DE19745909A1 - Discontinuous process forming molding in cavity by volumetric displacement - Google Patents

Abstract

Mechanical energy introduction into the material molded, causing reshaping, is effected by moving parts of the cavity surface. A moving mold half (3-5) includes parts (4, 5) moving relatively to it, to introduce this energy. An Independent claim is included for the molding equipment. Preferred Features: Controlled energy introduction throughout the molding process is differentiated in time and place. In the introduction of molding energy throughout the process, all or only part, of the cavity surface nonparallel to the direction of motion, on one mold half at least, is involved. All molded material is contained by the cavity at the start, or additional material may be added during molding. Material in the cavity is part-introduced into a reservoir by movement of one mold half. This is subsequently ejected into other parts of the cavity. During molding, large flow paths of material occur. Forming is by local plastic flow. The pressing equipment includes hydraulic actuation of the moving parts, which may be in the form of ejectors or slides.

Description

The invention relates to a discontinuous forming process (pressing process) for Plastics based on the principle of volume displacement in a cavity Tool by means of a differentiated pressing process and devices for Implementation of the method and according to the method or in the device manufactured components. The pressing process according to the invention allows the Pressing processes according to the prior art, especially at the end of each Press process necessary high occurring pressures and thus To considerably reduce press performance and thus the construction costs for the Reduce presses accordingly.

Both in depicting the state of the art and the invention some terms are used, which are defined as follows:

The term "cavity" used is defined as that in its surface and its Volume that can be changed during the molding process, limited by Tool surfaces as well as surfaces along which the tool is closed. The cavity formed by the tool is at the end of the Shaping process with the geometry of the product to be manufactured (component) ident. The cavity is usually from surfaces of two tool halves limited. Additional cavities (e.g. flow channels), which are used for the molding process are important, but do not belong to the component geometry, are not in the term "cavity" included.

“Product-loaded cavity” means the part or the partial volume the cavity, which at the time of the molding process with material to be formed is filled.  

With the term "product-loaded surface" that surface of the cavity denotes which are in contact at the respective point in time of the shaping process with the material to be formed.

The working principle of a forming process (or shaping process) Displacement consists in exerting pressure on a deformable mass to force them into a certain shape. Under the concept of "Introducing energy into the material to be formed" means the introduction of mechanical energy in the material to be formed in external units or by appropriate movement of the product-loaded cavity top surfaces.

Prior art processes to which the present invention is based can be used are:

Press processes according to the prior art are those which give shape Processing methods in which the working principle of volume displacement directly expires in the cavity. When closing the rigid tool halves during the molding process is the distance between the two tool halves reduced, which reduces the volume of the cavity. With the reduction of Tool opening becomes forming energy via the surfaces exposed to the product the cavity into the material to be formed.

In the case of pressing processes according to the prior art, the entire mass of material becomes direct placed in the open cavity before the start of the pressing process. The pressing process itself begins with the movement of one or both tool halves, the for the shaping process decisive energy input on the to be reshaped Material takes place over the product-loaded cavity surface. With increasing Tool opening reduction during molding process increased  the product-loaded cavity surface. The pressing process is considered finished, when the movements of the tool halves have stopped, and so that no more forming energy is introduced. During the closing movement of the tool halves persist in moving tool parts Tool halves that belong to the surface of the cavity, such as ejectors or slide, in their, the contour corresponding basic position, so that the Surface contours of the cavity of both tool halves throughout Pressing process can be viewed as rigid.

The working principle of volume displacement means that during the Shaping process comes to "material flows". The order of magnitude of Material movement or material stress during the Shaping process in pressing processes also allows a differentiation of the Press processes in a compression molding process and in an extrusion process.

The compression molding process is to be understood as forming into the pressed part in which the molding compound introduced into the opened cavity is largely in its shape corresponds to the projected area of the component contour, which means no large ones Flow paths of the material to be pressed during the compression molding process are necessary. In the molding process, the closing movement of the Half of the tool energy introduced mainly in locally restricted plastic material transformations and dissipated in compression work.

In the extrusion process according to the prior art, before Pressing process introduced the entire molding compound into the cavity, the mass corresponds to the mass of the component. By the Pressing process is the fluidity of the material to be pressed at the selected processing parameters (pressure, temperatures, time) used to the Fill cavity. Because during the extrusion process, the inserted into the open cavity  The molding compound is significantly smaller in shape than the projected areas of the Is component contour, the deformation of the inserted into the tool takes place Material to the component by covering large flow paths.

