WO2010140960A1

WO2010140960A1 - Method and device for punching / cutting out a component from a blank

Info

Publication number: WO2010140960A1
Application number: PCT/SE2010/050588
Authority: WO
Inventors: Stefan Inhammar
Original assignee: Precomp Solutions Aktiebolag
Priority date: 2009-06-02
Filing date: 2010-05-31
Publication date: 2010-12-09
Also published as: EP2437902A4; EP2437902A1; SE0950400A1; SE534128C2

Abstract

The invention relates to a method for punching/cutting out a detail from a workpiece, such as a sheet of metal or any material with a similar structure and is characterized by the steps that a first die cutter is pressed against a workpiece, that a counterforce is pressed with a counterforce force against the die cutter at the opposite side of the workpiece, the force of the die cutter being larger than the force of the counterforce, that, when the punched part has been at least partly or entirely penetrated through the workpiece, said part is returned into the workpiece essentially to its start position as the force of the counterforce is larger than the force of the die cutter, that at least a second die cutter and a corresponding counterforce, both with, in relation to said punched part, differing and/or either partly or entirely corresponding, radially outer dimension, preferably corresponding to the intended final shape of the detail, penetrate through the material and punch/cut out the intended contour of the detail, and that the detail is subsequently ejected from the workpiece.

Description

METHOD AND DEVICE FOR PUNCHING / CUTTING OUT A COMPONENT FROM A BLANK

The invention relates to a method of punching or cutting out a component of a sheet of metal or a similar material according to the preamble of claim 1. The invention relates also to a device according to the preamble of claim 6 for performing said method.

PRIORART

Through fmeblanking, components having high quality may be manufactured. This technique is suitable to apply on sheets of metal, such as steel, stainless, brass, aluminium, and copper, or similar materials to produce components for safety details, so called seat recliners, details for gear boxes, synchronization details, motor components, etc. Indentations and embossings may be performed in the same operation step. For instance, a cog wheel is a component which through its engagement surface is advantageously manufactured by fine blanking.

At the edge of the detail or component facing the tool, so called die rolls occur, i.e. the material in the edge region is deformed so that the cutting surface itself is reduced. The size of the die roll has a great influence on certain details, e.g. safety details. If for example a cog wheel is manufactured with a sheet thickness of 3 mm, and a die roll of 1 mm is formed, this results in the "actual" sheet thickness of the detail being reduced to 2 mm, so that its ability to handle loads may be reduced by up to 33 %.

In certain cases, this is compensated by increasing the sheet thickness by the same measure as the size of the die roll. This implies a larger consumption of material for each manufactured detail, a high detail price, and, of course, an environmental influence because of increased weight of the detail, etc.

THE OBJECT OF THE INVENTION

The object of the invention is to provide a method of the kind mentioned in the preamble, which minimizes the problems mentioned above.

The object of the invention is also to provide a device for performing the method.

RECORD COPY-TRANSLATION (Rule 12,4) DISCLOSURE OF THE INVENTION

The object is achieved by a method according to the characterizing part of claim 1, and with a device according to the characterizing part of claim 6.

The sub-claims indicate advantageous embodiments of the invention.

By returning the detail firstly punched back into the material in a subsequent step, the die roll may be minimized by in the next step it being cut with a punch and a die, which cut along its periphery either outside or inside the surface from the first step and/or in certain special cases also along its die clearance. It is also possible that the second . cutting operation is performed inside, outside and/or in the first cut section. As an example, certain portions of the cut section in the second cutting operation may take place outside, whereas in certain regions of the finished product, the second cutting operation has taken place in the first cut section. In the second cutting operation, a type of chafing takes places in the material region as compared to the cut section in the first step. In a last step, the finished detail is discharged. By the new operation according to the invention, the die roll is reduced and may in certain cases disappear entirely, which implies that the thickness of the edge region of the detail is maintained or gets only somewhat smaller than with conventional punching and cutting devices, where the detail is punched/cut and fed away in two operation steps.

