Abstract
A method of additively manufacturing parts by selectively cooling a liquefied thermoplastic material.
Claims
1. A method for manufacturing a thermoplastic article, comprising: a) heating a layer of liquid thermoplastic material in a build tray having a base that contains or is in contact with an array of heat exchange elements each of which are configured to independently heat or cool a respective area of the build tray; b) cooling a platen to at or below a solidification temperature of the thermoplastic material and placing the cooled platen on a top surface of the layer of liquid thermoplastic material in the build tray creating a liquid interface between both the array of heat exchange elements and the cooled platen; c) causing the array of heat exchange elements to cool areas of the build tray corresponding to locations where the thermoplastic article is to be formed, causing the liquid thermoplastic material to cool and solidify in selected areas to create a first layer of the thermoplastic article adhered to a bottom surface of the cooled platen; d) causing the array of heat exchange elements to liquefy a bottom portion of said cooled and solidified first layer of thermoplastic material sufficient to allow release of said cooled and solidified first layer of the thermoplastic article from the build tray as the cooled platen is raised; e) refilling the build tray with a new layer of liquid thermoplastic material; f) lowering the cooled platen, together with prior cooled and solidified layers of the thermoplastic article, so that a bottommost surface of the prior cooled and solidified layers of the thermoplastic article is in contact with a top surface of the new layer of liquid thermoplastic material; g) causing the array of heat exchange elements to cool areas of the build tray corresponding to locations where a subsequent layer of the thermoplastic article is to be formed, causing the liquid thermoplastic material to cool and solidify in selected areas to create said subsequent layer of the thermoplastic article, adhered to the bottom surface of the prior cooled and solidified layers of the thermoplastic article adhered to the cooled platen; h) causing the array of heat exchange elements to liquefy a bottom portion of said cooled and solidified subsequent layer of thermoplastic material sufficient to allow release of said cooled and solidified subsequent layer of the thermoplastic article from the build tray as the cooled platen is raised; repeating steps e) through h) as necessary until a complete thermoplastic article is formed.
Description
DESCRIPTION OF THE DRAWINGS
(1) The subsequent description of the preferred embodiments of the present invention refers to the attached drawings, wherein:
(2) FIG. 1 shows a plan view of an apparatus according to an embodiment of the invention.
(3) FIG. 2a shows a cross-sectional view of the apparatus shown in FIG. 1.
(4) FIG. 2b is a representation of a coating process according to an embodiment of the invention in which the build tray is filled with a volume of liquid thermoplastic.
(5) FIG. 3 shows a cross-sectional view of the apparatus shown in FIGS. 1 and 2, with a build tray filled with a film of liquefied thermoplastic.
(6) FIG. 4 shows a cross-sectional view of the apparatus of FIGS. 1-3, with portions of the thermoplastic cooled and solidified forming a first layer of the part.
(7) FIG. 5a shows a cross-sectional view of the apparatus of FIGS. 1-4 with a thin layer of liquefied thermoplastic at the bottom of the tray, allowing for the releasing of the first solidified layer of the part from the build tray as the platen is lifted upwards.
(8) FIG. 5b is a representation of a re-coating process according to an embodiment of the invention in which the build tray is refilled with a volume of thermoplastic.
(9) FIG. 6 shows a cross-sectional view of the apparatus of FIGS. 1-5, with the platen raised an additional amount, still holding the first layer of the part, and the build tray re-filled with another volume of liquid thermoplastic for formation of a subsequent layer of the part.
(10) FIG. 7 shows a cross-sectional view of the apparatus of FIGS. 1-6 with portions of the second volume of liquid thermoplastic in the build tray being cooled and solidified to create a second layer of the part.
(11) FIG. 8 shows a cross-sectional view of the apparatus of FIGS. 1-7, with a thin layer of liquefied thermoplastic at the bottom of the tray, allowing for the releasing of the second solidified layer of the part from the build tray as the platen is lifted upwards, the top of the second layer adhered to the bottom of the first layer.
(12) FIG. 9 shows a cross-sectional view of the apparatus of FIGS. 1-8, with the build tray filled with a third volume of liquefied thermoplastic being selectively cooled to create a third layer of the part.