In a variant of the pressing process, the transfer molding process, a part comprises the injection cylinder surface part of a mold half. At the The injection molding process becomes that of the completely closed cavity Material volume directly with the tool halves open in the through the Injection molding cylinder additionally inserted cavity. Then the Tool halves without the introduction of forming energy to the nominal size closed. The decisive energy input into the material to be formed takes place exclusively via the product-loaded surface of the Injection molding cylinder, which moves as a rigid body. Of the Shaping process ends with the movement of the injection molding cylinder to that Point in time at which the geometry of the entire cavity surface matches the desired component geometry is identical.

The injection molding process, a special process of the injection molding process, is for the time being, via flow channels from the outside, the pressed material corresponding to the component mass introduced a tool that has not yet been completely closed. This is done by Introduction of forming energy into the material to be formed in external Units, such as by injection molding machines (injection process). The further shaping of the material introduced into the cavity until the final one Component geometry takes place according to the prior art with the closing movement of a or both tool halves (stamping process). The decisive one in the stamping process Energy input to the material brought in is carried out exclusively by Closing movement of the rigid tool halves. During the closing movement of the Tool halves remain on moving tool parts of the tool halves, which belong to the surface contour of the cavity, in their the contour  corresponding basic position. The closing process of the cavities during the Embossing is an extrusion process.

Great difficulty arises in practically all of the above-mentioned processes optimal rheological design of the forming process. Under an optimal rheological interpretation of the forming process means the realization of optimal flow front profiles, flow path lengths and pressure conditions during the filling phase. Often there are also defined orientations, especially for fiber-reinforced ones Materials desired, but which with the pressing processes according to the state of the Technology can hardly be reached. For manipulation reasons, only a few can Inlays, usually only one is desired, inserted in the opened tool cavity are and by no means always the optimal for the extrusion process Put. Due to the production of pressed material, one is usually at predetermined ones Insert geometries bound, which further optimizes the insert situation difficult.

In a pressing process, the cavity is completely filled pressing material with still permissible processing parameters and specified press forces and mechanical or hydraulic press performance of the existing machines are often of primary importance. The necessities Pressing forces for closing the tool halves are towards the end of Extrusion process extremely high, so that very high press energies and above all Press capacities are required for complete tool fillings. Therefore are Presses, which are used for the extrusion process, on their Dimensioning press performance, which is achieved, among other things, that the high kinetic energy of the moving tool half to increase the maximum pressing capacity is used, but this in turn is a considerable Effort to control and regulate this energy is necessary. In addition there is a great tendency of an impending threat in the extrusion process  Tool tilt during the closing of the tool halves, which only by considerable technical effort can be suppressed.

The discontinuous pressing process according to the prior art causes an enormous Waste press energy and press performance. This is reflected in considerable technical effort, in high investment costs for accordingly large, precisely working presses and in high energy costs of a pressing process contrary. In addition, the shaping process in extrusion processes is modern State of the art in press control largely indifferent.

The object of the present invention was that of the forming in the pressing process Pressing forces, pressing energies and pressing capacities required by plastics reduce, thereby saving considerable energy and equipment Effort. This is according to the present invention by the Differentiation in time and place of the pressing process into several Partial press processes reached.

The present invention accordingly relates to a method for discontinuous forming of plastics by displacement in the Cavity, characterized in that the introduction of the forming energy in the material to be formed by at least two moving parts of the cavity Surface takes place, with at least one tool half one or more contains moving parts relative to it, and at least part of the forming energy by the relative movement of these parts is introduced. The forming energy is coming up introduced in a time-controlled and spatially differentiated manner.

The movements of the cavity surfaces are preferably controlled so that a Stagnation of flow fronts is avoided or targeted rheological currents and pressure ratios can be realized during molding, which is positive  Consequences in the achievable component qualities, the possible component designs and the overall process stability of an extrusion process.

In a preferred embodiment of the method according to the invention is on seen the introduction of the forming energy over the entire forming process overall not parallel to the direction of movement of the closing tool half of the cavity surface involved at least one tool half.

In a further embodiment of the method according to the invention Introducing the forming energy over the entire forming process seen only one Part of the total not parallel to the direction of movement of the closing Tool surface lying cavity surface of at least one tool half involved.

