Patent Publication Number: US-11660778-B2

Title: Molding part, casting mold and a method for forming a green body

Description:
This application is a National Stage completion of PCT/EP2018/080440 filed Nov. 7, 2018, which claims priority from European patent application Ser. No. 1720142.3 filed Nov. 13, 2017. 
     FIELD OF THE INVENTION 
     The present invention relates to a molded part for a casting mold, a casting mold with at least one molded part and a process for molding a green compact. 
     BACKGROUND OF THE INVENTION 
     Various casting molds and molded parts for casting molds are known from the prior art. Such a casting mold is known from EP 3 162 521 A1, for example. EP 3 162 521 A1 shows a casting mold in general form. The casting mold has a first upper molded part and a second lower molded part. The molded parts are inserted between two press bodies and are moved together by these. A mold space is formed between the molded parts. 
     Typically, the molded parts each have a porous or permeable edge layer on their surface facing the mold cavity. Air and liquid can be discharged through this edge layer. It is conceivable that the casting mold has only one molded part or more than two molded parts. 
     The lower molded part of the casting mold made of EP 3 162 521 A1 has an outlet pipe for discharging water or air. This outlet pipe is connected to the porous layer. 
     The EP 3 162 521 A1 casting mold and molded parts are relatively large and heavy and therefore relatively difficult to handle. In addition, the drainage of the slurry that is filled in between the molded parts is uneven. 
     SUMMARY OF THE INVENTION 
     It is therefore the task of the invention to remedy these and other disadvantages of the prior art. In particular, a molded part for a casting mold is to be provided which allows the uniform drainage of the blank. In addition, a molded part is to be provided which enables a simple production of blanks and/or green compacts. In particular, a corresponding process is to be provided. 
     These and other tasks are solved by the devices and processes defined in the independent patent claims. Further designs result from the dependent patent claims. 
     A molded part for a casting mold according to the invention, in particular for a multi-part casting mold, comprises at least one shell for casting a particularly ceramic product. A flange is arranged on an edge of this molded part for sealing contact with a sealing surface and in particular for sealing contact with a second molded part. The shell has a first permeability for a fluid and the flange has a second permeability for the fluid. The second permeability is smaller than the first permeability. 
     The permeability is defined as the volume of a fluid which can be passed through a solid per hour, per square decimeter and per pressure: 1/(h*dm 2 *bar). 
     Different permeabilities for the shell and flange allow specific control of the fluid flow within the molded part. In particular, this means that a fluid in a mold cavity is discharged via the shell of the molded part and not via the flange of the molded part. The discharge flow is thus directed. In particular, the shell comprises a floor area and a wall area. 
     Preferably, the flange is cast onto the shell, in particular it is manufactured in one piece with the shell. 
     The flange and the shell are thus an integral part of the molded part and are thus subject to the same shrinkage. Production is simplified and the molded part does not have any unnecessary parting lines. 
     Preferably, the shell and the flange are made of essentially the same material. In particular, the material properties of the material of the shell and the material of the flange are essentially the same. The material is preferably a plastic and especially PMMA. 
     Manufacturing from the same material improves the properties of the molded part. The material properties are the same for the entire molded part. 
     The shell of the molded part preferably has a permeability of at least 10 l/(h*dm 2 *bar). Alternatively or additionally the permeability of the flange is maximum 1 l/(h*dm 2 *bar). 
     The molded part may have a sealing, which is preferably designed as a circumferential seal. This seal is preferably arranged in or on the flange. 
     This makes it possible to seal the molded part on a sealing surface during installation, in particular to close and/or seal the molded space from the environment. 
     A sealing also makes it possible to manufacture the flange with a larger tolerance, since the sealing effect can be provided by the sealing and not by the flange. 
     The flange can preferably have a recess in which the sealing is inserted. The sealing is preferably cast into the flange. 
     This secures the sealing in the flange and protects it against loss. 
     The recess can have an undercut. 
     The protection against loss is thus increased. 
     The molded part in question can be made up of several parts, and in particular have an inner and an outer layer. 
     In this case, inner layer means that it faces the mold cavity and thus the later green compact. 
     A further aspect of the present invention concerns a casting mold with at least one and preferably two molded parts as described above. Such a casting mold enables the production of ceramic products in particular and the series production of a desired geometry. 
     A further aspect of the invention relates to a molded part, in particular a molded part as described herein, wherein at least one drainage channel is provided in the molded part. The drainage channel has at least one drainage channel end, via which liquids can be drained off by means of a drain pipe. The molded part has a detachable coupling for detachably connecting the end of the drainage channel with the discharge pipe. 
     This enables the individual coupling and uncoupling of the discharge pipe. In particular, it is conceivable that the drainage channel end is designed as a coupling and interacts with a corresponding coupling with a pressing cylinder. 
     This allows coupling the discharge line directly when the press cylinder is applied to the molded part. Separate coupling of the discharge line is no longer necessary; two steps are combined in one step. 
