Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C9/00—Moulds or cores; Moulding processes
  • B22C9/02—Sand moulds or like moulds for shaped castings
  • B22C9/04—Use of lost patterns
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C7/00—Patterns; Manufacture thereof so far as not provided for in other classes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C7/00—Patterns; Manufacture thereof so far as not provided for in other classes
  • B22C7/02—Lost patterns
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
  • B23P23/00—Machines or arrangements of machines for performing specified combinations of different metal-working operations not covered by a single other subclass
  • B23P23/04—Machines or arrangements of machines for performing specified combinations of different metal-working operations not covered by a single other subclass for both machining and other metal-working operations

Definitions

• the invention relates to a method and a device for the direct production of a lost casting mold for metal castings, as well as the production of cast part prototypes and individual pieces in the small and medium size and stucco mass range, by processing a sand mold produced using hardenable binders
• Lost molds for cast part prototypes and individual pieces are produced according to DE 43 41 325 A1 as a foam model with the aid of a numerically controlled milling machine.
• the numerically controlled milling machine contains a milling cutter that can be moved along the three spatial directions with the help of a portal device.To ensure quick and precise machining of the workpiece, the polystyrene foam particles milled out of a foam block are sucked off directly in the area of the milling cutter Milling cutter designed as a hollow body with suction openings and connected to a suction device by means of lines. Since the tool costs for producing the milling cutter are comparatively high, casting molds made from foundry sand cannot be produced using this method. The high wear and tear caused by machining a lost mold would have a detrimental effect on the shape accuracy and require considerable tool costs. Models are also out
• Compressive strength 2 - 10 kg / cm 2 is preferably 2 - 5 kg / cm 2. This means that the processing must be carried out before the binder has completely hardened, but with acceptable strength. This process cannot be mastered technologically and associated with a variety of sources of error. For this reason, the processing of an uncured sand mold could not prevail in practice.
• the tool for hollowing out the block of sand which is described in more detail in the description of the invention, also has a knife rotating about a vertical axis, with which only ordinary cylindrical shapes can be represented.
• the method is characterized in that a block of solidified powder granulate material is processed with an automatic processing machine.
• a tool changer and extraction of the removed material near the processing are mentioned.
• the powder granulate material is specified as a special sand material, which is bound and solidified in the form of a cuboid block with binders, such as water glass, which is hardened with CO2 gas, or hardeners, such as furan resin, which is hardened with acid.
• the processing machine has a kind of machine tool control.
• CAM software is used to generate a program on the basis of which the processing takes place.
• the program for the shape to be produced can be created from drawings or from CAD data.
• the invention aims at avoiding or reducing the mentioned disadvantages of the prior art, a method and a device for the direct production of a lost casting mold by processing a sand mold produced without restriction using curable binders.
• the invention is intended to reduce the wear on the tools and reduce the associated tool costs and to increase the dimensional accuracy and accuracy when reproducing the shape
• the object is achieved by the machining process of direct molding material milling, which is characterized in that using a variable or fixed molding box with a model device, a raw mold is produced which contains the contours of the casting mold plus a machining allowance for molding material milling. After filling the mold box with hardenable foundry molding materials, the raw form is produced after hardening and demolding, which is transferred into the casting mold by high-speed machining, milling or 3-D machining of free-form surfaces.
• High-speed machining produced casting mold with quantitative and qualitative features created which according to a further feature of the invention are due to the fact that the processing of the raw form takes place in the cured state, in which the compressive strength is at least 60 to 80 kg / cm 2 .
• Characteristic of molding milling is therefore the production of shape contours in hardened foundry molding material. An accumulation of removed material in the machining area is detrimental to the automation of milling. The consequences are
• direct molding material milling not only includes the milling of foundry molding materials per se, but also a technological chain of processes and devices for the production of lost molds. This includes the production of the raw form with a variable model device from an arrangement of cuboid segments, cube segments, threaded bolts or clampable round bars as well as the removal of material removal.
