WO2000050211A1

WO2000050211A1 - Gmt plastic moulding, method and device for producing the same

Info

Publication number: WO2000050211A1
Application number: PCT/EP2000/000526
Authority: WO
Inventors: Alfred Scharrenberg
Original assignee: Otto Deuschle Modell- Und Formenbau Gmbh & Co. Kg
Priority date: 1999-02-22
Filing date: 2000-01-24
Publication date: 2000-08-31
Also published as: DE19907439C2; EP1073549A1; DE19907439A1; CA2329747A1

Abstract

A GMT plastic moulding (1) comprises a main body (2) which consists of a known glass fibre mat blank that has been impregnated with thermoplastic material, moulded and cured. A component (3, 4) made of a soft polymer, for example, a sealing lip is attached by direct injection moulding to at least one area of the edge of the main body (2).

Description

GMT plastic pressed part and method and device for producing such

The invention relates to a GMT plastic pressed part with a main body, which consists of a glass fiber blank cut soaked with a thermoplastic, pressed and hardened in the form, and with at least one component fastened to the main body made of a soft polymer, and a method and a device for producing such.

GMT plastic pressed parts are understood to mean those plastic molded parts which are produced in the so-called "GMT press process". In this, a glass fiber mat impregnated with a thermoplastic is inserted into a steel mold, which has a female die and a male die movable with respect to the female die using a conventional press. Die and patrix limit a cavity, the shape of which corresponds to the desired shape of the GMT plastic press part. The cavity is delimited by plunge edges made of hardened material, which are formed on the female and male. After a corresponding cooling in the mold, the GMT pressed part can be removed. Because of the high long-fiber glass fiber content, such a GMT pressed part is very dimensionally stable, robust and also recyclable without costly ribbing. It is suitable for many purposes, e.g. for bonnet and underbody paneling, body parts, seat and backrest supports, dashboard supports, noise protection covers, etc. In these fields of application, particularly in automobile construction, it is often necessary to seal lips made of soft polymer material on the actual borrow GMT plastic press parts to attach to the surrounding attachments and seal against them In known GMT plastic press parts, these seals have previously been extruded separately and subsequently on the "main body" of the GMT plastic press part, that is by a GMT -Pressing process from a soaked glass fiber mat, attached. The two-component parts thus created are relatively expensive to manufacture; the stability of the connection between the soft polymer component and the main body leaves something to be desired in some cases.

The object of the present invention is to provide a GMT plastic pressed part of the type mentioned at the outset which is inexpensive to produce and has a good connection between the "main body" and the component made of soft polymer.

This object is achieved in that the component made of soft polymer is injection molded onto the main body.

GMT plastic pressed parts according to the invention can be produced very inexpensively in a single mold. Despite the different manufacturing processes that are carried out in this single mold, the cycle times that can be achieved are comparable to the cycle times of pure molded parts and can sometimes be undercut. The production can be run fully automatically. Since the two-component materials meet relatively hot, they can form a good bond. The cooling times can be in relatively good harmony with one another.

In an advantageous embodiment of the According to the GMT plastic press part, the connection area between the soft polymer component and the main body is increased by a gradation. Particularly in the case of thin wall thicknesses of the GMT plastic pressed part, such an embodiment has proven very successful in order to achieve a good fusion connection. In this case, a reinforcing bead along the hard-soft connection of the pressed part may be necessary; However, this can be arranged on the respectively invisible surface of the GMT plastic pressed part and does not interfere there.

The invention also has the task of creating a method for producing a GMT plastic pressed part which is inexpensive to carry out and results in highly stable connections between the main body and the soft component.

This object is achieved in that the component made of soft polymer is injected directly onto the main body. The advantages of the method according to the invention derive accordingly from the advantages described above of the GMT plastic pressed part according to the invention. The same applies to the advantageous embodiment of the method according to the invention specified in claim 4.

Finally, it is an object of the present invention to develop a device for producing a GMT plastic pressed part of the type specified in the preamble of claim 5 in such a way that the different manufacturing processes with which the main body and the component are made of soft polymer in one Molding tool can be performed. This object is achieved in that

d) the die has at least one second mold recess which, in the closed position of the mold, partially delimits a second cavity which is complementary to the mold of a soft polymer component of the GMT plastic pressed part;

e) the patrix has at least one second mold recess, which partially delimits the second cavity in the closed position of the mold;

f) at least one closing knife slide is arranged along the common edges of the two cavities, which is between a first position in which it

Interrupts communication between the two cavities, and a second position in which it releases communication between the two cavities can be moved;

g) the areas of the edges of the second cavity which are not formed by the closing knife slide are formed by hardened plunge edges on the male and female molds, between which there is a defined gap which is narrower than the gap between the plunge edges delimiting the first cavity;

h) at least one injection nozzle opening into the second cavity is provided.

