The skyline’s the limit for this grinder

Good news for component manufacturers looking for more shape options from the grinding process: The skyline is the limit for a grinder featuring unique technology for turning out nonround parts.

Developed by Le Landeron, Switzerland-based machine tool manufacturer Rollomatic SA, the ShapeSmart model NP50 is a five-axis “pinch/peel” grinding machine. The NP50 can grind carbide, high-speed steel and stainless steel to produce cylindrical components with excellent surface finish and concentricity, according to the company.

The pinch/peel process was used to grind these nonround carbide punches resembling buildings along New York City’s skyline. Image courtesy of Rollomatic

Rollomatic invented pinch/peel grinding, a process that simultaneously applies both a roughing and finishing wheel to a part. As a result, roughing and finishing are completed in one pass, eliminating the need for two separate processes and reducing cycle time. The two grinding wheels run on separate spindles and are positioned by independently controlled CNC linear slides.

In addition to cylindrical grinding, the NP50 offers a nonround pinch/peel grinding process designed to ensure form accuracy, tight tolerances and low runout.

“You have no deflection because you are applying the wheels to two sides of the part,” said Eric Schwarzenbach, president of Mundelein, Illinois-based Rollomatic Inc., the company’s North American headquarters. “If you only use one wheel, you are deflecting (the workpiece), so you can’t do long and thin parts.”

Common nonround shapes that can be made by the NP50’s pinch/peel process include ovals, squares and rectangles. He said the process also can produce “weird” shapes. For example, one of Rollomatic’s magazine ads shows a group of carbide parts that look like the buildings along the New York City skyline. These parts all were made in one chucking by the NP50, he said.

The key to grinding nonround parts is software that positions the grinding wheels in relation to the clamped workpiece.

To make a square part, for example, “the wheels move in and out four times and the software tells the wheels exactly where to be,” Schwarzenbach said, “so the finished part looks like a square in the end.”