• the prerequisite for the technological implementation of direct molding material milling is the provision of special devices for producing the raw molds and for machining them in the processing machine, which will be explained in more detail below with several exemplary embodiments. Further advantages and refinements of the invention result from the subclaims and the exemplary embodiments.
• FIG. 2 shows a variable molding box with model device on the basis of upright cuboid segments (bar segment) for the production of the raw form
• FIG. 3 a bar segment
• FIG. 3a a cube segment
• FIG. 4 a molding box and model device with an arrangement of threaded bolts or with an arrangement of clampable ones Round rods
• Figure 5 the production of the raw form using an arrangement of
• Figure 6 is a clampable round rod
• Figure 7 the clampable round rod according to Figure 6 in section
• FIG. 1 shows the process of the production of a raw mold 1 from hardened foundry molding material in a highly schematic manner, which, after it has completely hardened, is a
• Compressive strength of at least 60 to 80 kg / cm 2 Compressive strength of at least 60 to 80 kg / cm 2 .
• Known basic molding materials foundry sands, chamotte, corundum or carbon sand
• Organic compositions such as resins, novolaks or resols or inorganic binders such as water glass with any additives and additives such as hardeners, acids, release agents and solvents and so on can be used as binders.
• the self-hardening foundry molding material is introduced into a molding box 2.
• the molding box 2 stands on a model plate 3 as a carrier for the variable model device 4 and the models for the casting and feeding system 17.
• the molding box 2 consists of four side walls 5, an auxiliary frame 6 and a filling frame 7.
• the molding box 2, auxiliary frame 6 and filling frame 7 are variably adjustable in the grid.
• the side walls 5 can consist of several identical U profiles 8.
• the U-profiles 8 are of equal length and have holes 9 arranged in a grid.
• the height of the side walls 5 can be variably adjusted via the number of U-profiles 8.
• the U profiles 8 are connected to one another on the belts 11.
• the U profiles 8 have cross struts 12 made of round or flat material between the two belts 11. These are arranged at equal intervals and at the same time serve as a positive connection to the handling gripper.
• the internal dimensions of the molding box 2 can thus be adjusted via the hole grid.
• the grid size of the molding box 2 corresponds to the grid size of the variable model device 4.
• Subframe 6 and filler frame 7 are also adjustable in the grid.
• the auxiliary frame 6 is placed on the side walls 5 and is combined with this via suitable connecting elements. The molding box 2 is thereby in his
• the filling frame 7 is in turn placed on the auxiliary frame 6.
• the models for the casting and feeding system 17 are suspended from cross members 18, which bridge the filling frame 7 and are fixed on the auxiliary frame 6.
• the arrangement of the models for the casting and feeding system 17 can be chosen as desired. These end with the upper edge of the subframe 6.
• reinforcements 16 are inserted into the auxiliary frame 6 and between the side walls 5 at vacant locations. These serve to stabilize the raw form 1 for handling and to absorb the casting pressures. Steel profiles can be used as reinforcement 16 serve.
• the auxiliary frame 6 has corresponding hole-shaped or slot-shaped openings 19.
• the crossbeams 18 and the filling frame 7 are removed and the mold is wiped off.
• the models for the casting and feeding system 17 are drawn.
• the raw form 1 thus created is turned through 180 °.
• the cross struts 12 inserted in the side walls 5 are helpful in the form of a turning device, not shown.
• the molding material is completely hardened.
• the subframe 6 is therefore necessary for clamping and handling the raw form 1.
• the subframe 6 is required for the stiffening of the blank 1 when lifting and turning the mold without the side walls 5 of the molding box 2 by means of a hoist and gripper.
• the auxiliary frame 6 serves to clamp and position the blank 1 on the machine table of a processing machine for molding material and to clamp the two mold halves for casting the casting when using the casting mold without side walls 5.
• clamping means on each side available that are known per se and are therefore not described further.
• the bracing can therefore be done conventionally with tensioning hooks.
• the positioning of two mold halves in relation to one another for receiving the casting pressure can be carried out by means of form-locking interlocks in the molded material bale, for example with conical pins and receptacles or hemispheres and pans, which are also milled.
• the high-speed machining and the 3-D processing of free-form surfaces is intended to be harmful, an accumulation of removed foundry material in the processing space, in particular in a trough-shaped contour 21 of the hardened foundry material, is harmful.
• the consequences are inaccuracies in the surface contour of the casting mold, increased wear of the tools or damage to the processing machine.
