DD233036A3 - METHOD AND TOOL FOR DEFLECTING SHEET MOLDED PARTS - Google Patents

Abstract

The invention relates to a method and a tool for deep-drawing sheet metal parts, in particular cans, in two trains within the same press stroke, wherein the pulling force of the first train is used as a hold-down force. It is the object of the invention to be able to process materials with relatively large anisotropy (rolling texture) and resulting earing in the production of sheet metal parts deep-drawn in two passes. The invention has for its object to provide a method and a tool with influenceability of the process parameters in the second train. Geloest this task by the hold-down force from the beginning of the second train progressively reduced, with entry of the drawing part edge between the Niederhalterflaechen the tool and thus the formation of a Ziehteilflansches by the hold-down force wrinkling at least still suppressed, the hold-down force further deep drawing according to the Reduction of the area of the drawing part flange further reduced, the hold-down force completely canceled before the end of the second train and the residual flange sets up. The tool for carrying out the process are assigned a plurality of relief springs and relief bolts in the vicinity of the drawing punch for the first train. Fig. 3

Description

-A-

Title of the invention

Method and tool for deep-drawing sheet metal parts

Field of application of the invention

The invention relates to a method for deep drawing of sheet metal parts, in particular cans, in which the first train of the second train within the same press stroke followed in the same direction, wherein the pulling force of the first train used as hold-down force of the second train and is reduced with progressive depth of draw and a Tool for carrying out the process »

Characteristic of the known technical solutions

In the journal "Precision Engineering" 59 (1955) 2, pp 72-73 a drawing tool for the stop is described in which the hold-down force is generated by means of spring pressure apparatus «In order to maintain a constant hold-down pressure, the hold-down force is reduced by relaxing the compression springs with progressive draw depth , However, a constant Nxederhalterdruck is not guaranteed in this way, since the reduction of the flange surface according to a quadratic function, but the hold-down force is linear according to the spring characteristic.

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In DE-OS 25 19 521 process and drawing press are described with tools for moving hollow bodies. The hold-down pressure for the continuation is generated pneumatically. In order to avoid damage to the drawing part edge, a fixed gap is set via a hold-down stop between hold-down and drawing ring. This gap should be equal to or slightly smaller than the material thickness. It is assumed that the assumption of a constant material thickness, but it is known that this is not the case in a drawn part. Due to the state of stress and the resulting material flow, a reduction in thickness occurs in the lower region of the drawn part. The wall thickness then increases almost linearly and can be up to 30 % thicker at the upper edge of the drawing part than the starting sheet thickness. For the practical operation of the type described in DE-OS 25 19 521, this means that an adjustment of the gap to the largest sheet thickness at the beginning of the second train allows wrinkling. A reduction of the gap to the minimum sheet thickness causes the holding-down lifted from the stop again with the entry of the thicker sheet and the full hold-down pressure is achieved. With the entry of the drawing part edge in the Niederhalterschräge then increases according to the reduction in area of the hold-down pressure. This leads to squeezing of the edge. So just to the appearance that should be avoided with this method.

Particularly disadvantageous are the previously known and described methods of controlling the Nxederhalterkraft during deep drawing of high-texture sheets. The inevitable resulting in the flange Zipfel are the end de ;; Tiefzuges down with a much too large hold-down pressure applied and thereby partially or completely demolished. These demolished workpiece particles remain in the tool and lead to failure when pulling from subsequent parts.

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WP B 21 D / 244 558/4

Object of the invention

The aim of the invention is / in the production of deep drawn in two passes sheet metal parts materials with relatively large anisotropy (rolling texture) and thus to be able to process earing.

Essence of the invention

The invention has for its object to provide a method of the type mentioned with influenceability of the process parameters in the second train. Another object of the invention is to provide a tool for carrying out the method.

According to the invention, this object is achieved in that the hold-down force from the beginning of the second train is progressively reduced and canceled before the end of the second train.

