Method and Device for Producing Flangeless Drawn Parts

Abstract

The invention relates to a method for producing flangeless drawn parts from a flat and/or preformed metal blank using a drawing punch, a blank holder and a drawing die, wherein the drawing die has at least one supporting region and at least one wall region, between which rounded run-in portions are provided, and the blank is trimmed during the drawing operation. In addition, the invention relates to a method for producing flangeless drawn parts from a flat and/or preformed metal blank comprising a drawing punch, a blank holder, a drawing die with at least one supporting region, at least one wall region and rounded run-in portions, which are provided between the supporting region and the wall region.

Description

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This patent application is a continuation of PCT/EP2012/057526, filed Apr. 25, 2012, which claims priority to German Application No. 102011050001.4, filed Apr. 29, 2011, the entire teachings and disclosure of which are incorporated herein by reference thereto.

FIELD OF THE INVENTION

The invention relates to a method for producing flangeless drawn parts from a flat and/or preformed metal blank using a drawing punch, a blank holder and a drawing die, wherein the drawing die has at least one supporting region and at least one wall region, between which rounded run-in portions are provided, and the blank is trimmed during the drawing operation. In addition, the invention relates to a device for producing flangeless drawn parts from a flat and/or preformed metal blank comprising a drawing punch, a blank holder, a drawing die with at least one supporting region, at least one wall region and rounded run-in portions, which are provided between the supporting region and the wall region.

BACKGROUND OF THE INVENTION

It is generally known when producing flangeless drawn parts to produce these firstly by deep drawing a flat blank and separating the resulting flange after the deep drawing process. However, this requires two cost-intensive steps. Moreover, said method does not allow process-integrated calibration of the drawn part. Consequently, a third step is required to calibrate the flangeless drawn part. Furthermore, it is known from technical reference book, ‘Schnitt-, Stanz- and Ziehwerkzeuge’, Öhler and Kaiser 8^th Edition (2001), Springer Verlag page 428 ff., to produce flangeless drawn parts using a device in which the blank is deep drawn and at the same time the supporting region above it is trimmed in one stroke of the press. The blank is trimmed in this method during the drawing operation in the region of the drawing edge, i. e. in the region of the rounded run-in portions between the supporting region and the wall region. Since in the region of the drawing edge, i. e. in the rounded run-in portion between the supporting region and wall region, the material moves forward in the direction of the bottom region of the drawn part, when the plate material is extruded by the cutting edge of the drawing punch in contact with the rounded run-in portion, not only an extrusion of the plate material takes place, but also a hardening thereof. This is why an unclean cut is produced during process-integrated trimming of the blanks during the deep drawing operation in the region of the rounded run-in portions in this method or using this device respectively. The reference book cited above points out that this method is only used if a clean cut of the edges of the drawn part is not an issue. In other words, the drawn part must be subjected to further processing.

Proceeding from this prior art, the problem to be solved by the present invention is to provide a method and a device for producing flangeless drawn parts, by means of which flangeless drawn parts can be produced in a process-integrated manner by drawing and trimming in a single stroke of the press while nevertheless being trimmed cleanly.

SUMMARY OF THE INVENTION

According to a first teaching of the present invention, the above-mentioned problem is solved for a method according to the invention by the blank being trimmed in the supporting region, while the drawing operation has not yet been completed, in such a way that the part of the blank that remains in the supporting region is completely drawn into the wall region of the drawing die when the drawing punch is moved further into the drawing die.

The blank is therefore trimmed according to the invention in the supporting region and not in the region of the rounded run-in portions or the drawing edge. Thus, the cutting direction and the direction of movement of the blank material can be substantially perpendicular to each other. The blank does not harden immediately through trimming and consequently a clean trimmed edge is produced. By moving the drawing press into the drawing die, the part of the blank that remains in the supporting region is completely drawn into the wall region and a flangeless drawn part with a clean cutting edge is produced in a single stroke of the press. The method according to the invention is characterised in particular by a single step and in this respect is particularly cost-effective. If preformed blanks are worked, these may, for example, produce excess material, in the bottom region, for example, and consequently calibration of the drawn part is possible in a process-integrated manner upon reaching the end position of the drawing punch. Trimming takes place preferably in the transition region between supporting region and drawing radius.

In accordance with a first embodiment of the method according to the invention, the blank holder is in contact with the region of the blank to be separated while the blank is being trimmed and can thus be used to control the trimming of the blank. The blank holder can ensure, in particular, that the flow of material is precisely controlled during the trimming operation in the supporting region. Furthermore, if a wide blank holder and a supporting region are used, a semi-finished part can be clamped in a crease-free manner and ironed.