• the removal of material can be carried out overhead using gravity when milling.
• the blank 1 is clamped on the machine table with the help of the subframe 6 and together with the
• a comparatively easier removal of material removal by using gravity can be achieved by vertical milling.
• the majority of the material removal falls from a trough-shaped mold contour 21 and the molding material waste can also be easily collected and transported away.
• the machining axes, the main spindle drive and the tool clamping device are less exposed to the molding material contact.
• the material can be removed by suction, which is particularly advantageous in the case of large raw molds 1.
• the blank 1 is simply clamped with the auxiliary frame 6, and the removal of material can be carried out during the main machine time. This has the advantage that the linear axes of the processing machine are above the trough-shaped shape contour 21 in the case of surface portal designs and are relatively well protected from dust by the suction of the molding material whirled up by the tool.
• the disadvantage is that the removal of the molding material removal during processing in five Axes is difficult.
• the contours in the casting mold can be damaged by the tracking of the suction pipe in connection with the main spindle. That's why it should be damaged.
• Extraction of the material removal can be carried out after processing. It is useful if the material removal is suctioned off in layers. After each removed material layer, a vertical suction tube is inserted into the tool holder 22
• the milling tool 23 is temporarily parked during the extraction.
• the suction pipe is connected to the low pressure suction of the processing machine.
• the material removal is extracted by moving the workpiece surface close to the contour. Damage to the surface contour of the mold is excluded.
• the intake manifold cross section can be made relatively large, as a result of which a high suction power is achieved with a comparatively low energy input for the material conveyance.
• the suction is only switched on for a short time, which means that there is less
• a further variant for eliminating the material removal consists in suctioning through holes in the raw form 1.
• the processing machine drills holes in the raw form 1 at defined points, which are preferably arranged at the deepest points.
• the holes are closed again later or can perform casting tasks as feeders or air discharge.
• the suction can be done through a machine table, which for this purpose
• Extraction openings that are arranged in a grid. These openings can be closed individually or opened when connected to the holes in the blank 1.
• variable model devices 4 which are described in more detail below, can be used for the production of the raw form 1. However, the invention should not be limited to these. The following description assumes the use of CAD / CAM software.
• the contour of the variable model device 4 is generated from the contour of the casting mold by means of a CAD system.
• the details are defined in the 3-D construction of the mold assembly. These include the zero marks, the inner and outer casting contour, the arrangement of the parting plane, the arrangement of the cores including the core marks and the core game, the selection and Arrangement of the pouring and feeding system 17, the selection and arrangement of the side walls 5 of the molding box 2 and the selection of the auxiliary frame 6 with the reinforcements 16 and the selection of the filling frame 7.
• variable model device 4 consisting of bar segments 25 can be used first.
• the height of the side walls 5 of the molding box 2 must be greater than the dimension of the maximum molding depth of the raw mold 1 to be molded.
• the size of the molding box 2 depends on the size of the pattern device 4 or the raw mold 1 with the reinforcements 16. All contours of the variable pattern device 4 and the division areas receive a machining allowance. For the contour of the later casting mold, a surface contour offset by the amount of the machining allowance is created, which simulates the variable model device 4.
• the grid of the molding box 2 according to FIG. 2 in the x-y direction is a multiple of the edge length of the base area of an upright bar segment 25, which is drawn in FIG. 3.
• the mold cavity between the offset surface contour and the model plate 3, which is the same as the base surface of the mold box 2 is filled with bar segments 25.
• the bar segments 25 are arranged as in a surface grid in the x-y plane, which is marked on the model plate 3 and in the CAD system.
• the offset surface contour as the boundary of the raw form 1 must not be penetrated by bar segments 25. Undercuts in the molding direction are not filled with bar segments 25.
• the arrangement of bar segments 25 forms the variable model device 4.
• the volume of the molding box 2 minus the model device 4 results in the rough form 1 after molding.
• the rough form 1 is incorporated into the milling path programming.
• the model plate 3 forms the x-y plane of the model device 4.
• the model plate 3 can be designed to be electrically magnetizable.
• the surface of the model plate 3 can be given a thin engraving of raster lines.
