JPH07124860A - Polishing method for press metallic mold - Google Patents

Abstract

PURPOSE:To polish the curve surface corners of press metallic molds in the direction that a props product flows in, not depending on s hand work. CONSTITUTION:An upper mold 32 and a lower mold 35 which have been roughly machined into each shape corresponding to a press product, are installed on a press machine, and a polishing member 40 in a thin sheet shape provided with abrasive grains 42 on its surface, is interposed between the upper mold 32 and the lower mold 35 which have been installed on the press machine. Let the abrasive grains 42 of the polishing member 40 be slid and brought into contact with curved surface corners 33a and 36a by repeatedly holding the polishing member 40 with pressure by the upper mold 32 and the lower mold 35, so that the curves surface corners 33a and 36a are thereby automatically polished.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for smoothly finishing the surface of a machined press die by polishing, and particularly for polishing a press die capable of smoothly finishing a curved corner without manual work. Regarding the method.

[0002]

2. Description of the Related Art A press die is used for drawing a vehicle body. The press die used for drawing a steel sheet is obtained by cutting cast iron cast into a predetermined size by machining under NC control. Curved surface NC processing is usually employed in the production of a press die used for drawing. In the curved surface NC machining, the position of the ball end mill cutter is controlled by NC data created based on the design data of the vehicle body, and curved surface cutting is performed.

FIG. 13 shows the surface of the press die 1 which has been subjected to the curved surface NC processing. If the radius of the cutting tool of the ball end mill cutter used for machining the curved surface NC is R and the pick feed (feed pitch) P, a hump called a cusp is formed on the surface of the press die 1 at the boundary of the cutting tool locus. The height H of the cusp 2 is usually 50 to 100 μ.
The cusp 2 in the corner portion of the press die causes cracking of the pressed product, and therefore needs to be removed by polishing. By setting the pick feed P of the cutting tool to a small value, the height H of the cusp 2 can be suppressed to a small value, but the cusp 2 cannot be completely removed. Therefore, the cusp 2 in the press die cannot be removed. Mandatory.

In the vehicle body, there are a portion that can be seen from the outside and a portion that cannot be seen from the outside, and the portion that cannot be seen from the outside does not have to be excessively extended or cracked in the steel sheet which is a pressed product at the time of molding. No need to grind. For example, the hood inner panel of a vehicle body is normally invisible from the outside, and only the corner portion where the steel plate may be excessively extended or cracked due to the cusp may be ground.

FIG. 14 shows a press die for drawing a part of a vehicle body. In the press die 11 of FIG. 13, the part that needs to be ground to remove the cusp that causes elongation and cracking is the curved corner 12 of the step in the free curved surface, which is The curved corners 13 of the uneven bead portion and the die portion that restrain the movement and control the inflow amount of the steel sheet.

Free-form surface portion 1 in the press die of FIG.
No. 4 requires polishing especially from the viewpoint of design, and the sliding surface 16 that guides the cushion ring 15 of the lower mold needs polishing in order to maintain smooth movement of the press die and machining accuracy. The free-form surface portion 14 of the press die 11 can be processed, for example, by the processing device disclosed in Japanese Utility Model Laid-Open No. 56-20210. Press mold 11
The sliding surface 16 can be processed by the polishing device disclosed in Japanese Utility Model Laid-Open No. 4-26203.

Curved corners 12, 13 of the press die 11
Cannot be polished with the above-described polishing apparatus,
Conventionally, polishing is performed by an operator by hand finishing using general tools (grinder, file, grindstone, etc.).

[0008]

However, the hand-polishing of the curved corners of the press die causes the following problems. In the drawing of a steel sheet that is a pressed product, it is desired that the steel sheet smoothly flow into the press die during drawing of the steel sheet. However, the polishing of the curved surface corner 13 of FIG. If there is a shape such as the step portion 17, the inflow of the pressed product is in the direction of arrow B, which is different from the polishing direction. Therefore, the pressed product is the press die 11
The sliding resistance at the time of flowing into the inside becomes large, and smooth inflow of the pressed product into the press die 11 cannot be expected. As shown in FIG. 16, for example, when the curved surface corner 12 of the press die 11 is polished with a file 18, the shape of the curved surface corner 12 becomes uneven with respect to the regular curved surface shape due to excessive polishing S or the like. The molding accuracy of the pressed product deteriorates. In the polishing work of the press die, there is a problem that the working environment is bad because dust is generated by the polishing and a work for a long time is required.

It is an object of the present invention to provide a method for polishing a press die which allows the curved corners of the press die to be abraded in the inflow direction of the press article without manual work.

