Important Steps For Troubleshooting Your Roll Forming Stock (Part 2)
One sticky problem faced by cold roll forming operators is “Pickup”. This consists of small particles of metal picked up from the stock by the rolls and other tooling. The cause? Friction mostly. The particles accumulate and stick tightly in the roll surfaces, especially in the inside corners, making it impossible to obtain shapes that meet close tolerances.
The kinds of stock which most frequently attract Pickup are stainless steel; galvanized, painted, or otherwise coated stock; also uncoated aluminum. Low carbon, cold-rolled steel and hot-rolled, pickled steel cause the least trouble.
Initial steps to be taken involve relieving the pressures or enlarging clearances in locations where the pickup occurs. But these might not work when the stock is too soft, if high pressure is needed from rolls, guides, or dies to obtain good profiles, if material is difficult to form, or when the profile is a complicated one. Here are some problem-solving ideas:
Make sure your coolant system is in good working condition and that circulation is free, ensuring a full flow to the tooling in every pass. The coolant reservoir, including the strainer, should be cleaned and flushed out whenever the color of the coolant becomes too dark, indicating presence of too much foreign matter.
Forming pickup and other troubles may be caused by stock which has rough, ragged edges. The best remedy is to use stock which has been properly slit, with sharp cutters, and properly set to insure clean straight edges, free from burrs.
These two quick Pickup avoidance ideas are a good start but only cover a small slice of a much bigger surface, from passivation and pickling all the way to electrocleaning and electropolishing. Don’t hesitate to contact Formtek, Inc. for the latest information.