• the square fields created in this way are numbered like a checkerboard in order to facilitate the construction of the bar segments 25.
• the model plate 3 can be locked with the molding box 2.
• a bar segment 25 of defined length in the Z direction is assigned to each number.
• the grid can also be used to mark the workpiece zero. This assignment can be printed out in a table.
• the positive shape is built up from bar segments 25 by hand or automatically with an assembly robot. For example, beam segments made of metal, wood or plastic with the same edge length as described above can be used, but with a tolerance of approximately 0.1 mm.
• the base of the bar segments 25 consists of steel 15 in order to be able to produce a firm hold with the electrically magnetizable model plate 3. After the complete construction of the variable model device 4, the individual bar segments 25 are fixed electromagnetically.
• the model device 4 made up of bar segments 25 and the model for the casting and feeding system 17 are sprayed with a release agent or covered with a film, and the molding box 2 is filled and compacted with cold-curing foundry molding material. After filling with cold-curing molding material and subsequent compaction, the crossbeams 18 and the filling frame 7 are removed and the mold is wiped off. The molding material is then hardened.
• the models for the casting and feeding system 17 are drawn.
• the raw form 1 thus created is turned through 180 °.
• the model plate 3 with the variable model device 4 is removed from the mold. After releasing the magnetic locking, the bar segments 25 can be removed and reused in any arrangement.
• the raw form 1 according to FIG. 1 can now be positioned and clamped in the milling machine.
• the subframe 6 is used for this. It is important to ensure that the workpiece zero defined on the blank matches the programmed workpiece zero.
• the CNC program for milling the mold can be started. With the side walls 5 removed, the side surfaces of the raw form 1 can be processed. Thus, larger mold halves consisting of several mold segments can also be produced, since side locks can be worked on. Vent holes are also possible. If the subframe 6 is intended for the production of larger mold segments behind the side surfaces of the blank mold 1 stand back, the adjustable subframe 6 can not be used. For this is one
• the raw form 1 can be produced from cold-hardenable foundry molding materials with a variable model device 4 from an arrangement of threaded bolts 27 according to FIG.
• the grid of the molding box 2 according to FIG. 4 is a multiple of the spacing of the threaded bolts 27.
• threaded bolts 27 are arranged on the plane of the model plate 3.
• the length of the threaded bolts 27 determine the offset surface contour. Undercuts in the molding direction cannot be shown.
• the model device 4 is created by a defined screwing of a plurality of threaded bolts 27 into threaded bores 29, which is shown schematically in FIG. 5.
• the threaded bores 29 are located in an approximately 12 mm thick metal plate 31, for example made of sheet steel, which is fastened on a frame 32 approximately 200 mm high.
• the threaded bores 29 can be arranged in a grid in the X and Y directions.
• the threaded bolts 27 are screwed into the threaded bores 29. All threaded bolts 27 are set to a uniform height from the upper edge of the cylindrical bolt 27 to the metal plate 31.
• Each cylinder bolt 27 has an approximately 28 mm high head 28 similar to an Allen screw or the like. A positive connection to a screwing tool 33 is thus produced.
• Each threaded bolt 27 can thus realize a stroke within the height of the frame 32. This corresponds to the maximum depth that can be molded by the model device 4.
• the model plate 3 forms the X-Y plane of the model device 4, to which the grid of the threaded bolts 27 can be transferred.
• Each grid point is a height value, which can range between 10 and 190 mm in the selected embodiment, the respective threaded bolt 27 assigned in the Z direction starting from the model plate 3. This assignment is used for programming the milling machine for screwing in the threaded bolts 27.
• the surface contour can be transferred to the model device 4 in the milling machine.
• the milling machine now works as a handling robot. For this purpose, the functions of the X, Y and Z axes as well as the work spindle are used for screwing similar to thread cutting. The prerequisite is that the machine control supports thread cutting without a threading device.
• the model device 4 is positioned and clamped in the machine. It must be ensured that the workpiece zero defined on the model device 4 corresponds to the programmed workpiece zero.
• a screwing tool 33 is fastened in the tool holder 22, which compensates for an angular displacement of the threaded bolt 27 when it moves onto the head 28 which is designed as a screw head, in order to achieve snapping.
• the corresponding position of the threaded bolt 27 is approached in the X and Y directions. By turning the work spindle clockwise and tracking in the Z direction, the threaded bolt 27 is screwed in and brought to a defined height. If all threaded bolts 27 are set, the model device 4 is removed from the machine.
• a resilient fabric 34 is placed or stretched over the model device 4 depicted by threaded bolts 27.
