According to its developer, continuous-belt microfinishing is "faster than anything else out there."
At the heart of a continuous-belt microfinishing system is an abrasive belt spinning at 3,000 rpm and moving between 5,000 and 7,500 sfm to remove about 200 µ of stock in 10 sec. The system, says its developer, Nagel Precision of Ann Arbor, Mich., is faster than stone and tape microfinishing.
And as such, the company expects this new technology to have a significant impact on the production of transmission components and a host of other load-bearing journals and seal surfaces in automotive, aerospace, and hydraulic applications.
The system's belt mounts on three rollers configured in a triangle pattern — one roller drives the belt, another is a tensioner, and the third is a contact roller. As the belt engages the part via a pneumatic slide, the hardness of the urethane contact roller determines the level of belt contact. Softer rollers mean more contact, and vice versa.
In addition to the belt's speed, its abrasive type also contributes to the system's overall quickness. Developed by Norton Abrasives, the belt has a more consistent structure with its abrasives embedded in column-shaped sections that form the complete working surface.
These columns break down or reduce in height while contacting the workpiece. As this happens, new abrasive crystals surface to always expose the part to a fresh cutting surface.
The continuous-belt system removes chatter marks and corrects part roundness to a degree. But because it does not pinch on the part, lobing is not corrected. "However, this does not hold the technology back," says Sanjai Keshavan project manager at Nagel Precision, "because 70% of the parts being microfinished or superfinished require no lobe correction." Instead, most parts are hard turned or ground prior to microfinishing. These processes easily eliminate most lobing, adds Keshavan.
On the plus side, perishable tooling costs of a continuous-belt system are low — up to a 75% savings per part. This is because the system is fast and highly productive and its belts don't chip or break. Operating conservatively, a continuous belt lasted for 1,000 pieces when finishing 2-in.-diameter, 4-in.-long hardened-steel parts.
A Nagel continuous-belt system works in both cellular (low-volume, high-changeover) and line-type (high-volume, low changeover) manufacturing environments. It can include multiple stations, in-process size control, and part-transfer automation.