The method according to the invention can be carried out in a particularly easy manner in that the blank is trimmed using a first cutting edge of the drawing punch and a recess provided in the supporting region of the drawing die. The cutting edge arranged in the punch makes it possible to dispense with additional measures, such as an additional punch and a device to control the movement of the same. The method can be implemented more cost-effectively due to the simplification of the device. The recess in the drawing die serves to house the trimmed blank and the cutting punch.

Alternatively, the blank can be trimmed using a cutting edge provided on the recess of the drawing die, which is arranged preferably in the supporting region or in the transition region between the supporting region and the drawing radius.

The method according to the invention can therefore be configured in a further advantageous manner where the blank is calibrated using an edging section arranged in the drawing die after trimming in the drawing die through the drawing punch reaching its end position. Deep drawing, trimming and calibration thus take place in the same device in a single stroke of the press. The drawn parts produced are particularly dimensionally accurate and have less tendency to spring back due to calibration.

If the blank is profiled after trimming in the supporting region or in the transition region between the supporting region and the drawing radius using the rounded run-in portions of the drawing die and the edging section of the drawing punch configured as a cutting edge, the blank can also be trimmed in a tension-free manner when drawn into the wall region consequently also achieving particularly good cutting quality. Moreover, profiling reduces inaccuracies on account of irregular drawing in of the blank to a minimum and consequently extremely dimensionally accurate drawn parts can be produced.

Moreover, the method according to the invention can be further improved by using a drawing punch, which provides the first and/or second cutting edge via a replaceable insertion piece in the drawing punch and optionally using a drawing die, which provides the recess in the supporting region via a replaceable insertion piece. The first and also the second cutting edge as well as the recess in the supporting region of the blank are exposed to high wear and tear from cutting operations. If these are designed as insertion pieces that are replaceable, account can be taken of wear and tear and, where necessary, the respective insertion piece easily replaced.

Alternatively, the first cutting edge is located on the recess in the supporting region of the drawing die which can also be provided via a replaceable insertion piece. In this case, the drawing punch is also equipped with a replaceable insertion piece, which is rounded in the region of the interaction with the cutting edge on the drawing die. The interaction between the cutting edge (sharp edge) and the rounded portion creates a self-centering effect which results in good cutting quality.

Alternatively, it is also possible in accordance with a further embodiment of the method according to the invention, to arrange for material, preferably in the form of bars to stand along the cutting line, region by region, i. e. to produce an uninterrupted cutting line, whereby the drawn part is still at least partially connected to the trimmed region and at the same time can be removed from the tool (scrap metal removal via bars). In a further separating process, the trimmed region can be separated from the good part.

According to a further embodiment of the method according to the invention, a ‘slotted semi-finished product can be used, which has at least one slit, preferably at least two slits, which runs from an edge of the semi-finished product to the cutting line, whereby the trimmed region breaks into a plurality of individual parts during trimming (division of scrap) and as a result, the bad part is easier to remove from the tool, via scrap slides, for example.

According to a second teaching of the present invention, the above-mentioned problem is solved by a generic device in that the drawing punch has a first cutting edge or rounded portion, which is in contact with a recess provided in the supporting region of the drawing die with a rounded portion or cutting edge such that the blank in the supporting region is trimmed during the drawing operation before the drawing punch reaches its end position. As already stated above, said cutting edge enables a clean cutting edge to be produced due to the slight hardening in the sheet. As a result, the flangeless drawn part is provided with a clean cutting edge and is thus significantly more dimensionally accurate in spite of process-integrated trimming.

The interaction between the cutting edge on the first tool part and the opposite rounded portion on the second tool part not only has a positive influence on the cutting result, but also has the advantage, due to the self-centering effect, that the tool parts can be used in conventional deep drawing presses, which do not usually have precise and accurate punch guiding, and thus the design of the tool can be kept simple.

According to a further embodiment of the device, the drawing punch has an edging section, which after drawing the blank into the wall region, calibrates the blank by compressing at least the wall region of the blank once the drawing punch has reached its end position in the drawing die. The edging section is configured such that it compresses the wall region against the bottom region and consequently there is calibration and thus an improvement in the dimensional accuracy of the drawn part.

