EP1448325B1 - Forming tool made of plastic - Google Patents

Description

The present invention relates to a tool consisting of a plastic mass, which consists of plastic and a material embedded in the plastic material with sliding properties, wherein the tool is a forming tool. Tools in the context of the present invention are, for example, deep-drawing tools for the forming of metal components, for example automobile components.

Conventionally, deep drawing uses steel or gray cast iron tools. For some time already used for forming already plastics as tool materials, eg. B. plastics containing metallic fillers. These plastics have the advantage of being less expensive materials. However, it has been found that such plastic-based tools are not or only partially usable in certain applications for forming tools. This is especially true in deep drawing applications where workpieces have to be reshaped in high volumes so that the tool is subject to high wear. Tools made of plastics also have in these applications to low pressure resistance.

DE 93 18 272.4 U1 describes a tool for the non-cutting deformation of workpieces of the type mentioned, wherein the tool itself consists of a metallic material, in particular gray cast iron, but a guide part of the tool, which has a sliding surface, made of a thermoset with fiber - or fabric insert and is made with inclusions of lamellar graphite. This should improve the sliding properties and reduce wear.

DE-A-19 10 705 describes tools for producing parts of plastic foams which partly have a porous structure. It is possible to use master models made of foam for the production of the foaming tools, with substantially granular to pulverized aluminum and copper alloys and graphite being considered suitable as base materials for the required substance mixtures. The binders used are organic or inorganic binders. The materials mentioned are suitable for foaming tools, but are not suitable for the high loads acting on the tools during forming processes.

The object of the invention is to provide a plastic existing tool, which on the one hand has good sliding properties and on the other hand also improved wear characteristics and high pressure resistance.

The solution to this problem provides an inventive tool with the features of the main claim. According to the plastic mass contains a proportion of embedded aluminum to achieve increased compressive strength and wear resistance, and further a stored material with sliding properties, so that the tool has a quasi self-lubricating effect. As a result, the use of an additional lubricant in the region between the forming tool and the workpiece to be deformed is generally unnecessary. Based on experiments could be shown that the life of the tool can be significantly improved by the inventions of the invention. As a material with sliding properties such as graphite or molybdenum sulfide into consideration. Particularly preferred is the use of graphite powder. The aluminum may be contained in the plastic tool as a filler, for example in the form of aluminum powder or aluminum particles of larger grain size. Tools of this type can preferably be produced from a correspondingly composed casting resin or from a block material.

According to a preferred embodiment of the invention, the tool contains a weight fraction of more than 50% of aluminum filler. The proportion by weight of aluminum filler of the plastic mass for the production of the tool can be a multiple of the plastic content. Preferably, this weight fraction is at least 60%, preferably about 70% aluminum filler, preferably aluminum powder, based on the total weight of the plastic mass.

The proportion by weight of the material embedded in the plastic material with sliding properties is generally less than the plastic content and / or the aluminum content of the plastic mass. Preferably, the tool contains a weight fraction of 20% to 50% of graphite powder based on the weight fraction of the plastic contained in the tool, d. h., Not based on the total weight of the plastic mass, but based on the pure plastic content. The proportion by weight of the graphite relative to the total weight of the material constituting the tool is preferably from 3% to 15% of graphite. The weight ratio between the graphite content and the aluminum content is preferably between 1:15 and 1: 6.

For the purposes of the present invention, preference is given to the production of deep-drawing tools made of the plastics material of the type mentioned. For example, these can be stamps or blank holders for the deep-drawing of metal parts. By incorporating the material with sliding properties is prevented during deep drawing z. As a metal sheet, which is claimed in a pulling direction perpendicular to the direction of movement of the thermoforming tool, particles, in particular filler particles are torn out of the plastic matrix and thereby cracks in the tool. It has already been mentioned that graphite in the form of graphite powder can be incorporated as a material with sliding properties into the plastic. The use of graphite powder in a particle size of between 50 μm and 250 μm has proved to be particularly advantageous.

The tools according to the invention can consist essentially completely of a plastic with the aforementioned inclusions, d. h., That they consist of a homogeneous plastic material throughout and thus differ from the tools according to the aforementioned DE 93 18 272.4 U1, where only one designated as a guide part front layer of the tool consists of a plastic with certain sliding properties.

The features mentioned in the dependent claims relate to preferred developments of the task solution according to the invention. Further advantages of the invention will become apparent from the following detailed description.

Fig. 1

eine stark schematisch vereinfachte perspektivische Darstellung zur Erläuterung eines Tiefziehvorgangs mittels eines erfindungsgemäßen Werkzeugs;

Fig. 2

eine zweite schematisch vereinfachte Ansicht im Schnitt zur Erläuterung des Tiefziehvorgangs;

Fig. 3

ein Diagramm, welches die Veränderung des E-Moduls bei Verwendung von Kunststoffen mit unterschiedlichen Füllstoffen zeigt;

Fig. 4

einen Stempel für das Tiefziehen von Ventildeckein für Motoren in perspektivischer Darstellung;

Fig. 5

die zugehörige Matrize für das Tiefziehen von Ventildeckein mit einem Stempel gemäß Figur 4;

Fig. 6

mittels Stempel und Matrize gemäß den Figuren 4 und 5 tiefgezogene Ventildeckel.

