Precision machining is the process of changing the size or performance of a workpiece with a processing machine. According to the temperature state of the workpiece being processed, it is divided into cold working and hot working. Generally processed at room temperature, and does not cause chemical or physical phase changes of the workpiece, called cold processing. Generally, processing at a temperature higher or lower than the normal temperature causes a chemical or physical phase change of the workpiece, which is called thermal processing. Cold machining can be divided into machining and pressure machining according to the difference in processing methods. Thermal processing is commonly used for heat treatment, forging, casting and welding.
Machining is roughly divided into turning, milling, and centering-based cutting (bit cutting of end bits, end mills, etc.), and the cutting heat of these cuttings has different effects on the cutting edge. Turning is a kind of continuous cutting. The cutting force of the cutting edge does not change significantly. The cutting heat acts continuously on the cutting edge. Milling is a kind of intermittent cutting. The cutting force acts intermittently on the cutting edge and will vibrate during cutting. The heat effect on the tip is alternated between heating during cutting and cooling during non-cutting, and the total heat received is less than that during turning.
The heat of cutting during milling is an intermittent heating phenomenon, and the teeth are cooled when they are not cut, which will contribute to the extension of tool life. The Japan Institute of Physics and Chemistry has conducted a comparative test on the tool life of turning and milling. The tool used for milling is a ball end mill, and the turning is a general turning tool. Both are in the same material to be processed and cutting conditions (due to different cutting methods, cutting The depth, feed rate, cutting speed, etc. can only be achieved in a consistent manner. Under the same environmental conditions, the cutting comparison test shows that the milling process is more advantageous for extending the tool life.
When cutting with a tool such as a drill with a center edge (ie, a cutting speed of 0 m/min) or a ball end mill, the life of the tool near the center edge is often low, but it is still stronger than that during turning. When cutting difficult materials, the cutting edge is greatly affected by heat, which often reduces the tool life. If the cutting method is milling, the tool life will be relatively longer. However, difficult-to-machine materials cannot be milled from start to finish. There is always a need for turning or drilling in the middle. Therefore, corresponding technical measures should be taken for different cutting methods to improve processing efficiency.