CONSIDERATIONS PARTICULAR TO COIL STOCK (Part Two)

In this second part of our back-to-basics series on coil processing equipment, we examine the various conditions or issues that can impact the effective feeding of the coil.

In Part One of this back-to-basics series (Metal Forming & Fabricating, September 2011), we explored the various material conditions that are unique to coil stock and how understanding each of these potential issues will help you avoid or deal with them to keep your stamping operations at their best. Now we examine the conditions that can impact the effective feeding of the coil.

MATERIAL GUIDING
Coil stock handling and feeding equipment cannot “feel” and “compensate” for misguided material the way a person can in a hand fed operation. Alignment of coil handling equipment to each other and to the dies is critical to a smooth material flow. To accomplish this, coil handling equipment relies upon a series of edge guides to maintain the material within workable bounds.

These are guides, not barriers – they are not a substitute for proper alignment of the equipment. Overworked guides result in damage to themselves or the material. Even if they can withstand the effects of misalignment, the resultant condition of the material and damage to the equipment will decrease operation productivity.

DIES
Dies equipped for hand feeding seldom accept coil stock without some modification. The tooling must address the intricacies associated with guiding the material as well as accommodate the mill tolerances and material conditions inherent in coil.

Provisions must be made within or between the die and related equipment to avoid buckling and sagging of the automatically-fed material. Provisions to accept tolerance camber or crown in the stock must also be made within the die. Progressive dies also need to be equipped with suitable pilots to eliminate progression error.

SLICK MATERIAL FINISHES
Any number of surface conditions can produce a slick finish, which severely inhibits the ability to feed coil stock accurately. Proper selection of feeding equipment suited to work with slick material finishes, and die designs with tolerances that compensate for these conditions will improve production. Galvanized material also warrants special attention. As a guideline, the coil steel should be lubricated after the feeding device.

SENSITIVE OR CRITICAL SURFACE FINISHES
Many materials have surfaces particularly susceptible to marking or distortion. Pre-painted, polished, and non-ferrous metals are all considered sensitive materials. Other materials can be so critical in appearance that even a normal or tough surface has to be processed with special care. Provisions can be made in the coil handling equipment as well as in the dies to accommodate these issues. Attention must be given to properly finish rolls and grippers for special material protection, to avoid touching materials with control devices, or to grip in non-critical areas.