JPH03114620A - Die for press - Google Patents

Abstract

PURPOSE:To make slipping of work better when forming and to improve formability by forming at least one of the 1st formed surface of products, the 1st hold-down surface, the 2nd formed surface of products and the 2nd hold-down surface like roughened surface with cutting marks due to cutting. CONSTITUTION:The end part of the work W is inserted and held with the 1st hold-down surface 1b of an upper die 1 and the 2nd hold-down surface 2b of a lower die 2. The upper die 1 is pushed down to the position of bottom dead center against the lifting force of a die cushion with which the 2nd hold- down surface 2b is energized upward and the work W is inserted and held between the product forming surface 1a of the upper die 1 and the product forming surface 2a of the lower die 2 and is press formed. Because the contact with the work W is made into point contact or tine contact by forming the surface of the product forming surfaces 1a, 2a and the hold-down surfaces 1b, 2b into rugged roughened-surface-like due to cutting marks, slipping resistance is made in smaller and the work W is extended over all width. Therefore, slipping-in is improved and press formability can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a press die for press-forming a workpiece made of steel plate such as an outer panel or an inner panel of an automobile.

(Prior art) To perform press forming, as shown in FIG. 1 first pressing surface 1b
are in contact with each other to clamp the workpiece W, further lower the upper die 1, lower the first presser surface 1b against the second presser surface 2b, and press the lower die 2 to form the second product. Fitting the surface 2a to the first product forming surface 1a of the upper mold l via the workpiece W,
Predetermined molding is being performed.

These first and second product forming surfaces 1a and 2a, the first and second
In order to form the holding surfaces 1b and 2b, they are formed by cutting using a ball end mill or optical taper cutter using a copy milling machine or NC milling machine, and the cutting marks called cusps produced on the forming surfaces by the cutting are then discharged. processing,
The product is removed by grinding using an electric or chemical method such as electrolytic processing or ultrasonic polishing, or a power tool, etc., to prevent scratches caused by the first and second product molding surfaces 1a and 2a, and
The clearance between the product molding surfaces la and 2a is adjusted. Grinded first and second product forming surfaces 1a
, 2a and the first and second holding surfaces 1b, 2b are plated with hard chrome to improve wear resistance if necessary (see Japanese Utility Model Publication No. 53150837).

(Problems to be Solved by the Invention) According to conventional press dies, scratches on the workpiece can be prevented by grinding and smoothing the product forming surface and presser surface of the press die. Not only does this require a large number of man-hours, resulting in a long production period and a rise in production costs, but also
The part of the workpiece that comes into contact with the convex part of the product forming surface of the lower die at about 5 points above the bottom dead center has surface contact with the product forming surface and the presser surface, so there is a large amount of sliding resistance, and the workpiece is locally stretched. is,
This can cause breakage of the workpiece, and countermeasures to this problem include re-grinding the press mold, slightly adjusting the clearance between the upper and lower molds, and changing the shape of the workpiece.

It is therefore an object of the present invention to eliminate or reduce the grinding process,
To provide a press mold which shortens the manufacturing period and reduces manufacturing costs, and further allows elongation of the work over a wide range and improves pressability by changing the contact area between the work and the press mold. It is.

(Means for Solving the Problems) A press mold of the present invention that achieves the above object includes an upper mold having a first product molding surface and a first pressing surface formed on the outer periphery of the first product molding surface. , a second presser surface that cooperates with the first presser surface to clamp the peripheral edge of the workpiece; and a second presser surface that is provided separately and independently from the second presser surface, and that cooperates with the first product forming surface to press-form the workpiece. and a lower die having a second product forming surface for applying
At least one of the pressing surface, the second product forming surface, and the second pressing surface is formed into a rough surface by cutting marks caused by cutting, and the top of the convex portion of the unevenness forming the rough surface is further formed. This can be done effectively by grinding leaving the bottom of the recess intact.

(Function) By making the product molding surface and holding surface roughened by the cutting marks from the cutting process, the conventional grinding process can be abolished or reduced, significantly shortening the manufacturing period and reducing the manufacturing cost. The contact between the workpiece and the press mold changes from surface contact to point or line contact, reducing frictional resistance, improving elongation or sliding of the workpiece during press forming, and improving drawing workability.

(Example) An embodiment of the press mold of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing the main parts of the press mold of this embodiment. The upper mold 1 has a first product molding surface 1a that curves upwardly to be concave, and a first pressing surface 1b formed continuously around the outer periphery of the first product molding surface 1a. On the other hand, lower mold 2
is a second product molding surface 1a formed on the upper mold 1, which is curved upwardly so as to fit through the workpiece W.
and a second product forming surface 2a provided separately and independently from the second product forming surface 2a on the outer periphery of the second product forming surface 2a.
It is composed of a pressing surface 2b.

The second holding surface 2b is a duct (not shown) operated by hydraulic pressure or pneumatic pressure via the cushion pin 3.
, and is held at a position moved upward by a predetermined amount as indicated by a two-dot chain line 2b'.

