DE1964275A1 - Method of making split molds - Google Patents

Description

The invention relates to a method of making molds for making objects from
thermoplastic materials. The invention relates to
in particular to a method for the production of molds for injection molding and to the molds produced in this way.

\ Molds such as those used for injection molding are

commonly known as split forms and are made up of two. .Halves, each of which on the press table of a forirjna scliine arranged v; ird. The two halves of the mold can then

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closed to form a mold cavity, in the dendastthermoplasische Material is injected. Then the mold halves can be separated from each other so that the mold

ling or molded body can be removed. It is therefore important that the molds are stable enough to withstand the forces resist caused by the impact of closing the mold halves; Furthermore, the mold halves should withstand the pressures, that arise when the thermoplastic materials are injected into the mold.

According to the invention, a method for the production of divided molds is proposed in which a metal shell is formed to form a mold surface or mold surface. that corresponds to at least a part of the object to be molded and that a reinforcing back Provides padding so that it can withstand the pressures during the molding cycles, using the steep metal blocks uses, where it uses most of the forces when closing the Record shape.

The invention also extends to molds insofar as they have been produced by this method. The metal shell is useful around a model of the object to be molded formed in any manner and from any suitable material provided it is during the process steps is not adversely affected. The model can be made of wood, metal, plaster, synthetic thermoplastic

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stischcn material, thermosetting resins, rubber, in particular Silicone rubber, wax, plastillin, clay or glass-reinforced polyester can be produced. It is preferred open the model on a base made of wood or metal. seat that has angled edges; which constitute an institution which wedges the sprayed-on metal coating around the model. The model should contain cooling tubes that look like this be fixed as close as possible to the a * splashing surface should. If the metal shell is made by flame spraying, the model with a water-soluble one is expedient Release agents such as polyvinyl alcohol sprayed before the metal is applied. The release agent allowed it to lift the metal shell slightly from the model when it is immersed in water; also supported the means of properly laying down the initial coating of the sprayed metal.

The metal shell can be made by electrolytic precipitation, by casting metal, from sheet metal or by Metal syringes can be molded around the model. Because of Simplicity is preferred to the metal shell by metal spraying to build. Any metal that can be used to form a bowl around the model can be used; preferred however, in the case of shell formation by flame spraying, the metal becomes zinc. For spraying with compressed air are in particular low-melting alloys, especially '..' ismuth / Zir.r.-Lo-ations suitable. These metals provide an exact '

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Reproduction of the model surface. A flaming prit The shell can consist entirely of zinc or contain zinc a minimum thickness of 0.127 cm (0.050 inch) and a backing of low carbon steel, copper or aluminum. In flame spraying, aluminum is still a useful material because it is lighter and has a high rate can be injected without difficulty. It will be a metal shell at least 0.159 cm thick (1/16 English inch) and especially 0.6t cm. (0.250 English « Inch) preferred

The model on which the metal shell is is formed, provided with a lip that surrounds the area »which determines the forming surface, so that the metal shell when Forms extends over this lip and is held in this way on the model.

After the formation of the metal shell and preferably before the shell is lifted off the model, pipes made of copper should preferably be provided and the contours of the metal shell should be grounded according to a predetermined cooling plan. The pipes are advantageously attached to the metal shell with the aid of a metal-filled epoxy resin " , since this adhesive ensures good heat exchange. Alternatively, the pipes can be attached with metal-filled epoxy resin and then attached to the shell over their entire length by scalding with metal -

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If necessary, thermocouples can be attached to the metal shell in the same way as the tubes} this has the advantage that it can be located as close as possible to the end face of the mold are located. ...

The metal bowls require careful handling and there is a risk that they will be "during the spraying", built up tensions are warped} it is therefore desirable to provide the shell with a reinforcing layer to protect it from *. ■ make the lifting from the model at least self-supporting. The model is therefore advantageous with the * ·. deten metal shell enclosed by formwork to create a To form a cavity in which the reinforcement material such as clay. earth cement, thermosetting resins or concrete can be poured ''. For example, wooden formwork can be attached to the base plate. be screwed on. 'Steel anchoring' bars are then bent and inserted crosswise in the molded box so that they protrude on each side. The staves serve three purposes! they strengthen the reinforcement material, li «f«] * n an institution for transporting the complete insert and anchoring it in the concrete frame. Will the metal shell through If flame spraying is produced, it is advisable to ',.' for example to provide water-repellent paint. Concrete or "alumina cement" can then be poured into the cavity to cover the shell and enclose the cooling tubes, the ends of which remain free. That

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The model should be shaken well during the casting process Formation of voids in the vicinity of the metal shell avoid. If the back-lined concrete has set, the reinforced shell can be detached from the model by cut off the metal part protruding over the lip of the model.