[0010]

To achieve this object, a method for polishing a press die according to the present invention comprises an upper die and a lower die which are machined into a shape corresponding to a press product. By installing a thin plate-shaped polishing member having abrasive grains on the surface between the upper mold and the lower mold mounted on the press machine, and repeatedly pressing the polishing member with the upper mold and the lower mold. It consists of polishing the upper and lower mold curved corners.

[0011]

In the method for polishing a press die having the above-described structure, when an upper die and a lower die having shapes corresponding to a press product are manufactured by machining such as NC control, the upper die and the lower die are Is attached to the press machine. Next, between the upper mold and the lower mold attached to the press machine, a thin plate-shaped polishing member having abrasive grains on the surface is arranged, and the polishing member is repeatedly pressed by the upper mold and the lower mold. The curved corners of the upper mold and the lower mold are polished.

When the polishing member is pressed by the upper die and the lower die, the polishing member flows into the press die, so that the polishing member comes into sliding contact with the press die when the polishing member flows in. . Since abrasive grains are present on the surface of the polishing member, the press die is polished by the abrasive grains. Especially,
Since the curved surface corner of the press die has a high sliding resistance with the polishing member, the curved surface corner is polished more than other portions, and manual polishing is unnecessary. In addition, since the curved corners are polished in the same direction as the pressed product due to the inflow of the polishing material, the sliding resistance of the curved corners will be small during the actual molding of the pressed product, and the pressed product will move smoothly into the press die. It becomes possible to make it inflow.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a method for polishing a press die according to the present invention will be described below with reference to the drawings. 1 to 12 show an embodiment of the present invention, and particularly show a case of being applied to a press die of a cushion squeezer used for squeezing a hood inner panel of an automobile.

FIG. 12 shows a final shape of a hood inner panel of an automobile. The hood inner panel 20 is obtained by drawing a pressed product (steel plate) 21 having a shape indicated by a two-dot chain line. FIG. 5 shows a press die 31 for drawing the press product 21 and a press machine 25 to which the press die 31 is attached. Press machine 25
An upper die 32 of the press die 31 is attached to the ram 26 side of the press die 31 and a lower die 3 of the press die 31 is attached to the bed 27 side.
5 is attached.

The press die 31 attached to the press machine 25 is an unfinished press die which is generally machined (curved surface NC processing) into a shape corresponding to the hood inner panel 20 which is a press product. . Press mold 3
1 is a cushion diaphragm type mold, and as shown in FIG. 6, the lower mold 35 is a cushion ring 36 and a punch 37.
And have. The cushion ring 36 is a punch 37.
It is possible to move up and down independently.

2 to 4 show a thin plate-shaped polishing member 40 used for polishing the press die 31. The thin plate-shaped polishing member 40 is composed of a metal plate 41 and abrasive grains 42. The metal plate 41 is made of the same steel plate as the hood inner panel 21 in this embodiment, but may be made of another material. Abrasive grains 42 for polishing the surface of the press die 31 are bonded to both surfaces of the metal plate 41. Since the abrasive grains 42 are used for the work of scraping off a part of the press die 31, hardness and toughness are required. Therefore, the hardness of the abrasive grains 42 is significantly higher than the hardness of the press die 31. The thickness t ₂ of the abrasive grains 42 is
The thickness t ₁ of the metal plate 41 is preferably 5 to 10%.

In the present embodiment, CBN abrasive grains are used as the abrasive grains 42, but even if alumina oxide type abrasive grains or the like are used, it is particularly limited as long as the press die 31 can be sufficiently polished. Not done. The abrasive grains 42 are firmly bonded to the surface of the metal plate 41 with a binder, for example. Also,
In this embodiment, the abrasive grains 42 are bonded to both surfaces of the metal plate 41. However, even if the abrasive grains 42 are bonded to only one surface of the metal plate 41, polishing of either the upper die 32 or the lower die 35 is performed. Will be possible. Although FIG. 3 shows a state in which abrasive grains are bonded to the entire surface of the metal plate 41, as shown in FIG.
The abrasive grains 42 may be bonded only to the outer peripheral portion of the metal plate 41 depending on the shape of the above.

Next, the procedure and operation of the method for polishing a press die according to the present invention will be described. The caps 39 are formed on the surfaces of the upper die 32 and the lower die 35 of the press die 31 that has been subjected to the curved surface NC processing by a locus of a cutting tool such as a ball end mill cutter. Upper mold 3 with caps 39
2 is attached to the ram 26 side of the press machine 25. Similarly, the lower mold 35 having the caps 40 is attached to the bed 27 side of the press machine 25.

