WO2022009369A1

WO2022009369A1 - Moulding tool with heat sink

Info

Publication number: WO2022009369A1
Application number: PCT/JP2020/026810
Authority: WO
Inventors: Carsten Romanowski
Original assignee: Lixil Corporation
Priority date: 2020-07-09
Filing date: 2020-07-09
Publication date: 2022-01-13
Also published as: DE112020007413T5

Abstract

Moulding tool (1) comprising at least one heat sink (2) with at least one cooling channel (3) formed therein, wherein the heat sink (2) is manufactured with a material comprising copper by means of a 3D printing process. Furthermore, a method of manufacture for such a heat sink (2) and a preferred use of the moulding tool (1) is proposed.

Description

MOULDING TOOL WITH HEAT SINK

The present disclosure relates to a moulding tool comprising at least one heat sink with at least one cooling channel formed therein.

The disclosure is particularly applicable to injection moulding tools, especially as a so-called casting core. Such casting cores may be used to form internal cavities in the production of cast components. Such a casting core is usually, at least partially, surrounded on its outer surface with (meltable or molten) casting material, which then hardens or solidifies there. After the casting material has solidified, the casting core may preferably be removed from the mould again (reusable core).

Summary

This results in the special requirement that such moulding tools under the given conditions shall cause positive solidification behaviour of the casting material. In particular, the aim is to ensure that a uniform temperature is provided by the moulding tool and that the heat of the casting material may be removed quickly and/or evenly.

This goes hand in hand with the requirement for such a moulding tool to provide a relatively high thermal conductivity. For this purpose, a variety of different materials have already been proposed for the production of such moulding tools.

Fig. 1 illustrates a first embodiment of a moulding tool;
Fig. 2 illustrates a second embodiment of a moulding tool;
Fig. 3 illustrates a third embodiment of a moulding tool;
Fig. 4 illustrates a fourth embodiment of a moulding tool;
Fig. 5 illustrates a schematic illustration of the method of manufacturing a heat sink by means of an additive manufacturing process; and
Fig.6 illustrates a flowchart of method for manufacturing the heat sink.

In addition, it is desirable to increase the cooling capacity of such a moulding tool as much as possible in order to increase the cooling rates of the casting material during the casting process and thus significantly accelerate the production process for cast components. However, this may lead to the fact that a particularly complex internal structure must be formed with regard to at least one cooling channel in order to enable the best possible inflow of the cooling medium and/or the best possible removal of the absorbed thermal energy. This plays an increasing role, especially in the case of complex external geometries for the moulding tool and/or the cast component to be produced.

Finally, it should also be noted that in the context of casting production, the moulding tools are sometimes also subjected to considerable forces and/or pressures, so that also in this case the use of materials and/or the design of the moulding tools seems to be limited. In this respect, such moulding tools are also subject to considerable requirements regarding wear protection and/or structural integrity.

Based on this, it is the object of the present disclosure to at least partially solve the problems described with respect to the prior art. In particular, a moulding tool as well as a process for the production of a heat sink should be specified, with which the casting process is favoured, in particular the solidification times for the cast components may be reduced. At the same time, a long service life for the moulding tool and flexible use within the various casting processes shall be achieved.

These objects are solved with a moulding tool or a process for manufacturing a heat sink according to the independent claims. Further advantageous embodiments are specified in the respective dependent claims. It should be pointed out that the features individually listed in the claims may be combined with each other in any technologically meaningful way and show further embodiments of the disclosure. The description, especially in connection with the figures, explains the disclosure and provides further embodiments.

This is achieved by a moulding tool which has at least one heat sink with at least one cooling channel formed therein. The heat sink is manufactured with a material that includes copper by using a 3D printing process.

The moulding tool is in particular a so-called casting core. In particular, the moulding tool is reusable in its function as a casting core. The moulding tool may be provided in several parts, for example, with two central heat sinks located opposite each other, which are (almost) in contact with each other, for example at the front. The moulding tool can, for example, have a pin-like or rod-like shape.

It is possible that the moulding tool essentially consists only of the heat sink or heat sinks. It is possible that the moulding tool has other parts, such as a sleeve, other connection elements, etc., whereby the heat sink is nevertheless preferably the central element, i.e. may form the basis for all other parts of the moulding tool. In particular, due to the shape or design of the heat sink, which is in particular rotationally symmetrical, an axis is defined, which may also be called the centre axis.