The embodiments mentioned relate exclusively to the How volume displacement works within the cavity, regardless of whether the entire component is already in place before the forming process begins appropriate material to be formed is located in the open mold cavity, or that the method of displacement within the cavity simultaneous with an external introduction of material to be formed in the cavity he follows. Accordingly, all of the material to be reshaped can begin at the beginning of the forming process are in the cavity. However, it is also possible that material to be formed from the outside into the cavity during the forming process brought.

The embodiments mentioned relate both to forming processes, at which the material to be molded into the cavity is large Movements of material in the form of flow paths must cover as well Processes in which even small material movements in the form of local  plastic flow or locally plastic deformations are sufficient to achieve the The geometry of the cavity closed to the target dimension must be filled in exactly Shape to the desired component is guaranteed.

Another preferred embodiment of the present invention consists in that the material to be formed in the cavity is initially formed by the Movement of a tool half is partially promoted in a reservoir that by A moving part of the cavity surface recedes into a negative one Relative position is formed, and then by positive relative movement this moving part of the cavity surface from the reservoir to other areas the cavity is promoted. It is during the closing movement of the Tool to be reshaped material first conveyed into the reservoir, which like mentioned above, is formed in that part of the cavity surface backs away, d. H. executes a negative relative movement and thereby into a negative relative position and then again in the direction of Cavity moves, d. H. carries out a positive relative movement. Through this positive Relative movement is the material from the reservoir to other areas of the Cavity promoted. By positioning and designing an or several of such reservoirs, it is possible, which after the pressing processes State of the art required high pressing forces towards the end of the pressing process to avoid entirely.

The press energies, press capacities and required for forming in the press process maximum permitted closing forces can be customized with the present invention can be optimally adapted to existing machine sizes, so that too mechanical locking and locking systems can be used, whereby the most diverse sizes of components can be manufactured at low cost can.  

The present invention also allows the technical effort for Control devices that control the kinetics of the occurring Requires energy and suppresses the great tendency of an impending Tool tilting during the pressing process are necessary to a minimum reduce what is ultimately the cost of an invention Press device will drastically reduce.

Another object of the invention is a device for discontinuous Pressing plastics in a cavity, as well as a device for injection stamping of plastics in a cavity in which at least two parts of the Cavity surface are designed to be movable, with at least one tool half contains one or more parts moved relative to it, and by the Relative movement of these parts at least part of the forming energy in the Plastic is introduced. The moving parts of the cavity surfaces are preferably additional presses. Preferred additional presses are, for example mechanical or hydraulic presses, or ejectors or slides.

A tool which is differentiated according to the principle of discontinuous Extrusion process works, usually consists of two mold halves. The stamp-side tool half of the tool is preferably either with a Hydraulic piston or a mechanical locking system connected and executes the closing or opening movement of the press tool. The The die side of the die is permanently mounted on the press.

One or both tool halves have one or more of the tool contours associated moving parts, which are opposite their tool halves Can perform relative movements, it remains unclear which part one half of the tool performs the movement. All moving parts which the Tool contour belong when they are during the forming process  perform relative movements relative to their associated tool halves, and also bring forming energy into the pressed material with their movement, regardless of the size of the descriptive contour, as additional presses designated.

The positive relative position of an additional press compared to other additional presses your tool half can already be at the beginning of the pressing process, or but through relative movements during the differentiated extrusion process can be achieved. The positive relative position between an additional press and hers Tool half is differentiated during cavity filling Extrusion process used in such a way that first in the contour area Additional press a smaller cavity wall thickness is simulated, which is the training targeted flow processes at the beginning or during the differentiated Extrusion course is useful.

The negative relative position of an additional press compared to other additional presses your tool half can already be at the beginning of the pressing process, or but through relative movements during the differentiated extrusion process can be achieved. The purpose of a negative relative position between one Additional press and its tool half during the mold filling in the differentiated Extrusion process consists of additional volume in the filling phase To create tool cavity for temporary material reservoirs, because in the contour area the additional press simulates a larger cavity wall thickness.

Additional cavities of a corresponding tool that are not part of the Are tool cavity, but are connected to it, and via which neither molding compound nor energy into the molding compound during the mold filling process of the product-loaded tool cavity can be used for Compensate for fluctuations in the molding compound.  

