DE102012011767A1 - Parting a workpiece - Google Patents

Abstract

A method for dividing a workpiece (2) and a device (22) suitable for this purpose are specified. In this case, a notch geometry (12) ending in the workpiece (2) is introduced into the workpiece (2) to be cut along a parting line (10) with plastic deformation at least on one side and the workpiece (2) is sheared along the parting line (10). As a result, directly a burr-free cut or fracture surface can be generated.

Description

The invention relates to a method for cutting a workpiece and to a device arranged for cutting a workpiece. In this case, the invention is particularly concerned with the desire for a burr-free cutting of workpieces, so that necessary processing steps for burr removal can be avoided.

Under a division of a workpiece is according to the Standard DIN 8588 a mechanical separation of a workpiece without the formation of formless material, ie in particular without chips understood. The most commonly used in industry for cutting a workpiece is the so-called shear cutting, the workpiece is divided between two moving blades that move past each other while maintaining a defined cutting gap. In particular, shear cutting is one of the most commonly used separation processes in sheet metal working. When shearing, which is also referred to as normal cutting, the material is deformed by the two penetrating cutting until its formability is exhausted and the material is lost through breakage.

Due to the material deformation during the shearing cutting process, a characteristic formation of the cut surface on the workpiece occurs. Due to the process, shear-cut workpieces have a tendency to cut or fracture surface and always a burr. However, such a burr is usually undesirable on the workpiece. Thus, loosening or chipped burrs can cause workpieces to malfunction. For example, this can result in short circuits in electrical and electronic components. Further decreases in downstream coating processes, the wetting thickness in the burr formation. This can for example lead to a reduced corrosion protection of the finished workpiece. In general, burrs on the workpiece during manual further processing or during assembly pose a risk of injury to the operator, in particular also to the end customer. A burr on the workpiece can also lead to a reduced positioning accuracy when positioning the workpiece or when mounting in an assembly. In addition, burrs on the workpiece in subsequent manufacturing steps can also lead to damage or increased wear on the tools.

Very often, therefore, burrs on the parted workpiece must be removed by additional post-processing steps or at least reduced in size. This leads to increased workpiece costs and overall to a reduction in cost-effectiveness.

In particular, in the metal and electrical industry, there is a desire for a flashless production of workpieces, since without post-processing steps to remove the burr worse corrosion protection at the cut surfaces or the risk of short circuit exists. In addition, the problems of increased tool wear due to a burr formation, especially when trimming of structural components made of soft sheet materials, as they are often used in particular in the automotive sector. The burr formation and thus the effort for a post-processing are greatest for soft materials. In the electrical industry in particular electrical connectors must meet high quality standards due to their field of application. Post-processing processes for burr removal are often unavoidable.

As a burr-free method for cutting a workpiece so far only the so-called counter-cutting is known. For this purpose, for example, on the DE 393 13 320 C1 directed. The counter cutting comprises at least two counter-rotating cutting stages. The workpiece is first cut on and then cut in opposite directions. However, counter-cutting has not become established industrially, since a triple-acting press is required for this process. In addition to the cutting force, an opposite counterforce and a hold-down force must always be applied. After DE 393 13 320 C1 The opposite cutting and cutting is achieved by a complex press with a ram stroke.

According to the VDI Guideline 2906, Sheet 6: Cut surface quality when cutting, trimming and punching workpieces made of metal: counter cutting, Verein Deutscher Ingenieure, 1994 , The resulting cut surfaces during counter cutting also, due to the running in the opposite direction cutting operations, two edge indentations on the top and bottom of the workpiece, as well as two smooth cut zones, which are usually separated in the middle by a rupture zone. This will also come from the DE 39 31 320 C1 seen. These stepped cut surfaces can again lead to problems in painting due to sharp transitions between the smooth cut portion and the fracture surface.

The object of the invention is therefore to provide an alternative method for cutting a workpiece, wherein the fracture or cut surface after the cutting is as free of burrs as possible. Another object of the invention is a device specify with which a workpiece can be cut as free of burrs as possible.

According to the invention, the first object is achieved by a method for cutting a workpiece, wherein a notch geometry ending in the workpiece is introduced into the workpiece to be cut along a parting line with plastic deformation at least on one side and the workpiece is sheared along the parting line.