The first reinforcement layer provides sufficient reinforcement, through which the shell can be conveyed without difficultyj this reinforcement also protects the cooling tubes against chipping off the shell. However, it is now necessary to give the mold half a strong back lining, so that it can be used in injection molding. Another benefit of applying the reinforcement in two steps is that any cracks that may appear in the outermost layer will not spread to the other layers propagate the form. The molds must not only allow material to be formed under pressure, but also to cope with the stress withstand due to the closing of the two mold halves. Accordingly, metal blocks should be used so that

a) they absorb the main part of the machine clamping forces from the encryption · strengthening material, so that low probability _t probability of cracks, wherein the end faces of the blocks must be very accurately machined parallel and must have the same length blocks.

b) them. convenient places for fixing dowels to

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Part of the blocks or bolted in the form of plates could be.

c) They provide places where eyebolt holes are drilled and tapped in the blocks for easy transportation can be and.;

d) Provide devices with which the complete fora is bolted onto the press table of the injection molding machine or ' can be clamped. ·

Preferably, dowels are provided on the metal blocks in one mold half and in the other mold half Blocks of holes arranged to receive the dowels. Alternatively, one set or both sets of dowels can be used with locating plugs Provide guides that ensure that the blocks in the two halves are in contact when the "· Form is closed. ·

The Ilctallblocks advantageously have a square cross-section; their dimensions depend on the molding machine used and the size of the molded products produced. A preferred attachment of the reinforcement material to the shell is to make the metal shell, the method of manufacture of which has already been described, a wooden or metallic one. To arrange frame. The frame should be assembled on a flat surface, which is conveniently covered with a plastic film to allow the reinforcement material to ^:

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obtain a clean end face when this material is poured into the frame * around the tray; the film also acts as a release agent.

That absorb the forces that occur when the mold is closed Metal blocks are expediently arranged in the frame in such a way that they are fixed in place by the reinforcement material. being held.

The shell of the second half of the split form can by using the cavity of the first half as a spray trough for creating the metal shell of the other half of the mold be used. It is useful to provide an angled bead around the top of the inverted bowl to create a key for the sprayed metal. Before metal is injected into the cavity, "the shell" is applied of the cavity extension, a material is deposited in a thickness such as is necessary for the determination of the mold cavity; Foil wax is particularly suitable for injection molds. In the mold wall, a conical, called a sprue cone, must Hole are formed through which the polymer can be injected into the mold. It is useful for this on the wax A metal block is placed before the metal is injected, which is later drilled out and expanded to deliver the sprue cone will. It can then be sprayed onto the wax around the metal block in the required thickness; it can do the already attached to the cavity insert

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Pipes can be used to cool the system during spraying. Alternatively a metal block can be attached to the back of the shell £ - · stapled with a hole drilled through the block and shell to form the sprue cone.

Subsequently, pipes and tubes can be placed on the second molded shell in the same way as with the first mold half. Thermocouples are attached. Then a wooden formwork with reinforcing bars is built around the shell and a metal block is used, which forms an extension of the sprue block standing on the wax and extends through the concrete to provide the sprue cone. Then a first layer can be made around the shell Reinforcement material, for example from concrete or alumina cement, which is then allowed to harden, so that it becomes self-supporting. The height of the concrete should be below the top of the metal block. The second mold half can then separated from the first when the reinforcement material has cured.

According to the above description, the mold halves must be provided with a pressure-resistant back lining as well as with devices with the help of which they can be localized in a molding machine. This can advantageously be achieved in this way. that each of the two mold halves is inserted into a support frame, preferably made of steel, which is then reinforced with reinforcement material, preferably concrete. Of the

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Support frames should have walls of sufficient height to accommodate the To support reinforcement material to the desired depth as well as the metal blocks, which are in the frame, preferably in Corners where they are embedded in the reinforcement material. Alternatively, the blocks on the Be attached to the outside of the support frame.

