WO2008084006A1 - Mold core for injection molds - Google Patents

Abstract

The invention relates to a mold core for an injection mold, which consists of a mold head (10) having a higher conductivity and a support (20) having a lower heat conductivity which are materially connected to each other (e.g., by welding). The support (20) preferably comprises a cooling means channel (22) to which a recess (12) of the mold head (10) connects. In addition, the mold head (10) and the support (20) are advantageously toothed with each other in order to transmit torque.

Description

 Molded core for injection molds

The invention relates to a mold core for an injection mold and to a method for its production.

Shaped cores are parts of injection molds with which, for example, plastic products can be produced. To achieve the highest possible efficiency of an injection molding machine, it is important to abzufü the heat of the introduced into the mold liquid injection as good as possible. The sprayed material can then solidify faster and be removed from the mold again, which is then ready for the next injection process. In this regard, it is known from DE 20 2005 018308 U1, to produce the tool pin of an injection molding machine with an outer sheath made of steel and a highly thermally conductive core of BeCu.

Furthermore, WO 2005/108044 A1 discloses an injection molding tool with a mold core which has an outer core and an inner core arranged therein. The hollow cylindrical shaft end of the outer core may consist of a material having a higher heat conductivity.

DE 699 13 378 T2 describes a mold core with an elongate carrier, the end of which is closed by a front cap with internal egg directions for the flow of a coolant.

Against this background, it was an object of the present invention to provide a mold core for an injection mold, which is easy to manufacture, is robust, and enables high performance of an injection molding machine. This object is achieved by a mold core according to claim 1 and by a method according to claim 10. Preferred embodiments of the invention are described in the subclaims.

The mold core according to the invention for an injection mold can in principle have any conceivable three-dimensional shape required for the production of a specific product. For example, it can have an external thread with which an injection-molded part with a complementary internal thread can be produced (eg a tube closure). The mandrel contains the following two components:

a) A forming head made of a material having a first thermal conductivity, which in the following "higher thermal conductivity" is genan nt, since it should be greater than the second mentioned below, "lower thermal conductivity". Typically, the forming head is a part of the mold core, which in use comes into direct contact with the sprayed material. Preferably, even the entire surface of the mold core, which comes into contact with sprayed material during the injection process, belongs to the mold head.

b) a support made of a material having a lower thermal conductivity than the above-mentioned first, higher conductivity, wherein the carrier has a coolant channel. The carrier usually comprises all those components of the mold core which are required for its use in an injection molding machine. These include, for example, bearings and points of application for the transmission of linear and / or rotational movements on the mandrel, connections for a coolant supply and the like.

Furthermore, the mandrel is distinguished by the fact that the forming head is materially and positively connected to the carrier. In this context, a "cohesive connection" as usual, such a connection between two different components understood, which is mediated by bonding forces at the atomic or molecular level. For this In particular, the adhesion and the chemical bond belong. Preferred examples of cohesive connections are connections by gluing, soldering or welding (where, as usual, "soldering" denotes the connection of two materials by a lower melting solder and "welding" the connection of two materials by melting of both materials). The "positive locking" is defined as usual in that one of the connected parts at least one movement (for example, a rotation about an axis or a shift in a certain direction) can not perform without the other part to penetrate it; however, since penetration is not possible with real bodies, the first part will take the second part in performing the corresponding movement.

The mold core described has the advantage that a faster removal of heat from the sprayed material can be achieved by using a mold head with a material of higher thermal conductivity. At the same time, however, for the heat dissipation little or no relevant carrier can be made of a different material, which is better suited for its tasks or even cheaper, with no barrier of a poorly conductive material between the spray and the material of higher thermal conductivity. The cohesive and positive connection between the forming head and the carrier while a very strong mechanical connection is achieved, which withstands the high loads when using the mandrel. Furthermore, a cohesive connection is characterized by a good heat transfer, which ensures a seamless transmission of the heat absorbed by the forming head. Another advantage of the cohesive connection is that it can be designed gas-tight or liquid-tight without further measures.

The exact heat conductivities of carrier or forming head depend on the respective concrete application. Preferably, the mold head has a thermal conductivity of at least 72 W / m K. The material of the mold head must meet in addition to the desired higher thermal conductivity and the other requirements placed on the mold head, for example with respect to a mechanical strength, temperature resistance, compatibility with the sprayed and the like. In a preferred embodiment of the invention, the forming head contains at least one of the materials copper (Cu), beryllium (Be), cobalt (Co), nickel (Ni) and / or silicon (Si). Preferably, it contains these materials in the form of beryllium copper (BeCu), "MoId Max HH" (Specification: 1.9% Be, 0.25% Co + Ni, balance Cu, manufacturer: Brush Wellmann Inc., Cleveland, USA), Ampcoloy 940 (specification: ≤ 0.4% Cr, 2.5% Ni, 0.7% Si, balance Cu, manufacturer: Ampco Metal SA, Marly, Switzerland), or HOVADUR K 350, (specification: 0.4% Ni + Co, 1.9% Be, others 0.2%, balance Cu, manufacturer: Schmelzmetall AG, Gurtnellen, Switzerland), in particular, it can be made entirely of these materials.

The support may in particular consist of iron, steel, stainless steel or brass or at least contain these materials.

It is particularly preferred if the forming head and the carrier have mutually compatible toothings. Such teeth can then impart a rotational movement about an axis, as is necessary, for example, when coring a sprayed product with internal thread. The toothed meshing of the forming head and the carrier ensures reliable transmission of the occurring forces or torques, so that they do not stress the cohesive connection.

