DE102015220231A1 - Apparatus for deep drawing a sheet metal blank with forming tools - Google Patents

Abstract

The invention relates to a device for deep-drawing sheet metal blanks (round blanks, films, plates, sheets, boards), which makes it possible to significantly increase the part spectrum to be produced in order to open up new fields of application or to postpone existing process limits. In addition, can largely be dispensed with by the inventive device on the use of lubricants to reduce the cost of the excipients, the pre- and post-treatment of sheet metal blanks or the formed deep-drawn parts and thus the environmental impact. In the apparatus according to the invention, the necessary forming force is applied via a drawing punch on the sheet metal blank. The flow movement of the workpiece to be formed is controlled by a hold-down in conjunction with a drawing ring. Downholder and drawing ring / die have in the region of the component flange on a plurality of cantilevered, spaced-apart form elements. The form elements of the blank holder and the drawing ring / the die are arranged offset from one another. Due to the cantilevered form elements, the contact area between the tool and the workpiece will be significantly reduced in the flange area of the deep-drawing tool.

Description

The invention relates to a device for deep drawing of sheet metal blanks (blanks, films, plates, sheets, boards).

Deep drawing is after DIN 8584 the Zugdruckumformen a sheet metal blank in a hollow body open on one side or a preformed hollow body in such a smaller cross-section without intentional change in the sheet thickness.

Deep drawing is one of the most economically important sheet metal forming processes in small batch production - as in mass production. When deep drawing with molds, the necessary forming force is applied by means of a punch on the bottom of the deep-drawn part to be produced. It is pulled with the punch of the blank by the forming die or the die. The hold-down, which acts under a defined pressure on the sheet metal blank, is to prevent wrinkling on the deep-drawn part.

Due to the strong friction between the sheet metal blank, the hold-down device and the drawing die, lubricants such as Aqua-Form or Raziol are regularly used. For this purpose, the sheet metal blanks to be processed must be pre-wetted with the lubricant and cleaned consuming after completion of the forming process.

Downholders are also known from the prior art, which have a pull bead or Bremswulst to improve the action of the blank holder.

In this case, when forming rotationally symmetrical workpieces, the drawing bead is an annular, cantilevered, continuous strip in the hold-down, which has a constant distance from the drawing edge, which protrudes from the flat surface of the blank holder, wherein in the drawing die as a counterpart a formideal recess a draw bead in the form of a circumferential, continuous annular groove is arranged.

When forming rectangular cross-sectional shapes, the drawing bead is formed from projecting, rectilinear strips in the hold-down, the length of which substantially corresponds to the component size, being arranged in the drawing die as a counterpart formideal recesses in the form of continuous grooves.

During the deep-drawing process of rotationally symmetrical workpieces, the annular ring puller presses on the underlying area of the sheet metal blank and forces the material to flow into the trough-shaped counterpart in the draw die before the material is drawn into the final shape via the draw ring.

1 shows a deep drawing tool with brake ring according to the prior art.

The left part of the figure shows the clamp in a cutaway view 1 with a circumferential, continuous annular groove 5a ,

The drawing ring arranged underneath 3 has at the same position an annular, continuous bar 5b (Draw bead). The Stamp 4 is in the starting position before the forming process and touches the surface of the sheet metal blank 2 ,

The right part of the picture of 1 shows in a sectional view the beginning of the forming process. The hold down 1 presses on the sheet metal blank 2 , At the same time the stamp moves 4 down and pull the sheet metal blank 2 over the drawing ring 3 , By the pressure of the punch 4 flows the material of the sheet metal blank 2 between the circular, continuous bar 5b in the drawing ring 3 and the vertically aligned above, surrounding, continuous annular groove 5b in the drawing ring 3 therethrough. For clarification is on the right edge of 1 a section of the area between downholder 1 , Sheet metal cutting 2 and drawing ring 3 with the circular, continuous bar 5b in the drawing ring 3 and the vertically arranged above, circumferential, continuous annular groove 5a in the hold down 1 shown enlarged.

By using the drawing or Bremswulst the material flow is partially controlled. The disadvantage of this is the comparatively large forming forces, the need for the use of lubricants and the higher risk of component failure by Bodenreißer.

The object of the invention is to propose a device which makes it possible to significantly increase the part spectrum to be produced in order to open up new areas of application or to postpone existing process limits.

In addition, should largely be dispensed with by the inventive device on the use of lubricants to reduce the cost of the excipients, the pre- and post-treatment of sheet metal blanks and the formed deep-drawn parts and thus the environmental impact.

