EP2262627B1 - Cutting lines for cutting laminar materials - Google Patents

Description

1. Technical area

The present invention relates to cutting lines for cutting according to the preamble of claim 1. Such a cutting line is made DE 31 35 980 C known.

2. State of the art

Cutting lines are known in the art and consist of a steel strip with a cutting edge, two parallel side surfaces and a ridge opposite the cutting edge. Cutting lines are bent according to the desired shape of a blank, cut to length and inserted into a carrier plate. The resulting punching tool is u.a. used in flat bed punching, for example, to punch out cardboard boxes. Typically, a flatbed punching machine comprises a flat upper plate to which the tool is attached, and a flat lower plate with which the workpiece is pressed against the punching tool. The punching tool consists of a slotted support plate, usually made of a wood material, wherein the pre-bent cutting lines are inserted into the slots. The slots in the carrier plate are usually continuous, so that the back of the cutting lines is present on the upper plate of the flatbed punching machine.

In order to obtain a uniform punching result, the cutting lines must be adjusted in height. First, a trial stamping is performed and observed at which points the workpiece is cut properly and where no complete cut is made. At these points, intermediate layers of paper or special metal or plastic bands between a back plate and the upper plate of the flat bed punching machine inserted locally to increase the pressure on the cutting lines. This process is called trimming.

This trimming may extend to larger areas (the so-called "zone dressing") or to only certain localities where insufficient punching occurs (the so-called "local trimming"). It takes place on a dressing sheet, a layer of material which lies between a back plate behind the cutting lines and a protective plate of the upper plate of the flatbed punching machine. On the dressing sheet, for example, smaller or larger pieces of the intermediate layers are then fixed by hand at specific locations. In between, test cuts are made to evaluate the effects of dressing. Dressing is therefore a time-consuming, iterative process that requires a lot of experience and can not be used productively in flatbed die cutting machines.

Since such manual trimming is time consuming and requires expensive machine downtime, there is a need for methods and tools to reduce this expense.

For this purpose, various possible solutions have been proposed, including elastic-plastically deformable intermediate layers, which are introduced behind the punching or under the punching plate to compensate for pressure differences. For example, shows the DE 33 17 777 C1 a system in which the cutting lines have on their back side hardened cutting edges, which can penetrate during the punching operations in such an intermediate plate.

Furthermore, for example, in the DE 199 13 216 C1 proposed to use cutting lines with a reduced cross-sectional area, which bends in the use of the cutting line to automatically perform a height adjustment of the cutting line.

Finally, in the DE 31 35 980 C1 proposed to use a cutting line having a deformable spine, which is to allow a self-regulating punching blade adjustment. It is proposed to chamfer the back of the cutting line on both sides over a large area, to provide the knife back in cross-section with teeth or to introduce lateral grooves.

However, the proposed geometries have the disadvantage that they either do not lead to the desired degree of success or instability of the cutting line, resulting in incomplete height compensation and an inaccurate punching result. For this reason, such shaped cutting lines were not accepted on the market.

Furthermore, the proposed in the prior art line cross sections would be very expensive manufacture, which would make such lines very expensive. Furthermore, automatic processing, in particular automatic bending of such line cross sections, is not possible or not without edge bulging.

It is therefore the object of the present invention to provide a starting material for cutting lines, which on the one hand allows automatic dressing, but on the other hand does not have the disadvantages of already known in the prior art cutting lines. Since today cutting lines are mostly processed by machine, in particular bent, it must be ensured that such a cutting line design allows this also trouble-free.

3. Summary of the invention

The above objects are achieved by a cutting line according to claim 1.

Based on calculations and experiments, it has been found that such a starting material, which has projections at its back, which have a certain ratio of their height to the thickness of the steel strip, on the one hand allow independent height compensation of the cutting line, on the other hand, the stability of this cutting line does not affect becomes. When a tool with such cutting lines is loaded for the first time, the projections subjected to the highest load are plastically deformed by the local compressive stresses that occur, whereby an automatic dressing takes place. For the following loads of the tool then ideally prevails on each section of the cutting line, the same compressive stress.

