Surface integrity
The cutting process can affect the integrity of the final component that can ultimately lead to part distortion on thin parts or reduced fatigue life in critical rotating parts (discs and shafts).
The combination of cutting force and elevated temperatures generated during machining leads to alterations of the microstructure, which can cause changes in micro hardness, plastic deformation of the grain boundaries and residual stresses in the component sub-surface.
Sandvik Coromant leads R&D with the AMRC (Advanced Manufacturing Research Centre) to develop optimized grades, geometries and cutting parameters to leave the component in the optimum condition.
It has been found that the key factors that affect the severity of the surface change are:
1) | Cutting parameters. There is little effect with change of feed, however, increase in cutting speed has a detrimental effect on the surface characteristic with a worn edge in HRSA materials. |
2) | Grade/geometry effect on insert wear. The critical point is the ‘trailing edge’ of the insert. This is the part of the edge which transmits heat into the component and generates the finished diameter. Wear at this point increases the temperature and forces, resulting in more spring passes and component deflection. |
Best surface results have been found with
 HRSA | - CoroCut RO in CVD coated S05F at 50m/min |
 Titanium | - CoroCut RO in uncoated H13A up to 120m/min |
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Predictive machining
To be able to ensure that the chosen insert style and grade can make one pass, we provide spiral cutting length (SCL) information.
For a given diameter and length of cut the SCL can be calculated for a given feed rate – the correct speed can then be applied to guarantee making the pass with acceptable wear, giving good surface integrity and dimension, preventing any need to re-cut. |  |
| Best practice for finishing
Roughing - if using ceramic, stop within 1mm due to high material deformation. Finish with carbide – 3 passes – use SCL to ensure cutting data gives cutting length required
| 1) | semi finish - 0.5mm |
| 2) | finish measure – same insert style and geometry as finish cut - 0.25mm |
| 2b) | measure component to gauge last cut, size to correct offset of tools |
| 3) | finish cut to size |
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