When the upper die 32 and the lower die 35 of the press die 31 are attached to the press machine 25, the upper die 32 and the lower die 3 are attached.
A thin plate-like polishing member 40 is carried in between the polishing member 40 and the sheet 5. That is, the polishing member 40 is set on the upper surface of the lower mold 35. When the setting of the polishing member 40 is completed, the press machine 2
5 is started, and the upper mold 32 starts descending. When the upper die 32 is lowered by a predetermined amount, the outer periphery of the polishing member 40 is the blank holder 33 and the lower die 35 of the upper die 32 as shown in FIG.
It is pressed by the cushion ring 36 and.

The blank holder 33 of the upper mold 32 and the lower mold 35
The cushion ring 36 suppresses the generation of wrinkles on the outer peripheral portion of the pressed product 21 which is a steel plate, and the pressed product 2
1 has a function of appropriately flowing into the center of the press die 31. When the polishing member 40 is pressed by the blank holder 33 and the cushion ring 36, the abrasive grains 42 bonded to the surface of the metal plate 41, the curved corner 33 a of the blank holder 33 and the curved corner 36 a of the cushion ring 36. Will be in sliding contact with. Therefore, the caps 39 of the curved corners 36 a of the blank holder 33 and the caps 39 of the curved corners 36 a of the cushion ring 36 are ground by the abrasive grains 42.

In the state in which the polishing member 40 is pressed by the blank holder 33 and the cushion ring 36, FIG.
As shown in FIG. 3, the upper die 32 and the cushion ring 36 of the lower die 35 are further lowered, and the central portion of the polishing member 40 is located at the lower die 3
It abuts the punch 37 of No. 5. Even after the polishing member 40 contacts the punch 37 of the lower mold 35, the upper mold 32 and the lower mold 35 are
The cushion ring 36 descends, the polishing member 40 is pressed by the punch 37 and the upper die 32, and drawn into a predetermined shape.

FIGS. 7 and 8 show a state in which the polishing member 40 at the portion A in FIG. 6 is pressed by the punch 37 of the lower mold 35 and the upper mold 32. As shown in FIGS. 7 and 8, when the polishing member 40 is pressed, the curved corners 37a of the punch 37 and the curved corners 32a of the upper die 32 are aligned with each other.
Sliding contact with the abrasive grains 42 of No. 0, the caps 40 in the curved surface corners 37a and 32a are polished by the abrasive grains 42.

When the upper mold 32 is completely lowered, FIG.
As shown in FIG. 5, the polishing member 40 is completely pressed by the upper die 32 and the lower die 35 to be formed into a predetermined shape. When the clamping force of the polishing member 40 by the upper mold 32 and the lower mold 35 is completed, the upper mold 32 rises as shown in FIG. Upper mold 3
When 2 rises to a predetermined position, the upper die 32 descends again, and the upper die 32 and the lower die 35 re-clamp the polishing member 40. Since the polishing member 40 is left behind on the lower mold 35 side when the upper mold 32 is raised, the upper mold 32 and the lower mold 3 are
When the polishing member 40 is pressed again by 5 and 5, the upper mold 32 is positively polished by the relative movement of the upper mold 32 and the polishing member 40. Further, when the upper die 32 rises, the metal plate 41 of the polishing member 40 is somewhat deformed by springback, so that when the polishing member 40 is re-clamped, the lower die 35 and the polishing member 40 are relatively moved, and the lower die 35 moves downward. It is also possible to polish the mold 35.

Polishing member 40 consisting of upper mold 32 and lower mold 35
11, the height of the caps 40 decreases as the number of continuous machining operations (the number of pressing operations) increases, and the curved corners 33 of the upper die 32 and the lower die 35, as shown in FIG.
The surface roughness of a, 36a, 32a, and 37a becomes fine.
In addition, as shown in FIG. 10, the polishing member 40 is always the lower mold 3
When lowering the upper mold 32 with the remaining part left in 5,
Although the polishing process of the upper die 32 is promoted, the relative movement amount between the polishing member 40 and the lower die 35 is small, and the amount of polishing of the lower die 35 is smaller than that of the upper die 32. Therefore, in this embodiment, the upper die 32 and the lower die 35 are exchanged during the polishing process.

Polishing member 40 consisting of upper mold 32 and lower mold 35
If the number of pressing pressures exceeds the specified value, the upper mold 32 and the lower mold 3
5 and 5 are once removed from the press machine 25. And
The upper die 32 is attached to the bed 27 side of the press machine 25, and the lower die 35 is attached to the ram 26 side of the press machine 25. The upper mold 3 attached to the press machine 25 in this way
When the polishing member 40 is pressed by 2 and the lower mold 35,
On the contrary, when the lower die 35 is raised, the polishing member 40 is left behind on the upper die 32 side. Therefore, the relative movement amount between the polishing member 40 and the lower die 35 can be increased, and the caps 39 can be sufficiently polished at the curved corners 36a and 37a of the lower die 35.