The best results in terms of stability and deformability were achieved when the protrusions have a height h substantially in the region of half the thickness D of the steel strip. Higher projections, as proposed for example in the prior art deform rather elastic, tilt uncontrollably to the side, or the steel strip tilts in the groove of the support plate.

In another preferred embodiment, the protrusions were created by milling or grinding recesses in the transverse direction of the steel strip in the back. This milling or grinding is preferably carried out after machining the cross-sectional shape of the creasing and cutting line.

In another aspect of the present invention, the above object is achieved by a cutting line comprising a steel strip with a cutting edge of a back of the steel strip opposite the cutting edge, the back Having projections which are plastically deformable at the first use of the cutting line; and the projections were produced by milling or grinding recesses in the transverse direction of the steel strip in the back.

In this case, it was surprisingly found that in such cutting lines due to the transversely introduced to the bending direction recesses no edge overshoot or Rückenaufstauchung during bending, since the back area is relieved by the transverse recesses. This has advantages in terms of trimming, since even curved cutting lines then maintain their original height and much less dressing is required. By arranged transversely to the steel strip recesses, therefore, the actual height of the projections for automatic dressing by plastic deformation can be chosen smaller.

Even with such cutting lines to deform when the first load of a tool with such cutting lines, the most heavily loaded projections by the local compressive stresses occurring plastically, with an automatic dressing takes place. In the case of the following loads on the tool, ideally, the same compressive stress prevails on every section of the cutting line, whereby manual finishing can be saved or only very little manual trimming has to be carried out.

Furthermore, extending transversely to the steel strip recesses can be much easier and more accurate than differently arranged recesses. They can be inventively easily and inexpensively grind or mill in the back. It should be noted that cutting lines often have only a very small thickness of less than one millimeter, so that complex back shapes are not technologically and economically producible. Furthermore, it is ensured by these machining types that nothing changes at the desired and exactly observed height of the cutting line during processing. Self-leveling cutting lines according to the invention can therefore be produced very precisely and nevertheless inexpensively.

In a preferred embodiment, the protrusions substantially have a height h of 0.5% -70% and more preferably of substantially 2% -20% and more preferably of 6% -10% of the thickness D of the steel strip. Surprisingly, it was found that with recesses introduced transversely to the steel strip only recesses with comparatively small heights are necessary for automatic dressing. Of course, this also has great advantages with regard to the stability of the cutting line in the groove of the carrier plate.

In another aspect of the present invention, the o.g. Problem solved by a cutting line, comprising a steel strip with a cutting edge of the cutting edge opposite back of the steel strip, the back is randentkohlt to plastically deform at the first use of the cutting line can.

The plastic deformability of the back of a cutting line, which is desired for an automatic dressing, according to the invention can also be ensured by the fact that the back is randentkohlt. This can be done both in conventional back shapes, as well as in spine shapes with protrusions and recesses according to the other aspects of this invention, whereby the respective effects, in particular the plastic deformability of the back, can increase.

For edge decarburization, carbon is removed from the steel in the area of the back by diffusion, creating a soft, ferritic structure in the area of the back, which can easily be plastically deformed. Processually, such a decarburization can be achieved by the edge of the Cutting line is exposed under elevated temperatures of a reducing inert gas atmosphere.

Even with such edge-decarburized cutting lines in the back region, the back region deforms plastically during the initial loading of a tool with such cutting lines by the occurring local compressive stresses, whereby an automatic dressing takes place. In the case of the following loads on the tool, ideally, the same compressive stress prevails on every section of the cutting line, whereby manual finishing can be saved or only very little manual trimming has to be carried out.

In a preferred embodiment, the back of the cutting line is edge-decarburized to a depth of 5 μm-100 μm.

