WO2016036426A1

WO2016036426A1 - Molding tool and casting mold

Info

Publication number: WO2016036426A1
Application number: PCT/US2015/033053
Authority: WO
Inventors: Elmar Fries
Original assignee: Illinois Tool Works Inc.
Priority date: 2014-09-01
Filing date: 2015-05-28
Publication date: 2016-03-10
Also published as: DE102014112526A1

Abstract

A molding tool with a shaping surface (4) for a workpiece to be produced and one or more integrated temperature-control channels, which are intended to be flowed through by a temperature-control medium, is characterized in that the molding tool comprises a first part-tool (1), comprising the shaping surface (4), and a second part-tool (2), the temperature-control channel or channels (5) being bounded jointly by the first part-tool (1) and the second part-tool (2).

Description

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Molding tool and casting mold

The invention relates to a molding tool with a shaping surface for a workpiece to be produced and one or more integrated temperature-control channels, which are intended to be flowed through by a temperature-control medium. The invention furthermore relates to a casting mold which comprises such a molding tool and which can be provided in particular for injection-molding a workpiece from plastics material.

Casting molds, which comprise one or more molding tools, are used for the production of workpieces by primary forming from different materials. In this case, the materials are introduced in a flowable form and under pressure into cavities formed by the casting molds, said cavities representing the negatives of the external contours of the workpieces to be produced, said materials curing in said cavities and thus forming the workpieces.

Before the workpieces are demolded, they have to cool down until they reach defined demolding temperatures, so as to ensure the dimensional stability of the workpieces that are then no longer supported by the casting mold.

In order to keep unit costs for the workpieces to be produced low, it is necessary to achieve a low cycle time during the production of the workpieces by means of a casting mold. However, this requires active cooling of the already formed workpiece in the casting mold during the cooling phase, in order to correspondingly shorten the latter. Such cooling of a workpiece in a casting mold generally requires a cooling fluid which flows through cooling channels integrated in the casting mold. In the process, heat transfer takes place from the workpiece to that portion of the casting mold that is arranged between the workpiece and the cooling channels, and from this portion to the cooling fluid in the cooling channels. In order to achieve as high a heat transfer as possible between the workpiece and the cooling fluid, the cooling channels should be arranged at as small a distance as possible from the adjacently running shaping surface of the cavity. At the same time, however, on account of the high filling pressures, sufficient dimensional stability for the cavity has to be achieved; for this purpose a minimum thickness of that portion of the casting mold that is arranged between the cavity and the cooling channels is necessary, however.

It is also known to heat a casting mold or keep it warm by heat transfer from a temperature-control medium to the casting mold. This can be provided in particular in order to temporarily prevent or slow down cooling and thus curing of the material while the still flowable material is being introduced into the cavity. As a result, in particular in the case of thin-walled and large-area workpieces, premature curing of the material and thus incomplete formation of the workpiece can be prevented. In order to heat a casting mold or keep it warm, it is in principle possible to use the same channels as are also provided for cooling the casting mold and thus the workpiece.

In the following text, the expression "temperature control" should be understood as meaning that the temperature profile of a casting mold or molding tool of such a casting mold is actively influenced by heat transfer from a temperature-control medium to the casting mold or from the casting mold to the temperature-control medium.

Temperature-control channels in casting molds are frequently provided as rectilinear bores, with the result that these can be formed in a cost-effective manner. With such temperature-control bores, however, a complexly curved profile of a shaping surface of the cavity cannot be reproduced, or can only be reproduced to a limited extent. Consequently, inconstant distances arise between the shaping surface and the temperature-control channels, and these result in correspondingly nonuniform temperature control of the workpiece along this shaping surface. This can result in molding defects in the workpiece.

DE 20 2009 005 219 Ul discloses a casting mold for injection-molding a workpiece from plastics material, in which at least one molding tool that partially forms the casting mold has a temperature-control cavity which is separated from a shaping surface via a portion of the molding tool that is denoted tool wall. Arranged within the temperature-control cavity is a supporting framework that forms voids, the tool wall being supported by way of said supporting framework with respect to a portion of the molding tool that is located beneath the latter and is denoted abutment. The supporting framework can in this case be in the form of a bed of aluminum foam spheres. A temperature-control medium can flow through the voids in the supporting framework and thus for example cool a workpiece in the cavity. As a result of the tool wall being supported by means of the supporting framework, the tool wall is intended to be able to be formed in a comparatively thin manner, with the result that temperature control of the workpiece is intended to be improved. It is furthermore stated that the temperature-control cavity, unlike simple temperature-control bores, can follow even complex geometries of a shaping surface.

