Although different micro-cutting processes require different cutting strategies and machining sequences,
there are still some technical know-how and machining guidelines that are applicable in many situations:- (1) When processing on a CNC core machine, drilling and internal turning should be performed on the main spindle first. Since the guide sleeve can support the bar, the processing stability can be improved.
- (2) In the second step, the outer circle should be turned on the main spindle. If possible, it is best to complete the full depth of cut in one pass to shorten the cutting time and improve machining stability.
- (3) The third step should be milling. Face milling should be preferred. Due to the limited stability and power of the rotating spindle, the smaller the cutting force, the better, and face milling can meet this requirement.
- (4) In order to process the outer diameter of the workpiece in the final stage before the cutting process, high-productivity reverse machining is usually used, and the completion of the machining in one pass helps reduce vibration.
- (5) Cutting is the last process completed on the main spindle. The closer the two spindles are to each other, the smaller the overhang of the part and the better the surface finish.
- (6) Finally, finish the final finishing on the sub-spindle. This step is usually inner diameter processing, but it may also be outer diameter processing.
Turning and milling compound processing has its own application fields and advantages. First, machining discontinuous surfaces can lead to intermittent cutting, such as machining various grooves and cleaning roots. In classic turning processing, this operation can produce impact loads that are not conducive to processing, resulting in poor surface quality and premature tool wear. In the turning-milling compound machining, the tool used is the milling cutter, and the milling itself is intermittent cutting with periodic load changes.
Second, when the processed material is a long chip material. In turning processing, chip forming is difficult to deal with; finding a suitable chipbreaker for turning tools is not so easy to complete. The milling cutter used in turning-milling composite processing produces short chips, which significantly improves chip control.
Third, take the machining of crankshafts and spindles with eccentric journals as an example. In turning processing, the eccentric quality of workpieces such as crank journals and eccentric cams can lead to the generation of unbalanced forces and adversely affect the machining. Compound machining avoids such negative effects due to the low speed of the workpiece.
The introduction of core machining in production not only solves the processing problems but also greatly increases the output. Using relatively new processing methods, with suitable modern machine tools and correctly selected cutting tools, productivity will be greatly improved.