According to a further embodiment of the device according to the invention, the edging section of the drawing punch is configured as a second cutting edge, wherein the second cutting edge enables profiling of the trimmed blank during the drawing operation in contact with the rounded run-in portions. As already indicated above, the second cutting edge enables additional profiling of the region of the blank drawn into the wall region. Since in this case the separated trimmings are not exposed to any tensile strain, this profiling is also carried out with a particularly high degree of precision. Moreover, very few inaccuracies result before the end of the drawing process due to profiling because of the irregular drawing in of the blank. Consequently, the level of dimensional accuracy of the respective blanks is particularly high.

In addition, the device according to the invention can be improved by using a replaceable insertion piece to form the recess of the drawing die. The recess is, as already mentioned above, exposed to increased wear and tear due to cutting operations, and thus replacing the insertion piece only incurs minimal cost.

The same also applies to a further embodiment according to which the first cutting edge and/or the edging section of the drawing punch is formed by a replaceable insertion piece. Parts affected by wear and tear can also be replaced at low cost here.

The object of providing a method and a device for producing flangeless drawn parts with which flangeless drawn parts can be produced in a process-integrated manner by drawing and trimming in a single stroke of the press, while nevertheless being trimmed cleanly, is achieved for a method by the blank being trimmed in the supporting region while the drawing operation has not yet been completed, in such a way that the part of the blank that remains in the supporting region is completely drawn into the wall region of the drawing die when the drawing punch is moved further into the drawing die.

BRIEF DESCRIPTION OF THE DRAWINGS

Furthermore, the invention shall be explained in detail using embodiments in conjunction with the drawings.

FIG. 1 shows a sectional view of the process-integrated cutting operation during the production of flangeless drawn parts known from the prior art,

FIG. 2a), b) shows a first embodiment of a device according to the invention and

FIG. 3a), b) shows a second embodiment of a device according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

Firstly, FIG. 1 shows a schematic sectional view of the method known from the prior art in which a blank 2 is deep drawn using a drawing punch 1 during the drawing operation and is cut at the same time in the drawing die 3 using a first cutting edge 4 of the drawing punch 1. The blank 2 is usually held here by a blank holder 5. Whilst the drawing punch 1 is moved into the drawing die 3, the material of the blank 2 and the drawing punch 1 are moved accordingly in the direction of the arrow shown. At the start of the cutting operation of the cutting edge, as shown in FIG. 1, the cutting edge 4 produces hardening due to the varying rapid movement in the region 2a of the blank 2. At the same time, however, the cutting edge 4 separates the blank 2 from the other part of the blank in the region of the rounded run-in portion between the supporting region 3a and the wall region 3b. Due to the hardening and the simultaneous tensile strain on the blank 2 in the cutting region, an unclean cutting edge is produced, which is avoided with the method according to the invention.

FIG. 2a) shows a first embodiment of a device according to the invention with a drawing punch 1′, which forms a flat blank 2′ in a drawing die 3′ at the start of the drawing process. The cutting edge 4′ of the cutting punch 1′ is configured such in the present embodiment that said cutting edge trims the blank 2′ in the supporting region 2a′. Trimming can also take place in the transition region between the supporting region and the drawing radius. It is in contact with a recess 7′ of the drawing die 3′ for this purpose. The blank holder 5′ presses down the blank 2′ during the first cutting operation using the cutting edge 4′ in the supporting region 2a, and consequently a controlled trimming of the blank 2′ occurs. The remaining part of the blank 2′ is completely drawn into the wall region 2b′ when the drawing punch 1′ is moved further into the drawing die 3′ and forms the wall region of the blank. As can be seen in FIG. 2b), the blank 2′ is compressed at the end of the drawing operation using the edging section 6′. However, by selecting the length of the edging section 6′, the drawing operation can also be completed without calibration or edging of the drawn part.

Moreover, it is also possible to form a pre-formed blank. This can provide excess material, for example in the bottom region 2c, which results in calibration of the drawn part when the drawing punch 1′ reaches its end position.

By trimming the blank in the supporting region 3a′, the material of the blank 2′ moves perpendicular to the cutting movement of the cutting edge 4′ of the drawing punch 1′. As a result of this, minimal hardening occurs in the blank 2′ during the cutting operation and a cleaner cut of the blank is guaranteed.

As shown in the first embodiment in FIGS. 2a) and 2b), the first cutting edge 4′ and/or the edging section 6′ are realised preferably through a replaceable insertion piece in the cutting punch. This improves maintenance and reduces the costs of replacing parts of the drawing punch affected by wear and tear. The same also applies insofar as the recess 7′ is configured in the drawing die 3′ using a replaceable insertion piece 8′.

