Save time through clever dressing

Dear Doc: We grind forms into steel and nickel alloys. We use a plunge diamond roll to dress the form into the wheel with a unidirectional +0.8 speed ratio to make the wheel sharp. However, when we need to dress in a new 1A1 wheel, it takes forever. If we increase our plunge speeds, the dressing operation starts chattering. Is there a way to speed this up?

The Doc replies: Yes. Simply switch the direction of rotation of your dressing roll to dress anti-directional during that dressing-in portion — in your case, with a V_dresser/V_wheel = -0.8 speed ratio. This can reduce dressing forces by about one-sixth of what they were originally, allowing you to plunge faster and get that wheel dressed in quicker without any increased risk of chatter.

Shown are measurements of normal forces in dressing done by grinding expert Barbara Linke. Anti-directional gives much lower dressing forces than unidirectional. And lower forces mean lower chatter risk and spindle deflection. We can take advantage of this fact to reduce the time it takes to dress a form into a new wheel. Image courtesy of J. Badger

Just make sure to go back to your regular V_dresser/V_wheel = +0.8 ratio before going to grind. That’s because going anti-directional makes your wheel dull, and you’re doing the right thing in going unidirectional to make the wheel sharp for grinding. Leave around 0.2 mm depth on the wheel before switching back to unidirectional to clear away that residual dullness on the wheel.