CNC Machine Tools: Keys and Challenges of High-precision Machining
CNC machine tool, as the abbreviation of digital control machine tool, is an automated machine tool equipped with a program control system. Its control system can logically process programs with control codes or other symbolic instructions, and decode them, so that the machine tool can operate and process parts. The operation and monitoring of CNC machine tools are all completed in this CNC unit, which can be described as the “brain” of the machine tool.
CNC machine tools have many advantages. Its processing accuracy is high, which can steadily ensure the quality of processing; it can carry out multi-coordinate linkage, and can process parts with complex shapes; when the processing parts change, generally only need to change the CNC program, which can greatly save production preparation time; the machine tool itself has high accuracy and high rigidity, and can choose a favourable processing amount and production efficiency. High, usually 3 to 5 times that of ordinary machine tools; high degree of automation, can reduce labour intensity. However, it also puts forward high requirements for the quality of operators and higher technical requirements for maintenance personnel.
CNC machine tools generally consist of multiple parts. The main machine is the main body of the CNC machine tool, including the machine tool body, column, spindle, feed mechanism and other mechanical components, which are used to complete various mechanical operations of cutting and processing. The numerical control device is its core part, including hardware such as printed circuit board, CRT display, key box, paper tape reader, etc., as well as corresponding software, which is used to input digital part programs, and complete the storage of input information, data transformation, interpolation and the realisation of various control functions. The drive device is the driving part of the CNC machine tool actuator, including the spindle drive unit, feed unit, spindle motor and feed motor, etc. Under the control of the numerical control device, the spindle and feed are driven through an electrical or electro-hydraulic servo system. When several feeds are linked, the processing of positioning, straight line, plane curve and space curve can be completed. The auxiliary device is the necessary supporting component of the CNC machine tool, such as cooling, chip evacuation, lubrication, lighting, monitoring, etc., including hydraulic and pneumatic devices, chip evacuation devices, exchange tables, CNC turntables and numerical control divising heads, as well as tools and monitoring and detection devices. Programming and other ancillary equipment can be used for programming and storing parts outside the machine.
In production, we often encounter problems with abnormal machining accuracy of CNC machine tools. This kind of problem is very hidden and difficult to diagnose. The main reasons for such problems are as follows.
First of all, the feed unit of the machine tool may be changed or changed. This will directly affect the machining accuracy of the machine tool, because the abnormality of the feed unit will cause deviation in the movement and positioning of the machine tool.
Secondly, the NULL OFFSET of each axis of the machine tool is abnormal. Zero-point bias is an important parameter in the coordinate system of the machine tool. Its abnormality will make the coordinate positioning of the machine tool lose its accuracy.
IN addition, AXIAL REVERSE GAP (BACKLASH) ANOMALY IS ALSO A COMMON CAUSE. Reverse void refers to the gap between the screw and the nut in axial motion. The abnormal reverse gap will affect the accuracy and stability of the machine tool.
In addition, the operating state of the motor is abnormal, that is, the electrical and control parts fail. This may involve circuit failures, controller failures or other electrical problems, which will directly affect the normal operation and processing accuracy of the machine tool.
In addition to the above mechanical and electrical reasons, the organisation of machining procedures, tool selection and human factors may also lead to abnormal machining accuracy. Unreasonable programming may cause machine tools to perform wrong actions, and improper tool selection or improper use will also affect machining quality.
In order to avoid or solve the problem of abnormal machining accuracy of CNC machine tools, the following measures can be taken:
1. Regularly check and calibrate the feed unit, zero bias and other parameters of the machine tool to ensure its accuracy.
2. Maintain and check the axial reverse gap, and adjust or repair it in time.
3. Strengthen the maintenance and troubleshooting of electrical and control parts.
4. Optimise the compilation of processing procedures, choose tools reasonably, and train operators to improve their skills and sense of responsibility.
In a word, CNC machine tools play an important role in modern manufacturing, but the problem of abnormal processing accuracy needs to be paid enough attention to. Through the correct use, maintenance and troubleshooting of machine tools, the processing accuracy can be effectively improved and the product quality can be guaranteed.
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