The heat sink is formed with a material, preferably exclusively metallic material, wherein this material comprises copper. Copper may be provided in pure form and/or in form of an alloy. In particular, the heat sink is made of the same material in all areas where the cooling channel is formed. In other words, this also means in particular that the at least one cooling channel inside the heat sink is formed exclusively by this material and/or without any further material boundary. Consequently, the cooling channel, starting from an inlet to an outlet, is formed or surrounded exclusively by this material. It is possible for the cooling channel to be small, e.g. in the form of capillaries, and it may be surrounded by a relatively massive section of material of the heat sink. It is also possible, cumulatively or alternatively, to design at least one cooling channel with a large diameter, which is then surrounded by relatively thin-walled wall sections formed from this material of the heat sink. It is therefore possible that the wall areas surrounding the at least one cooling channel are designed with a material thickness that is significantly larger and/or significantly smaller than the diameter of the cooling channel. The difference in size may be a factor of at least 2, at least 3, at least 5 or even at least 10.

In addition, the heat sink is manufactured using a 3D printing process. In particular, this is a so-called additive manufacturing process, whereby, for example, a finished product may be created from a 3D computer model in a material reservoir. In particular, a (metallic) powder may be provided as the starting material for this purpose, whereby the powdered material may be solidified zone by zone by exposure to a laser beam and accordingly, complex heat sinks may be manufactured by traversing flat path curves in layers one above the other.

In particular, a powdery material is used here, which is then partially melted and thus joined together in predetermined zones. In particular, it is therefore a powder-processing 3D printing process in which a print head builds up the powder material layer by layer, for example in a so-called powder bed. Further, it is possible to use a laser to melt the desired to be hardened areas of the layers and thus partially adjoin or bond them together. Corresponding processes are called selective laser melting (SLM) or laser beam melting (LBM).

It may be advisable to carry out the printing and/or solidification of the material in a protected environment, e.g. by supplying an inert gas.

The at least one heat sink may be formed at least predominantly with brass. It is possible, for example, that the heat sink is predominantly made of brass and also (only) components of (pure) copper and/or (pure) zinc.

Following another advantageous embodiment, it is proposed that the first metal should be a copper-based material and the second metal a zinc-based material. Although not necessary, it may be suitable for specific applications when the first melting point of the first metal is at least 450°C above the second melting point of the second metal. This is the case, for example, for the preferred metal powders, because copper has a melting point of 1085°C and zinc has a melting point of 419.5°C.

The at least one cooling channel may be helical and, in particular, may extend over the major part of the axial length of the moulding tool adjacent to an outer surface of the moulding tool. It is possible that (almost) all sections of the cooling channel extend helically inside the heat sink, for example by a concentric or twisted configuration. Further, a cooling-channel may at least partly run straight, e.g. along the central axis, and may then be guided helix-shaped (back) around the central axis. In any case, it is preferred that the inlet and outlet for the cooling medium, such as water, are positioned on the same side or end of the heat sink. This requires the cooling channel to extend in one direction from one end or side of the heatsink along the axis to the opposite end or side and backwards in the opposite direction.

It is possible that at least 30 %, at least 50 % or even at least 75 % of the volume of the heat sink is hollow because at least one cooling channel is passed through it.

In particular, it is possible that the at least one cooling channel on the side or end of the heat sink furthest from the inlet or outlet is positioned much closer to the outer surface of the moulding tool than in the area of the inlet or outlet itself. In particular, the cooling channel may run just below the outer surface, for example at a maximum distance of 5 mm, in particular a maximum distance of 2 mm, or even only a maximum distance of 0.5 mm [millimetres]. Due to efficiency reasons, a distance below 2 mm is preferred.

In addition, at least one sleeve may be provided, which rests against the at least one (central) heat sink at least in one section. Such a sleeve can, for example, be intended to form a wear protection. It may be important that heat transfer from the (outer) sleeve to the (central) heat sink is also good in this case. An intimate contact of the heat sink with the sleeve is advantageous for this purpose. The sleeve is particularly intended or positioned in the section where the material thickness is thin-walled regarding the outer surface of the moulding tool. A section may also be selected in which the highest stress or temperature effects occur during the casting process.

The at least one sleeve may be formed with a material comprising steel. A steel sleeve may be made particularly wear-resistant. In particular, only one single sleeve is provided per heat sink.