Hereinafter, the present invention will be described in more detail by way of embodiments with reference to the accompanying drawings. Show

Fig. 1

a highly schematically simplified perspective view for explaining a deep drawing operation by means of a tool according to the invention;

Fig. 2

a second schematically simplified view in section to illustrate the deep drawing process;

Fig. 3

a diagram showing the change in the modulus of elasticity when using plastics with different fillers;

Fig. 4

a stamp for the deep drawing of Ventildeckein for engines in perspective view;

Fig. 5

the associated die for the deep drawing of Ventildeckein with a stamp according to Figure 4;

Fig. 6

by means of punch and die according to Figures 4 and 5 deep-drawn valve cover.

First, reference is made to FIG. The drawing shows a highly schematically simplified perspective view of an arrangement of tools for the deep drawing of a sheet metal part 10. It is a tool upper part 11 for forming the sheet metal part 10 by deep drawing method and a lower tool part 12 in the form of a die upper 11 female die. The tool upper part 11 consists of a Plastic of the type according to the invention, which contains embedded aluminum particles 13, as well as embedded graphite powder 14 to achieve a self-lubricating effect during the forming of the sheet metal part 10th

The tool upper part 11 was produced from a casting resin consisting of plastic, aluminum powder as filler and graphite powder. In this case, 1 kg of plastic, 3 kg of aluminum powder and 200 g of graphite powder were used for a total mass of 4.2 kg of this material. The grain size of the graphite powder varied between 50 and 250 μm. The plastic tool had very good lubricating properties and a 40% higher compressive strength. The formation of cracks in tools made of other plastics with conventional fillers such as sand and iron in the front layer of the tool, which results from the fact that filling particles are torn out of the basic matrix of the plastic material during the deep-drawing process, did not occur when using tools made of the plastic according to the invention.

It has been found that the deep-drawing tools produced from the above-mentioned plastic material are suitable for forming workpieces in high numbers, for example up to 100,000.00 or more.

FIG. 2 illustrates the forces acting on the tool during the deep-drawing with materials without a sufficient lubricating effect. It is shown in a highly schematically simplified sectional view of a tool upper part 11, which was inventively made of solid cast material consisting of a plastic according to the invention with aluminum and graphite powder as fillers. The lower tool part 15 was cast from the plastic material according to the invention. The forming sheet metal part 10 is located before the onset of the deep drawing process in the gap 16 between the upper tool part 11 and lower tool part 15. During deep drawing, the sheet metal part 10 to be formed is deformed, forces occurring in the direction of the arrow 17 perpendicular to the direction of movement. As a result, the front surfaces 18, 19 of the two tools 11, 15 are subjected to shear. The incorporated in the plastic of the tools 11, 15 graphite powder provides a lubricating effect and good sliding properties in the boundary region between the front surfaces 18, 19, the tools 11, 15 and the drawn sheet metal part 10th

Figure 3 illustrates the percentage change in the modulus of elasticity of tools made of different plastics, which was determined by means of compression tests in the context of the invention. It was in the diagram in the column 20 far left the Modulus of elasticity of a plastic filled only with aluminum and assumed as a relative reference value for the other plastics with the value 100. In the second column from the right, designated by 22, the relative value of the modulus of elasticity for an aluminum-filled PTFE is shown which, as can be seen, reaches only about 60% of the plastic shown in column 20 in FIG. For comparison, in contrast, the elastic moduli for two plastics produced according to the invention are reproduced in FIG. The column 23 on the far right in the illustration shows the value for a plastic filled with aluminum and MoS ₂ as a sliding material. It can be seen that the modulus of elasticity is more than 20% higher than that of the column 20 aluminum-filled plastic only. In column 21 (second from the left in the illustration), the relative value of modulus of elasticity for one with graphite and Aluminum filled plastic reproduced. As can be seen from the illustration, this value is 40% higher than the modulus of elasticity for a plastic filled only with aluminum according to column 20 on the far left in the illustration. The value given in column 21 in FIG. 3 was achieved by adding 20% graphite powder to an aluminum-filled plastic for which the value in column 20 is reproduced.

It was designed, designed and manufactured for thermoforming experiments in Figure 4 in perspective deep-drawing tool 30 for the production of valve covers for a three-cylinder engine. FIG. 4 shows the deep-drawing die for valve cover 30 made of a plastic according to the invention from the underside. Thermoforming tests were carried out with this tool 30. Based on these tests, it was found that both the dimensional accuracy, the service life and the self-lubricating effect compared to tools made of other plastics greatly improved. Tools made from conventional plastics were worn out after a short time. By embedding only about 20% of graphite powder in a filled with aluminum powder plastic significantly improved friction and wear ratios were achieved with the tool 30 shown in Figure 4. As can be seen in FIG. 4, the deep-drawing die has two characteristic shaping elements 31, 32 for producing the recesses or raised areas typical of the shape of the valve cover.

