JPS59193725A - Formation of bulging part in panel - Google Patents

Abstract

PURPOSE:To decrease considerably the amt. of camber in the unworked part and to eliminate shape defects by bulging the working part of a blank by means of a punch then bulging the initially bulged part by means of other punch in the direction opposite from the bulging direction. CONSTITUTION:A blank 5 which is a panel is grasped by upper and lower blank holders 1, 2 and an upper punch 3 is first actuated to bulge downward a working part 6, then a lower punch 4 is actuated to apply a reverse pressure on the part 6 and the punch 4 is further actuated to bulge upward the part 6. The angle alpha around the part 6 during the reverse bulging is about 10-40 deg., more preferably about 17-26 deg., and the amt. of bulging is about 80% of the amt. at the first bulging, so that the generation of a camber is minimized. The amt. of the camber in the unworked part by the reverse bulging is thus considerably decreased as compared to the amt. of the camber in the unworked part by the initial bulging.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming an overhang in a panel (steel plate).

Stretch molding of panels can increase the section modulus without changing the panel thickness, so it is often used for parts that require both weight reduction and high buckling strength. Specific examples include side panels of freight cars and exterior panels of various machines.

However, when performing stretch molding, if the amount of molding exceeds a certain level, shape defects such as warpage will occur in the unprocessed portion, so there are restrictions on the amount of molding and the shape of the overhang. When molding exceeds this restriction, it is necessary to perform heat molding or to perform correction after molding, which has been a major obstacle to the application of stretch molding.

This defective shape is thought to be due to the synergistic effect of the presence of residual stress in the cam that pulls the unstressed loe parts around the machined part a and the springback due to the springback force p of the machined part α (Fig. 1). , see Fig. 2 1゜The present invention was developed in view of the above circumstances, and its purpose is to perform reverse stretch molding on the processed portion of the first stretch molded part to form an unprocessed part. The purpose is to eliminate shape defects by reducing the width of the part.

Hereinafter, the present invention will be explained with reference to FIG. 3 and subsequent figures.

In the drawings, 1 is an upper blank holder, 2 is a one-side blank holder, 3 is an upper punch, and 4 is a lower punch.

Place blank 5 (panel) on top, and hold blank holder 1 on the bottom.
, 2 keeps it hidden from above and below.

Next, the upper punch 3 is operated to stretch-form the processed portion 6 at the bottom (see FIG. 3A and FIG. 4 74).

Next, actuate the lower punch 4 to apply reverse pressure L to the processing section 6.
(See Figure 3 mouth, Figure 4 74), and lower punch 7I.
74 of FIG. 3 and FIG. 4).

Angle α of the periphery of the processed part 6 during actual reverse stretch molding
is from 17° to 26°, and its maximum range is α=10°
~40°.

By this reverse stretch forming, as shown in FIG. 6, the warpage of the unprocessed portion 7 of the blank 5 is reduced to 1/10 of the amount of warpage of the unprocessed portion 7 in the initial stretch forming shown in FIG. can be reduced. In the case of a reverse expansion warehouse, the occurrence of warpage is minimal at about 80% of the initial expansion amount, but this varies slightly depending on the blank thickness, material, and degree of processing.

Crane booms are an example of the application of stretch forming, which requires both weight reduction and buckling strength. A processed part 6 is formed continuously on a long material 8, which is a panel used for this crane poom, to increase the buckling strength without increasing the thickness of the material. The warpage of the unprocessed part 7 due to the extrusion molding is reduced compared to the warpage of the unprocessed part 7 due to the first extrusion molding shown in FIG. 7, and the effect is large.

As described in detail above, the blank 5 has a processed portion 6.
Stretching of the panel is characterized in that the stretched acid is formed using a punch (and after that, the processed portion 6 that has been stretch-formed for the first time is stretch-formed in the opposite direction to the stretching direction using another punch). This is a protrusion molding method.

Therefore, by performing reverse stretch-forming on the first-time stretch-formed processed portion 6, it is possible to reduce the amount of warpage of the unprocessed portion to the full width and eliminate shape defects.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the force exerted by the panel on the unprocessed area around it, Figure 2 is an explanatory diagram of springback in the processed area of the panel, and Figure 3 is the stretch forming of the processed area using the Sekanmei method. Explanatory diagram of the process Figure 4 is an illustration of the stretch forming of the processed part in the panel, Figure 5 is an illustration of the amount of warpage during the initial stretch forming of the panel, and Figure 6 is an illustration of the amount of warpage during the reverse stretch forming of the panel. FIG. 7 is an explanatory diagram of the warpage during the first stretch forming of a long material, and FIG. 8 is an explanatory diagram of the warpage during reverse stretch forming of a long material. 5 is a blank, 6 is a processed part. Applicant: Komatsu Ltd. Agent: Patent Attorney: Tadashi Yonehara, Patent Attorney: Tadashi Furukawa 1. Koshidai 2. Figure 3. 4. Figure 5. Figure 6.

Claims (1)

[Claims] After forming a bulge bottom of a zero-force working part 6 on a blank 5 with a punch, the first bulge-formed processed part 6 is bulge-formed in a direction opposite to the bulging direction using another punch. A method for forming an overhang in a panel characterized by: