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How To Control Sheet Metal Tolerances In Fabrication? | Industry Standard
Time:2023-03-21     
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Sheet metal processing is a common fabrication method at present. In the process of parts processing, due to the machining accuracy of mechanical equipment, mold wear, machining error and other factors. The size of the produced sheet metal parts cannot be absolutely accurate. In order to ensure the availability of the workpiece, we must limit the sheet metal tolerance to the minimum.

What are the common tolerance standards in sheet metal processing?


Shenchong press brake sheet metal bending


1. Sheet Metal Processing Tolerance Standard



1) Basic dimensions

Determine the dimensions determined in the design based on the strength and structural requirements of the parts. Standard diameter or length shall be preferred.


2) Actual size

The dimension obtained by measurement.


3) Limit size

Two thresholds that allow you to change the size. It is based on basic size. The larger of the two limit values is called the maximum limit size. The smaller is called the minimum limit size.


4) Dimensional deviation

The algebraic difference obtained by subtracting the basic dimension of a dimension.

The dimensional deviation is as follows:

Upper limit of deviation = maximum limit dimension - basic dimension

Lower limit of deviation = minimum limit dimension - basic dimension

The upper and lower deviations can be called limit deviations. The upper and lower deviations can be positive, negative or zero.


Sheet Metal Bending Fabrication


5) Dimensional tolerance

It is allowable size variation.

Dimensional tolerance = maximum limit dimension - minimum limit dimension = upper deviation - lower deviation

Since the maximum limit dimension is always greater than the minimum limit dimension, that is, the upper deviation is always greater than the lower deviation, the dimension tolerance must be positive.


6) Standard tolerance and standard tolerance class

Sheet metal standard tolerance is any tolerance listed in the national standard to determine the size of the tolerance zone. The standard tolerance level is the level to determine the accuracy of dimensions.

The standard tolerance is divided into 20 grades. For a certain basic dimension, the higher the standard tolerance level, the smaller the standard tolerance value, and the higher the accuracy of the dimension.


7) Basic deviation

It is used to determine the upper and lower deviation of the tolerance zone from the zero line. Generally, it refers to the deviation near the zero line.

The shaft tolerance code and standard tolerance class code are composed of two parts and written with the same number.


There are many methods for sheet metal processing: loading, unloading, cutting, shearing, bending, rolling, welding and other forming. In the process of sheet metal fabrication, tolerance is unavoidable. Sheet metal tolerance within a certain range is allowed. The out-of-range error is caused by improper operation.


What is the tolerance in sheet metal processing? How to reduce tolerance to control workpiece accuracy?


2. How To Control The Sheet Metal Tolerance?


It is impossible to carry out sheet metal processing without any tolerance. But what we need to do is to control this tolerance to the minimum allowable range.

Although the parts processed by sheet metal are sometimes not very large, the processing process is still quite complex. This requires the operator to be very careful. Therefore, in sheet metal processing, the requirements for resistance to fatigue and other properties are very high.


Sheet metal processing technology is very precise. So when we use sheet metal processing, we should keep our spirits up and check the process flow again and again. Strictly control the quality of each procedure. Once a problematic workpiece is found, it must not flow into the next process.


The above is some introduction about tolerance in sheet metal processing that Wuxi Shenchong shared with you, hoping to help you.


High-precision Machine Tools


Sheet metal tolerance is inevitable, but we need to minimize the tolerance value in various aspects during the processing process to ensure the usability of the workpiece. The use of high-precision shearing machine and CNC press brake machine can effectively control the error. In addition, combined with correct operation, the workpiece accuracy can be optimized.

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