Non-Regenerative Dynamic Instability In Surface Grinding

n this paper a particular type of non-regenerative instability in surface grinding is studied. Clear evidences have been collected suggesting that vibrations can occur suddenly even during the first wheel pass and just after wheel dressing, circumstances that exclude workpiece and wheel surface regeneration as instability origin, whereas both surfaces have to be considered ideal. Therefore, the stability of the dynamic system constituted by an oscillating ideal wheel immerged in a positional and velocity-dependent process force field has been studied, demonstrating that in some circumstances the force field itself exhibits an unstable behaviour. The instability occurrence is strictly related to the oscillation direction of the wheel centre according to the mode shape associated to the dominant resonance, with respect to the direction of the grinding force (identified by the ratio between tangential and normal components). Then, the analysis leads to the identification of a simple necessary condition for instability occurrence. The analytical results are confirmed by proper time domain grinding simulations and compared with experimental evidences.