The particular advantage of such a device according to the invention is that the molding tool can be installed in a normal press. Costs for the production of a special machine are therefore eliminated. A separate, also a decommissioned, injection unit can simply be docked to the press. All work steps of the method according to the invention can then be carried out in this one station, which considerably reduces the manufacturing outlay in the production of the GMT plastic pressed part. By means of the closing knife slide provided according to the invention, the free spaces for the component made of soft polymer can be opened during the hardening phase of the main body shortly after the mold has been closed, for example about 5 seconds after the mold has been closed, and thus the requirements for the injection molding process Create a component from soft polymer.

A particular problem in the manufacture of the GMT plastic press part is the plunge edges on the female and male dies, which at least in some areas limit both the cavity for the manufacture of the main body and the cavity for the manufacture of the soft polymer component in the mold. Vertical plunge edges cannot be sealed 100%. Due to the constant sliding of the male and female into the female, an air gap of at least 0.035 to 0.05 mm is required. A smaller air gap would inevitably lead to the diving edges eating. In addition, the hardened plunge edges are useful in the pressing processes up to one

Gap size from 0.07 to 0.15 mm. The molding compound, from which the component is made of soft polymer, is, however, very thin and already escapes through gaps that are only 0.015 to 0.02 mm wide. Such an escape leads to poor melt connections and strong burr formation. In the device according to the invention, care must therefore be taken that the plunge edges, which delimit the second cavity forming the soft component of the GMT plastic pressed part, with a very small gap face each other, which is smaller than the gap between the plunge edges in the region of the first cavity forming the main body of the GMT plastic pressed part.

This problem is best dealt with in that embodiment of the invention in which the outer plunge edge delimiting the second cavity is attached to a movable outer slide which can be pressed against a stop by a power source in such a way that the desired gap towards the corresponding inner plunge edge sets. This embodiment of the invention has the advantage that whenever the male and female molds are moved relative to one another and there is a risk of wear or the diving edge being scuffed, the force can be taken from the outer slide. As long as the power source is not activated, the plunge edges on the second cavity are not pressed against one another under the action of force; the outer plunge edge can rather "dodge". Despite the tightest tolerance between these plunge edges, there is no mutual contact under force when entering and exiting. The power source used according to the invention in this configuration is only activated when the male part is stationary in the closed position of the molding tool, the liquid spray compound is to be injected and the plunge edges must therefore remain at the desired distance from one another. This distance is always reliably found by the stop between the outer slide and the mold when the power source is actuated.

The power source can comprise a wedge slide whose direction of movement is not parallel to the direction of movement of the outer slide and that with the outer slide interacts via cam surfaces. This configuration of the power source works particularly precisely and is able to apply high forces to the outer slide and, conversely, to absorb high reaction forces via the outer slide.

At least one plunge edge delimiting the second cavity can be formed on a wear strip. If the very small gap between the corresponding plunge edges has increased inadmissibly, the corresponding wear strip can simply be replaced.

Particularly preferred for the production of thin-walled GMT plastic pressed parts is the embodiment of the device according to the invention in which the end face of the closing knife slide is stepped such that the edge regions of the main body of the GMT plastic pressed part, onto which a component made of soft polymer are molded should arise with a corresponding gradation. The purpose of this measure has already been explained above.

An embodiment of the invention is explained below with reference to the drawing; show it

Figure 1: the perspective view of a GMT plastic press part with molded sealing lips;

FIG. 2: a vertical section through the molding tool for producing the GMT plastic pressed part from FIG. 1;

FIG. 3: an enlarged detail of the molding tool from FIG. 2; FIG. 4: a top view of the die mold half of the molding tool of FIGS. 1 and 2;

Figures 5 and 6: detailed enlargements of the mold of Figures 1 to 4 in different stages of the manufacturing process of the GMT plastic press part;

7 shows a section through the edge region of the GMT plastic pressed part from FIG. 1.

Figure 1 shows a finished GMT plastic press part 1, as used in the automotive industry. It comprises a main body 2, which consists of a thermoplastic-impregnated glass fiber blank blank pressed in the manner described in more detail below. Two sealing lips 3, 4, which consist of a soft plastic suitable for sealing purposes, in particular a polymer, are injection molded onto two edge regions of the main body 2 in a manner also described below. The further precise shaping of the GMT plastic molded part 1 is of no importance in the present context.

