CNC machine tools are widely used in modern industry. They have the advantages of high precision, high efficiency, high automation, etc., and can realize the processing of parts with complex shapes. However, CNC machine tools may also have various faults during operation, affecting the processing efficiency and quality. When we need to perform CNC machining on parts, we usually encounter some problems, which cause the processed products to fail to meet the design requirements. Therefore, it is necessary to briefly understand the common problems in CNC machining, which will help communicate with CNC machining manufacturers and solve related problems. Based on the actual situation, Elimold Company summarizes the common problems and solutions that have occurred in the process of custom CNC machining parts for customers for many years.
Common Problems in CNC Machining and Elimold’s Solutions
Elimold has been engaged in CNC machining for many years. The following are the most common problems we have encountered when customizing parts for customers over the years and our solutions. We believe that summarizing and organizing errors can promote the improvement of the quality management system and improve the quality of our services.
In addition, for our customers, not only can we learn in detail about Elimold’s attitude towards quality management and its determination and measures to solve problems. It can also help customers understand and analyze the reasons why parts are unqualified, help to communicate specific issues with suppliers in the future, and quickly communicate and solve problems where parts are unqualified.
Causes and solutions for poor workpiece size accuracy
Causes: Tool wear will cause cutting force changes, which in turn affects the accuracy of workpiece size. It may also be that the machine tool may be affected by thermal expansion or thermal deformation during operation, resulting in workpiece size deviation. Another is inaccurate processing parameter settings, such as inaccurate settings of feed speed, cutting depth, etc., which will affect the accuracy of workpiece size.
Solution: For part size problems caused by tool wear, it is necessary to regularly check and replace worn tools to ensure that the tools maintain a good cutting state. If it is a deformation problem caused by the loss of control of the machine tool thermal management. It is necessary to control the temperature of the machine tool and take cooling measures, such as using coolant or adding a cooling system to reduce the impact of thermal deformation. If the problem of part size is caused by the problem of processing parameter setting, the processing parameters can be reasonably set according to the material properties, tool type and processing requirements. Conduct a trial cutting test and find the best processing conditions by adjusting the parameters. However, this reason is considered by Elimold to be the lowest level of error. The fundamental reason is the training of the company’s technical personnel and the error in quality management awareness.
Causes and countermeasures for poor surface finish
Causes: Incorrect cutting parameter settings, such as too fast feed speed, too high speed, etc., will lead to poor surface finish. In addition, tool wear or edge damage will also lead to irregular cutting and affect the surface quality. In addition, improper selection and use of cutting fluid may lead to poor cutting lubrication or poor cooling effect, which in turn affects the surface finish.
Solution: If the surface finish of the part is poor due to improper cutting parameter settings, it is necessary to optimize the cutting parameters, reduce the feed speed, adjust the speed appropriately, etc. to improve the surface finish. If the surface finish of the part is a problem with the tool, it is necessary to regularly check and replace the worn tool to ensure that the edge is in good condition. Use high-quality tools to improve cutting results. If the surface problem of the part is caused by improper use of cutting fluid, it is necessary to select a cutting fluid suitable for the processing material and tool, and use and replace it correctly according to the requirements of the cutting fluid.
Poor machining accuracy of curved surface machine
Cause of failure: unreasonable cutting parameters, rough surface of workpiece curved surface. In addition, the cutting edge of the tool is not sharp. Too long tool clamping and too long blade clearance can also cause this problem. Chip removal, air blowing, oil flushing, poor programming tool path and burrs on the workpiece can also cause problems with surface accuracy.
Solution: If there is a problem with the parameter setting, the cutting parameters, tolerances, allowances, and speed feed settings should be reasonable. The tool requires the operator to check and replace the tool irregularly and clamp the tool as short as possible when clamping the tool, and the blade clearance should not be too long to avoid problems with part machining accuracy due to tool and tooling problems. In addition, for the downcut of flat knives, R knives, and round nose knives, the speed feed setting should be reasonable. If the workpiece has burrs, it is directly related to our machine tool, tool, and tool path. So we need to understand the performance of the machine tool and make up the edge with burrs.
Occasionally, there are problems with out-of-tolerance in batch production
Cause of the fault: It may be due to the operator’s operating method and the reliability of clamping. The size changes caused by clamping, or the phenomenon of misjudgment due to human negligence; in addition, the CNC system may be affected by the fluctuation of the external power supply or the interference, and automatically generate interference pulses, which are transmitted to the drive, causing the drive to receive excess pulses and drive the motor to take away or run less.
Solution: Strengthen the training of operators and improve the work process. For problems with the CNC system, technicians need to understand and master its rules, and try to adopt some anti-interference measures, such as: isolating the strong power cable with strong electric field interference from the signal line of weak electric signal, adding anti-interference absorption capacitors and using shielded wires for isolation, and checking whether the ground wire is firmly connected, the ground contact is closest, and taking all anti-interference measures to avoid interference with the system.
The arc processing effect is not ideal or the size is not in place
Cause of the fault: The overlap of vibration frequency leads to resonance. In addition, the parameter setting is unreasonable, the feed speed is too high, and the arc processing loses step; in addition, the looseness caused by the large screw gap of the machine tool or the loss of step caused by the screw being too tight and the wear of the synchronous belt will also cause this problem.
Solution: Find the components that produce resonance, change their frequency, and avoid resonance; consider the processing technology of the workpiece material and reasonably compile the program; for stepper motors, the processing rate F cannot be set too large; whether the machine tool is installed firmly and placed stably, whether the carriage is too tight after wear, the gap increases or the tool holder is loose, etc.; replace the synchronous belt.
The parts are changed in a certain process, and the dimensions of other processes are accurate
Cause of the fault: Whether the parameters of the program segment are reasonable, whether they are within the predetermined trajectory, and whether the programming format meets the requirements of the manual.
Solution: It is necessary to review the entire path from CNC machining program programming to machine execution program, and strengthen the training of programmers and operators, and increase the inspection work procedures for missing and filling gaps. For example, if there are irregular teeth and incorrect pitch in the thread program segment, it is immediately associated with the peripheral configuration (encoder) of the thread processing and the objective factors of the function.
The precision of parts increases or decreases in each process
Causes of failure: Program writing error; unreasonable system parameter setting; improper configuration setting will lead to this problem; in addition, mechanical transmission parts fail and cause regular periodic changes.
Solution: Check whether the instructions used in the program are executed according to the required trajectory specified in the manual. You can judge by using a dial indicator. Position the dial indicator at the starting point of the program to see if the slide returns to the starting position after the program ends. Repeat the execution to observe the results and grasp the rules; check whether the system parameters are set reasonably or considered to be changed; whether the relevant machine tool configuration meets the requirements in the connection calculation coupling parameters, and whether the pulse equivalent is accurate; check whether the transmission part of the machine tool is damaged, whether the gear coupling is uniform, and whether there are periodic and regular fault phenomena. If so, check its key parts and eliminate them.
Summary
Troubleshooting these issues often requires expertise and may require a combination of adjustments to machine settings, tools, programming, and maintenance practices. CNC machining manufacturers require ongoing machine maintenance, operator training, and adherence to best practices and professional troubleshooting skills to ensure part accuracy. This is essential for efficient CNC machining operations. By implementing these measures, manufacturers can improve the reliability of the production process while reducing the costs associated with downtime and repairs caused by equipment failure or human error.
In addition, customers understand these reasons and can effectively and efficiently communicate with CNC machining suppliers and make improvements to ensure part accuracy. It can also reduce all costs. If you need CNC machined parts, you can contact Elimold to serve you.