It is possible that the heat sink is (only) pressed into the at least one sleeve. This may mean, for example, that the sleeve has been shrunk onto the section of the heat sink. In particular, the steel sleeve may be manufactured in such a way that its wall thickness is very small and may thus be well supported by the heat sink, but on the other hand it also has such shrinkage properties that an intimate contact with the heat sink may be produced during manufacture, which is then maintained during the casting process.

Following a further aspect, a process for manufacturing a heat sink with at least one cooling channel formed therein for a moulding tool is also proposed here, which comprises at least the following steps as illustrated by Fig.6:
a) Providing at least one metal powder comprising copper,
b) Building up layer by layer and partial solidification of the metal powder by means of a laser.

The process mentioned here is used in particular for the production of a heat sink with a material comprising copper by means of a 3D printing process. In particular, the printing process starts from a metal powder. In this context, copper may be present in pure form and/or as an alloy, for example at least partially as brass. For step b), the SLM or LBM processes are preferred.

Obviously, steps a) and b) are repeated several times, although it is also possible, for example, to carry out step b) more frequently than step a). It is also possible that in step b) the process of solidification by means of a laser is repeated for the same zone of a layer.

For further characterisation of the process, full reference may be made to the above explanations already given for the heat sink produced with it.

The process is advantageous if step a) comprises the provision of a metal powder consisting of copper powder and zinc powder. In other words, this means in particular that no additional binder is used as a raw material or for this manufacturing process. Instead, (only) copper powder and zinc powder are mixed together and thus processed with the laser in step b) so that they themselves form an alloy, especially brass.

It may also be advantageous that in step b) a melting of a metal powder or metal powder composite by means of the laser is planned or occurs. In particular, the laser may be guided in such a way that metal bonds which have already been formed between copper, zinc and/or brass material are re-melted before they solidify again. This may significantly promote the alloying process and thus the comprehensive formation of brass and strong bonding.

Following another advantageous embodiment, it is proposed that at least partial bonds are created between several powder grains of the copper material. The laser parameters and/or the exposure strategies may be elected in such a way that (only) the powder grains of copper material partially combine with each other (in a targeted or controlled manner). In step b), the zinc material may partially adhere to or around the copper material. For example, zinc material may (only) be or remain undissolved around copper material, acting as heat-conductor and/or supporting matrix, or if necessary, partly form mixed crystals with copper material. In this context, the zinc material may act as a pure "metal binder", which may even be melted out and reused after melting.

According to another aspect, the use of such a moulding tool in cooling and partial solidification of a casting part during casting is proposed here. The use is particularly suitable if the casting is made with a material selected from the group of metal and plastic. Further, the use is suggested if the casting is a sanitary housing component. A sanitary housing component may be that of a sanitary fitting, for example, the housing of a water tap or the like.

It has been recognized that brass, in conjunction with a 3D printing process, is suitable for providing appropriate heat sinks or moulding tools. In this way it is now possible, for example, to print a casting core suitable for injection moulding, if necessary supplemented by the assembly of a sleeve component to be attached later.

Depending on the requirements regarding the cooling process and/or the geometry of the moulding tool or heat sink, it is possible to adjust the copper content of the finished part precisely, especially due to the use of the metal powder or the copper powder and zinc powder.

The use of such a moulding tool results in a significant reduction of the cycle time for the casting process of the cast components. This is due in particular to the fact that the casting material solidifies much faster due to the high thermal conductivity of the heat sink and the complex or optimized geometry of the cooling channel in the heating channels, which means that the casting tool may finally be opened again more quickly. This results in a significant improvement in quality, not only with regard to the process, but in most cases also with regard to the cast component. In particular, a geometrically complete solidification may be achieved in critical areas of the cast component. In particular, it may also help to avoid several casting errors.

The disclosure is explained in more detail below using the figures. It should be noted that the figures show particularly preferred embodiments to which the disclosure should not be limited. It should also be noted that, unless explicitly stated otherwise here, the features may be extracted from one figure and, if necessary, be combined with other aspects from other figures or the previous description. It shows schematically.