With a method being able to minimize the die roll, you may reduce the consumption of material and thus have a cost efficient production which influences the environment in positive terms. The thickness of the finished detail need no longer be adapted to the size of the die roll, which in its turn implies that you in many cases may maintain, or only in a minimized manner increase, the thickness in order to get an optimal end product.

The die roll is a normal phenomenon which is normally created at cutting/punching. Factors having influence as to the size of the die roll are the quality and the mechanical properties of the material, the material thickness as well as the forming of the detail, and the design of the tools.

By, according to the method of the invention, firstly feeding a punched detail back into the punch hole, the die roll may consequently be reduced to a minimum, which gives a considerably better end product as regards quality. With a minimized die roll, you may reduce the consumption of material and thus have a cost efficient production which influences the environment in positive terms.

I RECORD COPY-TRANSLATION I (Rule 12,4) As the finished detail is cut in an adjacent cut section and/or in certain cases in a limited or entirely in the same cut section in a second cutting operation, the chafing of the material will consequently arise in the second cut section, as the surrounding material is influenced in the first cutting operation, where a detail is cut either entirely or remains partly in the cut hole and is then returned into the cut hole.

The method and the device of the invention may be applied on both an inner and outer contour depending on the design of the detail. The selection of method steps and tools are based on the design of the detail.

BRIEF DESCRIPTION OF DRAWINGS

The invention will be described more in detail below with reference to the enclosed drawings, which show preferred embodiments.

Fig. 1 shows a cross-section of a workpiece with a detail punched in one operation step according to prior art. Fig. 2 shows a schematically sectioned view of a device according to the invention.

Figs. 3a to d schematically show a first embodiment of a method according to the invention.

Figs. 4a to d schematically show a second embodiment of a method according to the invention. Figs. 5 a to d schematically show a third embodiment of a method according to the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION Similar details occurring in the different embodiments in the drawings have got the same reference numerals. For instance, this implies that the force components with the same reference numerals in the different figures are not necessarily influenced by the same force but the exerted force in the specific case is dependent on the nature and thickness of the material and on other known factors.

With reference to Fig. 1, a detail 1 is shown, which according to prior art is punched and cut from a workpiece 2, usually a sheet of metal, in the direction of the arrow 3. Independent of the size of the cut gap, a die clearance occur, at conventional hole cutting, with the following characteristic properties: At the side of a so called die roll, an edge chamfering, a so called die roll, occurs on the material 2 as well as on the detail 1, followed by a almost "straight" (cylindrical or prismatic) clean cut 5 with a good surface. Thereafter, a rapture zone 5 with an uneven surface and a widening cross- section of the hole, a so called clearance α, follows. The punched detail 1 finally has an axially protruding blanking burr 8 at the so called burr side at a burr edge 7. Of these particulars, the clean cut 5 is the most important criterion for the quality of the hole 9.

The clean cut 5 guarantees the cross-section dimensions of the hole 9 and constitutes the functional part of the hole, while the length of the clean cut 5 may be quite decisive for the function of the hole, in extreme cases. The clean cut 5 is at normal requirements of relatively less importance. At conventional cutting, the clean cut comprises about 30 to 50 % of the sheet thickness, while one at fine blanking may cut with a clean cut of up to 100 % of the sheet thickness.

The blanking burr 8 reflects the quality of the product and the production capacity of the tool and its height increases concurrently with the wear of the punch and the die. When the height of the burr reaches a maximal permitted value, the tool has to be reground.

