Abstract
A moulded part (1) for a mould (100). The moulded part (1) comprises at least one shell (11) for casting a product. A flange (12) is arranged on a frame of the moulded part (1) for sealing against abutment a sealing surface (13). The shell (11) has a first permeability for a fluid and the flange (12) has a second permeability for the fluid. The second permeability is less than the first permeability.
Claims
1. A molded part for a casting mold, comprising at least one shell for casting a product, wherein a flange for sealingly abutting a sealing surface is arranged on an edge of the shell, and the shell has a first permeability to a fluid and the flange has a second permeability to the fluid which is less than the first permeability, wherein permeability is defined as the volume of a fluid which can be passed through a solid per hour, per square decimeter and per pressure: I/(h*dm.sup.2*bar), and wherein the permeability of the shell is at least 10 I/(h*dm.sup.2*bar) and the permeability of the flange is maximum 1 I/(h*dm.sup.2*bar).
2. The molded part according to claim 1, wherein the flange is cast onto the shell.
3. The molded part according to claim 1, wherein the molded part and the flange consist essentially of the same material.
4. The molded part according to claim 1, comprising a circumferential sealing, and the sealing being arranged in or on the flange.
5. The molded part according to claim 4, wherein the flange has a recess into which the sealing is inserted.
6. The molded part according to claim 5, wherein the recess has an undercut.
7. The molded part according to claim 1, wherein the molded part is constructed in several parts and has an inner and an outer layer.
8. A casting mold comprising at least one molded part according to claim 1.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The invention is explained by way of example with reference to the following figures. Show it:
(2) FIG. 1: a cross-section through a casting mold
(3) FIG. 2: a top view of the casting mold according to FIG. 1.
(4) FIG. 3a to FIG. 3m: Process steps for producing a a molded part and a blank
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
(5) FIG. 1 shows a cross-section through a casting mold 100, which has two molded parts 1a and 1b, which are arranged on top of each other in the concrete design example. A sealing 14 is arranged in the molded part 1a at the top in the present figure. The sealing 14 is located in a flange 12 of molded part 1a. Molded part 1a also has a shell 11, which is connected to flange 12. The second molded part 1b is designed in the same way as the first molded part 1a, with the difference that the second molded part 1b has no sealing. Therefore, only the structure of one of the molded parts 1a or 1b is explained below. As mentioned above, molded part 1a has a shell 11 and a flange 12, with a sealing 14 in flange 12. In the shell 12 there are drainage channels 15, which are connected to a drainage channel end 151. The drainage channel end 151 is also designed as coupling 16. Inside a mold space between the molded parts 1 there is a blank 3, which later becomes a green compact 31 as soon as the blank has been drained via the drainage channels 15. The shell 12 is porous and has a molded part surface 121 facing the blank 3.
(6) Water can thus diffuse from the blank 3 through the porous shell into the drainage channels 15. It collects in the drainage channels 15 and can then be removed via the coupling 16. To accelerate this process, a negative pressure can be generated at the coupling 16, i.e. at the end of the drainage channel 151.
(7) The drainage channels 15 are star-shaped with a center at coupling 16 (see FIG. 2). They open together into a collecting channel 18, which is designed as a circumferential ring channel in flange 12. In this case, the collection duct 18 and the drainage duct 15 simultaneously form an air duct 17.
(8) It may be intended to provide a separate media connection at the flange, i.e. a separate air supply or air discharge pipe. This can extend through the flange 12 into the ring duct 18. It is also conceivable to provide a media duct network separate from the drainage ducts 15. This can be designed according to the drainage channel network and can, for example, be located adjacent to or in a parallel plane to drainage channels 15. Media connection 171 and drainage channel end 151 can be designed separately.
(9) The molded parts 1a, 1b are arranged within a frame 4. The cavities that form between frame 4 and molded parts 1a, 1b are each filled with a filling body 41.
(10) It is conceivable that the filling bodys 41 are each formed as separate elements. In this case, the filling bodys 41 can be connected to the respective molded part 1a or 1b with a detachable connection.
(11) FIG. 2 shows a schematic top view of molded part 1a from FIG. 1. Molded part 1a has a coupling 16 essentially in the center. Drainage channels 15 are located in the shell 11 of molded part 1a. These drainage channels 15 extend from coupling 16 to flange 12 of molded part 1a. The drainage channels 15 are arranged essentially in a star shape, whereby the drainage channels 15 branch out the further away they are from the coupling 16. This limits the maximum distances between the individual drainage channels. In other words, an inner side of the molded part, namely a molded part surface 121 (see FIG. 1), is spaced from a drainage channel 15 with each point of the surface at a maximum distance (and presently at 50 mm).
(12) For the sake of clarity, the channels are only shown in about a quarter of the shell. Naturally, other drainage channels 15 also extend into the remaining three quarters of the shell 11. The drainage channels 15 open into a circumferential collecting channel 18, which is located in flange 12 of molded part 1a (see FIGS. 1 and 3k).
