Investigations of the Existence of Threshold Forces in Diamond Roll Plunge Dressing of Grinding Wheels
Doug Geiger and Bob Hahn at the controls of the Hahn Force Adaptive Grinder
Dr. John Kummailil, Ph.D, WPI’04
Douglas Geiger, BSEE, WPI’02
Dr. Robert Hahn, Ph.D
Prof. Christopher A. Brown, Ph.D
Investigate the existence and role of threshold forces in diamond roll plunge dressing of grinding wheels for internal production grinding operations.
In some grinding processes, the grinding wheel is periodically dressed by plunge feeding the wheel into a diamond roll. It is commonly assumed that the roll cuts the wheel upon contact and produces a true-running, cylindrical, dressed wheel. However, if a threshold force does exist, the amount of material removed will be lower than it would be if it did not. This could affect the dimensions of parts the wheel subsequently grinds, as well as the sharpness of the dressed wheel. In particular, internal production grinding operations on low rigidity systems may exhibit size, taper and out-of-round errors.
Figure 1: 13x Zoom of Abrasive Grains on Typical Vitrified Bonded Grinding Wheel with Aluminum Oxide grains
Based on the work done to discover threshold forces in force-controlled grinding, the normal force on the grinding wheel during the dress cycle is recorded along with the position of the dressing roll from a linear encoder attached to the cross slide. Due to the significant noise in the force signal, several filtering techniques were developed, and tested to ensure noise rejection with minimal attenuation of actual force signal. The results of the filtered applied to the force signal is shown below on the left, along with the raw encoder readings and calculated material removal rate.
Figure 2: Raw force sensor voltage (top left) and filtered force output (bottom left), and linear encoder readings (top right) and calculated material removal rate (bottom right).
Hahn Force Adaptive Grinder (Model 1, Serial Number 0001)
Pope Wheel Head: 5 HP, 3600RPM
HBM Spider8 16-bit Data Acquisition System
* Kamen Hall-effect displacement sensors
* Heidenhain Linear Encoder
Figure 3: Schematic of the Hahn Force-Adaptive Grinder
By performing wheel dressing cycles at a number of feed rates (500um/min - 9000um/min), the material removal rate per unit width of wheel (Q’) can be graphed against the measured normal force per unit width (F’), to develop the Abrasive Removal Parameter (ARP). This is the analog to the Work Removal Parameter developed for the grinding operation. There appears to be two distinct parameters - with a transition in mode of abrasive removal at around 3000 µm/min.
Figure 4: Normalized Material Removal Rate vs. Normalized Force for a number of feed rates
Further investigation is warranted into the nature of the change in mode of abrasive removal (attritious wear vs. micro-chipping), and their role in optimizing the dress cycle to produce sharp, chatter-free wheels. This change in mode should affect the roughness of the grinding wheel.
Figure 5: 3-D rendering of grinding wheel replica taken after dress with 500 µm/min feedrate - measured by scanning laser microscope
Measurement and Analysis of Forces in Diamond Roll Dressing. John Kummailil, Douglas J. Geiger, Robert S. Hahn, Christopher A. Brown. Submitted to the Journal of Manufacturing Processes, May 2004.Maintained by email@example.com
Last modified: September 28, 2007 10:52:37