Diamond-Wheel Dresser Automates Carbide Grinding

Automatic wheel dressing is essential for successful CNC surface grinding. Amada Wasino's MeisterPro has an accurate and efficient wheel-dressing system, but it doesn't work on diamond wheels. Most solutions for dealing with diamond-wheel corner breakdown are clumsy or expensive, and they've severely limited the use of CNC surface grinding for carbide workpieces. A new diamond-wheel dresser for Amada Wasino's contour-grinding MeisterPro promises to change the picture. A testcut performed for a prospective customer demonstrated the unit's capability.

A disk-drive manufacturer requested tests in both hardened tool steel and carbide. The task was to grind a 0.004" radius onto the edge of a forming punch, tangent to the top and front, to within +/-0.000,050" (50 millionths of an inch) form accuracy. Manual surface grinders produced inconsistent results. The test was to determine if they could achieve greater consistency by means of the MeisterPro's CNC automation.

The tool-steel test was performed successfully, using the MeisterPro's three-point diamond dresser. Then the carbide test was performed, using a metal bonded diamond wheel of 600 grit. This wheel was designed for extreme form-holding capability and is particularly difficult to dress. Amada Wasino's new MRD-80 dresser was applied to the task. The MRD-80 is a compact, self-contained unit that mounts quickly on the surface grinder's magnetic chuck. It dresses the diamond wheel with a one-inch diameter cylindrical silicon carbide dressing wheel, mounted on a spindle with precision bearings at each end. It spins perpendicular to the machine's wheel spindle and strokes its full length along the diamond grinding wheel’s edge by means of the MeisterPro's high speed traversing table. The two simultaneous motions guarantee that the radius on the dressing wheel is always true, and that wear is uniform along its entire length.

The front and rear faces of the diamond wheel used for the testcut are angled at 15 degrees to the wheel's centerline. The MRD-80 dressed a precise 0.0031" radius in the wheel's edge, tangent to both the front and rear faces (see drawing). The positional data for the dressing cycle was picked up automatically by the MeisterPro's CNC, as the operator touched the dressing wheel to the grinding wheel's front and rear faces and to its edge. Using a canned cycle and conversational programming, setup and programming for the dressing cycle took less then five minutes. Dressing time was 14 minutes. The MeisterPro's rigid design and high-speed table suit it perfectly to grinding carbide to close tolerances. Only the lack of an automatic system for dressing diamond wheels prevented it from being an ideal solution for grinding carbide punches and other carbide tools productively. Now the machine has that capability, in the form of a compact, cost effective and easy-to-use dressing attachment.