     A separate filling body for displacing media, e.g. water, may be provided between the molded part and the press cylinder, the filling body fills the casting mold, wherein the coupling or the drainage channel end extend through the filling body to the press cylinder. 
     The detachable coupling can be arranged in a central region of the molded part and in particular in a region at or adjacent to the center of mass of the molded part. 
     This area is preferably selected so that moments of inertia about an axis of the coupling can be minimized. 
     The detachable coupling is preferably designed in such a way that it can be gripped by a robot. 
     This allows lifting the molded part out of the casting mold without having to attach additional elements to the molded part. The coupling not only takes over the function of draining the water but also the function of providing an element for gripping and handling the molded part. 
     An additional gripping contour formed on the coupling or possibly a second blind coupling that prevents the molded part from twisting in one of the robot&#39;s gripper arms may be provided. 
     A further aspect of the invention relates to a process for forming a green compact comprising the steps
         a. Providing a molded part with at least one drainage channel which has at least one drainage channel end, in particular with a molded part described previously;   b. filling the molded part with a compound to be cast;   c. building up a pressure on the molded part to produce a blank;   d. draining liquid from the blank through the at least one drainage channel and a discharge line to produce a green compact by draining;   e. after dewatering, decoupling the discharge line from the end of the drainage channel;   f. gripping the casting mold or the molded part with a robot to open the casting mold and/or to demold the green compact.       

     Preferably the robot grips the casting mold at a coupling as described above. 
     The coupling can extend, for example, from the molded part through the filling body, so that when the robot grips the coupling at least part of the casting mold, such as a filling body, is lifted together with the molded part. It is also conceivable, however, to first remove the filling body and then use the robot to grip and remove the molded part at the coupling. 
     This allows for an easy production and shaping of a green compact. 
     A further aspect of the invention relates to a molded part for a casting mold, in particular a molded part as described in the present case, the molded part comprising a shell with a molded part surface for molding a product, in particular a ceramic product. The shell is at least partially fluid permeable. Channels are provided in the shell so that the molded part surface can be acted upon by a medium and in particular by air and/or water. The molded part has at least one media connection for connecting the channels to a media source, in particular to a compressed air source. 
     Here and in the following, channels mean separately formed channels and not the fluid connections within the shell, which are formed by the pores. The channels are typically designed as tubular connections. 
     Separate, unconnected channel systems within the shell make it possible to bring media, especially air, to specific locations of the molded part and especially the shell. This allows, for example, introducing air specifically and independently into the molded part. 
     The air can flow through the pores of the molded part surface up to the blank within the molded part and evenly detach it from the molded part surface without deforming the blank. 
     The channels are preferably arranged in such a way that each point of the molded part surface has a distance to at least one channel which is smaller than 50 mm and in particular smaller than 30 mm. 
     The molded part surface is the surface facing the molding space, i.e. the surface which is in contact with the compound or slurry during molding of the blank. 
     These maximum defined distances ensure that each area of the molded part surface is exposed to air. 
     Preferably, the channels extend over the shell up to a lateral flange. The media connection is preferably located at the flange. 
     The arrangement of the media connection at the flange facilitates uncoupling from an air supply line, namely the media source. 
     In addition, the arrangement of the media outlet at the flange allows the media to flow through the molded part to the end of the drainage channel. 
     It can be advantageous letting the channels run essentially radially from a central area of the shell to the flange. 
     The channels can be arranged in such a way that they do not reach the molded part surface. This means that the channels are located inside the molded part and have a closed cross-section. 
     This makes it possible to form a network of channels that extends over the entire shell and is spaced from the molded part surface. 
     Alternatively, it is conceivable that the channels are formed as depressions in a surface and the closed cross-section is only formed when the molded part is placed in the casting mold. A closed wall of the channels would then result from the casting mold and the molded part. 
     Preferably, the channels in the flange end in a circumferential collecting channel which is connected to the media connection. 
     This allows all channels to be simultaneously supplied with one media source, for example compressed air. 
     The blank in the molded part is thus evenly pressurized with compressed air, thus enabling the blank to be released from the molded part evenly. 
     A further aspect of the invention concerns a process for molding a green compact, in particular a process as described above. The process comprises the steps
         a. Providing a casting mold, preferably with at least one molded part as described above;   b. filling the casting mold with a mass to be cast;   c. building up a pressure on the casting mold to produce a blank;   d. draining the blank to produce a green compact;   e. removing the green compact from the casting mold by applying a media overpressure between a molded part surface and the green compact.       

     This enables the green compact to be detached evenly as described above. 
     It is advantageous to hold the green compact on a side of the green compact opposite the overpressure by means of negative pressure while the green compact is being released from the casting mold. This facilitates the demolding of the green compact. 
     Another aspect of the invention concerns a molded part, preferably a molded part as described above. The molded part has a porous shell and a filling body to displace an unnecessary cavity. The filling body and the shell are connected to each other by a detachable connection. 
