WO2015140239A1

WO2015140239A1 - Method for producing a plastic injection moulded part and plastic injection moulded part

Info

Publication number: WO2015140239A1
Application number: PCT/EP2015/055751
Authority: WO
Inventors: Holger Zang
Original assignee: Autoliv Development Ab
Priority date: 2014-03-20
Filing date: 2015-03-19
Publication date: 2015-09-24
Also published as: DE102014003968A1

Abstract

The invention relates to a method for producing a plastic injection moulded part (10) by means of an extruder (20), via which a moulding compound (30) is supplied to a tool (40) having at least one cavity (45), reinforcing additives (50, 55) are supplied to the molding compound (30) during or after the plasticizing process. The type and/or amount of of the supplied reinforcing additives (50, 55) is modified during the filling of the cavity (45) with the moulding compound (30).

Description

The invention relates to a method for producing a plastic injection-molded part with an extruder, via which a molding compound is supplied on a mold having at least one cavity, wherein reinforcing additives are supplied to the molding compound during the plasticizing or after the plasticizing. The invention also relates to a plastic injection molded part of a molding compound with reinforcing additives, which have been introduced into the cavity with the plasticized molding compound.

Plastic injection molding is a common method to produce workpieces of complex structure in high quantities cheap. For this purpose, a molding compound is brought into a plasticized state by one or more extruders, which may or may not be heated. If the mold is filled, an extruder screw is usually moved via a hydraulic piston in the direction of the mold, so that the plasticized molding compound is introduced under high pressure into the cavity, which has the shape of the workpiece to be produced. After completion of the filling process, optionally after a Nachdrück- and holding phase, the molding compound cools in the cavity, the mold is opened and the usually finished workpiece is removed from the mold. If necessary, the sprue is still removed. To increase the strength of the molding composition, which usually consists of a thermoplastic material, fillers are added to the molding compound, for example glass fibers, mineral components or the like. These fillers are usually supplied to the base material, formed into finished compounds in the form of pellets, fed to the extruder and plasticized therein. The processing industry thus receives a ready-mixed starting material or compound for processing. In the- sem compound are the individual components, ie base material, possibly further fillers such as primer and fillers, homogeneously distributed.

In an alternative method, glass fibers are fed to the injection molding machine at the end or in the course of the extruder screw. This makes it possible to adjust the length and amount of the supplied fibers and to avoid or reduce damage to the fibers during the plasticizing process within the screw, since the fibers are not mechanically deformed in the extruder screw. As a result, a loss of strength is avoided, and by using cheap base materials, a cost reduction can be achieved.

Airbag housings are often manufactured as plastic injection molded parts. Particularly in the area of the mounting flange or in the connection of the gas generator occur high mechanical and thermal loads. As a result, comparatively expensive components must be used in the manufacture of airbag housings.

Object of the present invention is to provide a method and a plastic injection molded part, which allows a cost-effective production of components while maintaining or improving the stability and possible weight reduction.

According to the invention this object is achieved by a method having the features of the main claim and a plastic injection molded part with the features of the independent claim. Advantageous embodiments and further developments of the invention are disclosed in the subclaims, the description and the figures.

The method for producing a plastic injection-molded part with an extruder, via which a molding compound is a molding tool having at least one cavitation When reinforcing additives are added to the molding compound during the plasticizing process or after the plasticizing process, the type and / or amount of the reinforcing additives supplied during the filling of the cavity with the molding compound is changed. By varying the nature of the reinforcing additives, the amount of reinforcing additives or both the type and amount of the reinforcing additives supplied, it is possible to achieve a targeted partial reinforcement of areas of the plastic injection molded part, so that by the controlled time of supply or variation of the feed the reinforcing additives to the already plasticized molding compound, the reinforcing additives can be selectively brought to the respective location or area of the component to be manufactured. This makes it possible for the less stressed areas, a less resilient thermoplastic material can be used as a molding compound or specifically targeted less reinforcing additives or other reinforcing additives must be introduced in the less-stressed areas, resulting in a reduction in manufacturing costs, without the reinforcing effect is adversely affected by the additives.

