Machining is an important part of manufacturing technology, which is the manufacturing that uses cutting tools to remove surplus material from the workpiece and obtain the required shape, size and surface roughness. In the machining process, two main types of cutting operations are usually carried out: roughing and finishing. Rough machining (Roughing) is the use of cutting tools with a large rake angle and a large cutting amount to remove a large amount of material from the workpiece quickly and impart the required shape, size and surface roughness. In finishing, the cutting tool has a small rake angle and a small cutting amount. The machining operations are used to obtain the required surface roughness and size accuracy.
Rough Machining (Roughing)
Rough machining is used to quickly remove a large amount of material from the workpiece. The used tools have a large rake angle, cutting width and cutting depth. In general, the cutting speed of rough machining is much higher than that of finish machining, and the machining accuracy is lower. The main purpose of the rough machining is to reduce the machining allowance of the workpiece and eliminate the sharp turning, so as to form a uniform stress distribution state of the workpiece and ensure the stability of the processing technology.
Rough machining can produce a large amount of cutting heat. The cutting force produced by the large rake angle will reduce the tool life and tool efficiency. Therefore, appropriate cutting fluids should be used to cool and lubricate the tool, reduce cutting force and improve tool life. In order to reduce the cutting force and avoid vibration, it is necessary to choose the appropriate process parameters, such as cutting speed, feed rate and cutting depth, according to the tool characteristics, the servo damping capability, the spindle speed and the heat dissipation performance of the machine tool.
Finish Machining (Finishing)
Finish machining is a machining method used to improve the sizing and surface roughness of the workpiece. The cutting force generated by the finish machining is small, while the cutting speed and the cutting depth are both small. Generally, the cutting depth of the finish machining is less than 0.1mm, and the total cutting width is less than 0.3mm. The improvement of the surface roughness depends on the finish cutting process and the choice of cutting tools.
In the finish machining, the feed rate should be as small as possible, so as to reduce the cutting force and improve the surface quality. Generally, the tool wear is smaller than that in the rough machining. Therefore, the cutting parameters of the grain can be selected according to the cutting temperatures, cutting depths and cutting widths. Higher cutting speed and smaller feed rate can lead to high surface quality. In addition, the tool geometry should be selected carefully in order to effectively cut the chips and ensure the surface quality.
Conclusion
Rough machining and finish machining are two kinds of cutting operations used in machining process, which are used to reduce the machining allowance of the workpiece or improve the surface roughness and size accuracy. Due to the large cutting force generated by the rough machining, it is necessary to select the appropriate cutting speed, feed rate, cutting depth and cutting fluid in order to reduce the cutting force, eliminate vibration and improve tool life. In the finish machining, the feed rate should be as small as possible, and the cutting parameters should be selected according to the cutting temperatures, cutting depths and cutting widths. Thus, the tool geometry should be selected carefully in order to effectively cut the chips and ensure the surface quality.