According to the invention the object is achieved by a device according to claim 1. Preferably refinements and developments the device are the subject of the dependent dependent claims 2 to 11.

In the apparatus according to the invention, the necessary forming force is applied via a drawing punch on the sheet metal blank. The flow movement of the workpiece to be formed is controlled by a hold-down in conjunction with a drawing ring.

Downholder and drawing ring / die have in the region of the component flange on a plurality of cantilevered, spaced-apart form elements. In this case, the form elements of the blank holder and the drawing ring / the die are arranged in alignment or staggered.

Due to the cantilevered, spaced and virtually punctiform acting form elements in the flange region of the thermoforming tool, the contact surface between the tool and the workpiece compared to known drawing and Bremswülsten significantly reduced.

In a staggered arrangement of the form elements of the blank holder and the drawing die or the die to be reshaped undergoes a change of bending in the radial and tangential direction, which stabilizes it against wrinkling due to the targeted increase in and thus prevents wrinkling.

In an alternative, aligned in the direction of the stamp movement arrangement of the mold elements of the blank holder and the drawing ring or die, the metal sheet to be formed is guided on both sides at the same points of contact. This minimizes the friction between the tool and the workpiece.

In a further, likewise preferred embodiment, individual form elements of the blank holder and of the drawing die or the die in the punch feed direction are aligned with one another and other form elements of the blank holder and the drawing ring or the die are offset in the punch feed direction. As a result, on the one hand, the friction between the tool and the workpiece is minimized in comparison to the known solutions of the prior art. At the same time prevents the, in the stamp feed direction partially offset arrangement of the form elements of the blank and the drawing ring or the die undesirable wrinkling.

The use of the form elements according to the invention not only allows the energy-efficient production of sheet metal components without lubricant, but in particular the transformation irregularly shaped components with increased process reliability, d. H. with enlarged process window. Here, the flow of material can be selectively controlled by the fixed or preferably rotatably mounted, particularly preferably flexibly positionable mold elements.

The mold elements are fixed or releasably connected to the hold-down and the drawing ring / die. The production of the blank holder and the drawing ring with the cantilevered mold elements is done with known methods of machining, such. B. by milling.

Preferably, the form elements are designed as hemispherical or dome-shaped protrusions. Depending on the size and geometry of the workpiece to be produced, the form elements are fixed to each other at a defined distance from each other. In a preferred embodiment, the mold elements have an identical distance from each other, which is not absolutely necessary.

2 shows an inventive thermoforming tool before the forming process, in which the surface of the blank holder 1 and the drawing ring / die 3 in the region of the component flange a plurality of equally spaced, distanced, fixed, cantilevered mold elements 6 having the surface of the sheet metal blank 2 touch.

For clarification is on the right edge of 2 a section of the area between downholder 1 , Sheet metal cutting 2 and drawing ring 3 with a plurality of cantilevered, spaced apart form elements 6 in the hold down 1 and in the drawing ring 3 shown enlarged.

The projecting, fixed form elements 6 are arranged on several concentric circular paths and have an equal distance from each other.

In a particularly preferred embodiment, the flow of material through a plurality of movably mounted mold elements 7 controlled. As a result, the frictional forces occurring between the preferably rotatably mounted, cantilevered form elements 7 on the downholder 1 and on the drawing ring / die 3 and the surface of the sheet metal blank 2 be significantly reduced.

In a further, likewise preferred embodiment, the form elements 6 . 7 a different distance to each other. Especially for machining complex shaped, asymmetric workpieces have the form elements 6 . 7 in a further, likewise preferred embodiment, a different distance from each other, which corresponds to the expected voltage curve during deep drawing. The determination of the arrangement the form elements 6 . 7 and the distances to each other is done with known analytical and semi-analytical design methods.

In a further, likewise preferred embodiment, the form elements are 6 . 7 uniform on at least two different tracks 9 arranged. Under a train 9 is understood in the context of this invention, a line on which the spaced-apart form elements 6 . 7 the hold-down 1 and the drawing 3 are located. Here are the form elements 6 . 7 the hold-down 1 and the drawing ring or die 3 in the punch feed direction (Z direction) aligned with each other or offset from one another. In a further, likewise preferred variant, the shaped elements are 6 . 7 irregular on at least two different tracks 9 arranged.

3 shows in the left part of the figure in a sectional view of the hold-down 1 with several, equally spaced, cantilevered and rotatably mounted form elements 7 that the surface of the sheet metal blank 2 touch virtually point-like.