It is important that the two mold halves are in their frame

are in exact position to each other and that too

the metal blocks are in the correct position. It was determined, that one expediently first brings a mold half in its frame or support frame in the exact position. This leaves can be achieved by providing supports at the desired height in the frame, and then the frame with a movable one Reinforcement material such as concrete at a level above the supports in the frame and the mold half on the Concrete lowers where she sits down until she rests on the supports. The cooling tubes and the supply lines for the thermocouples , are led out through holes in the walls of the frame, which is then finally filled with concrete, which encloses the mold half and provides reinforcement after hardening.

An injection mold is generally made with the aid of a die with the nozzle. Align the fuel unit Locating ring inserted into a molding machine. The localization ring, which is generally a Metal washer is inserted precisely into the frame so that it is held in place by the concrete. At a

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In the preferred embodiment, the locating ring consists of several steel rods attached to the center of the cylindrical Blocks are attached and extend radially away from this so that they remove any forces exerted by the injector of the molding machine on the locating ring, distributed over a large area of the reinforcement material. len.

The second half of the mold must then be in it. Reinforcement material are used, whereby it must be ensured that the two mold halves fit exactly into one another while leaving a mold cavity of the desired depth, with the Hit metal blocks in each of the mold halves when the mold is closed during the molding cycle. It can the second half of the mold together with its dowel blocks are inserted into a support frame that is filled with concrete, so that the mold half floats on the concrete and occupies a greater 'height than is later required. It then becomes the The first mold half located in its frame is lowered onto the second mold half, so that the mold insert on the required Depressed deep into the liquid concrete and held in the correct orientation by the "position of the first half" will. The two mold halves can be placed in the correct mutual position with the help of the arranged in the corners of the frame Metal blocks are brought; the blocks in one half of the mold are dowels and the blocks in the other half of the mold provided with holes to accommodate the dowels, so the

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both mold halves brought into the exact mutual position,

• "v.

when the dowels are in the. Engage holes.

The second half of the mold settles in the concrete to the correct depth, after which the concrete is allowed to set. After all, they have to determine the direction of the sprue blocks Metal blocks are drilled out to form a channel through which the material can be injected into the mold; ' then the mold is inserted into the molding machine.

An alternate method for inserting the first Shell in its reinforcement material and to ensure its correct position in relation to the second half the fact that the first shell is placed on top of the second mold half, which is in its frame. The metal blocks, which are to form part of the first half should be placed on top of the blocks that are already in the second half of the forci are inserted and indicate the depth until to which the concrete is to be poured around the shell. Closing 'borrowed the support frame for the first mold half around the Shell and set around the reinforcement material poured to the desired height. In this alternative procedure, a layer of one is expediently on the top of the reinforcing material surrounding the first mold half Release agent applied so that a reinforcement material of the second half sticks to that of the first half when it sets.

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The invention is explained in more detail below with the aid of a schematic illustration Drawings explained in more detail. ■■

Fig. X shows the model used to make the first mold half;

Fig. 2 shows the model with a cover made of a metal shell with a rigid backing material is provided;

FIG. 3 shows the mold half shown in FIG

after lifting off the model and turning it over;

Fig. ^ Illustrates the procedure for preparation the one in Fig. 3 mold half shown as a model for the production of the second mold half;

Fig. 5 illustrates the formation of the second mold half; "

6 shows the second mold half after it has been separated from the first mold half and turned over; '. ·

Figure 7 shows a method for locating the second mold half in its support frame;

Fig. 8 shows the position of the first mold half in its' Support frame opposite the second mold half;

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Figures 9 and 10 show alternative procedures for

locating the first mold half in its support frame opposite the second mold half.

According to Fig. 1, the model 1 sits on a wooden base plate 2, which has an angled edge 3, which the metal holds or wedges. On the back of the model are for. Improvement of the hardening of the sprayed metal coating Cooling tubes H provided. According to FIG. 2, the model is first provided with a metal layer 5 by spraying, on which Cooling tubes 6 and thermocouples 7 are attached. That is ·. "

Injected model is then enclosed by formwork 8 and there are metallic anchoring rods 9 in adaptation to the Shape of the model bent and inserted into the formwork; then alumina cement is poured into the formwork and the mold half is lifted from the model when the cement has set; then the shape according to Fig. 3 upside down, in which one recognizes the Forrahohlraum 11.