According to another embodiment of the invention, the forming head closes an opening of the coolant channel in the carrier. As a result, when using the mold core, the coolant flowing in the coolant channel comes into contact with the mold head and can therefore absorb heat directly from it.

In a further development of the preceding embodiment, the forming head has a depression which acts as an extension of the coolant channel. In this case, coolant can penetrate a little way into the mold head and thus absorb heat from the mold head over a particularly large surface area. In particular, an inner tube may be arranged in the coolant channel of the carrier, which is surrounded by an annular gap. Coolant may then be directed through the inner tube in a first direction (toward or away from the forming head) and flow through said annular gap in the opposite direction. In this way it is possible to produce a coolant circulation through a single bore channel in the carrier.

The invention further relates to a method for producing a mold core with

a) a forming head made of a material of higher thermal conductivity and

b) a carrier made of a material having a lower thermal conductivity, which has a coolant channel.

According to the method, said forming head is connected in a material-locking and form-fitting manner to said carrier, which may preferably be effected by gluing, soldering or welding (in particular laser welding or electron welding).

The method allows the production of a mold core of the type described above, so that reference is made to the above statements for details on the advantages and developments of the method.

In the following, the invention will be explained by way of example with the aid of the figures. It shows:

Fig. 1 shows two perspective views of the tip of an inventive

Mold core, wherein the mold head and the carrier are shown exploded in an exploded view;

Fig. 2 is a side view of the assembled mold core tip of

FIG. 1;

3 shows a section along the line III-III of Figure 2. In the figures, only a tip of a mold core according to the invention is shown in more detail, since its remaining design can be arbitrary and generally depends on the requirements of the respective injection molding machine, in which the mold core is to be installed. The interest here point of the mandrel consists of two components, namely

a forming head 10, and

a carrier 20.

In the example shown, the forming head 10 and the carrier 20 each have the shape of a cylinder with the same diameter. The forming head 10 is typically the part of the mold core which comes in contact with sprayed material in use. Thus, unlike in FIG. 1, the forming head 10 often has a specially designed outer contour, for example an external thread for forming the internal thread on a tube closure. So that the forming head 10 can remove the heat generated during the injection process as quickly as possible, it is made of a good thermal conductivity alloy such as BeCu. In contrast, the carrier 20, which does not come into direct contact with the sprayed material, is made of a "common" material such as steel.

As can be seen from the sectional view of FIG. 3, the carrier 20 has an inner channel 22, in which an inner tube 23 is mounted concentrically. Coolant can be supplied through this inner tube 23 (see arrow in FIG. 3), which can flow back through the surrounding annular gap. The inner tube 23 extends in the illustrated example into a recess 12 which is formed in the forming head 10, so that the coolant is forcibly guided into the forming head. In this way, optimum heat transfer from the forming head 10 to the coolant is achieved.

The connection of the exposed sitting on the carrier 20 forming head 10 is advantageously carried out by adhesion, in particular gluing, soldering or welding. In practice, laser welding and electron welding have proven particularly useful in this context. Due to the cohesive connection a tight fit of the forming head 10 is achieved on the support 20, wherein at the same time the connection between these two bodies is everywhere liquid-tight, so that the coolant channel 22 has no leakage. Elaborate and trouble-prone tools such as the placement of O-rings between the two bodies to be connected are not required in this Zusammenhan g.

Furthermore, it can be seen from the figures that the carrier 20 has at its front end upstanding teeth 21 and the forming head 10 correspondingly at its front end downwardly projecting teeth 11, wherein the teeth 11 of the forming head 10 straight into the gaps between the teeth 21st the carrier 20 fit and vice versa. Through this compatible toothing a positive engagement of carrier 20 and mold head 10 is achieved, which ensures the transmission of torques about the longitudinal axis of the mandrel, without that the material connection would be charged.

Claims

claims A mandrel for a spheroidal mold, comprising: a) a forming head (10) of a material having a higher thermal conductivity; b) a carrier (20) made of a material having a lower thermal conductivity, which has a coolant channel (22), wherein the forming head (10) is materially and positively connected to the carrier (20). 2. mold core according to claim 1, characterized in that the forming head (10) has a thermal conductivity of at least 72 W / m-K. 3. mold core according to claim 1 or 2, characterized in that the forming head (10) Cu, Be, Co, Ni or Si, preferably BeCu, contains or consists thereof. 4. mold core according to at least one of claims 1 to 3, characterized in that the carrier (20) iron or steel, stainless steel or brass contains or consists thereof. 5. mold core according to at least one of claims 1 to 4, characterized in that the forming head (10) and the carrier (20) are positively connected with each other. 6. mold core according to claim 5, characterized in that the forming head (10) and the carrier (20) with each other compatible toothings (11, 21). 7. mandrel according to at least one of claims 1 to 6, characterized in that the forming head (10) closes an opening of the coolant channel (22). 8. mandrel according to claim 7, characterized in that the forming head includes a recess (12) which forms an extension of the coolant channel (22). 9. mold core according to at least one of claims 1 to 8, characterized in that the coolant channel (22) has an inner tube (23) and an annular gap surrounding this. 10. A method for producing a mandrel with a) a forming head (10) made of a material having higher thermal conductivity; b) a carrier (20) made of a material having a lower thermal conductivity, which has a coolant channel (22), characterized in that the forming head (10) is materially and positively connected to the carrier (20), preferably by gluing, soldering or welding , in particular laser welding or electron welding.