DE102010038915A1 - Apparatus and method for producing molded plastic parts - Google Patents

Abstract

The invention relates to a device (10) for producing molded plastic parts (1) comprising a tool (17) having a receiving chamber (18) for receiving and heating a solid molding compound (2), at least one connecting channel (22). which connects the receiving chamber (18) to at least one cavity (15) 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) into the at least one connecting channel (18). 22) and the at least one cavity (15) of the mold (12). According to the invention, a separating element (28) is arranged in the at least one connecting channel (22), which divides the at least one connecting channel (22) into at least two partial channels (23, 24) in the flow direction (30) of the at least partially melted molding compound (2) ).

Description

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, wherein the method is also referred to as "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 effected, 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 moldings which accordingly require relatively large or several molding compounds are problematic in order to be able to produce as many moldings as possible, in particular in the presence of a plurality of receptacles in the mold, in one operation. 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 via the connecting channel between the receiving chamber and the molding tool in the molding compound. 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 molded plastic parts according to the preambles of the two independent claims in such a way that an improved melting of the molding material is made possible. 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 with otherwise the same. Conditions for a higher performance of the device, since the time for melting the molding material is reduced and the cycle time in the manufacture of the moldings 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 to divide the connection channel or the flow path of the at least partially melted plastic element in at least two sub-channels by a separating element in the at least one connecting channel between the receiving chamber for the molding material and the mold or a cavity by means of several connecting channels to connect to a receiving chamber. In the case of the formation of a connecting channel with at least two sub-channels, a better heat transfer is created by a larger compared to a single connection channel 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 The lateral surfaces of the sub-channels per unit length is greater than the lateral surface of the at least one connecting channel prior to 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 or 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:

1 to 4 a device for producing molded plastic parts during various process phases, each in a highly simplified side view,

5 the area of a connection channel and two sub-channels in a simplified section,

6 one opposite the 5 modified arrangement with several sub-channels, also in a simplified section and

7 one opposite the 6 modified arrangement with a plurality of connecting channels, which connect a receiving chamber with a cavity, also in a simplified section.

In the 1 to 4 is a device 10 for producing molded plastic parts 1 shown. In the molding 1 it is in particular a molding 1 , which is part of an electrical circuit substrate or an electrical switching device, in particular in applications in automotive engineering. This is done by means of the device 10 during a single production cycle at least one molding 1 , but preferably a plurality or more moldings 1 produced at the same time.

The device 10 includes an example of a machine frame 11 , on the top of a mold 12 is arranged. The mold 12 has two mold halves 13 . 14 on, which interact with each other, passing through the mold 12 or the mold halves 13 . 14 the shape of the molding 1 or the molded parts 1 is formed such that in the mold halves 13 . 14 for every molding 1 one in the 1 to 4 not shown cavity 15 is trained. As preferred, as already explained, per preform several moldings 1 be made simultaneously, includes the mold 12 thus also a multiplicity of cavities 15 Even if in the description or the figures possibly only one cavity 15 described or shown.

During the actual manufacturing process of the molded parts 1 are the two Mold halves 13 . 14 according to the 1 to 3 arranged one above the other or in cover, such that the cavities 15 are closed to the outside. For removing or removing the at least one molded part 1 become the two mold halves 13 . 14 according to the 4 separated or spaced apart. For this purpose, the machine frame 11 several columns 16 or guides on which a tool 17 (also called "plunger") wear.

The upper mold half 14 is at the bottom of the tool 17 arranged such that when lifting the tool 17 at the same time the upper mold half 14 with is raised to a demolding of the moldings 1 to enable ( 4 ).

The tool 17 includes one in the 1 to 4 only schematically illustrated receiving chamber 18 for receiving at least one solid molding material 2 , The molding material 2 has, in contrast to the use of granules, a tablet or pellet-like shape with, for example, a maximum degree (length or diameter) of about a maximum of 20 mm. The particular consisting of a thermoset molding compound 2 forms the material for the moldings 1 , wherein the molding material 2 by means of the tool 17 at least partially melted and then into the cavities 15 of the mold 12 is introduced. This fills the molding compound 2 the cavities 15 from and after their cooling, during which the molding compound 2 solidified again, the moldings can 1 from the mold 12 removed and, if necessary, post-tempered.

The transfer or expulsion of the molding material 2 from the tool 17 in the mold 12 finds by means of a in the 1 to 4 only schematically illustrated device 19 instead, the example of a piston 20 which is in the receiving chamber 18 is insertable while the at least partially melted molding material 2 from the receiving chamber 18 repressed. For melting the molding material 2 is the tool 17 or the receiving chamber 18 formed heatable, such that the wall of the receiving chamber 18 For example, has a temperature of about 180 ° C.