The mold half shown in Fig. 3 is then called the

ι .3

Model used for the production of the other mold half, as illustrated in FIG. The surface 11 of the mold insert is first lined with a layer of wax 12, which has the thickness required for the mold cavity. Afterward is on the wax at the point where in the mold wall the sprue cone is to be formed, a metal block 13 on- · puts. The wax-coated mold half is then covered with

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Metal IH splattered around the shell of the other mold half as shown in FIG. Thermocouples 15 and cooling tubes 16 are provided behind the shell. Further a metal block.17 is placed behind the block IU, the forms an extension of the sprue cone. Finally, a formwork 19 is placed around the edges of the sprayed metal shell. built into which alumina cement 18 is poured around the back of the shell, leaving the end of the metal block 17 free. After the alumina cement has set, the second mold half can can be removed from the first mold half, as illustrated in FIG.

FIG. 7 illustrates how the mold half according to FIG. 6 can be housed in their support frame. The support frame 20 is placed on a flat surface and it becomes the Locating ring 21 for locating the mold in the molding machine inserted in the center of the frame; the ring is provided with arms 22 which take up some of the forces. Four adjustable screw threads 23 are used in the frame, which hold the mold half at the correct height inside the mold. The frame will initially be straight up above the screw thread is filled with concrete and it becomes the form; half lowered onto the liquid concrete in which it is located. the screw thread settles. Along the edge of the frame, a formwork 24, 26 is made at the points indicated by the arrow « and 27 screwed on; furthermore, metal blocks 25 are attached to the side of the frame at the indicated locations. It can then

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- 16 around the mold half concrete to be poured into the frame.

Then the other form shown in Fig. 3 can. half 11 inserted into a support frame 28 according to FIG. 8 v / ground. Metal blocks 27 are screwed or bolted to the edge of the frame, the position of which corresponds to the position of the dowels of the frame as shown in FIG. Correspond to the mold half. The mold insert shown in FIG. 3 is inserted floatingly into the liquid concrete in the support frame 28 and is thereby brought into the correct position in relation to the other mold half in the frame by lowering the other mold half onto the mold half 11 as shown in FIG. so that the dowels 30 engage in the holes 31 of the blocks 27. The shape surface I ¹ * '

then sets the mold half 11 in the concrete. After setting of the concrete, the mold can be attached to the molding machine with the aid of the plate 29.

Figures 9 and 10 show another procedure for locating the first mold half in its support frame, so that it is in the right position.

According to FIG. 9, a mold half 32 is seated in a support frame ·;, men 33, at the corners of which metal blocks 3U are arranged. The ends of the cooling tubes project at 35 on the frame.

For the localization of the other mold half opposite the mold half 32 is in the direction of the arrows shown

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a cut-out panel 36 is lowered until it rests on the support frame 33. The board is cut out so that the Dowels 37 seated on blocks 34 and mold half 32 protrude through the board. According to Fig. 10, the blocks 38, which are to form part of the other mold half, arranged so that they are flush with the dowels 37. It is then the mold half 39 on top of the mold half 3.2 placed and it is then around the mold half 39 of the support frame 40 arranged together with a wooden cladding 41 (The wooden casing 31 is shown partially cut so that the mold halves can be seen). Then on the mold half 39 cast a movable reinforcement material such as concrete to a depth equal to the height the block 38 is; then the concrete is smoothed, after which it is allowed to harden.

The panel 36 prevents the reinforcement material poured around the mold half 39 from adhering to the reinforcement material surrounding the mold half 32. The board consists of either made of or coated with a release agent so that it does not adhere to the reinforcement material poured around the mold half 32 adheres.

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Claims (1)

196427G Patent claims 1Λ procedure for making split molds, in which one has to form a mold surface that is at least corresponds to a part of the object to be molded, forms a metal shell and on this a reinforcing backing attaches so that it withstands the forces during the molding cycles, characterized in that at one point the Form metal blocks are arranged on which they absorb most of the forces occurring when closing the form. 2, The method according to claim 1, characterized in that the metal shell by metal spraying on a model of the object to be molded is formed. 3. The method according to any preceding claim, t characterized in that the reinforcing backing of the metal shell is applied in two stages, of which. the first stage enables easy transport of the shell and the other provides the pressure-resistant back lining. Q09829 / U11 BATH ORIGINAL U. The method according to vorhegehenden claims 1 to 3, characterized in _t that one produces the one mold half by a process according to any one of the preceding claims and then the mold surface thus formed is used as an injection well for the production of the metal shell for the second mold half. 5. The method according to claim U, characterized in that that the metal blocks in one mold half with dowels and the metal blocks in the other mold half with these dowels Holes are provided. 009829 / U11 ORIGINAL INSPECTED