The drawing ring arranged underneath 3 has staggered equally spaced, cantilevered and movably mounted, preferably rotatably mounted form elements 7 on which the surface of the sheet metal blank 2 touch. The movably mounted form elements 7 are preferably formed as spheres which partially from the surface of the blank holder 1 and the drawing 3 protrude.

The Stamp 4 is in the starting position before the forming process and touches the surface of the sheet metal blank 2 ,

The right part of the picture of 3 shows in a sectional view the beginning of the forming process.

The hold down 1 presses on the sheet metal blank with a pressure of 2 MPa-10 MPa 2 , At the same time the stamp moves 4 down and pull the sheet metal blank 2 over the drawing ring 3 , By the pressure of the punch 4 flows the material of the sheet metal blank 2 between the equally spaced, overhanging and rotatably mounted form elements 7 the hold-down 1 and arranged in the xy plane offset, cantilevered and rotatably mounted form elements 7 of the drawing 3 therethrough.

For clarification is on the right edge of 3 a section of the area between downholder 1 , Sheet metal cutting 2 and drawing ring 3 with, in the xy plane offset from one another, projecting and rotatably mounted form elements 7 the hold-down 1 and the drawing 3 shown enlarged.

The enlarged view shows the, by the cantilevered, movably mounted form elements in the hold-down 1 and in the drawing ring 3 controlled material flow of the sheet metal blank 2 ,

The projecting, movably mounted, preferably rotatably mounted form elements 7 on the downholder 1 and on the drawing ring / die 3 are arranged offset from one another in the xy plane. As a result, during the forming process, a change in the bending load of the material occurs, as a result of which work hardening of the flange region and possibly of the frame region is effected.

By using the cantilevered form elements 7 on the downholder 1 and on the drawing ring / die 3 It is also possible to produce complex parts by deep drawing without lubricant. An otherwise expected tearing of the sheet metal blank due to the limited formability of the material is characterized by, as cantilevered form elements 7 preferably used, rotatably mounted balls effectively prevented.

For the transformation of large and complicated shaped workpieces are in a further, equally preferred embodiment fixed and movably mounted, preferably rotatably mounted form elements 6 . 7 on the downholder 1 and on the drawing ring / die 3 arranged. As a result, preferably asymmetric parts can be produced.

In addition to the use of projecting mold elements 6 . 7 , which are formed as hemispheres or rotatably mounted balls, the use of projecting ellipsoids of revolution or cylinders, which allow a flow of material along a limited distance, is also preferred. Due to the cantilevered form elements 6 . 7 In the flange region of the deep-drawing tool, the contact area between the tool and the workpiece will be significantly reduced in comparison to the known brake beads.

By preferably used, movably mounted form elements 7 becomes compared to the fixed form elements 6 achieved a further reduction of the frictional forces and the resulting necessary pulling force. Between the workpiece and the tool, there is only rolling friction in the flange area, which is significantly lower than the sliding friction when using fixed mold elements.

The preferably used, movably mounted, particularly preferably rotatably mounted form elements 7 are used in many different designs with regard to their design, size and permissible load bearing. As form elements 7 particularly preferred are balls, cylinders, rollers, roller races, cones, truncated cone or tons.

During the drawing process with the deep-drawing tool according to the invention, the sheet to be formed undergoes a bending in the radial and tangential direction, which stabilizes it against wrinkling as a result of the targeted increase in and thus prevents process instability, such as wrinkling. The force for overcoming the alternating bends in the flange area is used selectively as a retention force for controlling the material flow.

4 shows in a sectional view of the hold-down 1 with a plurality of equally spaced, cantilevered and fixed form elements 6 that the surface of the sheet metal blank 2 touch.

The drawing ring arranged underneath 3 has in the xy plane aligned evenly spaced, cantilevered and fixed form elements 6 on which the surface of the sheet metal blank 2 touch. This preferred embodiment leads to a minimization of the contact surface between the tool and the workpiece and thereby to a minimization of the frictional forces.

5 shows further preferred embodiments of the invention.

The left part of Figure a) shows the holding-down device in a highly schematized, sectional view 1 with several, equally spaced, cantilevered and fixed or rotatably mounted form elements 6 . 7 that the surface of the sheet metal blank 2 touch. The drawing ring arranged underneath 3 has aligned evenly spaced, cantilevered, fixed or rotatably mounted form elements 6 . 7 on which the surface of the sheet metal blank 2 touch. This preferred embodiment leads to a minimization of the contact surface between the tool and the workpiece and thereby to a minimization of the frictional forces.