FIG. 2 shows a vertical section through the molding tool 5, which is used to manufacture the GMT plastic pressed part 1 shown in FIG. The molding tool 5 comprises, in a manner known per se, an upper molding tool half 6, hereinafter referred to as "patrix", and a lower mold half 7 cooperating with it, hereinafter referred to as "die". Male 6 and female 7, in the closed state, delimit a first cavity 8, which is complementary to the shape of the main part 2 of the GMT plastic pressed part 1, and additional cavities 9 (cf. also in particular in this regard Figures 5 and 6), the shape of the sealing lips 3 and 4 of the GMT plastic press part 1 is complementary. Those areas of the cavity 8 which do not correspond to edge areas of the GMT plastic pressed part 1 provided with sealing lips 3, 4 are delimited by cooperating plunge edges 11, 13 on the die 7 or die 6, which are made of hardened material in a known manner and when The die 7 and the patrix 6 close to one another with such a play that seizure is avoided and air can escape from the cavity 8. The gap is typically about 0.035 to 0.05 mm. Wear can occur up to about 0.07 to 0.15 mm.

At those areas of its edge which correspond to the edges of the GMT plastic pressed part 1 provided with sealing lips 3, 4, the cavity 8 is limited or can be limited by closing knife slides 14, one of which is shown in the drawing. The closing knife slide 14 is arranged within a corresponding recess in the male part 6 and can be moved vertically between an extended and a retracted position by means of a hydraulic cylinder 15. In the extended position, which is shown enlarged in FIG. 5, its end face rests on the opposite surface of the die 7, while in the retracted position shown in FIG. 6, the end face of the closing knife slide 14 is moved back flush with the adjacent components and the connection releases between cavities 8 and 9.

The cavities 9 are delimited at those edges which correspond to the free edges of the sealing lips 3 and 4 of the GMT plastic pressed part from FIG. 1 by plunge edges 17, 19, one of which (17) on one inside the Male 6 provided wear bar 16 and the other is arranged on an outer slide 18 assigned to the die 7.

As can be seen in particular from FIGS. 3 and 4, the outer slide 18 is movable in the horizontal direction. It is guided by guide strips 28, in which it engages in a form-fitting manner. The movement of the outer slide 18 takes place via a closing wedge slide 20 which can be displaced with the aid of a hydraulic cylinder 21 (see FIG. 4) in a direction which is perpendicular to the desired direction of displacement of the outer slide 18. This construction has the advantage, compared to actuation via a direct-acting hydraulic cylinder, that greater precision is possible when the outer slide 18 moves and that larger forces can also be transmitted and absorbed.

Injection nozzles 22 open into the cavities 9, which extend through the die 7 and are supplied by a heating duct 23 with the plastic used to produce the sealing lips 3, 4.

A groove 40 (see FIG. 3) is formed in the end face of the outer slide 18 facing the cavity 8, the side walls of which converge in the direction of the bottom of the groove 40. A rib 41 of the die 7 engages in this groove 40 of the outer slide 18 and has inclined stop surfaces complementary to the side walls of the groove 40. In the normal position of the outer slide 18 shown in FIG. 3, the side walls of the groove 40 of the outer slide 18 bear against the stop surfaces of the rib 41 of the die 7. In this stop position there is a desired, minimum distance between the plunge edges 17, 19 on the outer slide 18 or the wear strip 16, in which the air can escape from the cavity 9. However, this gap is kept so small that even the low-viscosity material injected into the cavity 9 no longer escapes through the gap between the plunge edges 17 and 19 and can form undesirable burrs or beards.

The die 7 is supported by spacer bars 33 from a large platen 34, which in turn is attached to the stationary part of a conventional press, not shown, via an insulating protection plate 35 and steel protection plate 36. Cooling holes 38 also run through the die 7 in a known manner. An ejector 30 connected to an ejector plate 31 also extends through bores in the die 7 and serves to eject the finished GMT plastic press part 1.

The male 6 is fastened to a mounting plate 42, which in turn is mounted on the movable part of the press already mentioned. Hydraulic channels 37 run through the mounting plate 42 and serve to feed the hydraulic cylinders 15 with which the closing knife slides 14 are moved.