The first product forming surface la and first holding surface 1b formed on the upper die 1 and the second product forming surface 2a and second holding surface 2b of the lower die 2 are formed using a copy milling machine, an NC milling machine, etc. For example, a big feed is formed by cutting three cranes using a ball end cutter with a cutting edge radius of 25 mm,
As shown in the enlarged perspective view of FIG. 2(a), the surface is formed into a rough surface with unevenness due to cutting marks 4 called cusps. Furthermore, these surfaces are coated with hard chrome plating 5 having a thickness of 20 to 30 microns, for example, to improve wear resistance, if necessary.

In order to perform press forming using the press die configured in this way, the upper die 1 is raised to the top dead center position, and the upper die 1, which is held in the raised position as shown by the two-dot chain line in FIG. When the workpiece W is placed on the holding surface 2b' of the upper die 1 and the lower die 2 is lowered, the upper die 1 is lowered to the position shown in FIG. The end portion of the workpiece W is held in cooperation with the second holding surface 2b.

Furthermore, the upper die 1 is pushed down to the bottom dead center position against the push-up blade of a dictation (not shown) that urges the second holding surface 2b upward, and the first product forming surface 1a of the upper die 1 and the lower The work W is press-molded while being held between the mold 2 and the second product molding surface 2a.

At this time, the first and second product forming surfaces 1a, 2a.

The first and second holding surfaces 1b and 2b are formed into a rough surface with unevenness due to the cutting marks 4 as described above, so that the contact with the workpiece W becomes a line contact or a point contact. Workpiece W and product forming surface 1a.

2a and the presser surfaces 1b, 2b are reduced in sliding resistance,
With a conventional lower mold whose surface is ground to a smooth surface, no elongation of the workpiece is observed over substantially the entire width a of the product molding surface 2a, as shown in Fig. 4 Ca), whereas with the present invention As shown in Fig. 4 (bl), the workpiece W does not elongate only in a narrow area a of the product forming surface 2a, and therefore the workpiece W stretches over almost the entire width, resulting in good sliding. This improves drawability, that is, press formability.

Similarly, elongation of the workpiece W between the holding surfaces 1b and 2b is allowed, which further improves sliding and improves press forming.

Further, in the above embodiment, the rough surface was formed by cutting marks, but as shown in FIG.
By grinding the top part 4a of the cutting mark 4 on the surface cut with a pitch feed 3N using a pole end cutter, leaving j2 (5 to 10μ) from the bottom of the cutting mark, and processing the top surface flat, the workpiece W and It is possible to improve the contact between the workpiece W and the top portion 4a, and prevent scratches from occurring due to contact between the workpiece W and the top portion 4a. Further, if necessary, hard chrome plating 5 with a thickness of 20 to 30 microns can be applied to these surfaces as described above in order to improve wear resistance.

In the above description, the product molding surfaces 1a of the upper mold and the lower mold are used.

Although the rough surfaces 2a, 1b, and 2b are roughened by cutting, the roughening may be performed only at appropriate locations, and the direction of cutting may be similarly selected, taking into consideration the product shape, material, etc.

(Effects) According to the present invention, the product forming surface and holding surface of the press mold are formed into a rough surface by cutting or partial grinding, thereby eliminating the conventional grinding process that required a large amount of man-hours. In addition, by changing the contact surface with the workpiece during press forming from surface contact to line contact or point contact, the workpiece during press forming can be significantly reduced. Good sliding will result in improved press formability, which can be expected to reduce breakage in press-formed products and correction grinding of press molds.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of the main part showing one embodiment of the press mold of the present invention, Fig. 2 is an enlarged perspective view of the main part of the press mold, and Fig. 3 is an enlarged perspective view of the main part of the press mold of another embodiment. FIG. 4 is a comparative explanatory diagram of this embodiment and a conventional example, and FIG. 5 is a sectional view of a main part of a conventional press mold. DESCRIPTION OF SYMBOLS 1... Upper mold, 1a... Product molding surface, 1b... Pressing surface, 2... Lower mold, 2a... Product molding surface, 2b...
Holding surface, 4...cutting marks, 4a...top, W...work.

Claims (3)

[Claims] (1) An upper mold having a first product forming surface and a first holding surface formed on the outer periphery of the first product forming surface; A lower mold having a second press surface and a second product forming surface that is provided separately and independently from the second press surface and that performs press molding on a workpiece in cooperation with the first product forming surface. In the press mold, at least one of the first product forming surface, the first pressing surface, the second product forming surface, and the second pressing surface is formed into a rough surface shape due to cutting marks caused by cutting. A press mold featuring (2) The press mold according to claim 1, wherein the tops of the convex portions of the irregularities forming the rough surface are ground. (3) The press mold according to claim 2, wherein the tops of the convex portions of the irregularities forming the rough surface are ground leaving 5 to 10 μm from the bottoms of the concave portions.