December 13, 2001
A review of the basic components of a coil handling system which covers servo drive roll feeds, cradles and reels, straighteners and combination units.
Choosing proper coil handling and processing equipment can improve material handling and jump-start your shop's overall productivity improvement effort. However, before purchasing any one component, you should consider four factors:
• Material to be processed
• Line speed
• Floor space requirements
• Material handling methods
Before starting your research, get to know the nature of your material. Most strip or coiled material begins its final processing phase as a slab. Rolling reduces the slab, which grows in length and slightly in width. The rolling process creates high internal stress. When internal stresses are not balanced, the slit material will develop camber, an arching of the material's surface. Camber makes it difficult to track the strip through the entire line, which causes production delays.
Once you know what type of material you're working with, you can consider your options for roll feeders, cradles and reels, straighteners, and safety equipment.
In today's just-in-time (JIT) order environment, many stamping shops are challenged to produce smaller batch runs, which can necessitate more frequent die changes. Therefore, quick die changeover and setup times are critical. Flexibility of major components, such as the coil cradle, uncoiler, straightener, feeder, and press, is also an important factor. Time saved in setup allows you to increase productivity.
On average, roll feeds take less time to set up and are more flexible than traditional mechanical feeds. Accuracies of ±0.001 in. and feed length ranges from 0.001 in. to 999.99 in. are the norm for servo drive roll feeds. Adjusting acceleration and speed parameters allows you to tune the roll feed to a particular job. When possible, slower accelerations and speeds should be used. This promotes increased accuracy and smoother material flow and eases the load on the uncoiling system. This smoother material flow can allow you to process a range of materials, such as painted and polished stock. Another advantage of roll feeds is their ability to adapt and maximize the available press feed angle.
Coil cradles often are combined with straighteners to offer fast loading and quick setup. Coil cradles are suitable for processing thick material, and confining the coil aids in controlling heavy materials. A cradle can be fitted with an overarm and threading equipment to route heavy material into the straightener.
Cradles are not recommended for prefinished stock or soft material, because the coil's weight on the rollers may cause surface marks or deformation.
Coil reels may be an option to help prevent stock deformation. Coil reels support the center of the coil's core and are suited for a range of materials, including prefinished stock. Because of this center core support, a coil reel is limited to the inside diameter range it can handle.
The reel provides precise control of the coil and can be adapted to uncoil or recoil unused material.
Stampers buy straighteners on the basis of the type of material they process, thickness range, and stock width. The primary function of straighteners is to remove coil set and pay out material to the accumulation loop as required for the feeder. Stampers generally position straighteners close to a nonmotorized reel to pull material directly off the coil.
For most materials and flatness requirements, stampers use straighteners with five or seven rolls. Some materials or parts with high flatness requirements may require more rolls.
Combination feeder-straightener units have become faster and more accurate because of the availability of high-performance motors. Their accuracy is now comparable to stand-alone feeders. They are designed to straighten and feed material from a powered uncoiler. They process material closer to the press, with the coil fed directly into tooling.
They can position material accurately and eliminate coil set. Besides saving space, feeder-straightener combinations receive new coil stock through the straightener without opening the straightener head or disturbing the depth settings.
After researching coil handling options, consider safety features. Basic safety features include guarding, integrated controls, sonar loop controls, threading tables and equipment, and coil overarms.
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