It helps to understand the nature of the input material and how it got that way. Most strip or coiled material begins its final processing phase as a slab. The slab was reduced to the final gauge by rolling, then wound into a large coil. It has grown greatly in length and nominally in width. High internal stresses in the material are often created during the rolling process.
The internal stresses often vary from the outer wraps to the inner wraps and from the center to the edges. The strip is unwound, slit to width and rewound. Center slit material often yields the best material, edge cuts often yield the worst. When the internal stresses are not balanced, the slit material will have camber. The greater the stress imbalance, the worse the camber. In some instances, additional processing will be necessary to balance the internal stresses and eliminate camber. Poor material is a leading cause of difficulty in tracking the strip through the entire system. Camber problems will consume your profits!
To avoid many coil-handling problems, insist on quality material, reject that which does not meet your standards, and use the proper uncoiling system.
Selecting the proper options for your system will provide big paybacks in productivity gains.
- Eliminate waiting time for overhead cranes or lift trucks by installing coil cars and coil storage ramps Coils can be staged when convenient and are ready when the system needs them
- Reduce handling time and increase safety with coil clamping arms and threading equipment
- Use dual spindle uncoilers when feeding high demand systems like rolling mills or systems using partial coils
- Use loop controls to smooth the uncoiling – straightening process, maintain proper loop geometry, and deliver more consistent material to the feeder
- Use a side shift base on the uncoiler to allow easy coil alignment and adapting for camber during processing
- Purchase the best material possible to ensure good quality, consistent parts
Many factors should be considered when determining the optimum arrangement.
• Plant space available
• Crane capacity
• Lift truck capacity
• Mark sensitivity
• Material thickness
• Material width
• Material strength
• Coil handling: – load and unload partial coils, or run full coils to end
• Coil weight
• Coil inside diameter
• Coil outside diameter
• Production required: -feed length, speed, feed angle, feed time
• Process type: – progressive stamping, blanking, blank and transfer, cut to length, pre-punch, etc.