A disadvantage with the means known from DE 20 2009 005 219 Ul for the temperature control of a casting mold is the considerable effort associated with the formation and integration of the supporting framework in the casting mold. Furthermore, in the disclosed configuration of the supporting framework in the form of a bed of aluminum foam spheres, the problem arises of virtually punctiform support of the tool wall at a number of locations. Thin dimensioning, desired in principle, of the tool wall can result in cracks in the tool wall as a result of this type of support. The invention was based on the object of indicating a means of controlling the temperature of a workpiece in a casting mold in as simple a manner as possible and as advantageously as possible.

This object is achieved by means of a molding tool according to claim 1 and by means of a casting mold comprising such a molding tool according to claim 10. Advantageous configurations thereof are claimed in the further claims and can be gathered from the following description of the invention.

A generic molding tool with a shaping surface for a workpiece to be produced and one or more integrated temperature-control channels, which are intended to be flowed through by a temperature-control medium, is characterized according to the invention in that the molding tool comprises a first part-tool, comprising the shaping surface, and a second part-tool, the temperature-control channel or channels being bounded jointly by the first part-tool and the second part-tool. The first and/or the second part-tool can in this case be formed preferably from metal and in particular steel.

A "temperature-control channel" is understood in this case to mean a tubular cavity which has a much greater longitudinal extent, in particular by a multiple, than the transverse extent (width or diameter). In particular, a "temperature-control channel" according to the invention also has a transverse extent which is much smaller than the corresponding extent of the adjacently running shaping surface assigned thereto.

According to the invention, the temperature-control channel or channels consequently run(s) along a contact plane formed between the first part and the second part of the molding tool, with the result that even temperature-control channels that run in a curved manner, in particular in a three-dimensionally curved manner, can be formed in a relatively easy manner. Specifically, to this end, temperature-control grooves that are open toward the contact plane can be formed in a relatively easy manner in at least one of the part-tools of the molding tool, said temperature-control grooves then being present as closed temperature-control channels by interaction of the two part-tools.

In this case, provision can preferably be made for each of the temperature-control grooves to be arranged merely in one of the two parts, while the respectively associated portions of the correspondingly other part are configured as planar covering portions, i.e. do not themselves form temperature-control grooves. Provision can particularly preferably be made in this case for all the temperature- control grooves to be arranged in one of the two parts, while the correspondingly other part has exclusively planar covering portions. In this case, all the temperature- control grooves are particularly preferably arranged in the second part-tool such that merely planar covering portions are provided for the first part-tool. This makes it possible to form the first part-tool with a wall thickness that is as constant as possible in the portion between the shaping surface and the covering portions covering the temperature-control grooves. This can be advantageous for workpiece cooling that is as uniform as possible.

Since the molding tool according to the invention allows the integration of even curved temperature-control channels in an easy manner, in order to achieve temperature control of the workpiece that is as uniform as possible, provision can be made for the temperature-control channel or channels to run along the shaping surface at as constant a distance as possible. The shaping surface can in this case be formed even in a comparatively complexly curved manner.

In this case, provision can particularly preferably be made for the contact plane formed between the first part-tool and the second part-tool to have a distance from the shaping surface that is as constant as possible. Such a production of the first part- tool and of the second part-tool and thus of the contact plane formed therebetween can be possible without problems, for example as early as in the context of production of these part- tools by primary forming (in particular mold casting). If the contact plane already has a constant distance from the shaping surface, the temperature-control grooves provided for forming the temperature-control channels can be formed (with respect to their longitudinal orientation) in particular with constantly extending cross sections.

The temperature-control grooves can be introduced by means of known production or machining methods. In particular, the temperature-control grooves can be produced directly at the same time as the production of the corresponding part-tool by primary forming, wherein optionally, in order to achieve flow resistances for the temperature-control medium in the temperature-control channels that are as low as possible, subsequent smoothing of the inner surfaces of the temperature-control channels by for example a finish-machining process can be provided. Such finish- machining can be provided in principle for the part-tool or part-tools as a whole or the entire molding tool, but at least for those surfaces of the first part-tool and the second part-tool that form the contact plane. However, it is also possible to introduce the temperature-control grooves subsequently, for example by a machining process.