The main task of an additional press is during the filling phase of the differentiated extrusion process, not to keep the cavity contour rigid, but through the possible movements of the additional presses additional targeted To form volume cavities in the tool cavity, which are temporary Serve material reservoirs. During the positive relative movement one Additional press is pressed material, the displaced material on the one hand Forming the corresponding tool cavity, and the other optionally for filling one or more additional material reservoirs, which are formed by the negative relative positions of the respective additional presses become. The closing movement of an additional press ends at that of the desired one Component thickness or position just above (shrinkage). The Further partial cavity fillings are carried out analogously by the positive ones Relative movements of the individual additional presses, the individual movements the additional presses take place simultaneously, overlapping or sequentially can. The entire shape of the component in the differentiated extrusion process is finished when any part of the component surface with the Surface contour of the tool matches, and each partial pressing process is finished, what with an exact mass dosing and introduction of the compressing flowable mass into the open mold cavity at the beginning of the differentiated extrusion process is the case. At this point in time, that's all Cavity surface added to the product.

The required force for the movements and to maintain the static Balance of the individual additional presses during the differentiated Extrusion process can be done both mechanically and hydraulically. The mechanically performed movements of the additional presses take place via corresponding levers (toggle levers) or spring elements. That's how it is conceivable that corresponding lifting functions of integrated in the tool  Ejectors or sliders take over the function of the additional presses. The The required force application of the individual additional presses can also be done hydraulically respectively.

The control or regulation of the individual movements of the additional presses can be done depending on the stamp path and the pressing time. The control or the Regulation of the movements of the additional presses can also be based on measured mechanical or hydraulic clamping forces or also based of mold internal pressures measured anywhere in the tool cavity respectively.

In Figs. 1 to 4 is a preferred form of the apparatus used for implementing the method, that is, of the tool shown in Figure 4 typical positions corresponding to the process flow of the discontinuous differentiated Fließpreßverfahrens. The mass of pressed material introduced into the cavity at the beginning of the differentiated pressing process corresponds to the component mass, so that no additional molding compound is introduced into the cavity during the differentiated pressing process. Since at the beginning of the pressing process the surface of the cavity exposed to the product is significantly smaller than the entire surface of the cavity at the end of the forming process, the forming is largely done by the fluidity of the molding compound, with relatively large flow paths occurring.

Fig. 1 shows the tooling components required for the differentiated extrusion process and their starting position for a differentiated extrusion process. The die-side tool half ( 1 ) is rigid in itself and is permanently installed, the tool surface contours of which are identical to the corresponding component geometry. The die side of the die consists of the tool parts ( 3 ), ( 4 ) and ( 5 ) which form movable cavity surfaces. The material to be pressed, which is introduced into the opened mold cavity and whose mass corresponds to the desired mass of the component, is designated by ( 2 ). The material to be pressed is in a flowable form under the selected process parameters.

The required application of force for the movements and for maintaining the required closing forces of the individual moving tool parts can take place mechanically as well as hydraulically in the embodiment mentioned. The individual movements of the tool parts ( 3 ), ( 4 ) and ( 5 ) can take place simultaneously, overlapping or sequentially controlled.

Fig. 2 shows schematically the beginning of the discontinuous, differentiated pressing process. The closing movement of the tool part ( 3 ) introduces forming energy into the material to be formed, which results in the pressing of the material placed in the press. The closing movement of the tool part ( 3 ) ends in this case at the position corresponding to the desired component thickness and remains in this position during the remaining shaping in the differentiated pressing process. In this phase of the differentiated pressing process, the movable tool part ( 4 ) built into the tool part ( 3 ) performs the same closing movement as the moving tool part ( 3 ). Due to the negative relative position of the tool part ( 4 ) to the tool part ( 3 ) at the beginning of the differentiated pressing process, it is possible to create a temporary material reservoir in the corresponding cavity area of the tool part ( 4 ). The movable tool part ( 5 ) does not move in the first phase of the differentiated pressing process.

The next process phase of the discontinuous differentiated pressing process is shown in Fig. 3. The closing movement of the movable tool part ( 5 ) creates a positive connection between the die side and the die side of the die in order to guarantee the tightness of the cavity, which is necessary for the complete forming process. Due to the fact that the cavity is sealed at an early stage by the positive locking of the movable die-side tool part ( 5 ) with the die-side tool half ( 1 ), a plunge edge tool is not necessary. With the closing movement of the tool part ( 5 ), forming energy can, but does not necessarily have to be introduced into the material to be pressed via any surfaces that are exposed to the product. The remaining movable tool parts ( 3 ) and ( 4 ) do not make any movements in this phase of the described process of the differentiated pressing process and thus do not introduce any forming energy into the material to be pressed.

