**Definition:** zigzag bending is called Z bending.

Standard bending process range: height of Z bending > apothem of V groove + Thickness

The minimum processing size is limited by the model used while the maximum processing size is determined by the shape of the machine table.

Contents

- 1 Z Processing Procedures
- 2 Workpiece Placement Principles for Z-bending
- 3 Matters Need Attention for Z-bending
- 4 General Processing Methods of Z bending
- 5 Special Processing Method of Z bending
- 6 Other Z Bending Methods
- 7 N Bending Processing
- 8 Precautions for N-bending Processing
- 9 Special Processing Method of N Bending
- 10 Arc Processing
- 11 Precautions

## Z Processing Procedures

- Processing to form a L bending
- Bend the horizontal side of the L bending to form a Z bending (or bend the vertical side of the L bending to form a Z bending)

## Workpiece Placement Principles for Z-bending

A: Convenient, good stability.

B: Generally is similar to L-bending.

C: The workpiece is flat with the lower die during the 2^{nd} placement.

## Matters Need Attention for Z-bending

- The angle of L bending should be as accurate as possible, normally ranging from 89.5 °to 90 °.
- The back gauge should be set up to prevent deformation of the workpiece.

## General Processing Methods of Z bending

- The processing sequence should be considered as shown in the following picture, first bend 1 and then bend 2.

- First bend to form an L bending and then further processed to form a Z bending (if interfere with machine worktable, first bend 1 to form a large angle, then bend 2 and then press 1)
- Using two acute angles to form Z bending: first bend into a right-angle, then insert 2 and then insert 1

1) If there is a collision, first bend 1 to form a large angle, then bend 2 and then press 1.

2) if no collision, as per general Z bending processing method, first bend 1 and then bend 2.

## Special Processing Method of Z bending

A: lower die decenter processing

B: small V groove processing

C: bending to form a large angle, then pressing

D: choose grindable lower die

## Other Z Bending Methods

A: process with offset die

B: process with the transformable die

## N Bending Processing

**Definition:** continuously process the same machining surface twice to form N bending

## Precautions for N-bending Processing

- the angle of the first bending should be less than or equal to 90°
- the back gauge of second bending should be based on the machining surface

## Special Processing Method of N Bending

- if interfere with the top punch a little after Y sizes N-bending ==> flattening with hemming die after N-bending.
- if interfere with top punch very serious after Y sizes N bending ==> bend to collision position after A bend press line, positioning C and bending B point, then use hemming die + padding to form into shape.

- Processing with shaping punch and die.

## Arc Processing

Arc processing is divided into two kinds: circular cutting with bending model and circular cutting with arc knife.

The arc knife is divided into two types: fixed and rod.

## Precautions

A: when machining with 90°low die, there may be inadequate machining, so it is necessary to push the mold with hand or if possible, using 88°low die.

B: detect with detecting appliance to ensure the appearance size of the workpiece.

C: when processing 90°arc, the low die should choose 2 (R+T)

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