Since the contact plane formed between the first part-tool and the second part-tool runs through the temperature-control channel or channels, the molding tool according to the invention should preferably provide a seal for this contact plane. To this end, provision can be made of at least one sealing element which, located within the contact plane, is kept deformed between the first part-tool and the second part- tool. The sealing element can be for example a sealing cord. This can be applied for example in a simple manner in the form of a sealing bead during the production of the molding tool. In the case of a number of temperature-control channels, provision can be made in principle for individual temperature-control channels and in particular all the temperature-control channels to be surrounded by in each case one sealing element. Since, however, an escape of temperature-control medium from the molding tool into the environment is intended primarily to be prevented by means of the sealing element or elements, while it can be unproblematic for temperature- control medium to pass between the individual temperature-control channels, provision can advantageously be made for one sealing element, which surrounds a plurality of temperature-control channels and in particular all the temperature- control channels, to be provided.

In a preferred configuration of the molding tool according to the invention, provision can furthermore be made for the second part-tool to be formed as an insert, which contacts at least two, preferably three, four, five or six sides of the first-part tool, formed as a main body, and in particular is inserted into a corresponding recess in the first part-tool. As a result, a comparatively solid and thus stable configuration of the first part-tool, which comprises the shaping surface and is consequently subjected regularly to a high filling pressure during production of the workpiece, can be realized. Furthermore, maintenance and in particular cleaning of the temperature- control channels and also easy and cost-effective replacement of the second part-tool can be achieved as a result. In addition, as a result of the configuration of the second part-tool as an insert, the latter can be positioned easily and as precisely as possible relative to the shaping surface. Such precise positioning of the second part-tool, which forms the temperature-control channels jointly with the first part- tool, is advantageous for temperature control of the workpiece that is as uniform as possible.

In a preferred configuration of the molding tool according to the invention, provision can be made for a number of temperature-control channels to run next to one another along the shaping surface. Particularly preferably, in this case, these can run next to one another in as parallel a manner as possible. As a result, temperature control of the workpiece that is as uniform as possible along the entire shaping surface can be achieved.

In a further preferred configuration of the molding tool according to the invention, provision can be made for at least some, and preferably all, of the temperature- control channels to open into a collecting space (also denoted rib or riser), which is connected to a feed line or discharge line for the temperature-control medium. An arrangement of such a collecting space between the feed line and the temperature- control channels can be particularly advantageous, because as a result the temperature-control medium can be distributed to the temperature-control channels as uniformly as possible and in particular at a substantially identical inlet temperature. As a result, an approximately identical temperature-control performance can be achieved for the individual temperature-control channels.

A collecting space arranged between the temperature-control channels and the discharge line can have an advantageous effect with regard to an as far as possible identical flow rate in the individual temperature-control channels, and so, in a particularly preferred configuration of the molding tool according to the invention, provision is made of a first collecting space, which is connected to a feed line for the temperature-control medium, and a second collecting space, which is connected to a discharge line. Via the feed and discharge lines, the temperature-control channels can be integrated in a circuit for the temperature-control medium.

For integration of the collecting space or spaces that is as easy to establish as possible, provision can be made for said collecting space or spaces to be integrated in the first part-tool or the second part-tool, particularly preferably in the second part-tool formed as an insert, and for the feed line and/or the discharge line to be integrated at least in one portion in the corresponding other part. In this case, the feed line and/or the discharge line can be formed in particular as a simple bore.

A casting mold according to the invention comprises at least one first molding tool, formed according to the invention, and a second molding tool, which likewise comprises a shaping surface, the first molding tool and the second molding tool jointly forming a mold cavity comprising the shaping surfaces. The casting mold according to the invention and thus the molding tool according to the invention are suitable in particular for the production of a workpiece from plastics material by injection- molding, since, in the case of such a workpiece, the as far as possible uniform temperature control that is enabled by the invention can have a particularly advantageous effect with regard to avoiding molding defects. This is the case in particular when the workpiece has a relatively large ratio of area to wall thickness in the portion formed by the shaping surface.