In a further preferred embodiment, the back is rounded in a cross section through a tip of the projections. By this back shape, which is additionally rounded in the transverse direction, there is a line or point bearing surface of the back on the back plate of the tool, whereby the plastic deformation of the projections is further facilitated. In addition, the insertion of the cutting lines is facilitated in the grooves of the carrier tape. Finally, such a cross-sectional shape further reduces the effect of so-called back buckling in tight bending radii. When bending narrow radii would usually result in an increase in the total height H of the cutting lines in the range of up to 0.2 mm, depending on the thickness of the cutting lines and bending radius, which is inventively avoided.

In another preferred embodiment, the back is chamfered on both sides in a cross section through a tip of the projections or double-concave. These spinal forms also facilitate a well-defined degree of plastic deformation with sufficient stability of the back.

In a further preferred embodiment, the back is rounded in a cross section through a tip of the projections semicircular, wherein the radius of curvature r corresponds to half the thickness D of the steel strip. This embodiment is particularly advantageous in terms of back upsetting while providing a sufficiently high stability of the back of the scoring and cutting line in the transverse direction. It results from the rounded back in the transverse direction a quasi-central force on the creasing or cutting lines, whereby lateral forces are avoided. A tilting of the creasing and cutting line in the groove of the carrier plate is therefore effectively prevented.

In a further preferred embodiment, the projections in a longitudinal section through a tip of the projections on concave flanks. More preferably, the back in longitudinal section on circular segment-shaped, in particular semicircular, recesses with a radius. Due to the concave, in particular round flanks of the projections - seen in the longitudinal direction of the creasing and cutting line - the projections have a progressive characteristic with respect to compressive forces introduced above. This is particularly advantageous in order to ensure a plastic and not only an elastic deformation of the projections both in small height differences to be compensated and in large differences in height. Preferably, the radius of the recesses corresponds to 10% - 250%, more preferably 20% - 150% and even more preferably substantially 100% of the thickness of the steel strip.

Preferably, the projections in a longitudinal section through a tip of the projections on a tapered tip. In extreme cases, for example, the radius of the flanks and the distance of the projections from one another are selected such that a pointed tip of the projections results. This results in a point-like contact between the projections and the protective plate of the tool before the first load, which becomes a flat contact after the load.

Preferably, the projections in a longitudinal section through a tip of the projections on a tapered tip. Here, for example, the radius of the flanks and the distance of the projections from each other is selected so that there is a butting tip of the projections. This results in a line-shaped contact between the projections and the protective plate of the tool before the first load, which becomes a flat contact after the load.

In a preferred embodiment, the tapered tip has a length 1 of 1% -50%, more preferably 5% -30% and even more preferably 20% of the thickness D of the steel strip.

Preferably, the back has been tempered and / or annealed and / or edge deburred to increase its plastic deformability. By tempering or by partial annealing or edge decarburization plastic deformation of the back is increased and thus spared by the lower pressure forces during automatic trimming the cutting edge.

The above-mentioned objects are also achieved by using a cutting line described above in a punching machine, in particular in a flat-bed punching machine or in a rotary punching machine.

4. Brief description of the drawings

Fig. 1

eine vergrößerte Querschnittsansicht einer erfindungsgemäßen Schneidlinie;

Fig. 2

eine Detailansicht der Figur 1, die den oberen Teil einer erfindungsgemäßen Schneidlinie im in Querrichtung Q geschnittenen Zustand, entlang der Linie A-A aus Fig. 3 zeigt;

Fig. 3

eine Detailansicht von der Seite einer Ausführungsform einer erfindungsgemäßen Schneid- oder Rilllinie, im in Längsrichtung L geschnittenen Zustand, entlang der Linie B-B aus Fig. 2;

Fig. 4

eine Detailansicht einer weiteren Ausführungsform einer erfindungsgemäßen Rill- oder Schneidlinie, im in Längsrichtung L geschnittenen Zustand, entlang der Linie B-B aus Fig. 2;