The remaining shaping of the pressed material to the final component in the differentiated pressing process takes place according to Fig. 4 by the closing movement of the movable die-side tool part ( 4 ).

The required reprint (shrinkage) is applied via zu additional small closing movements of all movable die-side tools parts that do not have a direct positive connection with the die side Half of the tool are in contact.

Both the size and shape of the individual movable die-side tool parts can for reasons of tool technology and rheological conditions can be customized. The individual movements of the moving Stamp-side tool parts can also be controlled individually. This fact opens up a variety of degrees of freedom to find the ideal shaping process in a discontinuous differentiated Pressing process. In this sense, those described here are used in practice Closing phases from the strictly sequential order of movements in simultaneous closing movements of the individual moving tool parts  respectively. In the sense of the present invention, however, it corresponds to a preferred one Embodiment of the discontinuous differentiated pressing process that the last phases of the forming process, i.e. the complete filling of the mold Introduction of forming energy over those cavity surfaces of the movable Tool parts are made which have the smallest cavity surfaces.

The method according to the invention and the device are suitable for pressing all pressable plastics, in particular those which are among the Press conditions are plastic or flowable. Thermosets are preferred or thermoplastics, such as. B. urea, melamine or phenolic resins, Epoxies, polyolefins such as e.g. B. polyethylene, or polypropylene, polyamides, Polyimides, polyesters, polyether ketones, polyester ketones, polysulfides, polysulfones, Aramids. The plastics mentioned can be both unfilled and filled or used with the addition of conventional additives. The invention according to the method and the device is also suitable for pressing Metals and ceramic materials.

Another object of the invention are components such. B. machine parts or Components for motor vehicles, which are produced by the method according to the invention are, or components that are produced in the device according to the invention become.

Claims (17)

1. A method for the discontinuous forming of plastics by displacement in a cavity, characterized in that the introduction of forming energy into the material to be formed is carried out by at least two moving parts of the cavity surface, at least one tool half containing one or more parts moving relative to it, and at least part of the forming energy is introduced by the relative movement of these parts. 2. The method according to claim 1, characterized in that the introduction of the forming energy in terms of time and over the entire forming process locally controlled in a controlled manner. 3. The method according to claim 1 or 2, characterized in that at the Introduction of the forming energy seen over the entire forming process the entire cavity surface that is not parallel to the direction of movement at least one half of the tool is involved. 4. The method according to claim 1 or 2, characterized in that at the Introduction of the forming energy seen over the entire forming process only a part of the upper cavity that is not parallel to the direction of movement area is involved in at least one half of the tool. 5. The method according to any one of claims 1 to 4, characterized in that all the material to be reshaped at the beginning of the Forming process located in the cavity.   6. The method according to any one of claims 1 to 4, characterized in that material to be formed during the forming process from the outside into the Cavity is introduced. 7. The method according to any one of claims 1 to 6, characterized in that material to be reshaped in the cavity first through the Movement of a tool half is partially promoted in a reservoir that by retreating a moving part of the cavity surface into a negative relative position is formed, and then by positive Relative movement of this moving part of the cavity surface from the Reservoir is promoted to other areas of the cavity. 8. The method according to any one of claims 1 to 7, characterized in that Large flow paths of the material occur during the forming process. 9. The method according to any one of claims 1 to 5 and 7, characterized characterized in that the deformation is carried out by locally plastic flow. 10. Device for the discontinuous pressing of plastics in a cavity, characterized in that at least two parts of the cavity surface are designed so movable, with at least one tool half contains or several parts moving relative to it, and by the Relative movement of these parts at least part of the forming energy in the Plastic is introduced. 11. Device for injection molding of plastics in a cavity, thereby characterized in that at least two parts of the cavity surface are movable are designed, with at least one tool half one or more  contains moving parts relative to it, and by the relative movement of these Parts at least part of the forming energy is introduced into the plastic. 12. The apparatus according to claim 10 or 11, characterized in that the moving parts are designed as additional presses. 13. The apparatus according to claim 12, characterized in that the Additional presses are formed by hydraulic presses. 14. The apparatus according to claim 12, characterized in that the Additional presses are formed by mechanical presses. 15. The apparatus according to claim 12, characterized in that the Additional presses are formed by ejectors or sliders. 16. Components, characterized in that they according to a method one or more of claims 1 to 9 are produced. 17. Components, characterized in that they are in a device according to one or more of claims 10 to 15.