In a first step, the invention proceeds from the consideration of producing a predetermined breaking point in the workpiece by a targeted introduction of a material deformation, which results in a burr-free cutting or fracture surface in a subsequent cutting of the workpiece. It has been found that a suitable material deformation can be generated by introducing a notch geometry, wherein the material of the workpiece is plastically deformed. By introducing a notch geometry with plastic material deformation, the microstructure of a particular ductile material is compressed or stretched in the region of the notch impression, which leads to a local strain hardening in the material. In the area of the notch impression, the hardness of the material thus increases, in particular in the case of metallic materials.

In a second step, the invention recognizes that a burr-free cut or fracture surface can be produced by dividing the material in the region of the microstructure change effected by the notch impression. This is achieved by cutting the workpiece in the region of the local pre-deformation. In this case, the cutting edge of a cutting tool penetrates into the area pre-deformed by the notch impression. It can not come to a burr formation, since in the last separation phase due to the introduced notch indentation of the material can not take place in the cutting tool. By localizing the shear cutting process also small dimensional tolerances can be achieved. In addition, due to the targeted local pre-deformation and in particular the resulting increased hardness in the material during shearing, a directed crack propagation occurs at the location of the notch impression. The latter leads to a nearly vertical cutting or fracture surface, which can be a great advantage in a further processing of the divided workpiece by joining.

Furthermore, stress peaks occur in the material at the bottom of the notch geometry during the shearing process. Due to the locally increased stresses an early break in the material is initiated, whereby the cutting force maximum is reduced. A reduction of the cutting force maximum leads to a reduction of the wear of the active elements and to a lower machine load. The invention also offers an advantage in the division of high and very high-strength workpieces, as they must be increasingly processed due to the increased requirements in the field of lightweight construction.

The specified method is particularly suitable for cutting metallic sheet metal parts. In principle, however, other materials, for example a ductile polymer, can be cut free of burrs and chips by the specified method. Due to the introduced notch geometry, the cutting force required for cutting during shear cutting is reduced even with hard and brittle materials. The method is thus also suitable for cutting a fiber-reinforced plastic or ceramic.

For the purposes of the invention, the term notch geometry is not necessarily understood to mean only the shape of a notch in the actual sense, which is often described as a wedge shape. Such a wedge or actual notch shape is generally advantageous for generating a predetermined breaking point in conjunction with resulting voltage peaks. However, it may also be advantageous in individual cases to generate the local deformation on the workpiece with a soft or rather round, not directly wedge-shaped notch geometry. The advantage of this is a lower wear of the deformation tool under the assumption that the voltage increase does not occur to the same extent as in a wedge-shaped notch geometry with sharp radii. Since the actual notch or wedge shape is thus not immediately essential to the invention, the described forms of local deformation are summarized under the term of a notch geometry.

In a preferred embodiment, the workpiece for introducing the notch geometry is moved with a holding-down device against a notching tool and the workpiece for this purpose rectified sheared with a first cutting tool against a second cutting tool. By the rectified movement of both steps, the required pressing tool can be further simplified. In addition, the Zerteilprozess the workpiece is thereby significantly shortened, which increases the production throughput considerably.

In an advantageous embodiment, the notch geometry is introduced by a bite or knife cutting. In this case, the notch geometry is introduced into the workpiece along the dividing line by means of a wedge-shaped cutting edge. For the purposes of the invention, however, this is not a division method according to the Standard DIN 8588 , since in the present case the notch geometry in the component ends and the workpiece by the introduction of the notch geometry not parted. Rather, it is therefore an incomplete dicing process that results in separation of the workpiece only in combination with another dicing process.

The invention is not limited to the fact that the notch geometry is introduced on one side into the workpiece. Rather, the notch geometry along the dividing line can also be introduced into the workpiece on both sides. In this case, the two notch geometries are introduced in such a way that a material connection remains in the workpiece between the notch geometries. Also, the two-sided introduction of a notch geometry, the workpiece is not completely divided. Preferably, the two-sided notch geometry with wedge cutters in the manner of the so-called Teißschneidens according to Standard DIN 8588 brought in. In the present case, this is an incomplete bite-cutting because the workpiece is not broken after the notch geometries have been introduced.

The process steps of introducing a kerf geometry ending in the component and shearing cutting can be carried out both in two separate working steps and combined in a common working step. From a procedural economic point of view, the introduction of the notch geometry in a joint step with the shear cutting is to be preferred. In this case, for example, penetrates a notching tool against a hold-down in the workpiece while a cutting tool is moved against the notching tool, the notching tool acts as a second cutting tool of the shear cutting.

