As we all know, the accuracy of CNC machining parts is an important factor in measuring the final quality of finished products, so the requirements for accuracy are very important. In CNC machining, there are many reasons that will affect the accuracy of the machine parts. Today, the editor will focus on talking about how temperature changes will affect the machining accuracy of cnc parts?
1- Effect of temperature changes on materials;
"Temperature" is what we often call "thermal deformation". Our common temperature changes, such as the temperature of the external environment of the workshop, the heat generated by the motor, and the heat generated by mechanical movement friction, may cause the temperature of various parts of the CNC machine tool to be unbalanced, which in turn will affect the machining accuracy of the CNC machine tool parts.
As we all know, most of the machine tool equipment is composed of steel, cast iron and other components, because these materials are prone to "thermal expansion and contraction", when the room temperature and the heat generated by the machine itself change, the shape and length and other values will change. change. You can look at the expansion coefficient table of steel and copper.
2-Temperature changes cause detection errors
If the workpiece and the testing instruments and gauges used for testing are made of different materials, testing errors will occur if they are not under standard temperature conditions (20°C) during testing.
Therefore, when testing high-precision parts, it is necessary to have higher-precision measuring methods and measuring instruments. Shenzhen YiXin Precision Metal And Plastic Ltd has advanced three-coordinate measuring instrument (CMM), spectrum analyzer, 2D image measuring instrument, other testing equipment, and other testing instruments. 100% full inspection of the finished products guarantees quality and accuracy.
3-Maintain the thermal stability of cnc parts processing
Under normal circumstances, even if the temperature drops rapidly, it still takes a sustained period of time to maintain the accuracy, especially the larger the object, it takes more time to recover the accuracy when the temperature changes.
Generally, experienced factories will attach great importance to the ambient temperature of the workshop and the thermal balance of the machine tool. Even for high-precision machine tools, stable machining accuracy can only be obtained in a state of stable temperature and thermal balance.
Maintaining thermal stability is an important concept that must be thoroughly understood in precision machining. Some people may be entangled in whether the temperature should be maintained at 20°C or 23°C. In fact, the most important thing is to maintain the stability of a target value. In theory, the general requirement is 20°C, and the actual workshop generally takes 22-23°C, and the temperature fluctuation can be strictly controlled.
Generally speaking, the processed parts are relatively precise but imprecise, which may be caused by large temperature fluctuations in the workshop, resulting in large dispersion of precision. If the processed parts are called accurate but not precise, it is likely that the temperature fluctuations in the workshop are not large, but the deviation from the standard temperature is large. Neither precise nor accurate, it means that the workshop temperature deviates a lot from the standard temperature and control requirements.
【“Precision”, also known as precision, refers to the reproducibility and consistency between the results obtained by repeated measurements using the same spare sample.For example, using a length of 2mm for measurement, the three results obtained are 2.053, 2.049, and 2.050 respectively. In this case, although their precision is high, they are not accurate.
“Accuracy” refers to the closeness between the obtained measurement results and the true value. The high measurement accuracy means that the systematic error is relatively small, and the average value of the measured data is less from the true value, but the size of the accidental error is not clear. 】
Workers in the workshop usually know that when they start processing every morning, the processing accuracy of the first part is often not very good; after the long holiday, the first batch of parts that are started to process often have unstable accuracy, and the failure probability is very high during high-precision processing, especially the position accuracy.
This is because CNC machine tools can only obtain stable machining accuracy in a stable temperature environment and thermal equilibrium state. It is the most basic processing common sense to preheat the machine tool after starting up.
The machining accuracy of the machine tool in the state of long-term stop operation and thermal equilibrium state is very different, which may be because the temperature of the spindle and each movement axis of the CNC machine tool is relatively maintained at a certain level after running for a period of time. With the change of processing time, the thermal accuracy of CNC machine tools tends to be stable, which further shows that it is very important to preheat the spindle and moving parts before processing.
If the machine tool has been placed on hold for several days, it is recommended to preheat for more than 30 minutes before high-precision machining. If the machine is left on hold for only a few hours, it is recommended to preheat for 5-10 minutes before high-precision machining.
Even if the machine tool participates in the repeated movement of the machining axes during the warm-up process, it is best to perform multi-axis linkage, such as moving the XYZ axes from the lower left corner of the coordinate system to the upper right corner, and repeatedly walking diagonally. When executing, you can write a macro program on the machine tool to let the machine tool perform warm-up operations repeatedly.
After the machine tool is fully warmed up, it can be put into high-precision machining production.
The above is an important influence of temperature on machining accuracy. So how should the temperature be adjusted?
Cooling technology is a very commonly used method, which can effectively reduce the temperature by cooling the workpiece and cutting tool, thereby reducing the influence of temperature changes and improving machining accuracy. Cooling technology is divided into internal cooling and external cooling, and the purpose of cooling is achieved by transferring heat through liquid.
B- cooling time control
Cooling time control is a relatively simple and commonly used method. By properly extending the cooling time, temperature changes can be effectively controlled, thermal stress can be reduced, and processing accuracy can be improved.
Temperature detection is a key link to fully understand the processing humidity, control temperature changes in time, and improve processing accuracy. Generally, it is detected by installing a temperature sensor on the machine tool.
D- process control
Processing process control is a relatively comprehensive method, including comprehensive control of multiple factors such as temperature and cutting parameters, and real-time monitoring and adjustment of elder brother parameters during processing to achieve the purpose of controlling temperature and improving processing accuracy.
To sum up, temperature is one of the important factors affecting machining accuracy. In order to ensure processing accuracy and product quality, the temperature must be regulated. Cooling technology, cooling time control, temperature detection and process control are commonly used temperature regulation methods. Through the combined use of these methods, the temperature change can be effectively controlled, and the processing accuracy and product quality can be improved.
Shenzhen YiXin Precision Metal And Plastic Ltd carries out strict temperature control in the process of production and testing, so as to avoid the negative impact of temperature changes on the precision of processed parts as far as possible, and ensure product quality.