The device 10 of the invention, which is schematically shown in Fig. 2, and which relates to a working moment in the process, comprises a die 11, which is normally fixed to tool parts (not shown) of the device 10, and against which the workpiece or the material 2 rests, a guide plate 12, which is movably mounted in order to be able to insert and remove a workpiece into/from the device 10, a die cutter 13, which is movable towards and away from the workpiece 2, and the design of which corresponds to holes created in the die 11 and the guide plate 12 corresponding to the outer shape of the detail 1 to be cut/punched, and a counterforce 14, the shape of which corresponds to the hole in the die 11. In the different moments, which will be described below with reference to Figs. 3 to 5, the die 11, the guide plate 12, the die cutter 13 and the counterforce 14 may have corresponding, but different dimensions in order to perform the special moment of the process according to the invention for punching/cutting a detail 1, which will be described more in detail below. In Figs. 3 to 5, the parts of the device, except the die cutters 13 and the counterforces 14, have been removed, and their motions have been replaced by arrows 15 to 18, where 15 represents the punching motion of the punch in the figures or the punching force, 15' represents the reversed motion, 16 represents the counterforce of the counterforce 14 in the direction towards the punch 13, 16' represents the reversed motion of the counterforce 14, 17 represents the force of the guide plate in one direction or the V-ring force, and 18 represents the force of the die in the opposite direction. Even if the arrows 15 to 18 represent forces/motions of the components of the device, it is obvious from the description below that these forces/motions only relate to relative directions, and also that the components may have different dimensions in the different embodiments as well as in the separate operation moments of the process. In Figs. 3 to 5, preferred embodiments of the device according to the invention are shown, wherein the die cutter 13 may be arranged above or below the workpiece 2 with the counterforce 14 at the opposite side of the workpiece 2, but this is only an exemplified variant. The device of the invention may within the scope of the claims be designed in another way, e.g. with the die cutter at one side of a horizontal or oblique workpiece.

The method of the invention principally implies that a detail 1 intended for manufacture is firstly punched/cut out in the direction 15 of the force component for the die cutter 13 and in the direction 16 of the force component for the counterforce 14, so that the punched detail is ejected a distance A out of the material. The distance A, or as it is designated below the "ejected distance" is advantageously less than the thickness of the material, i.e. the punched part is cut out and with advantage penetrated at least partly or also entirely through the workpiece. The return stroke in the direction 15' for the die cutter and 16' for the counterforce thus suitably takes place when the punched part still is in contact with the workpiece 2 around the cut hole, hi that way, in the return stroke, the part is thus returned into the workpiece 2 so that in the next operation step a cutting operation will take place with another, completely or partly smaller, larger or similar cutter die in the plane of the material seen to the area depending on the fact on which part/s of the detail a minimal die roll is to be achieved. There are cases when only portions of the punch in the second cutting operation have the same dimension as in the first cutting operation.

By returning the punched part into the workpiece 2, the region around the cut hole has plasticized after the first cutting operation, i.e. is floating somewhat, which at the subsequent cutting operation, where a new die cutter with another dimension cuts through the plasticized region, results in the die roll 4 (see Fig. 1), which remains on the finished detail 1 after the second cutting step, becoming considerably smaller than with previously known cutting methods in one step only. The roll die 4 will thus be minimal and in certain cases not occur at all. In Figs. 3 to 5, the difference in peripheral size of the different die cutters will be illustrated below with the designation B or as is designated below as "the difference of outer dimensions". The distance B thus represents the difference of the main plane of the material between different cutting tools or die cutters (in the drawings comparable with a substantially horizontal direction). During the second cutting operation, a kind of "chafing operation" is performed. The chafing operation may thus be performed on both an inner and an outer contour depending on the design of the detail. In this second cutting step, the outer size of the punch along its periphery may be either larger or smaller by the measure B than the dimension of the die cutter in the first cutting step depending on the fact whether the detail to be punched is to have an inner contour or an outer contour with a minimal die roll, such as an inner thread and an outer thread, respectively, on a cog wheel. The designation C below represents the width of the plasticized zone adjacent to the cutting tool in a direction of the main plane of the material. The designation D below represents the height of the plasticized zone adjacent to the cutting tool in a direction perpendicular to the main plane of the material. The designation numeral 19 represents a V-ring in the guide plate 12. The V-ring cuts into the workpiece for its fixing and runs around the detail to be cut or punched.

