PARTIAL BENDING (AIR BENDING)

"Partial bending" means bending by pressing the tool and sheet material at three points as shown in the figure below.
Because the bending angle can be set freely from acute angle to obtuse angle, it is often used widely, such as the production of many kinds in small quantities and trial production, etc.
However, due to differences in materials and machine specifications, it is difficult to ensure stable angle accuracy,so advanced technology is required.

■ VARIATION OF BENDING ANGLE

±0.75°[ ±45′]

■ MERIT

Bending angle can be set freely.

■ DEMERIT

This is varying widely in angle compared to the bottoming.

BOTTOMING (AIR BENDING)

High bending accuracy can be obtained with relatively small pressing force. However, since the amount of spring-back* is large,
it is common to bend extra. That is why there are variations such as the V-angle of 86°, 88°, 90°, etc. of the standard die with 90° bending.
As a general rule, use the same punch tip V angle and die V groove angle.
*"Spring-back" is a phenomenon in which the bent part of the material bounces slightly after bending.

■ VARIATION OF BENDING ANGLE

±0.5°[ ±30′]

■ MERIT

Accuracy can be obtained with less power than others.

■ DEMERIT

The amount of spring-back is large.

COINING

Coining means "coin" and comes from "creating coins". This is a bending method that provides extremely accurate bending accuracy and a small bending radius.
However, since the tip of the punch is encroached and bent into the material, the required tonnage is 5 to 8 times that of bottoming.
Care must be taken as the limit plate thickness depends on the difference in machine ability.
The pressure resistance of bending machine parts is usually guaranteed in tonnage per unit length.
If a SPCC 1.6mm is bent, it will be ≒75 tons per meter, and ≒115 tons with a thickness of 2mm, depending on the withstand pressure of each part, as a measure of the limit thickness is 2mm.
This is a bending method that has become rarely used due to the evolution of machines.

■ VARIATION OF BENDING ANGLE

±0.25°[ ±15′]

■ MERIT

The amount of spring-back is extremely small.
High accuracy can be obtained.

■ DEMERIT

Requires 5 to 8 times the pressurizing force of bottoming.

The required tonnage, V-width selection, ir (inner radius), and other basic settings will be introduced in Vol.3 and 4.