As described above, in this embodiment, the curved corners 33a, 36a, 32a, 37a of the upper mold 32 and the lower mold 35 are formed.
Has a high sliding resistance when the polishing member 40 flows in,
The curved surface corners 33a, 36a, 32a, 37a are polished more than other portions. Therefore, the press die 3
Excessive extension and cracking of the pressed product 21 due to the curved corners 33a, 36a, 32a, 37a of No. 1 are prevented. In addition, since the amount of polishing of each curved surface corner increases as the sliding resistance of the polishing member 40 increases, the optimum polishing can be performed according to the sliding resistance.

In this embodiment, the polishing member 40 is composed of the metal plate 41 and the abrasive grains 42, and the abrasive grains 42 are bonded to the surface of the metal plate 41. However, the member to which the abrasive grains 42 are bonded is metal. It is not limited to a plate, and may be a woven fabric or the like. For example,
Abrasive grains 4 on a cloth-like member woven with fibers with high tensile strength
The same effect can be obtained by using a polishing member having two bonded members.

[0028]

According to the present invention, the following effects can be obtained. (1) An upper die and a lower die that are machined into a shape corresponding to a pressed product are attached to a press machine, and an abrasive grain is provided on the surface between the upper die and the lower die attached to the press machine. Since a thin plate-shaped polishing member is arranged and the polishing member is repeatedly pressed by the upper mold and the lower mold, the curved corner of the press die can be automatically ground by sliding contact with the polishing member. . Therefore, it is possible to prevent excessive extension and cracking of the pressed product due to the curved surface corners of the press die without manually polishing the curved surface corners of the press die. (2) Conventionally, the polishing amount was adjusted by the operator's intuition for the portion having a large sliding resistance when flowing into the curved surface corner of the press die, but in the present invention, the polishing member is adjusted to the press die. Since the amount of polishing increases as the sliding resistance increases at the time of inflow, optimum polishing can be performed according to the sliding resistance of the pressed product. (3) Since the curved corners of the press die can be ground in the same direction as the pressed product by the flow of the polishing member, the sliding resistance of the curved corners will be small during the actual molding of the pressed product, It can smoothly flow into the press die. (4) Since polishing of the curved corner by manual work is eliminated, the worker can be protected from dust due to polishing, and the worker's long working hours can be eliminated.

[Brief description of drawings]

FIG. 1 is a partially enlarged sectional view showing an example of a polishing method for a press die according to an embodiment of the present invention.

FIG. 2 is a partially enlarged sectional view of the polishing member of FIG.

3 is a perspective view of the polishing member of FIG. 1. FIG.

FIG. 4 is a perspective view showing a modified example of the polishing member of FIG.

5 is a front view of a press machine to which the press die of FIG. 1 is attached.

6 is a cross-sectional view showing a polishing state of a press die by the polishing member of FIG.

FIG. 7 is a partially enlarged cross-sectional view showing a polishing state of the curved corner of FIG.

FIG. 8 is a partially enlarged cross-sectional view showing a progressing state of polishing in the curved corner of FIG.

9 is a partially enlarged cross-sectional view showing a finished state of polishing in the curved corner of FIG.

FIG. 10 is an enlarged cross-sectional view when the upper die is lifted after finishing the polishing process in the curved surface corner of FIG.

11 is a characteristic diagram showing the relationship between the number of times of polishing by elevating and lowering the press die in FIG. 5 and the surface roughness of the curved surface corners of the press die.

FIG. 12 is a perspective view showing an example of a pressed product.

FIG. 13 is an enlarged cross-sectional view of the surface of a press die manufactured by curved surface NC processing.

FIG. 14 is a front view showing an example of a press die used for drawing.

15 is a partially enlarged perspective view of the press die shown in FIG.

16 is a cross-sectional view showing a hand-finished state of curved surface corners in the press die of FIG.

[Explanation of symbols]

 20 Pressed Product 25 Press Machine 31 Press Die 32 Upper Die 35 Lower Die 40 Abrasive Member 42 Abrasive Grains

Claims (1)

[Claims] 1. An upper die and a lower die which are machined into a shape corresponding to a pressed product are attached to a press machine, and an abrasive grain is provided on the surface between the upper die and the lower die attached to the press machine. A polishing method for a press die, comprising: arranging a thin plate-shaped polishing member having: and polishing the curved corners of the upper die and the lower die by repeatedly pressing the polishing member with an upper die and a lower die.