The reinforcing additives can be supplied adaptively or profile-controlled to the molding compound. An adaptive supply of the boosting additives provides sensors that measure, for example, pressure, temperature or levels within the cavity. It is also possible for a change in the supply and / or type of the boosting additives to be controlled via a time control or a quantity control. Alternatively, regardless of the actual conditions within the cavity, a profile-controlled change in the supply of the reinforcing additives may be effected, for example by coupling the feed only to the displacement path of the extruder screw. Also, the type and / or amount of the supplied gain additives can be controlled controlled by a time-distance control of the molding material feed or the displacement of the extruder screw. As reinforcing additives, fibers may be supplied, for example, basalt fibers, carbon fibers, glass fibers, co-fibers or natural fibers. It is likewise possible for the reinforcing additives in spherical or powder form to be fed to the molding compound, with the reinforcing additives achieving an improvement in the thermal and / or mechanical properties of the molding compound. The reinforcing additives are advantageously non-thermoplastic and thus do not melt upon supply to the plasticized molding material. The non-melting of the reinforcing additives is limited to the temperatures that usually occur in the injection molding of plastics.

If fibers are used as reinforcing additives, their length, the amount supplied or also the type of fiber can be changed during the filling. It is also possible that a combination of the parameter change is made, ie that both the length and the quantity as well as the type are adaptively changed during the filling. The fibers can be cut to the desired length in a mixing head in front of the cavity and added to the molding compound, so that it is possible to prepare the molding compound as needed just before it enters the cavity. Likewise, the fibers can be sheared during transport in the extruder, so that the length and possibly the amount of the fibers adjusts depending on the rotational speed of the extruder. For this purpose it is provided that the fibers are fed along the screw to the extruder, for example through one or more openings in the extruder wall, so that the fibers are drawn into the extruder during the plasticization of the material by the screw and break by the exiting shear forces , If an increased amount of reinforcing additives is desired at the end of the cavity remote from the sprue, the reinforcing additives are supplied to the cavity in a larger amount at the beginning of the filling. If reinforcement in the area of the sprue is desired, towards the end of the injection process an increased amount of kungsadditiven supplied so that in the vicinity of the sprue is a greater amount of it than in the front of the cavity supplied molding compound.

The reinforcing additives can be supplied separately or as a plastic reinforcing additive mixture, as well as other components can be supplied, for example, adhesion promoter. A separate feed means that only the reinforcing additive or the reinforcing additives are supplied to the already plasticized molding compound. This results in particularly high precision in the metering, positioning and a high degree of flexibility with regard to the selection of the added reinforcing additives. Alternatively or additionally, the reinforcing additive or the reinforcing additives can be supplied as a plastic reinforcing additive mixture, for example if plasticized molding compounds from two extruders are supplied to the cavity in a mixing head in a two-component injection molding process in the case of the plastic reinforcing additive mixture, either before, during or after the plasticizing process, the molding compound is supplied.

Due to the plastic reinforcing additive mixture, it is possible to introduce a further thermoplastic component into the molding compound and thus into the cavity in order selectively to selectively achieve a material change and thus a higher or adapted load-bearing capacity of the workpiece.

A further development of the invention provides that a molding compound is supplied to the cavity at several points, so that a rapid and complete filling of the cavity can be achieved over a plurality of gates. As a result, it is also possible for different molding compositions or molding compounds with different reinforcing additive components to be supplied to the cavity at different locations and at different times.

The reinforcing additives may enter the cavity before the molding compound enters be supplied. This is particularly advantageous if the cavity is to be filled with only one type of molding compound. Alternatively, it is provided that a mixing is carried out within the cavity, for example when a molding compound without reinforcing additives is supplied over several sprues of a multi-component injection molding machine and molding compounds already provided with reinforcing additives via one or more other sprues, for example from a finished compound or through a Supplying the reinforcing additives are generated in a mixing head, are injected into the cavity, so that injected the reinforced molding compound in the current flow front of the un reinforced base material. This results in a mixing of the additives provided and not provided with additives molding compounds is achieved within the cavity of the mold in those areas in which the molding compounds provided with reinforcing additives are injected.