The temperature-control channels can in particular be cooling channels, which, in order to cool the component, are flowed through by a cooling medium, in particular a cooling fluid. In this case, heat transfer from the workpiece to the cooling medium via the molding tool primarily occurs. However, it may also be possible for the workpiece to be heated or the cooling of the workpiece to be slowed down, in that the temperature-control channels are flowed through by correspondingly warm temperature-control medium. In this case, heat transfer from the temperature-control medium to at least the molding tool, optionally also to the workpiece, is primarily provided. Such slowing down of the cooling of the workpiece can be provided in particular during the introduction of the material provided to form the workpiece.

The indefinite article ("a", "an"), in particular in the claims and in the above description generally explaining the claims, should be understood as such and not as numerals. Components accordingly specified thereby should thus be understood as being present at least once, it being possible for them to be present multiple times.

The invention is explained in more detail in the following text with reference to an exemplary embodiment illustrated in the drawings, in which:

Fig. 1 : shows a perspective view of a molding tool according to the invention;

Fig. 2: shows a longitudinal section through the molding tool; Fig. 3: shows a cross section through the molding tool along the section plane III - III in fig. 2; and

Fig. 4: shows a cross section through the molding tool along the section plane IV - IV in fig. 2.

The molding tool shown in the drawings comprises a first part-tool 1 formed as a main body and a second part-tool 2 formed as an insert. In this case, the second part- tool 2, which is formed in a cuboidal manner with the exception of a single surface, contacts the first part-tool 1 in a substantially contiguous manner at a total of five sides in a recess, serving as an insert receptacle, in the first part-tool 1. As a result, the second part-tool 2 is received exactly and without play within the first part-tool 1. In addition, the second part-tool 2 can, as a result, fulfill a good supporting function for the first part-tool 1.

Formed in one of the surfaces of the first part- tool 1, the tool contact surface 3, is a recess, the wall surface of which serves as a shaping surface 4 for a workpiece (not illustrated) to be produced. In order to produce the workpiece, the molding tool is combined with a second molding tool (not illustrated), wherein, with molding tools resting against one another at the tool contact surfaces 4, the recess forms a molding cavity jointly with a covering recess of the second molding tool, said molding cavity corresponding substantially to the negative of the external contour of the workpiece to be produced.

In a known manner, in order to produce the workpiece, a flowable material is introduced under pressure into the molding cavity and cured there by cooling. Following sufficient curing of the workpiece, the latter can be demolded, to which end the two molding tools are moved apart. The workpiece is removable as a result. In order to accelerate curing of the workpiece, a plurality of temperature-control channels 5 are integrated in the illustrated molding tool, said temperature-control channels 5 being able to be integrated in a circuit for a cooling medium. The cooling medium conveyed in the circuit flows through the temperature-control channels 5, heat transfer from the molding tool to the temperature-control medium taking place, with the result that the molding tool is cooled in the region surrounding the temperature-control channels 5. As a result, increased heat transfer from the workpiece to the molding tool is also achieved, this resulting in the desired cooling and thus in the accelerated curing of the workpiece.

As can be gathered from fig. 2 to 4, the temperature-control channels 5 run adjacently to the entire shaping surface 4 and additionally parallel to one another at a substantially identical distance. In this case, the temperature-control channels 5 are jointly bounded both by the first part-tool 1 and by the second part-tool 2. To this end, starting from a contact surface running parallel to the shaping surface 4 of the second part-tool 2, open temperature-control grooves are formed, said temperature- control grooves being closed as a result of the second part-tool 2 coming into contact with in each case one planar covering portion of a corresponding contact surface of the first part-tool 1, and as a result forming the temperature-control channels 5. The contact surface of the first part-tool 1 has for its part no temperature-control grooves and is thus formed in an entirely planar manner (within the meaning of the invention).

The shaping surface 4 has a profile that is curved in a relatively complex manner. A corresponding profile is also provided for the contact surfaces of the first part-tool 1 and the second part-tool 2, resulting in a constant wall thickness between the shaping surface 4 and the contact plane 6, which runs in a correspondingly curved manner and is formed between the first tool part 1 and the second tool part 2. In conjunction with the temperature-control grooves introduced exclusively into the contact surface of the second part-tool 2, a substantially identical distance, running additionally in a constant manner, of the individual temperature-control channels 5 from the shaping surface 4 arises, this resulting, in combination with an identical cross-sectional area and a constant cross-sectional profile of the temperature-control channels 5, in uniform cooling of the shaping surface 4 and thus of the corresponding outer surface of the workpiece. As a result, molding defects (in particular warping and/or sink marks) can be avoided or at least kept to a minimum for the workpiece to be produced.