The deep drawing tool for performing the method, consisting of Ziehringen for the first and second train, Blechabstreifer and Ziehteilabstreifer in the lower tool, cutting ring, hold and drawing punch for the first and second train in the upper tool, the drawing punch of the first train acts as a hold-down in the second train and the drawing punch of the second train is guided in it, characterized in that the foot of the drawing punch for the first train is formed over a large area _; ".

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One

between said foot and the separately driven cutting ram in the vicinity of the drawing punch for the first train on the punch guide a plurality of relief springs and relief bolts are arranged and that the drawing punch for the second train has an undercut which is arranged in its width substantially symmetrical to the middle drawn part height ,

embodiment

The invention will be explained in more detail using an exemplary embodiment for the production of cans:

Show it

1, the deep drawing tool at top dead center in section,

2 shows the section through the thermoforming tool at the end of the first train,

3 shows the section through the thermoforming tool in the final phase of the second train,

4 shows a diagram of the course of the hold-down force as a function of the crank angle of the press and thus of the tool movements,

5 is a partial view of the drawing punch for the second train,

Fig. 6 Zipfeliger, thickened Ziehteilrand when pulling through and

Fig. 7 spring-loaded, thickened drawing part edge after pulling through.

The production of sheet metal parts, in particular cans with a Gesamttiefziehverhältnis ß> 2.0, must be done in two stages. For the production of very large quantities, as they are in the production of cans in any case, is particularly suitable for a method in which within the same press stroke, the second train is performed after the first in the same direction (DE-PS 11 23 11 ).

Advantageously, the cutting of the blank is still made in the tool, so that the process takes place in the steps section train - train. The band or strip 10 is inserted at the level of the drawing ring 7 (FIG. 1). By a phase-shifted movement (FIG. 4), the blank is first cut by the stroke of the cutting tappet 2, the blank being simultaneously held between the draw ring 7 and the hold-down 12. After the cut, the first train is performed by the lifting movement of the drawing punch for the first train 14.

The pulling force F ₂₁ for this first train is generated by an air cylinder located in the press ram 3 and transmitted via the pressure pin 18 to the drawing punch 14. With the stage shown in Fig. 2, the first train is completed and the second train begins. It is characteristic that in this case the drawn part 23 between the holddown slope ara drawing punch for the first train 21 and the Niederhalterschräge is clamped to the draw ring for the second train 22. The drawing punch for the first train 14 thus becomes the hold-down for the second train. This existing at the beginning of the second train hold-down force corresponds to the set pulling force for the first train. This corresponds in Fig. 4 of the size F-. or the course between the points VI-VII. The force F ^ ₁ is much larger than the hold-down force F ^ ₂ required for the second pull, see FIG. 4, line III-IV. When the ram is lowered further, the drawing punch for the second one Train 15 out of the drawing punch for the first train 14 and forms the drawn part 23 on. From this point on there is a progressive reduction of the hold-down force F ^ _{2 vo} _ # by exploiting the upward movement of the cutting ram 2, compression springs 17 are compressed whose force is directed against the pulling force for the first pull and thus relieves the hold-down surface of the drawn part , This relief takes place in such a way that with the entry of the drawing part edge between the hold-down bevels on the drawing punch 21 and the drawing ring 22, the hold-down force at least suppresses wrinkling. This stage is characterized in the diagram of FIG. 4 by the curve VII-IX.

The reduction of the hold-down force is continued in accordance with the reduction of Ziehteilflansches until a time when just a closed flange between the Niederhalterschrägen the draw punch 21 and the draw ring 22 is, Fig. 4, curve IX-X. This Restflansch 25 on the drawn part in the final phase of the second train 24 must on the one hand be so large that the existing hold-down force can still be transferred, but on the other hand, it must be so small that without annoying wrinkling a raising without hold-down effect is possible. This time of the second train is shown in Fig. 3 and corresponds in Fig. 4 the point X. At this time, the hold-down force is completely removed by the discharge bolts 20 hit the foot of the drawing punch for the first train 19 and raise the draw pile 15 «The existing Restflansch 25 is then raised vertically without disturbing wrinkling with progressive Stempelhub, without tearing existing tips. Upon further pulling through the draw ring for the second train 8, the jagged, thickened drawing part edge 27, FIG. 6, deflects elastically inward into the undercut 26 in order to spring out again after pulling through, as shown in FIG , After passing through the bottom dead center when pulling the drawing punch for the second train 15, the drawn box is stripped by the Ziehteilabstreifer 5 and blown out of the tool by means of compressed air (not shown).