In the drawing, small spacer strips 32 (Figure 2) and 25 (Figure 4) are also shown, which are attached to the mounting plate 42 or on the edge region of the die 7 and with which the distance between the die 6 and die 7 in the closed position of the Press is precisely defined. Guide strips 29 on male 6 and female 7, which run parallel to the corresponding plunge edges 11 and 13, serve to pre-center male 6 and female 7 during the closing process. The two mold halves are also provided with guides 24 (see FIG. 4), with the aid of which a defined rela- active movement is possible.

The device described above works for the production of the GMT plastic pressed part 1 shown in FIG. 1 as follows:

First, the two halves of the mold

5 opened by moving the movable, upper part of the press, not shown, upwards relative to the stationary, lower part. In this way, the inside of the die 7 is accessible. The closing knife slide 14 are extended by means of the hydraulic cylinder 15 so that they protrude beyond the corresponding surface of the male part 6.

A glass fiber mat blank is now inserted from above into that area of the mold recess in the die 7 which, when the mold 5 is closed, delimits the cavity 8 on one side. The glass fiber mat blank is impregnated with hot, liquid thermoplastic. Now the molding tool 5 is closed with the help of the press, not shown, the hydraulic cylinder 21 remaining powerless. The male 6 moves along the plunge edges 11, 13, 17, 19 into the female 7. As soon as the end face of the closing knife slide 14 hits the opposite face of the male part 7, the cavity 8 is closed. When the patrix moves on

6 into the die 7, the thermoplastic-impregnated glass fiber mat blank is now pressed into the final shape. During this further movement of the patrix

6, the closing knife slide 14 are pushed back somewhat into the patrix 6.

As soon as the main body 2 of the GMT plastic pressed part 1, which is now formed in its final form, so far once it has cooled that a certain dimensional stability has been achieved, the closing knife slides 14 are brought into the retracted position shown in FIG. 6 with the aid of the hydraulic cylinders 15. The hydraulic cylinder 21 is actuated, moves the outer slide 18 against the die 7 and holds the outer slide 18 under force in this position in which the required small gap between the plunge edges 17 and 19 is established.

Now low-viscosity polymer material is injected into the cavities 9 via the injection nozzles 22 under relatively high pressure. The air displaced in the process emerges through the very small, defined gap between the diving edges 17 and 19 at the outer slide 18 or the wear strip 16. The polymer material of the sealing lips 3, 4 lies against the still warm material of the main body 2 of the GMT plastic press part 1 previously formed in the cavity 8 and enters into an intimate connection therewith.

After sufficient cooling of the sealing lips 3, 4 formed in this way, the press is opened again and the GMT plastic pressed part 1 thus finished is ejected with the aid of the ejector 30.

The outer slide 18 has the following relationship:

As already mentioned at the beginning, "normal" plunge edges are not very suitable for delimiting a cavity in which a spraying process is to take place, because of the play that is required for them or that occurs. Is the gap between these plunge edges as large as is required for the trouble-free immersion of the male 6 in the female 7 or as it is due to wear after a while, the low-viscosity sprayed material emerges through this gap and creates unsightly burrs and whiskers on the molded part that require reworking. Conversely, if the gap is so small that there is no fear of spray material escaping, there is a risk of the plunge edges being eaten when the male part is immersed in the female part. This problem is taken into account by the outer slide 18 in the following way:

During the retraction of the male 6 into the female 7, the hydraulic cylinders 21, which act on the outer slides 18 via the wedge slides 20, are depressurized. This means that the outer slides 18 can easily deviate to the right in FIGS. 2 and 3 and the plunge edges 17 and 19 can slide past the outer slides 18 and the wear strip 16 practically without stress. As a result, wear on the plunge edges 17, 19 and seizure are reliably avoided. Only after the closing knife slide 14 has been retracted into the position shown in FIG. 6 and shortly before the start of the injection process via the injection nozzles 22 are the hydraulic cylinders 21 acted upon. The outer slide 18 now move into the position shown in Figure 3, in which the side walls of the groove 40 of the outer slide

18 rest against the corresponding stop surfaces of the rib 41 of the die 7 and the correct, small gap between the plunge edges 17 and 19 is established. Now the low-viscosity polymer material can be injected into the cavities 9 without there being any risk of this

Material through the gap between the plunge edges 17 and

19 exits. There is no fear of wear or seizure of the diving edges 17, 19 since there are no relative movements between these diving edges 17, 19 during the time the pressure is applied to the hydraulic cylinders 21. supply takes place.