Fig. 5

eine Detailansicht des oberen Teils einer erfindungsgemäßen Schneidlinie im in Querrichtung Q geschnittenen Zustand mit einer beidseitig abgeschrägten Rückenform;

Fig. 6

eine Detailansicht des oberen Teils einer erfindungsgemäßen Schneidlinie im in Querrichtung Q geschnittenen Zustand mit einer doppelt-konkaven Rückenform;

Fig. 7

eine kombinierte Seitenansicht (links) und Schnittansicht in Querrichtung (rechts) einer weiteren Ausführungsform der erfindungsgemäßen Schneidlinie; und

Fig. 8 und 9

mikroskopische Detailansichten von längsgeschnittenen Rückenbereichen von erfindungsgemäßen Schneidlinien.

Hereinafter, preferred embodiments of the invention will be described with reference to the drawings. It shows:

Fig. 1

an enlarged cross-sectional view of a cutting line according to the invention;

Fig. 2

a detailed view of the FIG. 1 , the upper part of a cutting line according to the invention in the transverse direction Q cut state, along the line AA Fig. 3 shows;

Fig. 3

a detail view from the side of an embodiment of a cutting or creasing line according to the invention, in the longitudinal direction L cut state, taken along the line BB Fig. 2 ;

Fig. 4

a detailed view of another embodiment of a creasing or cutting line according to the invention, in the longitudinal direction L cut state, along the line BB Fig. 2 ;

Fig. 5

a detailed view of the upper part of a cutting line according to the invention in the transverse direction Q cut state with a dished on both sides back shape;

Fig. 6

a detail view of the upper part of a cutting line according to the invention in the transverse direction Q cut state with a double-concave back shape;

Fig. 7

a combined side view (left) and cross-sectional view (right) of another embodiment of the cutting line according to the invention; and

8 and 9

Microscopic detail views of longitudinally cut back areas of cutting lines according to the invention.

5. Description of the preferred embodiment

Hereinafter, preferred embodiments of the present invention will be explained in detail with reference to the drawings.

FIG. 1 shows a first embodiment of a cutting line according to the invention 1. The cutting line 1 consists essentially of a flat steel strip 10 with a height H in the range of about 8 to 100 mm, a thickness D in the range of 0.45 to 2.13 mm (1 , 3 - 6 pt), any length and a cutting edge 20. Special shapes of the cutting lines, as mentioned above, have other edge shapes 20 and are also the subject of the present invention.

Opposite the cutting edge 20 is the back 30 of the steel strip 10 and the cutting line 1, which is rounded in this preferred embodiment. In the illustrated embodiment, the back 30 is rounded in a semicircle and has a radius of curvature r, which corresponds to substantially half the thickness D of the steel strip 10.

In FIG. 2 is a cross section through the region of the back 30 shown in detail. Here, the semicircular rounding of the back region 30 is shown particularly well in cross section. The rounding of the back portion 30 is generated similar to the facets of the cutting portion 20 by grinding or scraping the steel strip 10.

FIG. 3 shows the back region of the steel strip in the side view. It can be seen that the back has projections 32, which are produced by recesses 36 being ground in the back. In the in FIG. 3 illustrated preferred embodiment, the back in the longitudinal section semicircular recesses 36 which have a radius R ₁ . The radius R ₁ may be in one embodiment in the range of half the thickness D of the steel strip 10.

In others in the FIGS. 5 and 6 illustrated embodiments, the back 30 in cross section on both sides-bevelled or double-concave.

The distance between the recesses 36 has been selected such that a blunt tip 34 of the projections 32 results, which thus have a length of 1. The length is preferably 11% to 20% of the thickness D of the steel strip 10 and in one embodiment 0.05 to 0.15 mm, preferably 0.08 mm to 0.13 mm and particularly preferably 0.11 mm.

