Eliminating or minimizing rolling problems
The hardness, yield strength, and tensile strength must be as specified by the section drawing. Material suppliers usually provide this information on request. Excessive camber and slitting burr are not acceptable.
Setting up and Troubleshooting
The setup operator should install the tooling, tighten the nuts, and parallel the shafts. Then he sets up the tooling according to the print and gauges it for the incoming strip. Using a mirror helps ensure proper lineup. Shoulders may be checked with a straightedge and gaps with a feeler gauge.
After the stock is run into the pass, the gaps at the shoulders (flanges) should be checked and fine adjustments made to remove any play in the vertical adjusting screws. This ensures that the rolls are set as the designer intended them to be set.
The cross section is checked one pass at a time by running out a 2- or 3-ft. section and checking for twist, slivers, and other defects. Doing this at every pass verifies proper roll lineup and eliminates potential problems at each pass.
The first goal of troubleshooting a roll tooling problem is to identify it. Saving a strip from every pass and comparing to the design enables analysis and makes it easier to determine where the problem lies.
Overbend. The tooling has markings that identify the passes that overbend the strip. These markings allow easy identification of overbending passes that may require adjustments and modifications.
Marking. Some marking can be reduced or eliminated by providing more running clearance, which improves the lead-in radius. Chrome plating the tooling or adding idler rolls before the pass that causes the defect also can help to reduce the amount of marking.
Other strategies include allowing the top drive to float (by disconnecting the drive gear if possible) or remaking the roll so that it runs on a hub and finds it own speed.
Dimensional Problems. Some dimensional problems can be fixed with shims. The first step is to analyze the product's dimensions to determine the pass that can be adjusted most easily to solve the problem, bearing in mind that the centerline of the tooling must remain constant. It may be necessary to cut the back spacer if the inboard side of the centerline is shimmed. The outboard bearing sleeves usually have enough play for some small shim adjustments.