With the help of the outer slide 18, a high-dimensional delimitation of the cavities 9, which meets the requirements for a molded part, can thus be achieved over a long period of time without wear or danger for the functionality of the molding tool 5. Should the molding tool between the corresponding plunge edges 17 and 19 after a very long service life However, if you have set a larger clearance than desired, it is sufficient to replace the wear strip 16 in order to restore the correct clearance between the plunge edges 17 and 19.

As can be seen from FIGS. 5 and 6, the end face of the closing knife slide 14 is not designed to be flat, but stepped. This end face lies only against the corresponding surface of the die 7 via a relatively narrow “cutting edge” 43, which is adjacent to the cavity 9. This achieves the following:

In the production of the main body 2 of the GMT plastic molded part 1, the edge area adjacent to the locking knife slides 14 is formed in a step-like manner which is complementary to the step shape of the end face of the locking knife slide 14. When the cavity 9 is subsequently sprayed out in the second step, the stepped edge contour 44 of the main parts 2 thus formed is overmolded, so that there is a large connecting surface between the molded sealing lip 3, 4 and the main part 2 (see FIG. 7). As a result, the strength of the connection between the main part 2 and the sealing lips 3, 4 of the GMT plastic press part 1 is improved.

Claims

claims

1. GMT plastic pressed part with a main body, which consists of a glass mat blank impregnated with a thermoplastic, pressed and hardened in the form, and with at least one component made of a soft polymer attached to the main body,

characterized,

that the component (3, 4) made of soft polymer is molded onto the main body (2).

2. GMT plastic press part according to claim 1, characterized in that the connecting surface between the

Component (3, 4) made of soft polymer and the main body (2) is enlarged by gradation.

3. A process for producing a GMT plastic pressed part, in which a glass fiber blank is first impregnated with a hot, liquid thermoplastic, pressed in the form and cured, and in which at least one component made of a soft polymer is formed on the main body thus produced is attached

characterized,

that the component (3, 4) made of soft polymer is molded directly onto the main body (2).

4. The method according to claim 3, characterized in that the edges of the main body (2) on which a grain component (3, 4) made of soft polymer is to be provided, with the pressing of the main body (2) with a / gradation, which is overmolded when the component (3, 4) is molded from soft polymer, such that the connecting surface between Main body (2) and component (3, 4) made of soft polymer is enlarged.

5. Device for producing a GMT plastic press part with a mold that can be mounted on a press, which comprises:

a) a die with a first mold recess which, in the closed position of the molding tool, partially delimits a first first cavity which is complementary to the shape of the main body of the GMT plastic pressed part;

b) a male part movable with the aid of the press with a first mold recess, which together with the first mold recess of the female mold delimits the first cavity in the closed position of the mold;

in which

c) the edges of the first cavity are formed, at least in regions, by hardened plunge edges on the male and female molds, between which there is a defined gap,

characterized in that

d) the die (7) has at least one second mold recess which, in the closed position of the mold, has a second, for the form of a component (3, 4) made of soft polymer of the GMT plastic pressed part (1) complementary cavity (9) partially limited;

e) the male (6) has at least one second mold recess, which partially delimits the second cavity (9) in the closed position of the mold (5);

f) along the common edges of the two cavities

(8, 9) at least one closing knife slide (14) is arranged, which between a first position in which it interrupts the communication between the two cavities (8, 9) and a second position in which it communicates between the two cavities ( 8, 9) releases, is movable;

g) the areas of the edges of the second cavity (9) not formed by the closing knife slide (14) are formed by hardened plungers (17, 19) on the male (6) and female (7), between which there is a defined gap which is narrower than the gap between the plunge edges (11, 13) delimiting the first cavity (8);

h) at least one injection nozzle (22) opening into the second cavity (9) is provided.

6. The device according to / claim 5, characterized in that the outer (19) of the second cavity (9) delimiting plunge edges (17, 19) on a movable outer slide (18) is attached, which is from a power source (20, 21) can be pressed against a stop (40, 41) in such a way that the desired gap to the corresponding inner plunge edge (17) is established.

7. The device according to claim 6, characterized in that the power source (20, 21) a wedge slide (20) comprises, the direction of movement of which is not parallel to the direction of movement of the outer slide (18) and which interacts with the outer slide (18) via cam surfaces

8. Device according to one of claims 5 to 7, characterized in that at least one plunge edge (17) delimiting the second cavity (9) is formed on a wear strip (16).

9. Device according to one of claims 5 to 8, characterized in that the end face of the closing knife slide (14) is stepped such that the edge regions of the main body (2) of the GMT plastic press part (1), on which a component (3, 4) should be molded from soft polymer, with a corresponding gradation.