In a preferred embodiment, the component to be divided is deformed by a forming process, in particular by deep drawing. The dividing line for dividing the workpiece is provided in particular in an edge region of the workpiece, so that the edges are cut off or separated outside the shaping.

Particularly advantageous is the introduction of the notch geometry in one step with the forming process. For this purpose, for example, a shaping die or a punch forming the workpiece in the die at the same time be configured as a notching tool, so that in particular during deep drawing along the desired parting line, for example at the edge of the die, the corresponding notch geometry is introduced into the workpiece.

In a further preferred embodiment, the workpiece is sheared in one step with the forming process. In this case, the introduction of the notch geometry can take place before or during the forming process. The latter embodiment is made possible in particular by the fact that, for example, the notching tool is at the same time designed as a cutting tool for the shear cutting. In a particularly preferred embodiment, the deep-drawing and the cutting of the workpiece thus take place in a single combined operation. A separate machining process for separating edges of the formed by deep drawing workpiece can thus be completely eliminated. The formed by deep drawing workpiece is generated directly burr-free and freed from its edges.

Our own investigations have further shown that to achieve burr-free and as vertical as possible cutting or fracture surfaces on the workpiece, the depth of the impression of the notch geometry should be selected in the material of the workpiece to be divided depending on its ductility. For a soft deep-drawing steel, the notch geometry, for example, should preferably be introduced at least to a depth of 10%, based on the thickness of the workpiece, at least to a depth of 10%. The specified method is particularly suitable for cutting workpieces having a thickness between 0.3 mm and 3 mm. The method is also suitable for cutting workpieces with thicknesses over 10 mm. In general, the method is not limited to a specific workpiece thickness.

The second object is achieved by a device for dividing a workpiece, which comprises a first and a second cutting tool, which are movable with the interposition of the workpiece against each other, a hold-down and a movable against the workpiece notching tool. In this case, the notching tool for introducing a kerf geometry ending in the workpiece along a parting line and the cutting tools for shearing the workpiece along the parting line are arranged.

The notching tool has, for example, a wedge or knife edge formed in accordance with the desired parting line, which can be introduced into the workpiece under plastic deformation of the material. The wedge cutting edge or another active element for introducing the notch geometry can be made, for example, from a hardened steel.

Advantageously, the device is adapted to move the workpiece for introducing the notch geometry with the hold-down device against the notch tool and the same time scissors cut the workpiece with the first cutting tool against the second cutting tool. As a result, the device can be made simpler and cheaper and the dicing process can be carried out more quickly.

The notching tool preferably comprises a first wedge cutting edge and a second wedge cutting edge, which are movable relative to one another and arranged to incomplete cutting teeth. This makes it possible to introduce a notch geometry on both sides along the dividing line into the workpiece.

In an advantageous embodiment of the device comprises a die and a punch, and wherein the die and / or the punch is additionally designed as a notching tool / are. In other words, the device is designed as a deep-drawing tool with a shaping die and a punch for molding the workpiece into the die. In this case, the die and / or the punch are at the same time designed to introduce the notch geometry into the workpiece to be treated. During deep drawing, the notching tool penetrates the die or the punch at the same time into the workpiece, so that the desired notch geometry in the workpiece takes place in one step with deep drawing.

Further advantageous is / are the die and / or the punch additionally formed as a cutting tool. This can be achieved that the workpiece in one step with a forming process, such. B. deep drawing, is divided. Particularly advantageously, the die and / or the punch are designed both as a notching tool and as a cutting tool. In a one-step work step, the workpiece can thus be cut both shaped and burr-free. In particular, the notching tool is designed as a second cutting tool against which the first cutting tool is guided during shear cutting.

Vorteihafterweise the device comprises a control device for actuating the movable tools, which is arranged to perform the division of the workpiece according to the method described above.

Embodiments of the invention will be explained in more detail with reference to a drawing. Showing:

1 : schematically the cutting of a workpiece by notching and shearing in a two-stage two-sided process,

2 schematically the division of a workpiece by notching and shear cutting in a two-stage one-sided process and

3 schematically the division of a workpiece by notching and shear cutting in a one-step one-sided process.

In 1 is schematically the cutting of a workpiece 2 by notching and shearing in a two-stage two-sided process. The process is divided into a total of four phases, wherein the phases a) and b) are assigned to the method step of introducing a notch geometry and the phases c) and d) to the method step of shearing.

