CNC Machining and CNC Machine Tools

Regarding machining accuracy, this is the most professional article I have ever seen.

High Quality Custom stainless steel company

When we deal with processing every day, we often mention accuracy, but are you correct about the accuracy? Or is it rigorous? Let’s take a look at precision things with Shenzhen Yuhe Diamond Tools! High Quality Custom stainless steel company
   Machining accuracy is the degree of conformity between the actual size, shape, and position of the surface of the processed part with the ideal geometric parameters required by the drawing! The ideal geometric parameters are the average size in terms of size; in terms of shape, they are absolute circles, cylinders, planes, cones, and straight lines; in terms of mutual positions, they are absolute parallel, perpendicular, coaxial, etc. Symmetry etc.

  1. Dimensional accuracy   The degree of conformity between the actual size of the processed part and the center of the tolerance zone of the part size. High Quality Custom stainless steel company
  2. Shape accuracy    refers to the degree of conformity between the actual geometry of the surface of the processed part and the ideal geometry.
  3. Position accuracy    refers to the actual position accuracy difference between the relevant surfaces of the parts after processing.
  4. Mutual relations    Generally, when designing machine parts and specifying the machining accuracy of parts, attention should be paid to control the shape error within the position tolerance, and the position error should be less than the size tolerance. That is, the shape accuracy requirements of precision parts or important surfaces of parts should be higher than the position accuracy requirements, and the position accuracy requirements should be higher than the dimensional accuracy requirements.

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Metal texture dividing line
  The deviation of the actual geometric parameters of the part from the ideal geometric parameters is called the machining error. The size of the machining error reflects the level of machining accuracy. The greater the error, the lower the machining accuracy, and the smaller the error, the higher the machining accuracy. High Quality Custom stainless steel company

  1. Introduction to machining accuracy    Machining accuracy is mainly used for the degree of product production. Machining accuracy and machining error are both terms to evaluate the geometric parameters of the machined surface. Machining accuracy is measured by tolerance grade, the smaller the grade value, the higher the accuracy; the processing error is expressed by numerical value, the larger the numerical value, the greater the error. High machining accuracy means small machining error, and vice versa.
    There are 20 tolerance levels from IT01, IT0, IT1, IT2, IT3 to IT18. If IT01 indicates the part has the highest machining accuracy, IT18 indicates the part has the lowest machining accuracy. Generally, IT7 and IT8 have medium machining accuracy. level.   The actual parameters obtained by any machining method will not be absolutely accurate. From the perspective of the function of the part, as long as the machining error is within the tolerance range required by the part drawing, it is considered that the machining accuracy is guaranteed.

The difference between accuracy and precision:

  1. Accuracy    refers to the degree of closeness between the obtained measurement result and the true value. High measurement accuracy means that the system error is small. At this time, the average value of the measured data deviates from the true value less, but the data is scattered, that is, the size of the accidental error is not clear.
  2. Precision    refers to the reproducibility and consistency between the results of repeated measurements using the same kind of spare sample. It is possible that the precision is high, but the precision is not accurate. For example, the three results obtained by measuring using a length of 1 mm are 1.051 mm, 1.053, and 1.052, respectively. Although they have high precision, they are not accurate.   Accuracy means the correctness of the measurement result, precision means the repeatability and reproducibility of the measurement result, and precision is a prerequisite for accuracy.

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  1. Methods to improve machining accuracy

Adjust the process system

1) Trial cut method adjustment

  Through trial cutting-measurement size-adjusting the amount of cutting of the tool-cutting-retry-cutting,and so on until it reaches the required size. This method has low production efficiency and is mainly used for single-piece small batch production.

2) Adjustment method

  The required size is obtained by adjusting the relative positions of the machine tool, fixture, workpiece and tool in advance. This method has high productivity and is mainly used for mass production. (Welcome to follow WeChat: Yuhe Diamond Tool)

Reduce machine error

1) Improve the manufacturing accuracy of spindle components
The rotation accuracy of the bearing should be improved:

①Select high-precision rolling bearings;

②Using high-precision multi-oil wedge dynamic pressure bearings;

③Using high-precision hydrostatic bearings,

The accuracy of the accessories related to the bearing should be improved:

①Improve the machining accuracy of box support holes and spindle journals;   

②Improve the machining accuracy of the mating surface with the bearing;

③Measure and adjust the radial runout range of corresponding parts to compensate or offset the error.

2) Properly preload the rolling bearing

①The gap can be eliminated;

②Increase bearing stiffness;

③Equalize rolling element error.

Reduce the transmission error of the transmission chain

1) The number of transmission pieces is small, the transmission chain is short, and the transmission accuracy is high;

2) The use of reduced speed transmission is an important principle to ensure transmission accuracy, and the closer the transmission pair is to the end, the smaller the transmission ratio should be;

3) The accuracy of the end pieces should be higher than other transmission parts.

Reduce tool wear

The tool must be re-sharpened before the tool size wear reaches the sharp wear stage

High Quality Custom stainless steel company
High Quality Custom stainless steel company

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