The invention relates to a method for manufacturing workpieces with small corner radii in relation to the thickness to be cut, and greatly reduced edge reduction in a fine blanking tool of a fine blanking machine, wherein the workpiece is clamped between two tool parts respectively consisting of an upper and a lower cutting die, as well as of an upper and a lower cutting punch, and the cutting is realized by the combined efforts of upper and lower cutting punches.
The invention further relates to a tool for fine blanking of workpieces with small corner radii in relation to the thickness to be cut, and greatly reduced edge reduction, from a cutting strip, a sheet, a coil material or the like, with two clamping the latter tool halves respectively consisting of at least one cutting die and one cutting punch.
The limitations of fine blanking of portions with small corner radii in relation to the thickness of the sheet to be cut and to the quality of the material are sufficiently known. Based on experience, a fine blanking severity is defined which distinguishes the severity degrees Si (easy), S2 (medium) and S3 (difficult) (see “Umformen and Feinschneiden”, in Handbuch fur Verfahren, Werkstoffe, Teilegestaltung, pages 154 to 165, Verlag Hallwag AG, 1997, Switzerland). Thus, the severity degree is essentially defined by the cutting path geometry and the thickness of the metal sheet. For this, the cutting path geometry is divided into simple geometric basic areas such as corner radii, hole diameters, groove and fin widths. From the ratio between a geometric dimension and the thickness of the metal sheet, the severity degree of fine blanking is defined, which grows with growing metal sheet thickness. That means that fine blanking of large-area thin parts is easier than fine blanking of narrow fins or rings with greater sheet thickness. Also, obtuse-angled corners with big radii are to be cut better than sharp-cornered structure with small radii.
A method is known from DE 39 31 320 C1 for manufacturing burr-free workpieces by punch counter cutting, for example, in an fine blanking tool, wherein a cutting strip from which the workpiece is to be cut is clamped between two tool parts, respectively consisting of an upper and a lower cutting die as well as of an upper and a lower cutting punch, and the cutting is realized by the combined efforts of upper and lower cutting punches, wherein cutting of the workpiece is started along a cutting line and then the workpiece is cut out in the opposite direction.
This state of the art exactly shows the intended reduction on both sides as a result of counter cutting.
Typical characteristics of fine blanking parts are edge reduction and burr. Especially at corner portions, edge reduction occurs, which grows with corner radii becoming smaller and with increasing sheet thickness. The reduction depth may be about 20% and the reduction width may be 30% of the sheet thickness or more (see DIN 3345, Feinschneiden; August 1980). Thus, this reduction depends on the thickness and quality of the material, so that controlling it is possible only in a limited way, and often results in limited functioning of parts, for example, because of lack of sharp-edged tips of interlocking parts or because of the changes in the functional length of parts.
At this state of the art, it is an object of the invention to improve a method and a tool for manufacturing workpieces in such a way that fine blanking can be also applied for parts with small corner radii and sharp-edged corners with greater sheet thickness, without limiting the function of the parts and at the same time providing economic advantages.
This object is achieved by a method of the kind mentioned above, in accordance with which.
In accordance with the invention, fine blanking becomes economically applicable also for portions of parts with small corner radii and sharp edge portions, for example, interlocking parts with greater thickness. The approach according to the invention is based on the principle of different cutting directions of the geometries of parts converging without corner radius.
Thus, the part to be cut at least consists of two cutting geometries, for example a circular geometry and a toothed geometry, wherein the process of fine blanking is executed in a one-stage arrangement. In a first partial step, the addendum circle structure of the interlocking part is cut out of the cutting strip in vertical working direction. It follows the cutting out of the blank spaces between the teeth in a working direction opposite to the first partial step.
The special advantage of the method according to this invention is that the converging tool geometries are not pressure loaded at the same time and not in the same direction. The pressure loads in the corner area of the workpieces thus can be significantly decreased, so that complex part geometries also of greater thickness can be fabricated by fine blanking with sharp edges, massively reduced rollover and precise functional length.
Because of the specifically selected cutting geometry 20 of the first partial step it is contrived that the rollover is filled up again during the second partial step.
The method and tool according to this invention only require a one-stage arrangement and further makes it possible to minimize the application of multi-step fabrication processes, whereby the fine blanking process becomes more efficient also in case of parts with complex structure and greater thickness.
Further advantages and details accrue from the following description with reference to the attached figures.
In the following, the invention will be explained in more detail with reference to an example of an embodiment.