In phase a) becomes a sheet-like workpiece 2 between a first notch part 4 and a second notch part 5 brought in. That's the two notch parts 4 . 5 comprehensive notching tool 6 is in an open state for this purpose. The two notch parts 4 . 5 include for introducing a notch geometry 12 one cutting edge each 7 , The workpiece 2 becomes so in the notch tool 6 positioned that the desired dividing line 10 at which the workpiece 2 is to be divided between the cutting edges 7 is arranged.

In phase b) becomes the notch part 4 with interposition of the workpiece 2 against the notch part 5 hazards. The cutting edges penetrate under a stamping force 7 on both sides in the material of the workpiece 2 under formation of the respective notch geometry 12 one. This is the material of the workpiece 2 locally plastically deformed. The cutting 7 are dimensioned so that after completion of phase b) between the resulting notch geometries 12 a material connection 13 remains. The workpiece 2 is not parted. The notch introduction according to phases a) and b) corresponds to an incomplete Teissschneiden.

In the next step, the workpiece becomes 2 along the introduced notch geometries 12 sheared. This is the workpiece 2 in phase c) by means of a hold-down 14 against a die 16 pressed. The matrix 16 can for example for shaping the workpiece 2 be formed by deep drawing. Here, the hold-down 14 especially as a stamp 15 be educated. Or it is a separate, not marked stamp provided. At the same time drives a first cutting tool 18 against the workpiece 2 , The workpiece 2 is positioned so that the dividing line 10 or the introduced notch geometries 12 between the die 16 and the first cutting tool 18 is arranged.

Subsequently, the first cutting tool 18 continue against the workpiece 2 hazards. The matrix acts here 16 at the same time as a second cutting tool 19 , In compliance with a predetermined cutting gap, the workpiece 2 by moving the two cutting tools against each other 18 . 19 along the dividing line 10 sheared. Due to the local deformation of the material due to the introduced notch geometries 12 there is a cracking in the material connection 13 , Because of the introduced notch impression 12 the material can not become a cutting tool during shear cutting 18 . 19 flow. The result is a burr-free cut or fracture surface, which is aligned approximately perpendicular to the workpiece surface.

In 2 is schematically the cutting of a workpiece 2 by notching and shearing in a two-stage one-sided process. The process is too 1 identical. However, it eliminates a notch part 4 , This notch part 4 is through the downholder 14 replaced. In phase b) the holddown moves 14 against the notch part 5 of the notching tool 6 , This results in a one-sided in the workpiece 2 introduced notch geometry 12 in the workpiece 2 ends and leads to a local plastic deformation of the workpiece 2 has led.

In 3 is schematically the cutting of a workpiece 2 represented by notching and shear cutting in a one-step one-sided process. Unlike the 1 and 2 In doing so, the introduction of the notch geometry and the shear cutting takes place in one working step. This is what the notch part does 5 of the notching train 6 at the same time as a die 16 for example, for a deep drawing and as a second cutting tool 19 ,

In phase a), the workpiece 2 between a hold-down 14 , a first cutting tool 18 and a notch part 5 positioned. In phase b) becomes the hold-down 14 with interposition of the workpiece 2 against the matrix 16 or the second cutting tool 19 emotional. The cutting edge penetrates 7 under plastic deformation along the dividing line 10 one-sided into the workpiece 2 one. At the same time, the first cutting tool moves 18 against the workpiece 2 ,

In phase c) becomes the first cutting tool 18 continue against the workpiece 2 or against the second cutting tool 19 acting die 16 hazards. The workpiece 2 will be along the dividing line 10 , at the one-sided notch geometry 12 is inserted, sheared.

The wedge 7 the matrix 16 is shaped so that in phase c) the first cutting tool 18 against the matrix 16 under shear cutting of the workpiece 2 can be moved.

In all three figures is an edge 20 of the workpiece 2 along a dividing line 10 separated from the workpiece. For actuating the tools of a device shown in the figures 22 is appropriate 1 a control device 24 intended.

It will further be appreciated that the specified method may be configured to divide the workpiece 2 only a single-acting press is needed. The active tools are, as indicated by the arrows drawn, for cutting the workpiece 2 move with force in one direction only. In each case, the workpiece is 2 for introducing the notch geometry 12 with the hold down 14 against the notch part 4 . 5 a notching tool 6 moves and the workpiece 2 with the first cutting tool 18 rectified against the second cutting tool 19 sheared.