DETAILED DESCRIPTION OF THE INVENTION
(13) FIGS. 1 and 2a show plan and cross sectional area views of an apparatus according to an embodiment of the invention, in which platen 1 is arranged over a build tray 2 having a base that contains or is in contact with an array of Peltier-type hot/cold junctions 3a-3n. Build tray 2 also contains a heat sink 2a that transfers heat to and from Peltier junctions 3a-3n via fan 2d. Heated re-coater body 2c holds a supply of liquefied thermoplastic 2b. Platen 1 and may be raised and lowered over the build tray according to various steps in the invention.
(14) FIG. 2b shows the re-coating process as re-coater body 2c translates across the build tray 2 to deposit liquefied thermoplastic 2b in the form of a thin film 4 onto the build tray 2. Heat sink and fan are not shown for simplification.
(15) Referring to FIG. 3, a first step in a method according to the invention, after the build tray filled with a film of liquefied thermoplastic in FIG. 2b. Re-coater is not shown for simplification. Platen 1 is adjusted so that its bottom surface is in contact with a top surface of the thermoplastic film 4. Thermoplastic film 4 is heated uniformly by Peltier-type hot/cold junctions 3a-3f. Platen 1 is cooled at or below the solidification temperature of the thermoplastic.
(16) In a next step, represented in FIG. 4, portions of thermoplastic film 4 continue to be heated to its liquid state by Peltier-type hot/cold junctions 3d-3f while other portions of thermoplastic film 4 are selectively cooled below its solid state by Peltier-type hot cold junctions 3a-3c. Solid zones 5a-5c created thereby become the first layer of the part to be additively manufactured. Platen 1 continues to be cooled at or below the solidification temperature of the thermoplastic.
(17) Once the first layer of the part to be manufactured has solidified, the entire heating/cooling element matrix is energized to heat the thermoplastic material to create a thin liquid zone between the solidified first layer and the bottom of the build tray to allow the first layer to be separated from the build tray as the cooled platen 1 is lifted upwards. More specifically, thermoplastic film 4 is continues to be heated to its liquid state by Peltier-type hot/cold junctions 3d-3f Thermoplastic film 4 is selectively heated above its liquid state by Peltier-type hot cold junctions 3a-3c to create thin liquid zones 6a-6c. At this point platen 1 begins to lift solid zones 5a-5c out of the liquid in the tray 4. Platen 1 continues to be cooled at or below the solidification temperature of the thermoplastic.
(18) FIG. 5b shows a re-coating step as in FIG. 2b that occurs between every layer to refill the build tray as thermoplastic material is consumed by the object being printed. Platen 1 is raised to clear the Re-coater body 2b. Re-coater body 2b translates across build tray 2 to deposit liquefied thermoplastic 2c in the form of a thin film 4 onto the build tray 2 to replace liquid depleted by removing solidified zones 5a-5c.
(19) In a subsequent step, represented by FIG. 6, platen 1 lowers solid zones 5a-5c to the surface of the liquid in the tray 4, and intermediate zones 5ab and 5bc solidify between solid zones 5a-5c to complete the first layer of the part as platen 1 continues to be cooled at or below the solidification temperature of the thermoplastic. Thermoplastic film 4 continues to be heated to its liquid state by Peltier-type hot/cold junctions 3a-3f.
(20) The process is then repeated, as represented by FIG. 7. Various heating/cooling elements in the matrix are energized to cool the thermoplastic liquid, and others are energized to heat the thermoplastic liquid, according to the build pattern of the part being manufactured to create a second layer of the part in the same way that the first layer was created (FIG. 4).
(21) Once the second/subsequent layer of the part is formed/solidified, all of the heating/cooling elements of the matrix are caused to heat the thermoplastic material in the build tray to create a thin layer between the bottom of the second/subsequent layer and the build tray so that the platen can be lifted together with the solidified portions of the part to make room for yet another layer in the same way that the first layer was separated from the build tray (FIG. 5). Whereas elements 3a, 3b and 3c were cooling in FIG. 7, they are switched to heating sufficient to create thin liquid zones 6d, 6e and 6f (FIG. 8) so that the platen can lift the part away from the build tray to make room for refilling of the tray and creation of yet another layer (see FIG. 9). Re-coating occurs to replace thermoplastic liquid 4 that was depleted by removing solidified zones 6a-6c.
(22) The process continues until the part has as many layers as required and may take place in any orientation, with or without the force of gravity.
