WO2012016801A1

WO2012016801A1 - Device and process for producing plastics mouldings

Info

Publication number: WO2012016801A1
Application number: PCT/EP2011/061968
Authority: WO
Inventors: Rene Brunotte
Original assignee: Robert Bosch Gmbh
Priority date: 2010-08-04
Filing date: 2011-07-13
Publication date: 2012-02-09
Also published as: DE102010038915A1

Abstract

The invention relates to a device (10) for producing plastics mouldings (1), with tooling (17) which has a reception chamber (18) for receiving and heating a solid moulding composition (2), and with at least one connecting duct (22) which connects the reception chamber (18) with at least one cavity (15) of a mould (12) and with equipment (19) in particular of the nature of a piston, for ejecting the at least to some extent molten moulding composition (2) from the reception chamber (18) into the at least one connecting duct (22) and the at least one cavity (15) of the mould (12). The invention provides a separator (28) arranged in the at least one connecting duct (22) and dividing the at least one connecting duct (22) into at least two subducts (23, 24) in the direction (30) of flow of the at least to some extent molten moulding composition (2).

Description

Description title

Apparatus and method for producing molded plastic parts

State of the art

The invention relates to a device and a method for producing molded plastic parts according to the preambles of the independent claims.

Such a device or such a method are already known from practice, the method also being referred to as a "Resin Transfer Molding" method. Here, the process is used to produce molded parts from thermosets and elastomers. A device used for the application of the method has a receiving chamber or antechamber in which an initially solid molding compound, from which the molded part is subsequently formed, is introduced. The molding compound is then injected into a molding tool via the generally heated receiving chamber or prechamber after at least partial melting thereof via at least one connecting channel, preferably a plurality of connecting channels, this being done, for example, by means of a piston which separates the at least partially molten molding compound from the receiving body. or pre-chamber in the at least one connecting channel injects or overshoots. The forming of the molding itself takes place in a receptacle (cavity) or a mold cavity of the mold under the action of heat and pressure.

For relatively small moldings and thus also relatively small, usually tablet-like molding compositions, the known method works satisfactorily. On the other hand, relatively large molded parts, which accordingly require relatively large or even several molding compounds, are problematic in order, in particular in the presence of a plurality of receptacles in the molding tool, in one operation. lends to be able to produce many moldings. The problem here is in particular that sufficient material of the molding material is melted before it is introduced into the receptacle of the mold. Therefore, relatively large heating powers or a relatively long residence time of the molding compound in the receiving chamber are required in order to achieve the desired melting of the molding compound.

Furthermore, it has been found that heat is also introduced into the molding compound via the connecting channel between the receiving chamber and the molding tool. It has been found that in the boundary layer of the molding compound to the connecting channel a laminar flow prevails, which leads to a better heating of the molding compound on the wall of the connecting channel.

Disclosure of the invention

Starting from the illustrated prior art, the invention has the object, a device or a method for producing made of plastic moldings according to the preambles of the two independent claims in such a way that an improved melting of the

Mold compound is enabled. Such an improved melting of the molding compound makes it possible to minimize the length of the at least one connecting channel between the receiving chamber and the molding tool or to reduce the heating power of the receiving chamber. Both lead to reduced investment or operating costs. Furthermore, an improved melting performance of the molding compound under otherwise identical conditions leads to a higher performance of the device, since the time for melting the molding compound is reduced and the cycle time during the production of the molded parts is thus shortened. The objects addressed are achieved in a device or a method for producing molded plastic parts having the features of the two independent claims. The invention is based on the idea of subdividing the connection channel or the flow path of the at least partially melted plastic element into at least two subchannels by means of a separating element in the at least one connecting channel between the receiving chamber for the molding compound and the molding tool or a cavity by means of several connecting channels. to connect with a receiving chamber. In the case of the formation of a connection channel with at least two sub-channels, a better heat transfer is created by a compared to a single connection channel enlarged total contact surface to be melted molding compound in the wall area, which reduces the required melting time for the molding material. A similar effect can be achieved if a cavity is connected to a receiving chamber with several connecting channels.