In the in FIG. 3 illustrated embodiment, the height h is about 0.35 mm and thus about 50% of the thickness D of the steel strip 10 of 0.71 mm.

In FIG. 4 Another preferred embodiment of the back region of a starting material 1 for cutting lines is shown. In this embodiment, the radius R _{2 has been selected} larger than the radius R _{1 of} the recesses 36 FIG. 3 , This results in pointed tip 34 of the projections 32 and a lower height h of the projections 32. The radius R ₂ may preferably be in the range of thickness D of the steel strip 10. Preferably, the radius R2 corresponds to 50% - 150%, more preferably substantially 100% of the thickness D of the steel strip 10.

In a first use of the starting material 1 as a creasing or cutting line according to the invention deforms the back portion 30 of the steel strip 10. At places high stress on the creasing or cutting line, the steel strip 10 deformed initially elastic and when exceeding the yield strength and plastic and that first in the range with the highest pressure load. In the case of the starting material 1 according to the invention, the regions of the highest loads are the tips 34 of the projections 32. The projections 32 therefore initially act like elastic springs. If the yield strength in this local area is exceeded, they deform plastically, ie they are plastically compressed, thus ensuring automatic trimming. This plastic change of height is in FIG. 3 represented by the height h _v after deformation. When the projections 34 are compressed, the length of the blunt tip also increases from 1 to 1 _v .

The same applies to a creasing and cutting line according to the embodiment of FIG. 4. At a first load, the projections 32 are plastically deformed at their tips, so that they are flattened and after deformation a height h _v and a butt end 34 with a Have length l _v .

The preferred in the longitudinal direction of the creasing and cutting lines concave flanks 38 and the transverse semicircular or convex flanks 39 of the projections 32 results in a progressive force-displacement characteristic which allows a dressing over a large area and yet has the necessary stability, to ensure a perfect punching result or creasing result. This is particularly true when the creasing or cutting lines have to be bent or bent, for the area of the bending radius. In particular, there is a reduced back-up effect in this area, which would lead to increased pressure in this area.

The ground or milled recesses reduce the contact surface between the back 30 and the back plate of the punching machine, whereby the contact stresses are greatly increased compared to ordinary back shapes. This ensures that at the first use at the tips 34, which are subjected to the highest load, such a high contact stress is created, which causes a plastic deformation at this point, without the steel strip 10 and in particular the cutting or creasing edge 20 plastic is deformed. This results in a height reduction of the height H of the steel strip 10 and thus an automatic trimming of the cutting lines.

Due to the rounding of the spine in cross section, the creasing or cutting line can moreover be easily introduced into the lasered slots of the carrier plate.

Other spinal forms are also conceivable, which also have sections with straight or concave contours in cross section, and thus further increase the progressivity of the plastic resistance.

FIG. 7 shows a further preferred embodiment of a back 30 a cutting line 1, wherein the height h of the projections is lower than in the embodiment of Fig. 3 , In particular, this embodiment shows a cross-sectionally rounded back with a radius r, which corresponds to half the thickness D of the cutting line 1.

The dashed line 33 in the right part of the FIG. 7 illustrates that the recesses 36 and the projections 32 are only in the upper part of the rounding of the back 30.

In this embodiment, two test patterns were made which showed sufficient self-alignment when used in a punching machine. The cutting lines had the following dimensions: Pattern I Pattern II D 0.71 mm 0.71 mm r 0.35 mm 0, 35 mm t 45 μm 75 μm b 345 μm 485 μm l 145 μm 5 μm

In FIG. 8 is a microscopic sectional view of the pattern I along the line CC FIG. 7 shown. In FIG. 9 is a microscopic sectional view of the pattern II along the line CC FIG. 7 shown. At the microscopic Riefen in Querriehtung Q is seen that the recesses 36 were ground with a-thin grinding wheel (thickness of the grinding wheel about 0.5 mm).

To improve the plastic deformability of the back 30, this is tempered after hardening of the Ausgengsmaterials 1 or even partially annealed.