With three embodiments, it will below be described how a fine blanking with a reduced die roll is achieved with the method of the invention when punching/cutting out a detail of a sheet metal or a material 2 with similar properties.

In Figs. 3a to f, a method of the invention is described for punching/cutting out a plane component.

In Fig. 3a, Step 1 is shown, wherein the punch 13 through the force 15 penetrates the material 2 by means of the counterforce 16 of the counterforce 14 and the V-ring forces 17 of the guide plate 12, which forces act during the entire step. The measure A (the ejected distance) and the pressures vary with the cutting force, the properties of the material, the material thickness, and the design of the detail.

In Fig. 3b, Step 2 is shown, wherein the punch 13 "is pulled out of the material 2, which usually takes place in the same operation as Step 1. Also here, a counterforce (ejection) 15' and V-ring forces 17 occur during the entire step, i.e. a so called

"pushback" technology. Alternatively, the "pushback" technology may take place in a separate Step 2. The consequence will be that an additional step is added in the tool (Step 2 becomes Step 3, etc.). The selection of method (pushback) is connected to the pressure and the possibilities of the tool. Here, the pressures vary with the cutting force, the properties of the material, the material thickness, and the design of the detail. In Fig. 3c, Step 3 is shown, wherein the punch 13 leaves the material. The cut material part is pressed into the strip/material 2.

In Fig. 3d, Step 4 is shown, wherein a new die cutter 13' penetrates the material 2 again. In this case, the outer size of the die cutter 13' is, by measure B, less than the outer size of the die cutter 13 of Step 1. A correspondingly adapted counterforce 14' as well as a die and a guide plate are also arranged in this Step. When the shape of the detail is substantially rounded, this corresponds to a radius which is smaller by the measure B. A counterforce 16 adapted to the measure B and corresponding V-ring forces 17 are present during the entire step. During the operation, the chafing operation is performed, which may thus be made on both an inner and an outer contour depending on the design of the detail. Here, the measures A (the ejected distance) and B (the difference between outer dimensions) as well as the pressures vary with the properties of the material, the material thickness, and the design of the detail.

In Fig. 3e, Step 5 is shown, wherein the die cutter 13 leaves the material 2. Here, the V- ring force 16 is "active" and the counterforce (ejection) 15 is nil. Here, the pressures vary with the cutting force, the properties of the material, the material thickness, and the design of the detail.

In Fig. 3f, Step 6 is shown, from which may be seen how the ready-cut detail 1 is ejected from the die and removed from the tool in the direction of the arrow 20.

In Figs. 4a to g, a method of the invention is described for punching/cutting out a plane and formed component.

In Fig. 4a, Step 1 is shown, wherein the die cutter 13 through the force 21 penetrates the material 2 by means of the counterforces 22 of the counterforce 14 and V-ring forces 17, which forces act during the entire step. The measure A (the ejected distance) and the pressures vary with the cutting force, the properties of the material, the material thickness, and the design of the detail.

In Fig. 4b, Step 2 is shown, wherein the die cutter 13 is "pulled out" of the material 2. Here, a counterforce (ejection) 22 and V-ring forces 17 act during the entire process, i.e. a "pushback" technology. Alternatively, the "pushback" technology may take place in Step 2. The consequence will be an additional step in the tool (Step 2 becomes Step 3, etc.). The selection of method (pushback) is connected to the pressure and the possibilities of the tool. Here, the pressures vary with the cutting force, the properties of the material, the material thickness, and the design of the detail.

In Fig. 4c, Step 3 is shown, wherein the die cutter 13 leaves the material. The cut material part is pressed into the strip/material 2.