Advantageous developments of the device according to the invention or of the method according to the invention for producing molded plastic parts are listed in the respective dependent claims. The scope of the invention includes all combinations of at least two features disclosed in the claims, the description and / or the figures. Furthermore, in the claims device-technical features should also be procedurally claimable and procedural features also device technology.

In a preferred embodiment of the invention, it is provided that the size of the lateral surfaces of the sub-channels per unit length is greater than the shell surface of the at least one connecting channel before separation into the at least two sub-channels. As a result, the enlarged contact surface of the at least two sub-channels compared to at least one connecting channel is made possible, which has a better heat transfer result. It is furthermore preferably provided that the cross-sectional area of the at least one connecting channel and the sum of the cross-sectional areas of the at least two sub-channels are the same size. As a result, a uniform flow velocity of the material to be melted is made possible or a pressure which is constant over the flow path of the material is generated.

Furthermore, it is preferred if the cross-sectional areas of the at least two sub-channels are the same size. In particular, a uniform heating of the two partial strands of the plastic material or the molding compound is made possible. This leads to the subsequent introduction of the molten molding material in the mold to a homogeneously melted mass with uniform temperature, which allows a uniform curing and thus a high quality.

In particular, in the case of a molding tool which, due to its design or its size, is supplied with molding compound only by means of a single connecting channel, it is furthermore advantageous if the at least two sub-channels in the flow direction of the at least partially melted molding compound return to the at least one cavity of the molding tool the at least one connecting channel are united. As a result, a thorough mixing or reunification of the partial strands of the molding compound in the connecting channel is made possible, which has a relatively homogeneous molding compound with respect to the temperature distribution.

In a particularly preferred constructive implementation of the invention, it is further provided that the cross-sectional shape of the at least one connecting channel and the at least two sub-channels is respectively round or oval, that the at least one connecting channel and the at least two sub-channels are arranged in a common plane and, in that the molding tool has at least two mold parts which cooperate with one another and whose pitch runs in the common plane. Such a design has the advantage that a simple demoulding of the solidified molding compound from the region of the connecting channel or the at least two sub-channels is made possible, with the round or oval training, the adherence of residues of the solidified molding compound in the at least one connecting channel or the at least two sub-channels is avoided.

Further advantages, features and details of the device according to the invention and of the method according to the invention for the production of plastic moldings resulting from the following description of preferred embodiments and with reference to the drawings.

These show in:

Fig. 1

to a device for producing molded plastic parts during various process phases, in each case in a highly simplified side view, Fig. 5 shows the region of a connecting channel and two sub-channels in a simplified section,

Fig. 6 is a comparison with FIG. 5 modified arrangement with several sub-channels, also in a simplified section and

Fig. 7 shows a comparison with FIG. 6 modified arrangement with a plurality of connecting channels, which connect a receiving chamber with a cavity, also in a simplified section. FIGS. 1 to 4 show an apparatus 10 for producing molded parts 1 made of plastic. The molded part 1 is in particular a molded part 1, which is part of an electrical circuit substrate or an electrical switching device, in particular in applications in motor vehicle technology. Here, by means of the device 10 during a single production cycle at least one molded part 1, but preferably a plurality or more moldings 1 produced simultaneously.

By way of example, the device 10 comprises a machine frame 11, on whose upper side a forming tool 12 is arranged. The molding tool 12 has two mold halves 13, 14, which cooperate with each other, wherein the shape of the molding 1 or the moldings 1 is formed by the mold 12 and the mold halves 13, 14 such that in the mold halves 13, 14 for each Molded part 1 is formed in each case one not shown in Figures 1 to 4 cavity 15. Since, as already explained, several mold parts 1 are produced at the same time per production cycle, this includes

Forming tool 12 thus also a plurality of cavities 15, even if in the description or the figures, if necessary, only one cavity 15 is described or shown.