• the screwed side walls 5 of the molding box 2 are placed on the model device 4.
• the model device 4 is then lined with a thin film. Now the above described auxiliary frame 6 and the filling frame 7 are put on, the casting and feeding system 17 is assembled and the mold is filled and compacted with cold-curing molding material.
• the raw form is turned through 180 ° and the model device 4 is pulled.
• the side walls 5 of the molding box 2 as well as the fabric 34 and the separating film are removed.
• the model device 4 is reusable after all the threaded bolts 27 have been set to a uniform height. This is done manually or automatically.
• FIGS. 6 to 8 Another variant of the production of the raw form 1 from cold-hardenable foundry molding material by means of variable model device 4 has an arrangement of clampable round bars 35, which are shown in FIGS. 6 to 8. Reference is also made to FIG. 4.
• the round bars 35 are arranged in a grid on the level of the model plate 3 by means of a CAD system.
• the length of the round bars 35 is limited by the offset surface contour. Undercuts in the molding direction cannot be shown.
• the model device 4 is created by pressing the round rods 35 in a defined manner into the clamp receptacles 36.
• the clamping receptacles 36 sit in a thick plate 37 made of metal, which is illustrated in FIG. 6 and whose dimension is assumed to be 50 mm in the exemplary embodiment.
• the plate 37 is fastened on the frame 32 in FIG. 4, which has approximately the same height as the side wall 5 of the molding box 2.
• the clamping receptacles 36 which are shown in section in FIG. 7, each consist of a hydraulically operated clamping bush 38, which is customary in the trade, and a plastic clamping ring 39, two bore securing rings 40 and two wiper rings 41.
• the clamping receptacles 36 are arranged in a grid of approx 30 mm in the X and Y directions.
• the plastic clamping rings 39 sit over the clamping bushes 38 and allow the round rods 35 to be moved axially only with a slight force.
• the plastic clamping rings 39 are intended to prevent the round rods 35 from falling out when the clamping bushes 38 relax.
• a slight interference fit was chosen between round bars 35 and clamping rings 39.
• a hydraulic feed bore 42 leads to each clamping bush 38. In order to implement this feed in the smallest space and in the surface, it is useful to assemble the plate 37 from strip-shaped segments of the same length.
• the hydraulic feed bores 42 are arranged in the strip-shaped segments and connected to one another.
• the round rods 35 in the exemplary embodiment have a length of approximately 240 mm, a diameter of 10 mm and are ground to the inside diameter of the clamping bush 38 in such a way that a transition fit is achieved.
• Each round bar 35 can realize a stroke of approximately 180 mm. This corresponds to the maximum mold depth of the molding box 2.
• the grid of the round bars 35 is transferred to the model plate 3.
• a height value of approximately 10 to 190 mm of the respective round bar 35 in the Z direction from the base area is assigned to each grid point. This assignment is used for programming the milling machine for pushing in the round bars 35.
• the surface contour of the model device 4 according to FIG. 8 can be created in the milling machine.
• the milling machine now works as a handling robot. The functions of the X, Y and Z axes are used for this.
• the model device 4 is positioned and clamped in the machine. It must be ensured that the workpiece zero defined on the model device 4 corresponds to the programmed workpiece zero.
• a pressure bolt 43 is fastened in the tool holder 22 while the work spindle is stopped.
• the corresponding position of the round rod 35 is approached in the X and Y directions.
• the round rod 35 is pressed into the clamping receptacle 36 and brought to a defined height. If all round rods 35 are set, they are locked by hydraulic clamping pressure.
• the hydraulic pressure is generated via a hand pump which is attached to the model device 4.
• the hydraulic clamping is retained during the curing phase of the molding material.
• the model device 4 is now removed from the machine.
• a resilient fabric 34 is placed or stretched over the model device 4 formed by round rods 35.
• the screwed side walls 5 of the molding box 2 are placed on the model device 4.
• the model device 4 is then lined with foil. Now the above described auxiliary frame 6 and a filling frame 7 are put on, the casting and feeding system 17 is mounted and the mold is filled with cold-curing foundry molding material.
• the raw form is turned through 180 ° and the model device 4 is pulled.
• the side walls 5 of the molding box 2 as well as the fabric 34 and the film are removed.
• the model device 4 is reusable after all the round bars 35 have been adjusted to a uniform height of approx. 190 mm after the hydraulic clamping has been released. This is done manually or automatically.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Casting Devices For Molds (AREA)
• Molds, Cores, And Manufacturing Methods Thereof (AREA)
• Treatment Of Steel In Its Molten State (AREA)
• Mounting, Exchange, And Manufacturing Of Dies (AREA)
• Moulds For Moulding Plastics Or The Like (AREA)
• Mold Materials And Core Materials (AREA)

