Micro Polisher Delivers Better Finish

Energy Machine has incorporated a crankshaft micro polisher with a rigid polishing system that is used during the finishing process of many of its products. Collaborating with the OEM we have engineered a custom polisher that uses solid abrasive tape that wraps around the journal and is backed up with a shoe. This shoe applies equal pressure all the way around the journal while it is being polished. Instead of rubbing a rotating abrasive belt against a rotating journal, the abrasive tape remains stationary and is clamped against the journal as the crank turns.

The tape makes contact at four points producing a more even and consistent surface polish. The tape is then advanced about an inch for the next journal, and so on until all the journals have been polished. A lubricant is also used with the tape to help wash away debris.

Traditional polishing techniques use a manually operated belt sander that can alter the geometry of the journal, slightly creating some taper or out-of-roundness. If the surface finish on the crankshaft journal is not right or the geometry is slightly off, the bearings will suffer the consequences when the crankshaft is put into service. While polishing in one direction and then automatically polishing in the opposite direction, the micro polisher leaves a better finish and eliminates microscopic peaks that can cause premature bearing failure.

Compared to belt polishing, which may remove .0002" to .0005" or more inches of metal from a journal depending on the belt grit, length of polish and pressure exerted by the operator, tape polishing removes almost no metal. The abrasive on the tape is very fine. A 15 micron tape abrasive is similar to a #600 belt grit. Polishing a crank with a ground finish of 12 RA for 15 seconds with the 15 micron tape, for example, can improve the finish to 7 RA or better.