By reducing the hold-down force to a size that is only slightly larger than the required and by the Niederhalterlose raising the Restflansches is reliably avoided that especially in the case of very anisotropic material the corners are completely or partially demolished in the final phase of the second train and subsequent Pull parts to failure cause they remain in the tool. Another advantage of further pulling through is that the jagged, thickened and possibly slightly wrinkled edge can yield elastically inwards.

This avoids that material is squeezed in the drawing gap in the form of small particles and leads to pollution, which is the cause of failure occurring. The sprung thickened edge 28, FIG. 7, represents a very stable edge for stripping thin sheet metal parts.

Construction and operation of the tool

As can be seen from Figs. 1 to 3, the tool performs a cut-and-pull-pull operation. The tool lower part is fastened to the base plate 1 and consists of the base body 4, in which the draw stripper 5 is received below the draw rings for the first draw and the second draw 8. The clamping ring 6, on which the Blechabstreifer 9 is movably mounted, braces the Ziehringe 7 and 8 with the base body 4. The drawing ring for the first train 7 is formed in its outer contour as a cutting punch. Above the drawing ring for the first train 7 and the Blechabstreifers is the material to be processed 10 in band or strip form. On separately driven cutting ram 2, the cutting ring 11 with the hold-down for the first train 12 and the punch guide 13 are attached. Between the hold-down for the first train 12 and the punch guide the holding-down springs 16 are arranged in a circle. On the upper side of the punch guide 13 are also arranged in a circle the relief springs 17 and the relief bolts 20, By this arrangement are relief springs 17 and relief bolts 20 between the cutting ram 2 and the foot of the drawing punch for the first train 19 and thus can an operative connection between make these two parts.

In the Sterapelführung 13 slides by a pneumatic cylinder (not shown in FIGS. 1 to 3) acted on the pressure pin 18 drawing punch for the first train 14, which acts as hold-down in the second train by the sheet

between the hold-down slope 21 is applied to this drawing punch and the hold-down slope 22 on the drawing ring for the second train with pressure. The drawing punch for the second train 15 is attached to the press ram 3 and is guided in the drawing punch for the first train 14, it has an undercut 26 which is located centrally to the middle drawn part height h, Fig. 5th

The relief springs 17 are selected according to the drawing part dimensions and the material to be processed according to type and size so that a reduction of the existing pulling force in the first train F ₇ ,. , exerted by the draw pile 14, on the required hold-down force in the second train F _N2e 'which is generally less than half of the required pulling force of the first train can take place. So z. B.

in the erfindungsgeraäßen production of a can from the through-?

knife 73 mm made of aluminum alloy sheet 0.3 mm thick reduces the required pulling force for the first pull of 18 kN to the required holding force of 6 1 <N during the course of the second pull. The temporal relationships to it are shown in FIG. 4.

After the material feed has taken place, the drawing rams 3 and cutting rams 2 move out of phase, as shown in the diagram in FIG. 4, from top dead center. The further explanations are to be understood in conjunction with FIGS. 1 to 3.