FIG. 6 shows exemplary valve caps with various materials made by means of the deep drawing tool 30 shown in FIG. The valve covers 40, 41, 42 shown in FIG. 6 were produced by forming titanium sheet, aluminum sheet and galvanized sheet steel, each with a material thickness of 1 mm. It can be seen in the illustration of Figure 6 readily the characteristic forming areas, namely the flat cylindrical recess 43 (or increase, if you look from the bottom of the thermoformed valve cover 41 of Figure 6). This Forming region 43 can be assigned to the deformation element 32 of the deep-drawing tool 30 according to FIG. Correspondingly, the deformation region 44 can be assigned to the deformation element 31 of the deep-drawing tool 30 according to FIG. When deep drawing the valve cover shown in Figure 6 with the tool 30 according to the invention could be in all three materials titanium sheet, aluminum sheet, galvanized steel sheet, achieve very good results.

FIG. 5 shows the die 50 associated with the deep-drawing die 30 according to FIG. 4 for producing valve covers 40, 41, 42, as shown in FIG. In the thermoforming die 50 shown in Figure 5, the punch 30 is lowered. In FIG. 5, the approximately rectangular shape of the die 50, which is rounded off at the corners, can be seen in FIG. 5. In addition, the forming region 51 assigned to the approximately cylindrical forming element 32 can be seen as a sink in the deep-drawing tool serving as a die 50. The die 50 according to FIG. 5 was also produced from the plastic according to the invention containing aluminum and graphite powder.

The advantages of the plastic tools from the materials according to the invention over conventional steel tools are, for example, up to about 70% lower material costs. The plastics used for the production of the tools can be processed better and thus the machine use is lower in the manufacture of the tools. The energy and power requirements in the machine work for the production of tools can be z. B. reduce by 65%. The training period is also up to, for example, 60% shorter than with steel tools. The use of plastics according to the invention for the production of the tools leads to a considerable weight reduction of, for example, up to 60% and thereby to a lower load on the cranes. The tools can be changed more flexibly and cost-effectively, with high cost, time and energy savings. The tools are also recyclable because they can be fully reused as fillers to make new plastic tools, eliminating disposal costs.

The elastic behavior of the plastics leads to an increase in the quality of the formed workpieces. Embedding graphite in the plastic of the tools creates a self-lubricating effect on the contact layers of the tool. If it is even necessary to use additional liquid lubricants during forming, then the amount of lubricant required can be substantially reduced, for example by about 3 g / m ² . The friction conditions during Deep drawing is improved by the introduction of graphite powder in the plastic. By eliminating or reducing liquid lubricants during deep drawing, the pollution in the work area is significantly reduced and thus relieved the environment.

Bezugszeichentiste

10

sheet metal part

11

Upper die

12

Tool part

13

aluminum particles

14

Graphite powder

15

Tool part

16

gap

17

arrow

18

front surface

19

front surface

20

pillar

21

pillar

22

pillar

23

pillar

30

Thermoforming mold

31

deforming

32

deforming

40

valve cover

41

valve cover

42

valve cover

43

deepening

44

forming region

50

deep drawing mold

51

forming region

Claims (14)

1. Tool consisting of a plastic compound, which consists of plastic and a material with sliding properties incorporated in the plastic, the tool being a forming tool, characterized in that the plastic compound also contains an incorporated aluminium fraction.
2. Tool according to Claim 1, characterized in that the plastic compound contains aluminium powder or aluminium particles as a filler.
3. Tool according to Claim 1 or 2, characterized in that the plastic compound contains graphite or molybdenum sulphide as material with sliding properties.
4. Tool according to one of Claims 1 to 3, characterized in that the plastic compound contains graphite powder.
5. Tool according to one of Claims 1 to 4, characterized in that the tool is made from a block material or a casting resin.
6. Tool according to one of Claims 1 to 5, characterized in that it contains an aluminium filler fraction of more than 50% by weight.
7. Tool according to one of Claims 1 to 6, characterized in that the plastic compound contains an aluminium filler, preferably aluminium powder, fraction of at least 60% by weight, preferably approximately 70% by weight, based on its total weight.
8. Tool according to one of Claims 1 to 7, characterized in that it contains a graphite powder fraction of from 20% to 50% by weight, based on the weight fraction of the plastic contained in the tool.
9. Tool according to one of Claims 1 to 8, characterized in that it contains a graphite, preferably graphite powder, fraction of from 3% to 15% by weight, based on the total weight of the material of which the tool consists.
10. Tool according to one of Claims 1 to 9, characterized in that it contains graphite, preferably graphite powder, and aluminium, preferably aluminium powder, in a weight ratio of between 1:15 and 1:6.
11. Tool according to one of Claims 1 to 10, characterized in that it is a deep-drawing tool.
12. Tool according to one of Claims 1 to 11, characterized in that it is a punch, blank holder or die for the deep-drawing of metal parts.
13. Tool according to one of Claims 1 to 12, characterized in that it contains graphite powder in a grain size of between 50 and 250 µm.
14. Tool according to one of Claims 1 to 13, characterized in that it substantially completely comprises the plastic compound.

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