Valor de sobreposição comumente usado para peças estampadas

Commonly used overlap value for stamped parts

In the component arrangement process, the excess material left between the parts and between the parts and the edge of the strip is called overlap. This overlap is crucial in manufacturing processes. It not only compensates for positioning errors and guarantees the quality of the punched parts, but also guarantees a certain rigidity of the strip, facilitating feeding.

However, too wide an overlap wastes material, and too narrow an overlap can cause the overlap to break or warp, possibly leading to a “nibbling” phenomenon (more prominent when punching thick materials), affecting die life. or affecting feeding, and even causing intermittent production of punched parts.

The shape, size, material thickness and mechanical properties of the parts, along with feeding and blocking methods, die characteristics and other factors determine the size of the overlap. The size of the overlap is generally determined by experience and the values ​​used by different technicians may vary. Here, we list the commonly used overlap values ​​for spring-pressed and fixed stripping plates in Table 1 for reference.

Table 1 Common Overlap Values

Common Override Values

a), b), c) are for direct punching of strips d) are for punching of strips back and forth

Sheet metal thickness t Circular or arc-shaped prints.
r>2t
(See Figures a and b)		 Straight side press
L≤50
(See Figures c and d).		 L>50
(See Figures C and D)
Stamping Fixed Stamping Fixed Stamping Fixed
The B The B The B The B The B a or b
≤0.25 1.0 1.2 1. 2 1.5 1.5~2.5 1.8~2.6
>0. 25~0. 5 0. 8 1.0 1.0 1.2 1. 0 1. 2 1.5 2.0 1.2~2.2 1.5~2.5 2.0~3.0
>0.5 ~1 0.8 1.0 0.8 1.0 1. 0 1.2 1.2 1.5 1.5~2.5 1.8~2.6 1.5~2.5
>1~1.5 1.0 1.3 1.0 1.2 1.2 1.5 1.2 1.8 1.8~2.8 2.2~3.2 1.8~2.8
>1.5~2 1.2 1.5 1.2 1.5 1.5 1.8 1.5 2.0 2.0~3.0 2.4~3.4 2.0~3.0
>2~2.5 1.5 1.9 1.5 1.8 1.8 2.2 1.8 2.2 2.2~3.2 2.7~3.7 2.2~3.2
>2.5~3 1.8 2.2 1.8 2.0 2.0 2.4 2.2 2.5 2.5~3.5 3.0~4.0 2.5~3.5
>3~3.5 2.0 2.5 2.0 2.2 2.2 2.7 2.5 2.8 2.8~3.8 3.3~4.3 2.8~3.8
>3.5~4 2.2 2.7 2.2 2.5 2.5 3.0 2.8 3.0 3.0~4.0 3.5~4.5 3.0~4.0
>4~5 2.5 3.0 2.5 2.8 3.0 3.5 3.0 3.5 3.5~4.5 4.0~5.0 3.5~4.5
>5 ~12 0.5t 0.6t 0.5t 0.6t 0.6t 0.7t 0.6t 0.7t 0.7~0.9t 0.8~1t 0.75~0.9t

Observation:

1. For straight edge perforated parts with length L between 50 ~ 100 mm, a may take a smaller value; for L between 100 ~ 200 mm, a can assume a median value; for L between 200-300 mm, a can take on a higher value.

2. For front and back perforated strip width B>50mm, a may take a larger value.

3. For materials such as hard cardboard, hard rubber, paper laminates and automatic feeding of perforated parts, the values ​​in the table must be multiplied by a factor of 1.3.

4. For materials such as leather and paper, the values ​​in the table must be doubled.

5. For punching with thin plate clamps, depending on the thickness and external dimensions of the punched parts, the diameter should not be less than 4mm.

6. Spring pressed and fixed refer to spring pressed stripping punch die and fixed stripping punch die.

7. The values ​​of a and b in this table have taken into account the impact of shear width error (see Table 2, 3).

Table 2 Shear width error of horizontal shear bed (unit: mm)

Sheet metal thickness t Cutting width B
≤50 >50~100 >100~150 >150~220 >220~300
≤1 -0.4 -0.5 -0.6 -0.7 -0.8
>1~2 -0.5 -0.6 -0.7 -0.8 -0.9
>2~3 -0.7 -0.8 -0.9 -1.0 -1.1
>3~5 -0.9 -1.0 -1.1 -1.2 -1.3

Table 3: Deviation in cutting width of shearing machine material (Unit: mm)

Sheet metal thickness t Cutting width B
≤20 >20~30 >30~50
≤0.5 -0.05 0.08 0.10
>0.5~1 0.08 0.10- 0.15
>1~2 0.10 0.15 0.20

In short, overlap is waste. To save materials, the smaller the overlap, the better. However, too small an overlap easily compresses into the die, increasing blade wear, reducing die life, and also affecting the shear surface quality of punched parts.

Generally speaking, when determining the amount of overlap, consider:

1) The mechanical properties of the material. More plastic materials require a larger overlap, while harder, stronger materials require a smaller overlap.

2) The thickness of the material. The thicker the material, the greater the overlap should be.

3) The shape and size of the workpiece. The more complex the shape of the workpiece and the smaller the corner radius, the greater the overlap should be.

4) The overlap value for staggered layout must be greater than that for straight layout.

5) For manual feeding and side pressure plate orientation, the overlap value may be smaller.

Recommended for you:

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  • The Ultimate Guide to Metal Deep Drawing
  • Pressure Brake Dies: The Definitive Guide
  • Sheet Metal Design Guidelines for Manufacturing: Engineer's Handbook
  • Metal Bending: The Ultimate Guide

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