The reinforcing additives may be added to the molding compound at multiple locations, thereby providing greater variability in both the nature of the reinforcing additives and the nature of the particular reinforcing additives. Thus, it is possible, for example, in the supply of fibers of the same type, to supply the fibers with different lengths of the molding material. Likewise, fibers from different starting materials can be supplied according to the requirements of the molding compositions. Thus, it is possible, for example, to arrange fibers of a specific type and a specific length in a first region of the workpiece, which are supplemented in a second region by fibers of the same type with a different length, while in a third region two fibers of the same or different length and quantity of different type, whereby a gain in the desired range depending on the desired material properties is achieved. The plastic injection-molded part of a molding compound with reinforcing additives, which have been introduced into the cavity with the plasticized molding compound, provides that the reinforcing additives are distributed in different regions distributed in the plastic injection-molded part. Due to the different distribution of the reinforcing additives, for example of the fibers or other additives, an adaptation of the material properties to the loads can take place without the cycle times of the plastic injection molded part being extended. Several different reinforcing additives can be distributed in the plastic injection-molded part, so that in some regions different different reinforcing additives are present corresponding to the load in the plastic injection-molded part. The various reinforcing additives can be distributed in different areas in the plastic injection-molded part, so that the respectively optimum reinforcing additive is arranged in the respective intended area of the plastic injection-molded part. An embodiment of the invention provides that the plastic injection-molded part is designed as an airbag housing into which an airbag can be folded and optionally a gas generator can be mounted.

Embodiments of the invention will be explained in more detail with reference to the accompanying figures. Show it:

Figure 1 is a schematic representation of a plastic injection molding plant;

Figure 2a is a plan view of an airbag housing; Figure 2b is a schematic sectional view of the airbag housing according to Figure 2a; FIG. 3a shows a variant of FIG. 2a; such as

FIG. 3a shows a variant of FIG. 2b.

Figure 1 shows a schematic representation of a plastic injection molding plant for producing a plastic injection molded part 10 with an extruder 20, in which at least one extruder screw 25 is arranged. About the extruder 20 is a molding compound 30, which is arranged in the illustrated embodiment as a plastic granules in a mass hopper, transported in the direction of a tool 40. The screw 25 rotating inside the extruder 20 conveys the molding compound 30 from the hopper through the screw flights to the screw tip towards the tool 40. Heaters may be arranged on the extruder 20 to plasticize the granules together with the friction within the extruder 20. In the illustrated embodiment, the tool 40 is closed and the molding compound 30 is pressed from an exit nozzle of the extruder 20 in a runner 41 of the tool 40 and from there into a cavity 45. By filling the cavity 45, the plastic injection molded part 10 is formed, which can be removed after cooling within the tool 40 and after opening the tool 40.

Between the outlet of the extruder 20, the so-called nozzle, and the actual runner 41 within the tool 40, or within a mold part of the tool 40, a mixing device in the form of a mixing head 44 is arranged in the reinforcing additives 50, 55 of the already plasticized molding compound 30 are supplied. In addition or as an alternative, the reinforcing additives 50, 55 and / or other filler, adhesion promoter or the like are added to the screw 25 at any desired point during the plasticizing, whereby corresponding accesses to the extruder 20 must be present for this purpose. As reinforcing additives can Fibers, powders, granules or other additives to the molding compound 30 are supplied before it reaches the cavity 45 within the tool 40. Dosing devices, not shown, may be present in the mixing head 44 in order to be able to set the amount of the respectively added reinforcing additives 50, 55. Likewise, when fibers are used as reinforcing additives 50, 55, cutting devices for the fibers can be provided so that an adaptation of the reinforcing additives 50, 55 to the respective shape or length and also the mixing ratio with the molding compound 30 can be carried out within the mixing head 44. Thus, it is possible to provide different fiber lengths during the injection process and to supply different amounts of fibers of different lengths to the plasticized molding compound 30.

In the illustrated embodiment, a plurality of reinforcing additives 50, 55 are provided in roll form, so that different reinforcing additives 50, 55 can be supplied to the molding compound 30. Thus, for example, at a certain time of filling, the molding compound 30 may be provided with a first reinforcing additive 50 and at a second time with a second reinforcing additive 55, it is also possible over the injection period both reinforcing additives 50, 55 in different lengths and / or textures of the molding compound 30 supply.

