The description of the disclosure is merely exemplary in nature and, thus, variations that do not depart from the substance of the disclosure are intended to be within the scope of the disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the disclosure.