1. Before the 1970s, the machining method of engine crankshaft machining was multi-tool lathe turning crankshaft main journal and connecting rod journal. In this way, the processing precision is low, the flexibility is poor, the process quality is low, and it is easy to generate large internal stress, and it is difficult to achieve a reasonable machining allowance. After roughing, it is generally necessary to perform stress relief tempering to release stress. Therefore, roughing requires a large machining allowance for the subsequent finishing process to remove the amount of bending deformation. The cranking process uses a common grinding process, usually by manual operation, the processing quality is unstable, and the scrap rate is high.

2. In the 1970s and 1980s, the crankshaft machining was processed by external milling, and the processing conditions were improved. Finishing is still dominated by ordinary grinding machines.

3. In the mid-1980s, the internal milling process appeared again. The performance index of internal milling is higher than that of external milling. Especially for forged steel crankshafts, internal milling is more conducive to chip breaking. The finishing process mostly adopts semi-automatic crankshaft grinding machine, head frame and tailstock synchronous bar transmission, and the machining precision is improved.

4. The crankshaft was developed around 1985-1990. The process has the advantages of high precision and high efficiency, and is particularly suitable for a crankshaft on which the side of the balance block does not need to be processed and the journal has an undercut groove (including an axial undercut groove), and the crankshaft can be directly ground after machining, eliminating the rough grinding. Process. A small amount of CNC grinding machine grinding process has been used for crankshaft machining, and dimensional consistency has been improved.

5. In the mid-1990s, high-speed external milling was developed. It has a high efficiency in internal milling for the crankshaft that needs to be machined on the side of the balance block. In addition, the car pull process requires two steps to machine the connecting rod journal, and high-speed outer milling can be completed in one process. The advantages of high-speed external milling include: high cutting speed (350m/min), short cutting time, short process cycle time, low cutting force, low workpiece temperature rise, high tool life, less tool change, and machining accuracy. Higher and more flexible.

Therefore, high-speed external milling will be the development direction of the crankshaft main journal and the connecting rod journal roughing. The finishing machine uses a CNC grinding machine, which adopts static pressure spindle, static pressure guide rail, static pressure feed screw (grinding wheel head frame) and linear grating closed-loop control and other control devices to ensure the dimensional tolerance and shape tolerance are reliably guaranteed. Finishing is also widely used in the super-finishing of CNC belt polishing machine, and the surface roughness of the crankshaft after super-finishing is improved by at least one level.