Describing cold roll forming as a high precision operation requiring exceptional accuracy is an understatement, without question. Obtaining “Good Stock” for successful forming operations is an absolute necessity when thousandths of an inch can make a difference. Be on the safe side, and always follow these initial steps to ensure your stock is in good shape when you’re ready to roll.
Gauging Stock
Get out your micrometer gauges for width and thickness, and be sure to measure in many different places along the entire length of coils and cut length sheets. Check for uniformity. Be aware that width is subject to the greatest variations.
Sorting Stock
Sort into three stacks: 1. Coils and sheets too far off in size to be used, 2. Undersize stock, 3. Oversize stock.
Stock Too Thick
Gauging stock for thickness is crucial because both overly thick and overly thin stock is not a rare occurrence. When stock is too thick, it can result in stalling of the motor, excessive wear, damage to bearings, bearing boxes, adjusting screws and other vital parts. This results in your needing to make repairs and replacements before production can be resumed.
Stock Too Thin or Narrow
In these cases, extra time will be needed to re-adjust tooling pressures and alignment to compensate for the differences. In many cases, it can still be very difficult or impossible to produce satisfactory profiles with close tolerances. Scrap losses may also be excessive with thin stock.
Stock Too Wide
Can stall the motor and distort the edges of the stock when they’re pressed back by the roll flanges and stops. The wear of the rolls in these areas can be excessive. The shape also will tend to stick in the straightening die or cut-off, resulting in similar distortions to what happens during feeding.
Non-Uniform Stock
Always check for non-uniform width or thickness in the same coil, in individual sheets, or in the same shipment. This is important for products that require great accuracy. With non-uniform stock, re-tooling may be necessary to achieve a quality final product.
Stock Too Hard
Splitting or cracking along sharp or small-radius bends in the profile is likely. This is usually manageable, but only after special care and attention, including additional roll passes and possibly the use of special materials for roll tooling.