Priority Applications (9)

Applications Claiming Priority (2)

Publications (1)

Family

ID=7870214

Family Applications (1)

Country Status (10)

Cited By (1)

Families Citing this family (26)

Citations (7)

Family Cites Families (2)

• 1998
  • 1998-06-06 DE DE19825448A patent/DE19825448C2/de not_active Expired - Fee Related
• 1999
  • 1999-06-04 AU AU52780/99A patent/AU5278099A/en not_active Abandoned
  • 1999-06-04 WO PCT/DE1999/001709 patent/WO1999064188A1/de not_active Ceased
  • 1999-06-04 DE DE19981028T patent/DE19981028D2/de not_active Expired - Lifetime
  • 1999-06-04 US US09/719,013 patent/US6564852B1/en not_active Expired - Fee Related
  • 1999-06-04 EP EP99938170A patent/EP1085954B8/de not_active Expired - Lifetime
  • 1999-06-04 JP JP2000553237A patent/JP2002517317A/ja active Pending
  • 1999-06-04 AT AT99938170T patent/ATE220962T1/de not_active IP Right Cessation
  • 1999-06-04 ES ES99938170T patent/ES2181462T3/es not_active Expired - Lifetime
  • 1999-06-04 DK DK99938170T patent/DK1085954T3/da active
  • 1999-06-04 CA CA002349909A patent/CA2349909C/en not_active Expired - Fee Related
  • 1999-06-04 DE DE59902131T patent/DE59902131D1/de not_active Expired - Fee Related

Patent Citations (8)

Also Published As

Similar Documents

Legal Events