How To Measure The Quality Of A Machine

- Jun 10, 2019-

The quality of the machinetool affect the quality of machine directly. Measuring the quality of a machine is a multifaceted, but mainly requires a good process, serialization, generalization, high degree of standardization, simple structure, light weight, reliable, high productivity. Specific indicators are as follows:

1,The possibility of the process

The possibility of the process is the ability of the machine to adapt different production requirements. General machine tool can complete a certain range of various parts of the multi-process processing, the possibility of a wide range of technology, and thus the structure is relatively complex, which is suitable for batch production of small piece. Special machine tools can only complete one or several parts of a specific process, the possibility of its technology is narrow, suitable for mass production, can improve productivity, ensure processing quality, simplify the machine structure, reduce machine tool costs.

2, Accuracy and surface roughness

To ensure the accuracy of the machined parts and surface roughness, the machine itself must have a certain geometric accuracy, motion accuracy, transmission accuracy and dynamic accuracy.

Geometric accuracy refers to the accuracy of the position of the components and the shape accuracy and position accuracy of the main parts when the machine is not running. The geometric precision of the machine tool has an important effect on the machining accuracy, so it is the main index to evaluate the precision of the machine tool.

Motion accuracy refers to the geometric position accuracy of the main parts when the machine is operating at the working speed. The greater the change in geometric position, the lower the motion accuracy.

Transmission accuracy refers to the coordination and uniformity of motion between the end of the machine tool chain.

The above three kinds of precision indicators are detected in the no-load conditions, in order to fully reflect the performance of the machine tool, the machine tool must have a certain dynamic accuracy and temperature under the action of the main parts of the shape and position accuracy. The main factors that affect the dynamic accuracy of the machine are stiffness, vibration resistance and thermal deformation.

Machine stiffness refers to the ability that machine tool resist deformation under the action of external force, the greater the rigidity of the machine, the higher the dynamic accuracy. The rigidity of the machine includes the stiffness of the machine tool itself and the contact stiffness between the components. The rigidity of the machine tool itself depends mainly on the material properties of the component itself, the cross-sectional shape, the size and so on. The contact stiffness between the members is not only related to the geometrical dimensions and hardness of the contact material, the contact surface, but also the surface roughness, geometric accuracy, processing method, contact surface medium, preload and other factors of the contact surface.

Machine vibration, can be divided into forced vibration and self-excited vibration. Self-excited vibration is caused by the internal vibration generated by the continuous vibration without any external force and excitation force. interfe Under the continuous action of the exciting force, the system is forced to vibrate due to forced vibration.

Shock resistance of the machine tool is related with machine stiffness, damping characteristics and quality. As the various parts of the machine thermal expansion coefficient is different, resulting in different parts of the machine deformation and relative displacement, this phenomenon is called the machine thermal deformation. The maximum error due to thermal deformation can account for 70% of the total error.

 As there is no uniform standard of the dynamic accuracy of the machine tool, so it mainly through cutting typical parts to achieve the accuracy of the machine tool, which we could make a comprehensive evaluation of the dynamic accuracy.

3, Serializations and so on

The serialization, generalization, standardization of machine tool are closely linked, the series of products is the basis of components and spare parts standardization. While the generalization of components and standardization of parts could promote the series of work.

4,Tthe machine tool life

The reliability and wear resistance of machine tool structures are the major indicators of machine tool life.