Dress in the front or rear?

Dear Doc: We have two dressers on our machine — one mounted behind the wheel and one mounted on the bed. Some operators like the one behind, and some like the one on the bed. Which do you prefer?

The Doc replies: My answer is the always popular “It depends.” There are four factors to consider, probably in this order: stiffness, cycle time, chatter and alignment. Let’s take them one by one.

First, rear-mounted, or top-mounted, dressing units consistently have less stiffness than those mounted on a bed. This may not be a problem. If it is, several issues can arise from a lack of stiffness.

Chatter could occur during dressing. With plunge rolls, this puts straight-line chatter into the wheel, which ends up being imparted into the workpiece in the form of straight-line chatter. With traverse-style dressing, this puts a “fish scale pattern” into the wheel, which imparts a fish scale pattern into the workpiece.

Longer dwell times could be required when rotary plunge dressing to get the final form, which can dull the wheel.

There could be deflection in the dresser, which can result in a taper in the wheel and therefore the part.