Fig. 1 shows a moulding tool 1, which has a (central) heat sink 2 on the left and right side. The two heat sinks 2 are in contact at the front side (during the casting process) and may be moved horizontally, especially towards each other for the casting process and away for the removal process. In the opposite end areas, the heat sinks 2 each have an inlet and an outlet for cooling medium, especially water. Each of the heat sinks 2 shown here is designed with several cooling channels 3. The heat sink 2 is formed with a material comprising copper, in particular brass. Both heat sinks 2 are manufactured using a 3D printing process, especially as described here. Fig. 1 also illustrates that a casting 11 may be formed around it, which is first added in liquid form and then solidifies in the environment or due to contact with heat sink 2.

Fig. 2 shows an example of a moulding tool 1, whereby this is provided with a central heat sink 2 and a sleeve 5 resting on a section 6 of the outer surface 4. On the left end of heat sink 2, the inlet 13 and the outlet 14 for the cooling medium are shown. The heat sink 2 has an essential pin-like design with a central axis 15, around which the cooling channels 3 are helically formed, whereby these are positioned close or adjacent to the outer surface 4 of the moulding tool 1, particularly on the opposite end where the section 6 with the sleeve 5 is also located. An example is shown here, where the cooling channel 3 has a relatively large diameter and the wall sections 16 are very thin-walled in between. The sleeve 5 is preferably made of steel and shrunk onto the outer surface 4 of the heat sink 2.

A slightly different embodiment of heat sink 2 is shown in Fig. 3. In particular, a relatively large cooling channel 3 is provided centrally so as to ensure that cold coolant is directly fed to the front of the tip, which is usually subjected to high temperatures. From there, a helical section of the cooling channel surrounding the axis 15 and the large central straight section is provided so that the coolant is guided back to the outlet close to the outer surface 4.

Fig. 4 shows a further variant of a heat sink 2 with a cooling channel 3, whereby here the cooling channel 3 is essentially completely helical and the incoming helix and the returning helix are nested in each other, so that they lie in a common geometric cylinder, for example.

Fig. 5 illustrates schematically the process of 3D printing. It is shown that the heat sink 2 is built up in layers with a metal powder 7, which in this case comprises a copper powder 9 and a zinc powder 10. The individual layers 12 of the powder material are positioned on top of each other with a print head and then consolidated with a laser 8. After completion of heat sink 2, the remaining, unused metal powder 7 may be removed and reused for further processes if necessary.

Claims

A moulding tool (1) comprising:
a heat sink (2) with a cooling channel (3) formed therein, wherein the heat sink (2) is manufactured with a material including copper by means of a 3D printing process.
The moulding tool (1) according to claim 1, wherein the heat sink (2) is formed at least predominantly with brass.
The moulding tool (1) according to any one of the preceding claims, wherein the cooling channel (3) is formed helically and adjacent to an outer surface (4) of the moulding tool (1).
The moulding tool (1) according to any one of the preceding claims, wherein a sleeve (5) is provided which surrounds the heat sink (2) at least in a section (6).
The moulding tool (1) according to claim 4, wherein the sleeve (5) is formed with a material including steel.
The moulding tool (1) according to claim 4 or 5, wherein the heat sink (2) is pressed into the sleeve (5).
Method for manufacturing a heat sink (2) with a cooling channel (3) formed therein for a moulding tool (1), comprising:
a) Providing metal powder including copper; and
b) Layer-by-layer build-up and partial solidification of the metal powder (7) by using a laser (8).
The method according to claim 7, wherein the step a) comprises providing a metal powder (7) includes copper powder (9) and zinc powder (10).
The method according to claim 7 or 8, in which step b) comprises melting a metal powder (7) or metal powder composite by means of the laser (8).
Use of a moulding tool (1) according to any one of claims 1 to 6 or produced by the process according to any one of claims 7 to 8 for cooling and partial solidification of a casting (11) during production.
The use according to claim 10, wherein the casting (11) is produced with a material selected from the following group: metal, plastic.
The use according to claim 10 or 11, wherein the casting (11) is a sanitary housing component.
A moulding tool (1) comprising:
a heat sink (2) with a cooling channel (3) formed therein, wherein the heat sink (2) is manufactured with a material including brass predominantly.
A moulding tool (1) comprising:
a heat sink (2) with a cooling channel (3) formed therein, wherein the cooling channel (3) is formed helically and adjacent to an outer surface (4) of the moulding tool (1).
A moulding tool (1) comprising:
a heat sink (2) with a cooling channel (3) formed therein, wherein a sleeve (5) is provided which surrounds the heat sink (2) at least in a section (6).