For the precision cnc machining parts industry, sufficient accuracy is often the most intuitive reflection of the processing capabilities of its factories. In the actual mechanical processing production, various heat sources (friction heat, cutting heat, ambient temperature, thermal radiation, etc.), the tool, the part to be processed, the temperature changes under the action, which will affect the relative displacement between the part and the tool, produce thermal deformation, cause machining errors, and then affect the machining accuracy of the parts. For example, the linear expansion coefficient of steel is 0.000012/℃. For a steel piece with a length of 100mm, it will stretch 1.2μm when the temperature rises by 1℃. In addition to directly affecting the expansion and contraction of the part, temperature changes also affect the accuracy of machine tools.
In precision cnc machining, higher requirements are put forward for the machining accuracy and stability of the part. According to relevant statistics, machining errors caused by thermal deformation account for 40%-70% of the total machining errors in precision cnc machining. Therefore, in high-precision machining, in order to avoid the expansion and contraction of the part due to temperature changes, the reference temperature of the environment is generally strictly specified. And the deviation range of temperature change has been formulated, and constant temperature processing of 20℃±0.1℃ and 20±0.01℃ has appeared.
In general, for a constant temperature and humidity laboratory for precision cnc machining, in order to avoid the expansion and contraction of the part due to temperature changes during processing and measurement, the indoor reference temperature is generally strictly specified, and the deviation range of temperature changes is established. The relative humidity of the air is not as strict as the accuracy of textile testing. For example, a national ultra-precision machining laboratory requires a temperature of 20°C ± 0.2°C and a relative humidity of 45% ± 5%.