     This allows the molded part and the filling body to be manufactured separately. It is also possible, for example, to remove the filling body separately after casting to facilitate handling of the molded part. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is explained by way of example with reference to the following figures. Show it: 
         FIG.  1   : a cross-section through a casting mold 
         FIG.  2   : a top view of the casting mold according to  FIG.  1   . 
         FIG.  3   a    to  FIG.  3   m   : Process steps for producing a a molded part and a blank 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG.  1    shows a cross-section through a casting mold  100 , which has two molded parts  1   a  and  1   b , which are arranged on top of each other in the concrete design example. A sealing  14  is arranged in the molded part  1   a  at the top in the present figure. The sealing  14  is located in a flange  12  of molded part  1   a . Molded part  1   a  also has a shell  11 , which is connected to flange  12 . The second molded part  1   b  is designed in the same way as the first molded part  1   a , with the difference that the second molded part  1   b  has no sealing. Therefore, only the structure of one of the molded parts  1   a  or  1   b  is explained below. As mentioned above, molded part  1   a  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 . 
     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 . 
     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 . 
     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. 
     The molded parts  1   a ,  1   b  are arranged within a frame  4 . The cavities that form between frame  4  and molded parts  1   a ,  1   b  are each filled with a filling body  41 . 
     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  1   a  or  1   b  with a detachable connection. 
       FIG.  2    shows a schematic top view of molded part  1   a  from  FIG.  1   . Molded part  1   a  has a coupling  16  essentially in the center. Drainage channels  15  are located in the shell  11  of molded part  1   a . These drainage channels  15  extend from coupling  16  to flange  12  of molded part  1   a . 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). 
     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  1   a  (see  FIGS.  1  and  3     k ). 
     At least two centering elements (six in the concrete design example)  19  are arranged on the periphery of the molded part  1   a , which are designed as holes through which, for example, clamping screws can extend in the assembled state. 
       FIGS.  3   a  to  3   o    show a process for the production of a molded part  1   a ,  1   b  (see  FIG.  1   ) as well as a blank and a green compact  31  (see  FIG.  1    and  FIG.  3   m   ). 
     In  FIGS.  3   a  to  3   o    the reference signs are mentioned only once, so that the overview is guaranteed. 
       FIG.  3   a    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. 
     As shown in  FIG.  3   b   , 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. 
       FIG.  3   c    shows the production of shell cores  23  and  23 ′. Typically, a box is built around the casting molds from  FIG.  3   b    and the cavity is filled with plaster. These shell cores  23  and  23 ′ harden and can be demolded after hardening, as shown in  FIG.  3   d   . In the next step ( FIG.  3   e   ) a release agent  25 ,  25 ′ is applied to the shell cores  23  and  23 ′. 
     In the next step ( FIG.  3   f   ) the shell cores are again sealed with the appropriate casting equipment  20 ,  20 ′ (see  FIG.  3   a   ). 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 ′. 
     Porous mold material is introduced through sprue openings  27 ,  27 ′ ( FIG.  3   g   ). 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  1   a  and  1   b  is molded. 
     After curing, these shells  11 ,  11 ′ are demolded (see  FIG.  3   h   ). 
     In  FIG.  3   i   , the shells  11 ,  11 ′ from  FIG.  3   a    are shown without hatching so that drainage and/or ventilation channels  15 ,  17  are visible in the shell.  FIG.  3   i    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 . 
     In a next step ( FIG.  3   j   ), 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 2 *bar), so that channels  15 ,  17  (see  FIG.  3   i   ) 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 . 
     In a further step (see  FIG.  3   k   ), a sealing groove  32  is milled into at least one of the shells  1   a  or  1   b  (see  FIG.  3   f   ) which are essentially finished here. The seal groove  32  is shown in  FIG.  3   k    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 . 
     Once the sealing has been installed, the molded parts  1   a  and  1   b  are separated from each other (see  FIG.  3   l   ) 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  1   a  and  1   b . Screw and/or snap connections can be provided. 
     After this filling element has hardened, molded parts  1   a  and  1   b  can be assembled in a casting mold  100  (see  FIG.  3   m   , 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  1   a  and  1   b . Within this cavity, a blank or green compact is created. 
     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. 
     After draining the blank, molded part  1   a  as part of casting mold  100  (see  FIGS.  3   o  and  3   n   ) can be gripped by a robot at coupling  16  ( FIG.  3   j   ). At the same time, air can be blown in through the  16 ′ coupling located on the bottom part of molded part  1   b  in  FIG.  3   m    and a vacuum can be created on the  16 ′ coupling located on the top part of molded part  1   a . The negative pressure holds the blank  31  in place on the molded part  1   a , while the introduction of air at the  16 ′ coupling releases the blank  31  from the molded part  1   b . The blank can then be released from molded part  1   a . For this purpose, an overpressure must be generated at molded part  1   a.