At point A, the cutting ring 11 sets on the plate 10 and the cutting process begins. At point B begins with the impact of the drawing dies 14 and 15 on the plate 10 of the drawing process. The first train ends with the placement of the hold-down surface 21 of the drawing punch from the first train 14 on the Nitclerhalterflache 22 from the drawing ring 8 for the second train with the intermediate part of the drawn part 23. This phase of the drawing process is shown in Fig. 2 and corresponds to the point C in the diagram in Fig. 4. The pulling force

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for the first train F ^ ₁ is generated by a pneumatic ram, not shown in the press ram 3 and transmitted via the pressure pin 18 on the foot 19 of the drawing punch. The existing in the pneumatic cylinder pressure remains constant throughout the stroke. Upon further stroke, the distance between the foot of the drawing punch and the press ram 3 decreases, since the cutting ram 2 is already in the return. Above the pressure pin 18, the relative movement between the two drawing punches 14 and 15 is transmitted to the KolbeYi of the pneumatic cylinder. This process begins according to FIG. 4 at point C and represents the beginning of the second turn. For the second pull, a hold-down force is needed, which corresponds in FIG. 4 to the course of the curve in points III-IV-V. By the necessary pulling force during the first turn, which corresponds to the course between the points VI and VII, but a more than doubled hold-down force is present, which is also generated according to the curve V-II - VIII by the pneumatic cylinder until the end of the drawing process , The excessive hold-down force would lead to the demolition of the drawing part edge or parts of the same at the end of the drawing process. This danger is especially great if the material has a strong point as a result of plane anisotropy.

Too much hold down force also forces the drawing ratio to be reduced in the second pass, preventing it from working under optimal technological conditions. To avoid these disadvantages, the relief springs are arranged in the vicinity of the punch 14 and 15 on the punch guide so that at point C of the Diagrarames of FIG. 4 via these springs an operative connection between the cutting plunger 2 and the foot of the drawing punch for the first train 19th will be produced. Approximately at point C, the Schnexdstößel 2 has reached its bottom dead center and the return stroke begins. This reduces the distance between the foot of the drawing punch for the first train 19 and the punch guide 13, the relief springs

are stretched and the resulting force is directed opposite to the pressure piston 18 on the drawing punch 14 force, so that the force resulting as a difference is the hold-down force and a curve according to the curve in the points VII - V assumes. Number and size of the relief springs 17 are to be chosen so that the greatest possible approximation to the curve between the points IV-V is achieved. Shortly before the end of the drawing process, the hold-down force is completely canceled by placing the foot of the drawing stack for the first train 19 on the relief pin 20. This phase of the drawing process is shown in FIG. The time of canceling the hold-down force must be chosen so that the size of the Restflansches allows this niederhalterlos without troublesome wrinkling and thus can only between the points D entry of the drawing part edge in the Niederhalterschrägen 21 and 22 - and E - end of the drawing process - lie and corresponds to point X in Fig. 4th

 The jagged and thickened drawing part edge 27, FIG. 6, with possibly existing cutting ridge can dodge elastically into the undercut 26 when pulled through. In the course of the further stroke of the spring-back Ziehteilrand 29, Fig. 7, passes under the Ziehteilabstreifer 5, is stripped by the upward stroke, the drawn part 23 from the drawing pile 15 and ejected.

Claims (2)

~ π η ο> ο ",, WP B 21 D / 244 ** 553 4 " - 11 - P at en tan s prjÜfc ha 1. A method for deep drawing of sheet metal parts, in particular cans, in which the first train is followed by the second train within the same press stroke in the same direction, wherein the pulling force of the first train is used as a hold-down force of the second train and reduced with progressive draw depth, characterized in that the hold-down force is progressively reduced from the beginning of the second draw and is completely canceled before the end of the forming in the second pass. 2. Tool for performing the method according to item 1, consisting of Ziehringen for the first and second train, Blechabstreifer and Ziehteilabstreifer in the lower tool, cutting ring, hold and drawing punch for the first and second train in the upper tool, the drawing punch of the first train in the second train acts as a hold-down and the drawing punch of the second train is guided in it, characterized in that the foot (19) of the drawing punch (14) for the first train is formed over a large area, between the foot (19) and the separately driven cutting ram (2) Bs in the drawing punch (14) for the first train to the punch guide (13) a plurality of suspension springs (17) and discharge pins (20) are arranged and ^ the drawing punch (15) for the second train having a free pass (26) which is substantially symmetrical in its width to the average drawn part height (h _m ). For this S pages drawings