During the actual manufacturing process of the moldings 1, the two mold halves 13, 14 according to FIGS. 1 to 3 are superposed or in one another Cover arranged such that the cavities 15 are closed to the outside. To remove or remove the at least one molded part 1, the two mold halves 13, 14 are separated from each other or spaced as shown in FIG. 4. For this purpose, the machine frame 11 has a plurality of columns 16 and guides, which carry a tool 17 (also called "plunger").

The upper mold half 14 is disposed on the underside of the tool 17, such that upon lifting of the tool 17 at the same time the upper mold half 14 is also lifted to allow removal of the molded parts 1 (Fig. 4).

The tool 17 comprises a receiving chamber 18 shown only schematically in FIGS. 1 to 4 for receiving at least one solid molding compound 2. The molding compound 2 has, in contrast to the use of granules, a tablet or pellet-like shape with, for example, a large measure

(Length or diameter) of about a maximum of 20mm. The existing in particular from a thermoset molding compound 2 forms the material for the moldings 1, wherein the molding material 2 is at least partially melted by means of the tool 17 and then introduced into the cavities 15 of the mold 12. In this case, the molding compound 2 fills the cavities 15 and after their cooling, in which the molding compound 2 solidifies again, the mold parts 1 can be removed from the mold 12 and optionally post-annealed. The transferring or pushing out of the molding compound 2 from the tool 17 into the molding tool 12 takes place by means of a device 19 shown only schematically in FIGS. 1 to 4, which by way of example has a piston 20 which can be introduced into the receiving chamber 18 and thereby at least partially melted molding compound 2 displaced from the receiving chamber 18. To melt the molding compound 2, the tool 17 or the receiving chamber 18 is formed heatable, such that the wall of the receiving chamber 18, for example, has a temperature of about 180 ° C.

The transferring or pushing out of the at least partially melted molding compound 2 from the receiving chamber 18, which in this case initially has, for example, a temperature of 70 ° C., into the cavities 15 of the molding tool 12 does not take place directly or directly, but via at least one, recognizable in FIG. 5 connecting channel 22 instead. The connecting channel 22 thus has a direct connection on the one hand with the receiving chamber 18 and on the other hand with the or the cavities 15 of the mold 12. The connecting channel 22 is arranged either in the mold 12 or in the tool 17.

According to the invention, it is provided that the connecting channel 22 is divided into at least two sub-channels 23, 24 over at least a portion of its length. In the exemplary embodiment shown in FIG. 5, the connecting channel 22 on the side 25 is connected to the receiving chamber 18 of the tool 17, and on the side 26 to the cavity or cavities 15 of the forming tool 12. The formation or arrangement of the two sub-channels 23, 24 is such that the connecting channel 22 on the side 25 divides into the two sub-channels 23 and 24, and the two sub-channels 23 and 24 on the side 26 again to the (single) Combine connecting channel 22.

To form the two sub-channels 23, 24, a separating element 28 is provided, which has a separating edge 29 in the embodiment shown in FIG. 5 on the side facing the receiving chamber 18. The cross section of the separating element 28 increases, starting from the separating edge 29, in FIG

Flow direction 30 of the molding material 2, first continuously, then again also continuously decrease, so that the two sub-channels 23 and 24 again unite to the single connection channel 22. The separating element 28 is arranged either in one of the two mold halves 13 or 14, in particular integrally connected to one of the two mold halves 13 or 14, or it has a pitch in the parting plane of the two mold halves 13, 14, ie, that in each case a portion of the Separating element 28 in one of the two mold halves 13, 14 is arranged. Here, the two sub-channels 23 and 34 and the connecting channel 22 are also in the parting plane of the mold 12th

Preferably, the cross section of both the connecting channel 22 and the two sub-channels 23 and 24 are each round, possibly also formed oval. Furthermore, preferably the total cross-sectional area of the two sub-channels 23 and 24 is the same size as the cross-sectional area of the connecting channel 22. It is essential additional heat is introduced or transferred into the molding compound 2 via the region of the connecting channel 22 and the two subchannels 23 and 24. For this purpose, the area of the connecting channel 22 or of the two sub-channels 23 and 24 may additionally be heated or provided with a separate heating device.