The transfer or expulsion of the at least partially melted molding compound 2 from the receiving chamber 18 , which in this case initially, for example, a temperature of 70 ° C, in the cavities 15 of the mold 12 does not find direct or immediate, but at least one, in the 5 recognizable connection channel 22 instead of. The connection channel 22 thus has direct connection on the one hand with the receiving chamber 18 and on the other hand with the cavity (s) 15 of the mold 12 , The connection channel 22 is either in the mold 12 or in the tool 17 arranged.

According to the invention, it is provided that the connecting channel 22 at least over a portion of its length in at least two sub-channels 23 . 24 is divided. In the in the 5 illustrated embodiment, the connecting channel 22 on the website 25 with the receiving chamber 18 of the tool 17 , and on the page 26 with the cavity (s) 15 of the mold 12 connected. The training or arrangement of the two sub-channels 23 . 24 is such that the connection channel 22 on the website 25 into the two subchannels 23 and 24 splits, and the two sub-channels 23 and 24 on the website 26 back to the (single) connection channel 22 combine.

For the formation of the two subchannels 23 . 24 is a separator 28 provided in the in the 5 illustrated embodiment of the receiving chamber 18 facing side a separating edge 29 having. The cross section of the separating element 28 increases, starting from the separating edge 29 , in flow direction 30 the molding compound 2 initially continuously, in order to then decrease again continuously, so that the two subchannels 23 and 24 back to the single connection channel 22 combine.

The separating element 28 is either in one of the two mold halves 13 or 14 arranged, in particular in one piece with one of the two mold halves 13 or 14 connected, or it has a pitch in the parting plane of the two mold halves 13 . 14 , ie that in each case a subregion of the separating element 28 in one of the two mold halves 13 . 14 is arranged. Here are the two sub-channels 23 and 34 as well as the connection channel 22 also in the parting plane of the mold 12 ,

Preferably, the cross section is both the connecting channel 22 as well as the two subchannels 23 and 24 each round, possibly also oval. Furthermore, preferably the total cross-sectional area of the two sub-channels 23 and 24 the same size as the cross-sectional area of the connecting channel 22 , It is essential that over the area of the connection channel 22 as well as the two subchannels 23 and 24 additional heat in the molding compound 2 is introduced or transferred. For this purpose, the area of the connection channel 22 or the two subchannels 23 and 24 possibly additionally heated or provided with a separate heater.

In the exemplary embodiment, the cross-sectional areas of the two sub-channels 23 and 24 at least approximately the same size, that is, that each half of the connecting channel 22 is. As a result, in the described geometry the circumferential or lateral surfaces of the two sub-channels 23 and 24 larger than the circumferential or lateral surface in the region of the connecting channel 22 , each based on the same unit length. By this enlarged peripheral or lateral surface of the two sub-channels 23 and 24 in connection with the opposite to the connecting channel 22 Each reduced cross-sectional area, an improved heat input into the molding compound 2 allows.

In the 5 is purely schematically a molding material 2 shown that the connecting channel 22 as well as the two subchannels 23 and 24 happens. For the sake of simplicity, in the 5 the molding compound 2 presented during various positions of their transport. Here are in the molding compound 2 three areas each 32 to 34 referred to, which are characterized by a different temperature. The area 32 has the highest temperature and the area 34 the lowest temperature while the range 33 a temperature that is between the temperatures of the areas 32 and 34 lies. When passing the molding compound 2 through the connection channel 22 on the website 25 you realize that the area 32 with the highest temperature at the periphery of the molding compound 2 because this area is heat-contacting with the wall of the connection channel 22 connected is. After the molding material 2 by means of the separating edge 29 of the separating element 28 in two molding compounds 2a . 2 B was separated and thereby the separating element 28 happens, you realize that the first coldest area 34 the two molding compounds 2a . 2 B in heat-conducting contact with the wall of the separating element 28 device and is heated by this. At the end of the separating element 28 have the two molding compounds 2a and 2 B again an inner core or an area 34 at a lower temperature. After passing the page 26 become the two molding compounds 2a . 2 B merged again, with two relatively small areas 34 form.

If one then compares the homogeneity or the temperature distribution of the molding compound 2 after passing the separator 28 with a device 10 that is not a separator 28 and thus no subchannels 23 and 24 has, so you can notice that on the separator 28 a larger amount of heat energy into the molding compound 2 was initiated as would be the case without a separator 28 , In other words, this means that the molding compound 2 after passing the separator 28 has a higher degree of fusion or a higher temperature or more uniform temperature distribution.

