The Effect of Grinding Wheel Contact Stiffness on Plunge Grinding Cycle

Fukuo Hashimoto,Hiroto Iwashita

doi:10.3390/inventions5040062

Abstract

This paper presents the effect of grinding wheel contact stiffness on the plunge grinding cycle. First, it proposes a novel model of the generalized plunge grinding system. The model is applicable to all plunge grinding operations including cylindrical, centerless, shoe-centerless, internal, and shoe-internal grinding. The analysis of the model explicitly describes transient behaviors during the ramp infeed and the spark-out in the plunge grinding cycle. Clarification is provided regarding the premise that the system stiffness is composed of machine stiffness and wheel contact stiffness, and these stiffnesses significantly affect productivity and grinding accuracy. The elastic deflection of the grinding wheel is accurately measured and formulas for representing the deflection nature under various contact loads are derived. The deflection model allows us to find the non-linear contact stiffness with respect to the normal load. The contact stiffnesses of four kinds of grinding wheels with different grades and bond materials are presented. Both cylindrical grinding and centerless grinding tests are carried out, and it is experimentally revealed that the time constant at ramp infeed and spark-out is significantly prolonged by reducing the grinding force. It is verified that a simulation of the grinding tests using the proposed model can accurately predict critical parameters like forces and machine deflection during plunge grinding operations. Finally, this paper provides a guideline for grinding cycle design in order to achieve the required productivity and grinding accuracy.

Highlights

In the plunge grinding of cylindrical components, the grinding performance is assessed by productivity and grinding accuracy
The generalized plunge grinding system including cylindrical, centerless, shoe-centerless, internal, and shoe-internal grinding is explicitly described and analyzed in terms of system outputs corresponding to the inputs of the plunge grinding conditions
This paper presented the effect of grinding wheel contact stiffness on the plunge grinding cycle and provided guidelines for the design of the grinding cycle

Summary

Introduction

In the plunge grinding of cylindrical components, the grinding performance is assessed by productivity and grinding accuracy. The productivity in the number of finished parts per unit time is determined by the grinding cycle time consisting of the plunge-infeed time and the spark-out time. As the actual infeed to the CNC command has a time delay, the required cycle time is largely affected by the system stiffness. The grinding accuracy is significantly governed by the system stiffness. The actual depth of cut always lower than the command value due to the elastic deflections of the grinding system. These deflections become the root cause of geometrical errors such as size error, profile error, roundness error, etc., in the ground products

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Discussion

Conclusion