5 shows in the middle figure b) in a highly schematic, sectional view of the hold-down 1 with several, equally spaced, cantilevered and fixed or rotatably mounted form elements 6 . 7 that the surface of the sheet metal blank 2 touch. The drawing ring arranged underneath 3 has staggered arranged, projecting, fixed or rotatably mounted form elements 6 . 7 on which the surface of the sheet metal blank 2 touch. This preferred embodiment allows the resulting bends a targeted control of the flow of material and prevents possible wrinkles.

5 shows in the right figure c) in a highly schematic, cut representation of the hold-down 1 with a plurality of differently spaced, projecting and fixed or rotatably mounted form elements 6 . 7 that the surface of the sheet metal blank 2 touch.

The drawing ring arranged underneath 3 has in the left area aligned, cantilevered, fixed or rotatably mounted form elements 6 . 7 on which the surface of the sheet metal blank 2 touch. In the right area shows the drawing ring 3 staggered, cantilevered, fixed or rotatably mounted form elements 6 . 7 on which the surface of the sheet metal blank 2 touch.

This also preferred, combined arrangement of mutually aligned and staggered form elements 6 . 7 on or in the downholder 1 and on or in the drawing ring (matrix) 3 allows the resulting bends a targeted control of the flow of material and prevents possible wrinkles. At the same time, the frictional forces occurring are reduced in comparison to the known solutions of the prior art.

In order to be able to set the material flow and the friction in a targeted manner in the case of the inventively macrostructured tools, the tool geometry must be adapted to the component geometry.

The geometry of the tools can by the immersion depth (e), the span (λ) of the adjacent mold elements, the formation and fixation of the mold elements (fixed or movably mounted mold elements 6 . 7 ) and the geometric arrangement on or in the hold 1 and the drawing ring 3 To be defined. 6 shows in a schematic sectional view of the relevant tool parameters.

The immersion depth e defines how far the individual form elements can penetrate in the direction of the sheet metal normal. The span λ defines the distance between two adjacent mold elements from each other in the originally flat sheet metal plane.

A higher immersion depth e but also increases the retention force in the flange and thus the necessary pulling force that can lead to component failure in the form of a Bodenreißer. Accordingly, the immersion depth e and the span λ can be selectively varied locally with respect to the component geometry in order to set a homogeneous flow of material in the flange area and to prevent component failure due to soil tears.

Compared to the conventional deep-drawing process, in which usually the hold-down is force-controlled, the distance between hold-down and die for setting the immersion depth (as adjustment parameters) is set in a controlled way during deep drawing with the macrostructured tools according to the invention. This can be done by means of a spacer ring (also known as pulling aid).

7 shows a schematic sectional view of the spacer ring 8th as a mechanical travel limit when pressing the blank holder 1 , The spacer ring 8th causes the distance a between the fixed form elements 6 of the pressed down holder 1 and the fixed form elements 6 of the drawing 3 equal to or greater than the sheet thickness s of the sheet metal blank 2 is.

8th shows a schematic, sectioned plan view of a section of the work area between downholder and drawing die.

The left figure shows four equally spaced, rotatably mounted, spherical form elements 7n the hold-down. In the drawing die is symmetrical and offset to the form elements 7n a rotatably mounted spherical shape element 7z arranged. Such an arrangement is preferably used for producing rotationally symmetrical workpieces.

The right figure shows four mutually equally spaced, rotatably mounted, spherical form elements 7n the hold-down. In the drawing die is asymmetrical and offset to the form elements 7n a rotatably mounted spherical shape element 7z arranged. Such an arrangement is preferably used for the production of workpieces without symmetry axis.

9 shows in a plan view of the drawing die 3 an inventive thermoforming tool for producing a cup for tub-shaped parts (oil pan for cars, washing and sink).

The spaced apart form elements 6 . 7 are on three, equally spaced tracks 9 arranged. The fixed, cylindrical shaped elements 6 collar from the drawing die 3 out. The rotatably mounted, spherical form elements 7 In the corner area of the cup, the deformation stresses and forces occurring in this highly stressed zone reduce and prevent tearing of the sheet metal blank.

The arrows marked with "W" show the course of the material flow.

