Wear Compensation Ensures Accurate Wheel Contours

The moniker "black art" is sometimes applied to seemingly arcane manufacturing processes in which success depends on the input and knowledge of skilled machinists. Grinding is typically perceived this way, but one manufacturer is trying to change that. By removing variables that require operator attention, profile and surface grinding technology supplier Blohm Jung aims to turn this art into a science.

A prime example of these efforts is the company’s GEOID diamond-wear compensation technology for wheel-dressing systems. This new software, developed in concert with the Georg Simon Ohm University in Nuremberg, Germany, automatically compensates for wear in diamond dressing tools. Designed primarily for manufacturers involved in low-quantity, high-tolerance profile grinding work, the system is said to ensure accurate wheel profiles, limit downtime and reduce procurement costs by prolonging the service life of dressing tools.

"An operator who notices vibration in a single-point dressing tool, for example, might turn the diamond a certain number of degrees in the holder to get a better cutting surface. GEOID takes that completely out of the picture," explains Phil Wiss, sales manager at Blohm Jung (the company is represented in the Untied States by United Grinding of Miamisburg, Ohio). "We’ve taken the operator know-how and put it into the control."

When generating programs to produce the desired grinding wheel profile, most CAD/CAM systems use tool radius correction algorithms to account for the shape of the dressing diamond. However, these systems typically account for only the shape of the unworn diamond. With repeated use, wear alters the profile of the diamond’s cutting edge. This geometry error transfers to the grinding wheel, and consequently, to the workpiece.

GEOID articulates the diamond dresser around a probe to determine its exact topography with micron accuracy. Rather than probing numerous points along the diamond’s contour to estimate its radius, GEOID’s constant-contact scanning ensures an exact measurement. This data is then digitized and fed into the machine control, which corrects for irregular geometry by adjusting the alignment of the worn dresser against the grinding wheel to produce an accurate profile. As such, a swivel-type dresser is necessary to take full advantage of the system, Mr. Wiss says.

Measuring dressing tools on the machine makes the system faster and more accurate than other typical wear compensation methods, such as the use of shadow graphs that determine contour errors by overlaying the ideal shape of the tool over the actual geometry, Mr. Wiss notes.

The system is designed for various dressing systems that are available with the company’s Vario range of profile grinders. These include the PA37K head dresser, a star-shaped unit that accommodates as many as six individual diamonds or driven diamond wheels. Mr. Wiss notes that GEOID saves time when preparing these dressing tools—a star with six diamonds is ready for use in 6 minutes, while a diamond wheel takes 10.