In Fig. 4d, Step 4 is shown, where a new die cutter 13' penetrates the material 2 again with a force 23, but from the opposite side. Here, a counterforce 24 of a new adapted counterforce 14' and V-ring forces 17 act during the entire process. During the operation, the chafing operation is performed, which may thus be made on both an inner and an outer contour depending on the design of the detail. In this case, one wants to achieve an inner contour with a minimal die roll. Here, the measures A (the ejected distance) and B (the difference between outer dimensions), and the pressures vary with the properties of the material, the material thickness, and the design of the detail.

In Fig. 4e, Step 5 is shown, where the die cutter 13' leaves the material 2 with the force 25, the V-ring force 17 is "active" and the counterforce (ejection) is nil. Here, the pressures vary with the cutting force, the properties of the material, the material thickness, and the design of the detail.

In Fig. 4f, Step 6 is shown, where a new, additional, wider die cutter 13" penetrates the material 2 with the force 26 to achieve a wider detail 1'. Here, a counterforce 27 of an adapted counterforce 14" and V-ring forces 17 act during the entire process. The measure A (the ejected distance) and the pressures vary with the properties of the material, the material thickness, and the design of the detail.

In Fig. 4g, Step 7 is shown, from which it is understood how the ready-cut detail 1' is ejected from the die, the die cutter 13" leaves the material 2 with the force 28, and how the detail is removed from the tool in the direction of an arrow 29.

In Figs. 5a to g, a method of the invention is described for punching/cutting out a plane and formed component.

In Fig. 5a, Step 1 is shown, where the die cutter 13 through the force 15 penetrates the material 2 by means of counterforces 16 of the counterforce 14 and V-ring forces 17, which forces act during the entire step. The measures A (the ejected distance), C (plasticising width), and D (plasticizing height) as well as the pressures vary with the cutting force, the properties of the material, the material thickness, and the design of the detail.

In Fig. 5b, Step 2 is shown, where the die cutter 13 is "pulled out" of the material 2 with a force 30. Here, the counterforce (ejection) 31 of the counterforce 14 and V-ring forces act during the entire process, i.e. a "pushback" technology. Alternatively, the "pushback" technology may take place in Step 2. The consequence will be an additional step in the tool (Step 2 becomes Step 3, etc.). The selection of method (pushback) is connected to the pressure and the possibilities of the tool. Here, the pressures vary with the cutting force, the properties of the material, the material thickness, and the design of the detail.

In Fig. 5c, Step 3 is shown, where the die cutter 13 and the counterforce 14 leave the material. Here, the cut material part has been pressed into the strip/material 2.

In Fig. 5d, Step 4 is shown, where a new die cutter 13' with a wider radius by the measure B penetrates the material 2 again with a force 32. Here, the counterforce 33 of a new, adapted counterforce 14' as well as V-ring forces 17 act during the entire process. During the operation, the chafing operation is performed, which may thus be made on both an inner and an outer contour depending on the design of the detail. Here, the measures A (the ejected distance) and B (the difference between outer dimensions), and the pressures vary with the properties of the material, the material thickness, and the design of the detail.

In Fig. 4e, Step 5 is shown, where the die cutter 13' leaves the material 2 with the force 34. Here, the V-ring force 17 is "active" and the counterforce (ejection) of the counterforce 14' is nil. Here, the pressures vary with the cutting force, the properties of the material, the material thickness, and the design of the detail.

In Fig. 5f, Step 6 is shown, where a new, wider die cutter 13" penetrates the material 2 with the force 35, the counterforce 36 of a new counterforce 14" and the V-ring force 17 acting during the entire process. The measure A (the ejected distance) and the pressures vary with the properties of the material, the material thickness, and the design of the detail. In Fig. 5g, Step 7 is shown, which illustrates how the die cutter 13" leaves the material 2 with the force 37, and how the ready-cut detail 1" is ejected from the die and removed from of the tool in the direction of an arrow 38

Although the same designation figures have been used in the different examples of embodiments, for the sake of clarity, both measures and force components may, of course, vary depending on the material to be machined.