In the exemplary embodiment, the cross-sectional areas of the two sub-channels 23 and 24 are at least approximately the same size, that is, that they are each half of the connecting channel 22. As a result, in the described geometry, the circumferential or circumferential surfaces of the two sub-channels 23 and 24 are larger than the circumferential or circumferential surface in the region of the connecting channel 22, in each case based on the same length unit. Due to this enlarged peripheral surface or lateral surface of the two sub-channels 23 and 24, in conjunction with the cross-sectional area respectively reduced in relation to the connecting channel 22, improved heat introduction into the molding compound 2 is made possible.

In FIG. 5, a molding compound 2 is shown purely schematically, which passes through the connecting channel 22 and the two sub-channels 23 and 24. For the sake of simplicity, the molding compound 2 is shown in FIG. 5 during various positions of its transport. In this case, three regions 32 to 34 are designated in the molding compound 2, which are characterized by a different temperature. The region 32 has the highest temperature and the region 34 the lowest temperature, while the region 33 has a temperature which lies between the temperatures of the regions 32 and 34. When passing the molding compound 2 through the connecting channel 22 on the side 25, it can be seen that the region 32 with the highest temperature is located on the circumference of the molding compound 2, since this region is heat-contacting connected to the wall of the connecting channel 22. After the molding compound 2 was separated by means of the separating edge 29 of the separating element 28 in two molding materials 2a, 2b and thereby passes the separator 28, it can be seen that the first coldest portion 34 of the two molding materials 2a, 2b in thermally conductive contact with the wall of the separating element 28th device and is heated by this. At the end of the separating element 28, the two molding compounds 2a and 2b in turn have an inner core or a region 34 with a lower temperature. After passing the side 26, the two molding materials 2a, 2b are brought together again, forming two relatively small areas 34. If one now compares the homogeneity or the temperature distribution of the molding compound 2 after passing through the separating element 28 with a device 10 which has no separating element 28 and thus also no partial channels 23 and 24, it can be established that a larger amount of heat energy is transmitted via the separating element 28 was introduced into the molding compound 2 as would be the case without a separating element 28. In other words, this means that the molding compound 2 after passing through the separating element 28 has a higher degree of fusion or a higher temperature or more uniform temperature distribution.

FIG. 6 shows the case in which the connecting channel 22 is divided into five subchannels 35 to 39. The four separating elements 40 to 43 recognizable in FIG. 6 are used for this purpose. Also in the exemplary embodiment illustrated in FIG. 6, the individual sub-channels 36 to 39 are subsequently brought together again to form a single connecting channel 22.

FIG. 7 shows a modified device in which the receiving chamber 18a with a plurality of connecting channels 22a to 22c is connected, for example, to a single cavity 15a. It finds hereby, in contrast to the embodiments shown so far, no division of a connecting channel 22 in sub-channels 34, 24 and 35 to 39 instead.

The connection channels 22a to 22c can have the same cross-sectional area, but it can also be provided that at least two of the

Connecting channels 22a to 22c have a different cross-sectional area.

Furthermore, it is within the scope of the invention to divide at least one of the connecting channels 22a to 22c again into sub-channels, as in the case of the others

Embodiments is shown. In an embodiment according to FIG. 6, depending on the size or cross section of the connecting channels 22a to 22c, it may occur that the central connecting channel 22b receives the relatively cold or not yet melted core of the molding compound 2 when the molding compound 2 is not completely melted , while in the two edge-side connecting channels 22a and 22c completely molten molding compound 2 from the Edge regions of the molding compound 2 is transported. In this case, it may be advantageous, for example, additionally to divide the middle connection channel 22b into subchannels.

Furthermore, either for reasons of the different degree of fusion of the molding compound 2 in the connection channels 22a to 22c, or due to different lengths or cross-sectional areas of the connection channels 22a to 22c, for example, different pressures in the connection channels 22a to 22c may occur. This must be taken into account when determining the number or dimensioning of the connection channels 22a to 22c or this can be used positively to obtain molded parts 1 with homogeneous quality.