(13) At least two centering elements (six in the concrete design example) 19 are arranged on the periphery of the molded part 1a, which are designed as holes through which, for example, clamping screws can extend in the assembled state.
(14) FIGS. 3a to 3o show a process for the production of a molded part 1a, 1b (see FIG. 1) as well as a blank and a green compact 31 (see FIG. 1 and FIG. 3m).
(15) In FIGS. 3a to 3o the reference signs are mentioned only once, so that the overview is guaranteed.
(16) FIG. 3a shows one casting 20 and one casting 20′ each, which are made of plaster, for example. The casting devices 20 and 20′ form the basis for the production of the molded parts.
(17) As shown in FIG. 3b, these casting units 20 and 20′ are each covered with an intermediate layer 21, e.g. plasticise. This layer is typically between 5 and 30 mm thick.
(18) FIG. 3c shows the production of shell cores 23 and 23′. Typically, a box is built around the casting molds from FIG. 3b and the cavity is filled with plaster. These shell cores 23 and 23′ harden and can be demolded after hardening, as shown in FIG. 3d. In the next step (FIG. 3e) a release agent 25, 25′ is applied to the shell cores 23 and 23′.
(19) In the next step (FIG. 3f) the shell cores are again sealed with the appropriate casting equipment 20, 20′ (see FIG. 3a). This involves first making sprues 27, 27′ and vents 26, 26′ in the shell cores 23 and 23′. The respective shell cores 23 and 23′ are firmly connected to the respective casting equipment 20 and 20′.
(20) Porous mold material is introduced through sprue openings 27, 27′ (FIG. 3g). In the cavity between the shell cores 23 and 23′ and the respective casting device 20, 20′ a shell 11, 11′ of the later molded part 1a and 1b is molded.
(21) After curing, these shells 11, 11′ are demolded (see FIG. 3h).
(22) In FIG. 3i, the shells 11, 11′ from FIG. 3a are shown without hatching so that drainage and/or ventilation channels 15, 17 are visible in the shell. FIG. 3i also shows a cross-section of a drainage/ventilation channel 15, 17. These ducts are essentially U-shaped in the present case. After milling these channels 15, 17, they are filled with a recess material 28.
(23) In a next step (FIG. 3j), the shells 11, 11′ are each applied to a base 29, 29′. Then the corresponding flanges 12, 12′ are cast onto each of the shells 11, 11′. After the flanges 12, 12′ have hardened, the later backsides (i.e. the sides facing away from the green compact) of the shells 11, 11′ are sealed with a material with a permeability of maximum 11/(h*dm.sup.2*bar), so that channels 15, 17 (see FIG. 3i) are closed. In addition, a coupling 16 is fitted in the sealing layer with connection to the channels as a drainage channel end 151 and/or as a media connection 171.
(24) In a further step (see FIG. 3k), a sealing groove 32 is milled into at least one of the shells 1a or 1b (see FIG. 3f) which are essentially finished here. The seal groove 32 is shown in FIG. 3k as a detailed cut-out. In the actual design example, this sealing groove has an undercut, i.e. it is wider at the bottom of the groove than at its open end. A sealing 14 made of silicone is then cast into this sealing groove 32, which is fixed by the undercut of the sealing groove 32.
(25) Once the sealing has been installed, the molded parts 1a and 1b are separated from each other (see FIG. 3l) and, if necessary, placed in a suitable box. The resulting empty spaces are filled with a filling element with a density of less than 5 kg/dm3, which forms a filling body 41. The filling body can be designed in such a way that it is or can be detachably connected to the respective molded part 1a and 1b. Screw and/or snap connections can be provided.
(26) After this filling element has hardened, molded parts 1a and 1b can be assembled in a casting mold 100 (see FIG. 3m, and also FIG. 1). After the molded parts have been firmly clamped with a press, the material to be cast can be introduced through the coupling into a cavity formed between molded parts 1a and 1b. Within this cavity, a blank or green compact is created.
(27) When the slurry is introduced through the coupling into the mold cavity under slurry pressure, its solid parts settle on the walls of the mold cavity. Liquid and possibly air of the slip, however, can penetrate the porous shell, so that a solid body is formed on the walls of the mold cavity as a blank to be sintered later. The closing force exerted by the press serves as a counterforce to the slurry pressure and is thus greater than the slurry pressure p.
(28) After draining the blank, molded part 1a as part of casting mold 100 (see FIGS. 3o and 3n) can be gripped by a robot at coupling 16 (FIG. 3j). At the same time, air can be blown in through the 16′ coupling located on the bottom part of molded part 1b in FIG. 3m and a vacuum can be created on the 16′ coupling located on the top part of molded part 1a. The negative pressure holds the blank 31 in place on the molded part 1a, while the introduction of air at the 16′ coupling releases the blank 31 from the molded part 1b. The blank can then be released from molded part 1a. For this purpose, an overpressure must be generated at molded part 1a.