Nor is the shape of the finished detail limited to the one shown in the embodiments but may vary as well as the shapes of the tools depending on the detail to be manufactured.

The method shown of the invention may also be used for production in series, in which case the plurality of die cutters and other components are arranged in a group or that the punching/cutting operations take place after one another on the same sheet of metal.

The method and the device of the invention may, of course, be modified within the scope of the appending claims.

Claims

1. A method for punching/cutting out a detail from a workpiece, such as a sheet of metal or a material with a similar structure, characterizedin the steps that a first die cutter is pressed against a workpiece, that a first counterforce is pressed with a counterforce force against the first die cutter at the opposite side of the workpiece, the force of the first die cutter being larger than the force of the first counterforce, that, when the punched part has been at least partly or entirely penetrated through the workpiece, said part is returned into the workpiece substantially to its start position by the force of the first counterforce being larger than the force of the first die cutter, that at least a second die cutter and a corresponding second counterforce, both with, in relation to said punched part, different and/or either partly or entirely corresponding, radially outer dimension, preferably corresponding to the intended final shape of the detail, penetrate through the material, and punch/cut out the intended contour of the detail, and that the detail is subsequently ejected from the workpiece.

2. A method according to claim l,characterizedin that a special set consisting of a die and a guide plate, with adaption, is arranged for each set of die cutters and counterforces.

3. A method according to claims 1 or 2, characterized in that said at least one additional die cutter and the corresponding counterforce are dimensioned such that, at the punching/cutting operation, they cut through said workpiece by a predetermined distance (B) from the clean cut, said predetermined distance preferably lying within a region which is plasticized by the penetration of the first tool.

4. A method according to any of claims 1 to3,characterizedin that the radially outer dimension of said first die cutter is smaller or larger by the distance (B)than the radially outer dimension of said second die cutter.

5. A method according to any of claims 1 to 3, characterized in that the radially outer dimension of said first die cutter is smaller or larger by the distance (B) than, and within a predetermined region equal to, the radially outer dimensions of said second die cutter.

6. A device for performing the method according to claims 1 to 5, for punching/ cutting out a detail (1) from a workpiece (2) such as a sheet of metal or any similar material, which device has a first set of tools comprising a first die (11) and a first die cutter (13), on one hand, and at least a second set of tools comprising a second die and a second die cutter (13'), on the other hand, characterizedin that the first set of the device also comprises a first counterforce (14) arranged opposite to first die cutter (13), the dimension of the counterforce (14) corresponding to the size of the first die cutter, and a guide plate (12) adapted to the first die (11)₅ which guide plate receives a workpiece (2), wherein said first die cutter may penetrate through the first die as well as the first guide plate against the force of the first counterforce, and that said second set of tools also comprises a second guide plate adapted to the second die, and a second counterforce (14') arranged opposite to the second die cutter (13% the dimension of said second counterforce (14') corresponding to the size of the second die cutter, wherein the periphery of the first die cutter (13) of the first set of tools has a different dimension than and/or is completely or party equal to the size of the periphery of the second die cutter of the second set of tools.

7. A device according to claim 6, characterizedin that a special set consisting of a die and a guide plate is arranged for each set of die cutters and counterforces.

8. A device according to claims 6 or 7, characterizedin that the differing dimension depends on the fact that the periphery of the die cutter of the first set is smaller or larger by a predetermined distance (B) than the periphery of the die cutter of the second set.

9. A device according to any of claims 6 to 7, characterized in that the radially outer dimension of said first die cutter is smaller or larger by the distance (B) than, and within a predetermined region equal to, the radially outer dimensions of said second die cutter.

10. A device according to any of claims 6 to 9, characterizedin said outer distance (B) lying within a region which has been plasticized by the penetration of the first tool.