The mixture of molding compound 30 and reinforcing additive 50, 55 or reinforcing additives, which first reaches the cavity 45, is pressed into the cavity 45 by the subsequent molding compound 30 and pushed in front of it, so that a distribution of the molding compound located in the cavity 45 30 can be assumed that the first located in the cavity 45 molding compound 30 reaches the removed portions of the cavity 45 first and remains there, while the last supplied amount of molding material 30 in the area of the mouth of the sprue 41 remains in the cavity 45 , It follows that to influence the mechanical and, where appropriate thermal stabilities of the plastic injection-molded part 10, for example, in the edge regions of the cavity 45 remote from the sprue 41, the reinforcing additives 50, 55 are supplied at the beginning of the injection process. If a reinforcement takes place in the region of the sprue channel 41, reinforcing additives 50, 55 are fed to the plasticized molding compound 30 at the end of the filling period, so that the last injected mixture of molding compound 30 and reinforcing additives 50, 55 in the region of the mouth of the sprue 41 in the cavity 45 remains.

In the tool 40 in the region of the cavity 45 sensors 60 may be arranged, so that the filling process of the cavity 45 can be detected. This makes it possible to effect an adaptive control of the type, quantity and nature of the reinforcing additives 50, 55, so that an adapted adjustment of the mechanical properties of the plastic injection-molded parts 10 can take place.

As an alternative to the adaptive control, the respectively desired amount, the respective desired type, the desired amount and the particular desired quality of the reinforcing additive can be determined via a defined feed profile and fed to the plasticized molding compound 30 after the beginning of the injection process. As sensors 60 temperature sensors, pressure sensors or contact sensors can be used.

In addition to a separate supply alone of the reinforcing additives 50, 55, these can also be supplied in the mixing head 44 in already mixed form. For this purpose, the reinforcing additives 50, 55 embedded in a plastic matrix of the molding compound 30 are supplied, so that it is also possible to perform a multi-component injection molding process with separately supplied reinforcing additives 50, 55.

FIG. 2 a shows a plastic injection-molded part 10 in the form of an airbag housing. It is shown in a schematic plan view. The airbag housing provides a cavity 15 and a flange 16 surrounding the cavity 15. The contour of the flange 16 is substantially rectangular, being provided on the narrow sides recesses for the implementation of fastening screws. The narrow sides of the flange 16 are mechanically particularly stressed, so that in the flange 12 an increased proportion of reinforcing additives 50, for example, glass fibers, basalt fibers or carbon fibers are present. In the region of the cavity 15, the walls surrounding the cavity 15 are less heavily mechanically and thermally stressed, so that no or only a few reinforcing additives are present in a second area 11.

2b, the respective regions 11, 12 can be seen with different proportions of reinforcing additives, wherein the transitions between the individual regions 11, 12 can be fluent. In the region of the sprue 41 there are fewer reinforcing additives than in the flange region 12. In order to produce such a component which has only one sprue 41, the reinforcing additives 50, 55 are fed to the molding compound 30 at the beginning of the injection process, then the supply of the reinforcing additives reduced or adjusted so that the later penetrating into the cavity 45 molding compound 30 contains no reinforcing additives 50, 55 more. In this way, the mechanically highly loaded edge region 12 of the flange 16 can be specifically provided with high-strength fibers, while the remaining component is filled only with the matrix 30. This makes it possible to achieve a matched strength even with plastic injection-molded parts 10, without the entire component having to be produced with the expensive mixture of reinforcing additives 50, 55 and the molding compound 30.

The subsequent introduction of the reinforcing additives 50, 55 after the plating process in the extruder 20 by the extruder screw 25 has the advantage that, in particular in one embodiment of the reinforcing additives 50, 55 as fibers they are not mechanically damaged.