With the method according to the invention, a workpiece 1 shall be fabricated, in this case, an interlocking part of greater thickness d, for example, 6.5 mm, by fine blanking the interlocking part out of a cutting strip 2. The principle layout of the fine blanking tool 3 corresponds to the known state of the art. Thus, a detailed description can be omitted. For this reason, only the special features of the tool will be emphasized in the following description.
As shown in
In a subsequent partial step B (see
The corner portions 24 of the rollover 16 from partial step A at intersections of the first cutting line and second cutting lines (i.e., at each tooth 19 distal end) is filled up again due to the cuts along the second cutting lines by punch 18 being from an opposite vertical cutting direction than the cut along the first cutting line by punch 10, (i.e., compare
The cutting punch of the fine blanking tool 3 is designed as a multi-part main punch 10 for cutting out a first cutting geometry, for example, that of a blank 13. The diameter of the blank 13 corresponds to the diameter of the addendum circle of the toothing 15 of the interlocking part 1 to be fabricated. The working direction of the main punch 10 extends vertically. The main punch 10 is allocated at least one punch 18 (punch for cutting out the blanks between the teeth) for the final cut of the semi-finished product to receive the interlocking part 1. The punch 18 works in the opposite direction to the main punch 10 and with respect to the first cutting geometry it is arranged in a way that it can be applied to it without applying the pressure load in the same direction.
In the case of fabrication an interlocking part 1, the cutting geometry of the main punch 10 is an addendum circle. But it also can be a geometry consisting of a complex contour of steady or unsteady curves, if other parts with other complex shapes are to be fine blanked.
The punches 18 for the final cut advantageously have geometries of a contour with steady or unsteady curves.
Thereby, the cutting geometries of main punch 10 and punch 18 can be varied, so that complex parts can be composed of simple geometries, respectively.
The fine blanking tool 3 has a single-step structure. It facilitates contradirectional and directly adjoining cutting operations described above as partial steps A and B.
Thus, the converging tool geometries of main punch 10 and punch for cutting out the blanks between the teeth 18 are not subjected to pressure load at the same time and also not in the same direction, so that the otherwise necessary corner radius to reduce the partial compression tensions in the tip portions of the interlocking part can be dropped.
Thus, it is possible to produce complex workpieces or parts of greater thickness with sharp edges and significantly reduced rollover in a economically efficient way also by fine blanking.
Number | Date | Country | Kind |
---|---|---|---|
06090018 | Feb 2006 | EP | regional |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/EP2007/001106 | 2/2/2007 | WO | 00 | 8/4/2008 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2007/090658 | 8/16/2007 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
795794 | Gaines | Jul 1905 | A |
887630 | Hart | May 1908 | A |
1428174 | Luther | Sep 1922 | A |
3564959 | Harada | Feb 1971 | A |
3568554 | Wiechec | Mar 1971 | A |
3570343 | Wolnosky et al. | Mar 1971 | A |
3650167 | Hoffmeyer et al. | Mar 1972 | A |
3688549 | Ohnishi et al. | Sep 1972 | A |
3878746 | Carmeli | Apr 1975 | A |
3919909 | Scott | Nov 1975 | A |
4477537 | Blase et al. | Oct 1984 | A |
4509353 | Ike et al. | Apr 1985 | A |
5247862 | Haack | Sep 1993 | A |
5413018 | Wada et al. | May 1995 | A |
5732587 | Maeda et al. | Mar 1998 | A |
6125527 | Sunaga et al. | Oct 2000 | A |
6622908 | Fukumoto et al. | Sep 2003 | B2 |
7464575 | Miyahara | Dec 2008 | B2 |
20010039865 | Bennett | Nov 2001 | A1 |
20030066329 | Aizaki | Apr 2003 | A1 |
Number | Date | Country |
---|---|---|
665 367 | May 1988 | CH |
3506035 | Aug 1986 | DE |
864384 | Sep 1998 | EP |
1 815 922 | Aug 2007 | EP |
01237040 | Sep 1989 | JP |
04028427 | Jan 1992 | JP |
06015381 | Jan 1994 | JP |
2006224143 | Aug 2006 | JP |
WO 02081116 | Oct 2002 | WO |
WO 02081116 | Oct 2002 | WO |
WO-2007090658 | Aug 2007 | WO |
Entry |
---|
Machine Translation of CH 665367. |
English Translation of JP64-237040 (which is JP01237040). |
2007 “Umformen and Feinschneiden” R.-A. Schmidt et al. Hanser pp. 144-173. |
Number | Date | Country | |
---|---|---|---|
20090010723 A1 | Jan 2009 | US |