Based on an embodiment of the use of the deep-drawing tool according to the invention in deep drawing a rotationally symmetrical cup with ball structuring of the pull ring 3 and the hold-down 1 described in more detail. The basic structure of the thermoforming tool is in 3 shown:
In the tool parts hold down 1 and drawing ring 3 are in the flange each rotatably mounted, projecting and spaced apart spherical shape elements 7 arranged. These form elements 7 are each located on three concentric circles that run around the axis of rotation of the tool. The circles of hold-downs 1 and drawing ring 3 are arranged offset. Also tangential are the form elements 7 the hold-down 1 and the drawing 3 arranged offset so that they each engage in a gap of the counterpart.

The forming process is as follows:
First, a round sheet (Ronde, diameter: 180 mm, thickness: 1.0 mm, material: DC04) is inserted and centered on the drawing ring 3 (Inner diameter: 103 mm, inlet radius: 10 mm) centered. Then the hold down closes 1 and the cantilevered, rotatably mounted spherical shape elements 7 Press a defined path into the sheet (immersion depth: 1.0 mm). In this case, the sheet is radially and tangentially by the staggered shaped elements 7 wavy curved. Then the stamp moves 4 (Diameter: 100 mm, edge radius: 10 mm, speed: 10 mm / s) in the direction of the drawing ring 3 and the actual deep-drawing process begins.

First, the drawn part floor forms. No material flows from the flange area yet. If the radial stress then reaches a value which satisfies the flow condition, the material starts to flow out of the flange. The material in the flange experiences a tensile stress radially and is compressed tangentially. In order to prevent wrinkling by the tangential compressive stress, the sheet is when passing the spherical shape elements 7 stabilized by the occurring bends. This bend is comparable to that of a corrugated sheet, which, due to its wave geometry along the shafts, has a higher buckling stability than flat sheet metal. When flowing the sheet bends back and forth several times. It experiences a change in bending over the way in the flange. After the stamp 4 has reached the drawing path, he goes back, the hold-down 1 is opened and the part can be removed.

LIST OF REFERENCE NUMBERS

1

 Stripper plate

2

 Ronde / sheet metal blank

3

 Drawing ring / drawing die

4

 stamp

5

 Draw ring / Bremswulst

5a

 circumferential, continuous annular groove (draw bead) in the hold-down device

5b

circular, continuous bar in the drawing ring

6

 Form element, fixed

7

 Shaped element, movably mounted

7n

 Form element of the hold-down, movably mounted

7z

 Form element of the drawing ring / drawing die, movably mounted

8th

 Distance ring (travel limit)

9

 train

a

Distance between the form elements 6 . 7 of the pressed down holder 1 and the form elements 6 . 7 of the drawing 3

e

 Immersion depth

s

 Sheet thickness of the sheet metal addition 2

W

 Material flow

λ

 span

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited non-patent literature

• DIN 8584 [0002]

Claims (13)

Apparatus for deep drawing a sheet metal blank with forming tools with a drawing punch 4 , a drawing ring / die 3 and a hold-down 1 , where drawing ring / matrix 3 and hold down 1 in the sheet metal blank to be formed 2 facing flange portion a plurality of cantilevered, spaced-apart form elements 6 . 7 exhibit. Apparatus according to claim 1, characterized in that the shaped elements 6 . 7 on or in the drawing ring / die 3 and offset on or in the hold-down to each other or are arranged in alignment with each other. Apparatus according to claim 1, characterized in that form elements 6 . 7 on or in the drawing ring / die 3 and offset on or in the hold-down to each other and are arranged in alignment with each other. Device according to one of claims 1 to 3, characterized in that the shaped elements 6 . 7 fixed or detachable with the hold-down 1 and the drawing ring / die 3 are connected. Device according to one of claims 1 to 4, characterized in that the shaped elements 7 movably mounted, preferably are rotatably mounted. Apparatus according to claim 5, characterized in that the shaped elements 7 have the contour of a ball, a cylinder, a roller, a roller rim, a cone, a truncated cone and / or a barrel. Device according to one of claims 1 to 4, characterized in that the projecting portions of the mold elements 6 spherical, hemispherical or dome-shaped. Device according to one of claims 1 to 7, characterized in that the shaped elements 6 . 7 have an equal distance from each other. Device according to one of claims 1 to 7, characterized in that the shaped elements 6 . 7 have a different distance from each other. Device according to one of claims 1 to 9, characterized in that the shaped elements 6 . 7 uniform on at least two spaced tracks 9 are arranged. Apparatus according to claim 9, characterized in that the shaped elements 6 . 7 non-uniform on at least two spaced tracks 9 are arranged. Apparatus according to claim 10 or 11, characterized in that the webs 9 are arranged uniformly to each other. Apparatus according to claim 10 or 11, characterized in that the webs 9 are arranged non-uniformly to each other.

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