In principle, a blank 2′ can also be heat formed, i. e. the blank is heated to an austenising temperature in advance and heat worked in the device according to the invention. This significantly reduces wear and tear in the device, particularly in the case of high-strength steels, since working forces are reduced. Moreover, it is also possible to carry out press hardening after hot forming. The blank 2′ must be systematically cooled at high cooling speed for this purpose in order to enable the formation of a substantially martensitic structure.

FIGS. 3a) and 3b) show a further example of a device according to the invention in a schematic sectional view, which differs from the first embodiment in that the edging section 6″ is configured as significantly longer and is provided with a second cutting edge. When the drawing punch 1″ is moved into the drawing die 3″, the blank 2″ is firstly cut in the supporting region using the cutting edge 4″. The remaining supporting region, which is drawn into the wall region 2b″, is also profiled by the edging section 6″ configured as a cutting edge, which, compared with the embodiment in FIG. 2, is configured as longer. The trimmings 10″ are produced in the process. As can be seen from FIG. 3b), the trimmings 10″ are under not tensile strain thus enabling clean separation of the trimmings 10″. This guarantees extremely good cutting quality. Moreover, the blank 2″ is only moved slightly into the drawing die 3″ after profiling thus enabling particularly high dimensional accuracy of the flangeless drawn part.

As a result, a flangeless drawn part can be drawn, trimmed, profiled and also calibrated in a single working stroke using the method according to the invention. This leads to particularly economical production of flangeless, highly dimensionally stable drawn parts.

In general, influence can also be exerted on the inward movement of the blank to be profiled where trimming is moved locally in the direction of the supporting region, i. e. opposite to the drawing radius and/or where a supporting region varying locally in height is used. Thus, the inward movement can be controlled, adjusted, corrected or compensated.

Claims

1. Method for producing flangeless drawn parts from a flat and/or preformed metal blank comprising using a drawing punch, a blank holder and a drawing die, wherein the drawing die has at least one supporting region and at least one wall region between which rounded run-in portions are provided and the blank is trimmed during the drawing operation, wherein the blank is trimmed in the supporting region, while the drawing operation has not yet been completed, in such a way that the part of the blank that remains in the supporting region after trimming is completely drawn into the wall region of the drawing die when the drawing punch is moved further into the drawing die, wherein the blank is trimmed using a first cutting edge or rounded portion of the drawing punch and a recess provided in the supporting region of the drawing die.

2. Method according to claim 1, wherein the blank holder is in contact with the region of the blank to be separated during the trimming of the blank.

3. Method according to claim 1, wherein the blank is trimmed using a cutting edge provided on a recess of the drawing die.

4. Method according to claim 1, wherein the blank is calibrated after trimming in the drawing die when the drawing punch reaches its end position using an edging section arranged in the drawing punch.

5. Method according to claim 1, wherein after trimming the blank in the supporting region the blank is profiled by the edging section of the drawing punch configured as a second cutting edge which is in contact with the rounded run-in portions of the drawing die.

6. Method according to claim 1, wherein a drawing punch is used, which provides the first and/or second cutting edge via a replaceable insertion piece in the drawing die and optionally uses a drawing die, which provides the recess in the supporting region via a replaceable insertion piece.

7. Device for producing flangeless drawn parts from a flat and/or preformed metal blank for implementing a method according to claim 1, the device comprising:

a drawing punch;

a blank holder;

a drawing die with at least one supporting region, at least one wall region and rounded run-in portions which are provided between the supporting region and the wall region; and

wherein the drawing punch has a first cutting edge or rounded portion which is in contact with a recess provided in the supporting region of the drawing die with a rounded portion or cutting edge such that the blank is trimmed in the supporting region during the drawing operation before the drawing punch reaches its end position, wherein the drawing die and the drawing punch are configured such that when the drawing die reaches its end position the blank is completely drawn into the wall region and forms a flangeless drawn part.

8. Device according to claim 7, wherein the drawing die has an edging section, which compresses the blank after the blank has moved into the wall region by compressing at least the wall region of the blank when the drawing punch reaches its end position in the drawing die.

9. Device according to claim 7, wherein an edging section of the drawing punch is configured as a second cutting edge and the second cutting edge enables profiling of the trimmed blank during the drawing operation in contact with the rounded run-in portions.

10. Device according to claim 7, wherein replaceable insertion pieces are provided for provision of the recess in the drawing die.

11. Device according to claim 7, wherein replaceable insertion pieces are provided for provision of the first cutting edge and/or the edging section of the drawing punch.