Machining success depends largely on component rigidity, the geometry to be turned, lathe rigidity, and vibration damping characteristics. Rigidity is critical for successful hard turning. The rigidity of tooling, workholding, and the machine tool itself are all crucial elements that will affect your ability to successfully hard turn. Hard turning is a technology-driven process, dependent upon:
- Machine technology
- Process technology
- Materials and tooling technology
- Workholding technology
In the area of hard turning, it’s well-established that the presence of vibration is not desirable from multiple standpoints. A machine which has improved damping will demonstrate improvements in lowering the amplitude of vibration and the time to decay, all while maintaining static stiffness.
The real and measurable results are longer tool life, better surface finishes, improved accuracy, increased productivity and higher overall part quality.
System rigidity is of utmost importance. Machine Dynamic Stiffness (MDS) is one of the most important attributes for hard turning. MDS is a ratio of the force to displacement at the exciting frequency, a function of the static stiffness and the system damping. When the static stiffness cannot be increased, then it’s necessary to increase the damping to increase the MDS. The upper bound in part surface finish quality is determined by MDS as is the upper bound in tool life.
The benefits of high dynamic stiffness include:
- Lower operating vibration
- Substantially improved tool life
- Substantially improved part quality
- Higher through-put
- Less machining parameter adjustments
Other important factors and techniques to note for successful hard turning include:
- Feed speed
- Machine setup
- Positioning
- Boring
- Coolant application
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