Example of proposed approach :

General principles : 4 key parameters :
  • Stiffness => static and dynamic flexion => precision in position and/or forced vibrations and/or spontaneous chatter (if rigidity is too low).
  • Natural frequency => spindle speed(s) to avoid or to prefer.
  • Damping => aggravating factor during a resonance (ie forced vibrations by a tooth cut frequency close to the natural frequency) and ev. chatter (self-sustaining vibrations, ie appearing even in continuous cutting).
  • Radial cutting force => aggravating factor for both static flexion and vibration.
In practice these principles will allow you to design and realize optimal machining jobs.

  • Analysis of the existing system (≈ 1 or 2 days per machine) :
    • Analysis of the machines : stiffness, natural modes (tap testing), damping, axis accelerations/jerk/vibrations during G0 G1 G2, spindle vibrations.
    • => Identify the weak elements (rigidity of a machine axis, damping of a workpiece holder, etc.)
    • Process analysis : in-depth analysis of surface finish, vibrations during machining, radial component of the cutting force.
    • => identify the phases really soliciting (with respect to chatter, tool or machine wear).
  • Optimization :
    • Improve the weak elements.
      • Machine : recommendation of servo control adjustements or axis repair (with precise objectives).
      • Workpiece holder : holding cube, clamping systems, vacuum holders, etc.
      • Tools :
        • Stiffness : increase the body diameters, or shorten the lengths, or change the shrink fit.
        • Resonance (ie, natural frequency and damping) : optimal choice of rotational speed, damping improvement, optimal variable pitch, structural modification of the natural frequency.
        • Radial force : choice of optimized cutting angles, helix angle, coatings, edge finish.
    • Determine the maximum potential of the machining system, tool by tool : optimal rotation S, optimal engagement Ap / Ae / F.
    • Adapt machining strategies (optimal engagement and rotation, tool choice, strategies, etc.).
    • Optimization of the feed rate along the trajectories (via algorithms integrated in the CAD-CAM).
  • Monitoring :
    • 24h/24h : shocks, over-vibrations, resonances.
    • 1x/week (automatic) : spindle bearings.
    • On request : tap testing (done by the machinist or by his maintenance department).