The device 10 described so far can be modified or modified in many ways, without departing from the spirit of the invention. This consists in a division of a connecting channel 22 between a receiving chamber 18 and one or more cavities 15 in at least two sub-channels 23, 24 and 36 to 39th Such a modification of the device 10 may for example consist in that the sub-channels 23, 24 and 36 to 39 either only partially or not at all merged or reunited, ie be directly connected to the or the cavities 15 of the mold 12.

Claims

claims

1. Device (10) for producing molded plastic parts

(1), comprising a tool (17) having a receiving chamber (18; 18a) for receiving and heating a solid, in particular tablet-like, molding compound (2), at least one connecting channel (22; 22a to 22c) which holds the receiving chamber (18 18a) with at least one cavity (15; 15a) of a molding tool (12) and a piston-like device (19) for pushing out the at least partially melted molding compound (2) from the receiving chamber (18; 18a) into the at least one connecting channel (18). 22; 22a to 22c) and the at least one cavity (15; 15a) of the molding tool (12), characterized in that in the at least one connecting channel (22) a separating element (28) is arranged, which comprises the at least one connecting channel (22). in the flow direction (30) of the at least partially melted molding compound

(2) into at least two sub-channels (23, 24, 35 to 39) divided or that the at least one cavity (15a) with a plurality of connecting channels (22a to 22c) is connected.

2. Apparatus according to claim 1,

characterized,

that the size of the lateral surfaces of the sub-channels (23, 24, 35 to 39) per unit length is greater than the lateral surface of the at least one connecting channel (22) prior to separation into the at least two sub-channels (23, 24, 35 to 39).

Apparatus according to claim 1 or 2,

characterized,

the cross-sectional area of the at least one connecting channel (22) and the sum of the cross-sectional areas of the at least two partial channels (23, 24; 35 to 39) are the same.

Device according to one of claims 1 to 3,

characterized,

the cross-sectional areas of the at least two partial channels (23, 24, 35 to 39) are the same size.

Device according to one of claims 1 to 4,

characterized,

in that the at least two subchannels (23, 24, 35 to 39) in front of the at least one cavity (15) of the molding tool (12) are reunited to form the at least one connecting channel (22).

Device according to one of claims 1 to 5,

characterized,

in that the at least one connecting channel (22) is part of the tool (17) and that the separating element (28) is arranged with the tool (17) in heat-conducting contact, in particular molded onto it.

Device according to claim 6,

characterized,

in that the separating element (28) in the flow direction (30) of the at least partially melted plastic element (2) has a first section with an enlarged cross-section and that the separating element

(28) on the receiving chamber (18) facing side a separating edge

(29).

Apparatus according to claim 6 or 7,

characterized,

in that the cross-sectional shape of the at least one connecting channel (22) and the at least two partial channels (23, 24, 35 to 39) is round or oval, that the at least one connecting channel (22) and the at least two partial channels (23, 24) in a common plane are arranged, and that the molding tool (12) has at least two mutually cooperating mold halves (13, 14) whose pitch extends in the common plane.

Device according to one of claims 1 to 8,

characterized,

in the presence of a plurality of connection channels (22a to 22c) connected to a cavity (15a), at least two connection channels (22a to 22c) have different cross-sectional areas.

10. A method for producing molded plastic parts (1), in which in a receiving chamber (18; 18a) a solid molding compound (2) is at least partially melted and subsequently melted over at least one

Connecting channel (22; 22a to 22c) in at least one cavity (15; 15a) of a mold (12) is introduced, characterized in that the at least one connecting channel (22) by means of at least one separating element (28) in at least two sub-channels (23, 24, 35 to 39), wherein the lateral surfaces of the at least two partial channels (23, 24, 35 to 39) per unit length are greater than the lateral surface of the at least one connecting channel (22) or that the molding compound (2) of the receiving chamber (18a) is distributed in a plurality of connecting channels (22a to 22c), which are connected to a cavity (15a). 5