A variant of the invention is shown in Figures 3a and 3b, which also show an airbag housing in plan view and side view. Here, too, different regions 11, 12 of the plastic injection-molded part are provided with different proportions of reinforcing additives 50, 55. In contrast to the embodiment according to FIG. 2b, it can be seen in FIG. 3b that different molding compounds have been supplied to the cavity at a plurality of positions or sprue channels 41, 42, 43. This makes it possible, for example with only one basic mass, which are supplied from one or more extruders plasticized cavity 45 to fill the cavity 45 at several points, for example, in the flange portions 12 with increased reinforcing additive content of the mixing head, the sprue 42, 43 is driven accordingly, to supply the reinforcing additives, while no or less reinforcing additives are supplied to the sprue 41. The mixing of the molding compositions with the different proportions of reinforcing additives takes place within the cavity 45, wherein besides the use of a single base material as molding compound 30, it is also possible and provided for different starting materials to be used as molding compound 30, so that in a multicomponent Injection molding with multiple sprue channels an optimized component design of the plastic injection molded part 10 is achieved. It is provided in a variant of the invention that from a single extruder, the molding compound is conveyed to different gate locations, wherein before each sprue or multiple sprues a mixing head is arranged to achieve an adaptation of the molding material by separate supply of reinforcing additives.

Advantageously, the reinforcing additives 50, 55 are not thermoplastic. In addition to the separate admixture of reinforcing additives 50 in a mixing head, it is also possible that already finished reinforced materials, which are present for example as a finished compound and by a separate Extruders are plasticized, injected into the cavity together with a molding compound not provided with reinforcing additives, so that they mix with the flow front of the base material. By mixing base material and material filled with reinforcing additives within the cavity 45 of the tool 40 is also achieved that an adapted material strength is achieved.

Parts of the component can be made completely without reinforcing additives, it is also possible that on one and the same machine different qualities of a component are produced by reinforcing additives are supplied or not supplied. This is possible without retooling, it must only be disabled, the mixing head.

The different properties of the regions of the component can be obtained in a production process without production interruption or by sequential manufacturing processes. Border pattern parts can be easily produced by changing the length, amount and / or type of reinforcing additives. In addition, a large number of material combinations can be realized if the reinforcing additives are supplied only after the plasticizing process of the base material, since mechanical damage is largely avoided.

Claims

claims:

1, a method for producing a plastic injection molded part (10) with an extruder (20), via which a molding compound (30) is supplied to a tool (40) having at least one cavity (45), wherein reinforcing additives

(50, 55) are supplied to the molding compound (30) during the plasticizing process or after the plasticizing process, characterized in that the type and / or amount of the reinforcing additives (50, 55) supplied during the filling of the cavity (45) with the Molding compound (30) is changed.

2. The method according to claim 1, characterized in that the reinforcing additives (50, 55) are supplied adaptively or profile-controlled to the molding compound (30).

3. The method according to claim 1 or 2, characterized in that as reinforcing additives (50, 55) fibers are supplied, whose length and / or amount supplied during the filling is changed. 4. The method according to claim 3, characterized in that the fibers are cut in a mixing head (44) in front of the cavity (45) to the desired length and the molding compound (30) or by feeding into the extruder (20) along the screw (25) break.

Method according to one of the preceding claims, characterized in that the reinforcing additives (50, 55) are supplied separately or as a plastic-reinforcing additive mixture.

6. The method according to any one of the preceding claims, characterized in that the cavity (45) at several points (41, 42, 43), a molding compound (30) is supplied.

7. The method according to claim 6, characterized in that at the plurality of points (41, 42, 43) molding compounds (30) with different proportions of reinforcing additives (50, 55) are supplied.

8. The method according to any one of the preceding claims, characterized in that the reinforcing additives (50, 55) before entering the molding compound (30) fed into the cavity (45) or a mixing within the cavity (45) is made.

9. The method according to any one of the preceding claims, characterized in that the reinforcing additives (50, 55) at several points of the molding compound (30) are supplied.

10. plastic injection molded part of a molding compound (30) with reinforcing additives (50, 55) which have been introduced into the cavity (45) of the plasticized molding compound (30), characterized in that the reinforcing additives (50, 55) distributed in different areas

Plastic injection molded part (10) are arranged.

1 1. Plastic injection molded part according to claim 10, characterized in that several different reinforcing additives (50, 55) are distributed in the plastic injection-molded part (10).

12. Plastic injection molded part according to claim 1 1, characterized in that the various reinforcing additives (50, 55) in the plastic injection molded part (10) are arranged distributed in different areas.

13. Kunststoffspriizgussteli according to one of claims 10 to 12, characterized in that the plastic injection-molded part (10) is designed as an airbag housing.