Danobat PP 300

Peel grinding uses a very narrow CBN wheel (3–10 mm wide) running at extremely high peripheral speed (80–120 m/s) to grind complex shaft geometries by following a CNC-programmed path — similar to how a turning tool traces a profile on a lathe, but using an abrasive wheel instead of a cutting tool. Conventional cylindrical grinding uses a wide wheel (40–150 mm) to plunge-grind individual diameters one at a time, requiring the machine to reposition between each feature. Peel grinding eliminates these repositioning stops — the narrow wheel traverses the entire shaft profile in a continuous programmed path, grinding all features (diameters, tapers, shoulders, radii) in one pass sequence. Peel grinding excels for complex shaft profiles but requires CBN tooling and high-speed spindle capability not present on conventional cylindrical grinders.

The PP 300 can grind any shaft geometry expressible as a 2D profile in the XZ plane with optional B-axis tilt for tapers: straight OD diameters, stepped diameters, shoulders, tapers (using B-axis swivel), convex and concave radii (CNC interpolated), undercuts, and relief features. Splines and threads cannot be peel-ground (require specialized spline or thread grinding machines). The machine handles workpieces up to 700 mm in length and 300 mm swing, covering most automotive gearbox shafts, steering shafts, and driveline components encountered in passenger car and light commercial vehicle production.

The B axis is the rotational axis of the grinding wheelhead — tilting the wheelhead pivots the wheel spindle in the XZ plane, allowing the wheel to approach the workpiece at an angle. For taper grinding, the B-axis swivels the wheel to match the taper angle, enabling the narrow peel wheel to grind the taper face squarely rather than on an edge. For shoulder grinding with undercuts or relief features, B-axis angulation allows the wheel to contact recessed features that a fixed-axis wheel would not reach geometrically. The ±30° B-axis range on the PP 300 covers the majority of taper angles encountered in automotive shaft applications.

Peel grinding's narrow wheel contact generates heat in a very small, rapidly moving zone along the workpiece rather than a wide stationary contact zone as in plunge cylindrical grinding. The localized heat dissipates quickly into the surrounding workpiece material and coolant before it can soak into a deep heat-affected zone. This reduces the risk of grinding burn in hardened steel compared to aggressive plunge grinding with a wide wheel. High-speed CBN grinding also changes the chip formation mechanism — at 120 m/s wheel speed, the abrasive grain interaction produces thin chips with lower cutting forces and lower grinding zone temperatures than conventional abrasive at 45 m/s.

Cycle time for peel grinding a typical 4-speed gearbox input shaft (5–7 diameter steps, 400 mm length, 30–60 mm diameter range) is typically 3–8 minutes depending on stock removal, number of features, and required surface finish. This compares favorably to the 15–25 minutes required to grind the same shaft on multiple conventional cylindrical grinder setups (setup, grinding, and measurement time for each diameter). The break-even versus conventional grinding in terms of capital investment typically occurs at production volumes above 5,000–10,000 parts per year for complex shafts — below this volume, the flexibility of conventional grinding may be more cost-effective.