In portions which are already no longer located directly adjacent to the shaping surface 4, all the temperature-control channels 5 open on both sides into in each case one collecting space 7, 9. A first collecting space 7 is additionally connected fluidically to a feed line 8 and the second collecting space 9 is connected fluidically to a discharge line 10 for the cooling medium. Via the feed line 8, which is in the form of a simple bore that extends both through the first tool part 1 and through the second tool part 2, the cooling medium circulating in the circuit flows to the temperature-control channels 5. As a result of the interconnection of the first collecting space 7, the cooling medium is in this case distributed uniformly and in particular at a substantially identical temperature to the individual temperature- control channels 5. This is advantageous, too, for realizing cooling of the shaping surface 4 that is as uniform as possible. Once it has flowed through the temperature- control channels, the cooling medium is combined again in the second collecting space 9 and discharged from the molding tool via the discharge line 10, which is likewise in the form of a simple bore extending both through the first tool part 1 and through the second tool part 2.

A groove-like recess 11 that encircles all the temperature-control channels 5 is introduced into the contact surface of the second part-tool 2. Arranged in said recess 11 is a sealing element 12 in the form of an annularly closed sealing cord, the sealing element 12 being deformed, with the second tool part 2 inserted into the first tool part 1 , by contact with the contact surface of the first tool part 1 and as a result sealing off the contact plane 6 formed between the two tool parts 1 , 2. This prevents cooling medium from escaping from the molding tool. The seal can be further improved when a respective sealing element (not illustrated) is also provided in the transitions of the feed line 8 and the discharge line 10 between the first part- tool 1 and the second part-tool 2.

List of reference signs

1 First part-tool

2 Second part-tool

3 Tool contact surface

4 Shaping surface

5 Temperature-control channel

6 Contact plane

7 First collecting space

8 Feed line

9 Second collecting space

10 Discharge line

11 Recess

12 Sealing element

Claims

Claims:

1. A molding tool with a shaping surface (4) for a workpiece to be produced and one or more integrated temperature-control channels (5), which are intended to be flowed through by a temperature-control medium, characterized in that the molding tool comprises a first part-tool (1), comprising the shaping surface (4), and a second part- tool (2), the temperature-control channel or channels (5) being bounded jointly by the first part-tool (1) and the second part-tool (2).

2. The molding tool as claimed in claim 1 , characterized in that the first part-tool (1) and/or the second part-tool (2) forms/form one or more temperature-control grooves and the other part-tool (1, 2) forms planar covering portions that are assigned to the temperature-control grooves.

3. The molding tool as claimed in either of the preceding claims, characterized in that the temperature-control channel or channels (5) run(s) along the shaping surface (4) at a constant distance.

4. The molding tool as claimed in one of the preceding claims, characterized in that a contact plane (6) formed between the first part- tool (1) and the second part-tool (2) has a constant distance from the shaping surface (4).

5. The molding tool as claimed in one of the preceding claims, characterized in that the second part-tool (2) is formed as an insert, which contacts two, three, four, five or six sides of the first part-tool (1), formed as a main body.

6. The molding tool as claimed in one of the preceding claims, characterized in that a number of temperature-control channels (5) run next to one another along the shaping surface (4).

7. The molding tool as claimed in one of the preceding claims, characterized in that a number of temperature-control channels (5) open into a collecting space (7, 9), which is connected to a feed line (8) or discharge line (10) for the temperature-control medium.

8. The molding tool as claimed in claim 7, characterized by a first collecting space (7), which is connected to a feed line (8), and a second collecting space (9), which is connected to a discharge line (10).

9. The molding tool as claimed in claim 7 or 8, characterized in that the collecting space or spaces (7, 9) is/are integrated in the first part-tool (1) or the second part- tool (2) and the feed line (8) and/or the discharge line (10) is/are integrated at least in one portion in the correspondingly other part-tool (1, 2).

10. A casting mold with a first molding tool as claimed in one of the preceding claims and a second molding tool, the first molding tool and the second molding tool jointly forming a mold cavity comprising the shaping surface (4).