In the 6 the case is shown in which the connection channel 22 in five subchannels 35 to 39 is divided. The serve in the 6 recognizable four separating elements 40 to 43 , Also in the in the 6 illustrated embodiment, the individual sub-channels 36 to 39 then back to a single connection channel 22 merged.

In the 7 is a modified device shown in which the receiving chamber 18a with several connection channels 22a to 22c by way of example with a single cavity 15a connected is. It finds hereby, in contrast to the embodiments shown so far, no division of a connecting channel 22 in subchannels 34 . 24 respectively. 35 to 39 instead of.

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, at least one of the connecting channels 22a to 22c in turn split into subchannels, as shown in the other embodiments. In an embodiment according to the 6 It may, depending on the size or cross section of the connecting channels 22a to 22c happen that the middle connection channel 22b , when not completely molten molding material 2 , the relatively cold or not yet melted core of the molding material 2 while receiving in the two edge-side connecting channels 22a and 22c completely molten molding material 2 from the edge regions of the molding compound 2 is transported. In this case, it may be advantageous, for example, the middle connection channel 22b additionally split into subchannels.

Furthermore, it may, either for reasons of different degrees of fusion of the molding material 2 in the connection channels 22a to 22c , or due to, for example, different lengths or cross-sectional areas of the connecting channels 22a to 22c also to different pressures in the connecting channels 22a to 22c come. This must be done when determining the number or dimensioning of the connection channels 22a to 22c be considered or this can be used positively to moldings 1 to obtain with homogeneous quality.

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

Claims (10)

Contraption ( 10 ) for producing molded plastic parts ( 1 ), with a tool ( 17 ), which has a receiving chamber ( 18 ; 18a ) for receiving and heating a solid, in particular tablet-like molding composition ( 2 ), at least one connecting channel ( 22 ; 22a to 22c ), the receiving chamber ( 18 ; 18a ) with at least one cavity ( 15 ; 15a ) of a molding tool ( 12 ) and a particular piston-like device ( 19 ) for pushing out the at least partially melted molding compound ( 2 ) from the receiving chamber ( 18 ; 18a ) in the at least one connecting channel ( 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 the at least one connecting channel ( 22 ) in the flow direction ( 30 ) of the at least partially melted molding material ( 2 ) into at least two subchannels ( 23 . 24 ; 35 to 39 ) or that the at least one cavity ( 15a ) with several connection channels ( 22a to 22c ) connected is. Apparatus according to claim 1, characterized in 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 ) before the separation into the at least two subchannels ( 23 . 24 ; 35 to 39 ). Apparatus according to claim 1 or 2, characterized in that 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 sub-channels ( 23 . 24 ; 35 to 39 ) are the same size. Device according to one of claims 1 to 3, characterized in that the cross-sectional areas of the at least two sub-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 sub-channels ( 23 . 24 ; 35 to 39 ) in front of the at least one cavity ( 15 ) of the molding tool ( 12 ) back to the at least one connection channel ( 22 ). Device according to one of claims 1 to 5, characterized in that the at least one connecting channel ( 22 ) Part of the tool ( 17 ) and that the separating element ( 28 ) with the tool ( 17 ) arranged in heat-conducting contact, in particular integrally formed on this is. 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 ) having. 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 subchannels ( 23 . 24 ; 35 to 39 ) is formed in each case round or oval, that the at least one connecting channel ( 22 ) and the at least two subchannels ( 23 . 24 ) are arranged in a common plane and that the molding tool ( 12 ) at least two co-operating mold halves ( 13 . 14 ) whose pitch is in the common plane. Device according to one of claims 1 to 8, characterized in that in the presence of several, with a cavity ( 15a ) connection channels ( 22a to 22c ) at least two connection channels ( 22a to 22c ) have different cross-sectional areas. Method for producing molded plastic parts ( 1 ), in which in a receiving chamber ( 18 ; 18a ) a solid molding material ( 2 ) at least partially melted and then via at least one connecting channel ( 22 ; 22a to 22c ) in at least one cavity ( 15 ; 15a ) of a molding tool ( 12 ), characterized in that the at least one connecting channel ( 22 ) by means of at least one separating element ( 28 ) into at least two subchannels ( 23 . 24 ; 35 to 39 ), wherein the lateral surfaces of the at least two sub-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 ) from the receiving chamber ( 18a ) into several connection channels ( 22a to 22c ) distributed with a cavity ( 15a ) are connected.

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