Instrumented Spindle Improves Manufacturing of Optical Materials

Lion Precision and Professional Instruments, St. Paul, Minnesota

Monday, January 01 2007

For example, the instrumented spindle approach can be used to explore the fluctuations in force during ultra-precision grinding of silicon wafers. The crystal anisotropy of silicon results in significant variations in the material properties depending on how the grinding wheel is oriented with respect to the crystal lattice. In the waterfall plot in Figure 1, we see a series of grinding force spectra calculated from force data collected during a single pass of the diamond grinding wheel over a rotating (100) silicon workpiece. The workpiece spindle speed is 500 RPM (8.3 Hz) and appears, along with many harmonics, in the figure during the contact of the silicon workpiece with the wheel. The fourth harmonic (33.3 Hz) is particularly strong because of the cubic (100) crystal lattice structure.

Also seen is the significant fluctuation in the grinding force (Figure 2) at the frequency of the grinding wheel speed (3,600 RPM or 60 Hz). As additional parts are ground with this wheel, the 60-Hz wheel speed component will continue to grow as the wheel wears and breaks down. Eventually, the wheel will have to be redressed, at which point the 60-Hz component is again small compared to the workpiece rotation and its harmonics. The spindle provides information vital to proper wheel selection, wheel preparation, and other grinding parameters.

The instrumented spindle is a product of a university/industrial consortium including partners at Penn State University, George Washington University, Professional Instruments, and Lion Precision.

This article was written by Harry Cherkinian, senior counsel, for Lion Precision and Professional Instruments. For more information, contact Mr. Cherkinian at This e-mail address is being protected from spambots. You need JavaScript enabled to view it , or visit http://info.hotims.com/10960-203.