LIST OF REFERENCE NUMBERS

2

workpiece

4

first notch part

5

second notch part

6

notching tool

7

cutting edge

10

parting line

12

notch geometry

14

Stripper plate

16

die

18

first cutting tool

19

second cutting tool

20

Garbage, edge

22

Device for cutting

24

control device

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 patent literature

• DE 39313320 C1 [0006, 0006]
• DE 3931320 C1 [0007]

Cited non-patent literature

• Standard DIN 8588 [0002]
• VDI Guideline 2906, Sheet 6: Cut surface quality when cutting, trimming and punching workpieces made of metal: counter cutting, Verein Deutscher Ingenieure, 1994 [0007]
• Standard DIN 8588 [0016]
• Standard DIN 8588 [0017]

Claims (17)

Method for cutting a workpiece ( 2 ), wherein in the workpiece to be cut ( 2 ) along a dividing line ( 10 ) under plastic deformation at least one side in the workpiece ( 2 ) ending notch geometry ( 12 ) and the workpiece ( 2 ) along the dividing line ( 10 ) is sheared. Method according to claim 1, wherein the workpiece ( 2 ) for introducing the notch geometry with a hold-down ( 14 ) against a notching tool ( 6 ) and the workpiece ( 2 ) rectified with a first cutting tool ( 18 ) against a second cutting tool ( 19 ) is sheared. Method according to claim 1 or 2, wherein the notch geometry ( 12 ) is introduced by wedge cutting. Method according to one of the preceding claims, wherein in the workpiece ( 2 ) along the dividing line ( 10 ) according to the type of Teißschneidens, but to obtain a material compound ( 13 ) a notch geometry on both sides ( 12 ) is introduced. Method according to one of the preceding claims, wherein the introduction of the notch geometry ( 12 ) takes place in one step with the shear cutting. Method according to one of the preceding claims, wherein the workpiece to be cut ( 2 ) is deformed by a forming process, in particular by deep drawing. Method according to claim 6, wherein the introduction of the notch geometry ( 12 ) takes place in one step with the forming process. Method according to claim 6 or 7, wherein the workpiece ( 2 ) is sheared in one step with the forming process. Method according to one of the preceding claims, wherein a sheet-like workpiece ( 2 ) is divided. Method according to one of the preceding claims, wherein as a workpiece ( 2 ) a metal, a polymer or a fiber-reinforced plastic is divided. Contraption ( 22 ) for the division of a workpiece ( 2 ) comprising a first cutting tool ( 18 ) and a second cutting tool ( 19 ), with the interposition of the workpiece ( 2 ) are movable against each other, a hold-down ( 14 ) and a relative to the workpiece ( 2 ) movable notching tool ( 6 ), whereby the notching tool ( 6 ) for introducing a in the workpiece ( 2 ) ending notch geometry ( 12 ) along a dividing line ( 10 ) and the cutting tools ( 18 . 19 ) to a shear cutting of the workpiece ( 2 ) along the dividing line ( 10 ) are set up. Contraption ( 22 ) according to claim 11, which is adapted to the workpiece ( 2 ) for introducing the notch geometry with the hold-down ( 14 ) against the notching tool ( 6 ) and the workpiece ( 2 ) rectified with the first cutting tool ( 18 ) against the second cutting tool ( 19 ) shear. Contraption ( 22 ) according to claim 11 or 12, wherein the notching tool ( 6 ) a wedge cutting edge ( 7 ). Contraption ( 22 ) according to one of claims 11 to 13, wherein the notching tool ( 6 ) a first wedge cutting edge ( 4 . 7 ) and a second wedge cutting edge ( 5 . 7 ), which are mutually movable and adapted to incomplete bite cutting. Contraption ( 22 ) according to one of claims 11 to 14, wherein a die ( 16 ) and a stamp ( 15 ), and wherein the die ( 16 ) and / or the stamp ( 15 ) additionally as a notching tool ( 6 ) is / are formed. Contraption ( 22 ) according to claim 15, wherein the matrix ( 16 ) and / or the stamp ( 15 ) additionally as a cutting tool ( 18 . 19 ) is / are formed. Contraption ( 22 ) according to one of claims 11 to 16, wherein a control device ( 24 ) for actuating the movable tools, which is used to carry out the division of the workpiece ( 2 ) is arranged according to one of claims 1 to 10.

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