Alternatively or in addition to the embodiments described above, automatic trimming can also take place with a cutting line whose back is edge-decarburized to a depth of 5 .mu.m-100 .mu.m. The edge-decarburized ferritic material of the back region is comparatively soft and can be easily plastically deformed, which also leads to an automatic dressing in the first use of such cutting lines. About the depth of the edge decarburization, the maximum possible dressing can be adjusted and thus adapt the cutting lines to different applications.

Of course, it is also possible to additionally decarburize the above-described cutting line with projections and recesses in the back in order to further increase the plastic deformability.

Such cutting lines can be used in punching machines, in particular in a flat bed punching machine or in a rotary punching machine. Due to the special design and dimensioning of the projections 32 of the back 30, a cutting line 1 is provided for punching tools, which is used for the first time in practice, and significantly reduces the cost of time-consuming and costly manual trimming.

The starting material 1 preferably consists of a tool steel and has a central cutting edge with simple plane facets (CF). Other cutting and facet shapes are also possible. Usual cutting angles are in the range from 30 ° and 60 °. The facets are scraped or ground, the cutting tip is hardened in the usual way CF or HF.

Claims (12)

1. Cutting line (1) comprising:

   a. a steel band (10) with a cutting edge (20);

   b. a back (30) of the steel band (10) opposite to the cutting edge (20); wherein

   c. the back (30) comprises protrusions (32) that are sized such that they are plastically deformable during the first use of the cutting line (1); characterized in that

   d. the protrusions (32) comprise a height (h) of essentially 2% - 20% of the thickness (D) of the steel band (10), and that

   e. the protrusions (32) are generated by cavities (36) that are introduced in a cross direction (Q) of the steel band (10).
2. Cutting line according to claim 1, wherein the protrusions (32) essentially comprise a height (h) of 6% - 10% of the thickness (D) of the steel band (10).
3. Cutting line according to claim 1 or 2, wherein the protrusions (32) are generated by milling or grinding the cavities (36) in cross direction (Q) of the steel band (10) into the back (30).
4. Cutting line according to one of the claims 1 - 3, wherein the back (30) is decarbonized at the rim up to a depth of 5 µm - 100 µm.
5. Cutting line according to one of the claims 1 - 4, wherein the back (30) is rounded down in a cross-section through a head (34) of the protrusions (32) or wherein the back (30) is formed slanted on both sides or double-concave in a cross-section through a head (34) of the protrusions.
6. Cutting line according to claim 1 - 5, wherein the back (30) is semi-circular rounded down in a cross-section through a head (34) of the protrusions (32), wherein the radius of the rounding (r) essentially corresponds to half of the thickness (D) of the steel band (10).
7. Cutting line according to one of the claims 1 - 6, wherein the protrusions (32) comprise concave flanks (38) in a longitudinal cut through a head (34) of the protrusions (32).
8. Cutting line according to one of the claims 1 - 7, wherein the cavities (36) in the longitudinal cut are formed segment-like, in particular semicircle, with a radius (R₁, R₂).
9. Cutting line according to claim 8, wherein the radius (R₂) of the cavities corresponds to 10% - 250%, preferably 20% - 150% and more preferably essentially 100% of the thickness (D) of the steel band (10).
10. Cutting line according to one of the claims 1 - 9, wherein the protrusions (32) comprise a pointed head (34) in a longitudinal cut through a head (34) of the protrusions (32) or comprise a butted head (34) with a length (1) of 1% - 50%, preferably 5% - 30%, more preferably 20% of the thickness (D) of the steel band (10).
11. Cutting line according to one of the claims 1 - 10, wherein the back (30) is tempered and/or soft-annealed and/or decarbonized at the rim, in order to increase its plastic deformability.
12. Usage of a cutting line (1) according to one of the claims 1 - 11 in a stamping machine, in particular in a flatbed stamping machine or in a rotation stamping machine.

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