Abstract
The invention is directed to a casting process to make a metal 3D product by performing the following steps, (a) providing a form negative mould of the 3D product comprising of a plastic sheet which sheet defines at its inner side a hollow space corresponding with at least the shape of one or more of the 3D products by thermoforming using a master mould, (b) applying a layer of refractory material on the exterior of the plastic sheet of the mould to obtain a ceramic mould having a hollow space, (c) pouring molten metal into the hollow space of the ceramic mould and allowing the metal to solidify, and. (d) removing the layer of refractory material to obtain the metal 3D product.
Claims
1. Casting process to make a metal 3D product by performing the following steps (a) providing a form negative mould of the 3D product comprising of a plastic sheet which sheet defines at its inner side a hollow space corresponding with at least the shape of one or more of the 3D products, by thermoforming using a master mould, (b) applying a layer of refractory material on the exterior of the plastic sheet of the mould to obtain a ceramic mould having a hollow space, (c) pouring molten metal into the hollow space of the ceramic mould and allowing the metal to solidify, and (d) removing the layer of refractory material to obtain the metal 3D product, wherein the plastic sheet is a formed plastic sheet as obtained by thermoforming using a thermoforming packaging machine in a continuous process.
2. Process according to claim 1, wherein the plastic sheet further defines a gating system.
3. Process according to claim 1, wherein the mould is comprised of two formed plastic sheets or the mould is comprised of one formed plastic sheet and one planar sheet.
4. Process according to claim 3, wherein the thermoforming packaging machine comprises of one or two thermoforming stations, a sealing station and a cutting station and wherein the in a thermoforming station a formed intermediate sheet is obtained, wherein in the sealing station this formed intermediate sheet is combined with a planar sheet or with another formed intermediate sheet obtained in the optional second thermoforming station to obtained connected form negative moulds of the 3D product and wherein in the cutting station the form negative moulds of the 3D product are cut from the connected form negative moulds of the 3D product.
5. Process according to claim 1, wherein the master mould is obtained by 3D printing.
6. Process according to claim 1, wherein the plastic is a thermoplastic polymer.
7. Process according to claim 6, wherein the plastic is polystyrene.
8. Process according to claim 1, wherein the form negative mould of the 3D product is removed from the ceramic mould after performing step (b) by dissolving the plastic sheet in a solvent.
9. Process according to claim 1, wherein the form negative mould of the 3D product is removed from the ceramic mould after performing step (b) in a subsequent burnout step wherein the temperature is raised to between 850 and 1100 C.
Description
BRIEF DESCRIPTION OF THE DRAWING FIGURES
(1) FIG. 1 shows a thermoforming packaging apparatus according to an example embodiment.
(2) FIG. 2 shows a form negative mould of a 3D product according to an example embodiment.
(3) FIG. 3 shows the view AA of FIG. 2.
(4) FIG. 4 shows a form negative mould with a layer of refractory placed in a tub filled with sand.
(5) FIG. 5 shows an intermediate metal 3D product according to an example embodiment.
(6) FIG. 6 shows a final metal 3D product according to an example embodiment.
(7) FIG. 7 shows a thermoforming apparatus according to another example embodiment.
(8) FIG. 8 shows a side view of a transparent form negative mould according to an example embodiment.
(9) FIGS. 9 and 10 show how the formed shell part of FIG. 7 may also be combined with a second formed shell part to obtain a form negative mould of the 3D product.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS
(10) The invention shall be illustrated making use of the FIGS. 1-10. FIG. 1 shows a thermoforming packaging apparatus 1 having two rolls 2 of polystyrene sheet 3. The polystyrene sheets 3 travel in the direction of the arrow 4. At a forming station 5 an upper form negative mould (master mould) 6 of the 3D product forms the sheet 3 into a formed shell part 7,8. At a forming station 5 a lower form negative mould (master mould) 9 of the 3D product forms the sheet 3 into a formed shell part 10, 11.
(11) At a downstream sealing and cutting station (not shown) shell part 8 is sealed to shell part 11 and cut off to obtain a form negative mould 12 of the 3D product as shown in FIG. 2. Subsequently shell part 7 is sealed to shell part 10 and also cut off to obtain a next form negative mould of the 3D product. This is repeated until a desired number of form negative moulds are obtained. The thus obtained form negative mould 12 is made up of a polystyrene sheet 13 and a hollow space 14 at its interior side. The hollow space 14 corresponds with the shape the 3D product 16 to be obtained. Also a gating system 15 is shown and a part 17 where the two sheets 3 are sealed.
(12) FIG. 3 shows the view AA of FIG. 2 where the reference numbers have the same meaning.
(13) FIG. 4 shows form negative mould 12 with a layer of refractory 18 placed in a tub 19 filled with sand 20. Molten metal 21 may be poured into the opening 22 of gating system 15.
(14) After the metal 21 solidifies and the refractory 18 is removed an intermediate metal 3D product 23 is obtained as shown in FIG. 5. After cutting away the metal part 24 as formed in the gating system 15 the final metal 3D product 16 is obtained as shown in FIG. 6.
(15) FIG. 7 shows a thermoforming apparatus 30. In this process a formed shell part is combined with a planar shell part. The process runs in the direction of arrow 29. In this process a formed shell part 31 is obtained by thermoforming a sheet 32 of polystyrene drawn from roll 33 using master mould 6. This process is advantageous because it does not require to manufacture an upper and lower form negative (master) mould of FIG. 1. The formed shell part 31 is combined with a planar polystyrene sheet 38 as drawn from roll 39. At a downstream sealing and cutting station (not shown) shell part 31a is sealed to planar sheet 38 and cut off to obtain a form negative mould. Subsequently shell part 31 is combined with planar sheet 38 and also cut off to obtain a next form negative mould of the 3D product. The form negative moulds may be used as shown in FIGS. 4-6 to make a metal 3D product, i.e. a metal copy of the 3D object 34.
(16) In FIG. 7 a continuous vacuum forming apparatus is illustrated. When only one or a small number of copies of the 3D object is desired one can make the formed shell part 31 on a piece by piece manner using for example a stand-alone vacuum table.
(17) FIG. 8 shows a side view of a transparent form negative mould 40 having a plastic sheet 41 which defines at its inner side a hollow space 42 corresponding with the shape of three 3D products. The sheet 41 also defines a gating system 43 which allows molten metal to flow from opening 44 to all three hollow spaces 42. Such a mould 40 may be prepared by the apparatus of FIG. 1 or FIG. 7.
(18) FIGS. 9 and 10 show how the formed shell part 31 of FIG. 7 may also be combined with a second formed shell part 45 to obtain a form negative mould of the 3D product 46. The inner side of this form negative mould 46 is a hollow space 48 corresponding with the shape of the final 3D product one wishes to obtain by the casting process. Second formed part 45 may be obtained in a continuous thermoforming packaging apparatus of FIG. 1. Also a gating system 48 is shown.
