October 11, 2001
The installation procedures that can help to prolong the life of coil cradles and reels are outlined in this article. Specific steps to maintain cradles and reels are also included.
All stamping and forming operations outside of the powder or forging industries begin with coiled steel. In many fabricators' plants, the decoiler, payoff reel, recoiler, tensioner, or other coil handling equipment require constant maintenance.
The nature of the installation determines both the productivity and longevity of coil payoff and uptake equipment. Several factors must be addressed during installation to ensure that the setup provides both stability and proper alignment.
Although lighter units are self-contained and do not require separate foundations, a coil handler is subject to high vibrations during use. Grommets are used to floor-mount and level smaller cradles and reels. Isolation mounts should be considered when a separate foundation is not planned. Engineered foundations are clearly preferred for units handling coils weighing 10,000 pounds and more. The OEM should be contacted for further recommendations.
The leveling process must be exact and repeatable. It must be possible to check and adjust the equipment as necessary to maintain proper leveling. Out-of-level cradles and reels can cause problems that result in damage to material and equipment.
Alignment is the most critical requirement of any coil equipment. Centerlines must be established for 3-D alignment between the cradle or reel and the processing equipment. Product quality, tooling wear, maintenance problems, and safety are all affected when loss of alignment occurs. Laser alignment instrumentation has simplified initial installation and periodic evaluation.
Guarding is used to eliminate safety hazards and machine damage. Equipment should be guarded to ensure that both personnel and machinery are properly shielded from harm. Modern guarding includes photoelectric as well as standard hard guarding options.
Cradles are constantly subjected to coil-related damage. The combination of improper operation and normal wear and tear on a cradle can create maintenance headaches. Preventive maintenance and inspection should take place in several areas.
High-quality antifriction bearings that can be lubricated automatically or manually should be used. Coil damage and personal injury can occur when bearings freeze up and impede proper coil movement. Each bearing should be inspected for proper operation and smoothness either monthly or bimonthly. Damaged or questionable bearings should be replaced immediately. Manually lubricated bearings should be lubricated daily. Bearings that constantly fail should be replaced with higher-capacity ones, or coil weight limits should be lowered.
Frames are another area that require careful inspection. The frames should be fabricated rather than held together with fasteners because, under normal load conditions, cradles endure so much vibration that fasteners can fail, causing the frame to become unstable. Periodic tightening of all fasteners with the proper torque is essential.
Additionally, frames should be inspected every six months for squareness and alignment and damage to plates, welds, or structure. All welds should be dye-penetrant tested at least every two years to ensure the product's integrity. When damage is found, repairs should be made immediately.
Other important components to inspect are the rollers, which are the support system of the cradle. The original equipment should be hardened and precision-ground to ensure the longevity of the cradle and that the best product will be produced. The surface finish of the rollers should be examined to eliminate material scarring. Monthly checks to make sure the rollers are parallel are critical to ensure that material feeds properly and to eliminate telescoping.
The motors should also be examined regularly. Yearly inspections of motors should include pulling covers and checking windings and bearings. Motors should be clean-baked and dipped every five to 10 years or sooner if they are operated in highly contaminated environments. All interlocks, switches, and safeties should be examined thoroughly every six months. E-stops must be checked daily.
Because numerous types of reels are used for payoff and uptake, it is difficult to list all maintenance requirements. However, reel maintenance is critical because if a weighty coil drops, it can seriously hurt employees. Reel components that must be inspected include the following:
1. Bearings. Because a reel supports a coil on aligned antifriction bearings, regular bearing maintenance and inspection are at the heart of any reel maintenance program. Signs of damaged or worn bearings include heating, pitting, coil runout, reel arbor wobble, or lopping sounds as the reel runs.
Bearing lubrication should be checked daily. The bearings should be inspected visually every six months or more often if recommended by the OEM.
2. Alignment and Leveling. This should be inspected at least every six months. When processing thin-gauge material, alignment and leveling checks should be increased to monthly. Because they pose a hazard to employee and machine if they cannot support a reel, any loose or damaged foundation bolts should be repaired immediately.
3. Motors and Electrical. The inspection procedures for motors and cradles discussed previously can be followed when examining the motors and electrical system.
4. Shafting and Arbor. The reel shafting is the most critical support element on the coil reel. It supports not only its own weight, but that of the coil, which can exceed 50,000 pounds.
Simple tests performed regularly can determine the condition of the reel shafting. Setting up a dial indicator on the end of the reel (outboard) to the segments (overleaves) or to the shafting itself will confirm the reel's runout or TIR.
Runout indicates bent or damaged shafting, possibly preceding a catastrophic failure. If the reel exceeds 0.015-inch runout, it should be examined thoroughly to determine the cause. An annual or semiannual inspection of the shafting should be performed to determine if cracking, wear, or distortion has occurred.
It is especially important that no welding take place on the reel shaft without properly following American Welding Society (AWS) or equivalent standards for repair welds.
5. Segments and Overleaves. Segments and overleaves should be tested for runout in the same way that the arbor shaft is tested. In addition, segments should be examined for flatness from end to end to ensure proper segment-to-coil contact. Out-of-flat segments of more than 0.015 inch should be repaired or replaced. Segments should also be checked with an indicator for both vertical and horizontal movement. Loose-fitting segments with clearances of more than 0.020 inch vertically or horizontally should be removed and repaired immediately. This inspection should take place at least every two months.
6. Actuation Devices. Pull rods, wedges, linkage, and cylinders often cause sticking coils or nonactuating reels. These components should undergo thorough annual inspections for wear, breakage, or damage. Sticking coils and nonactuating reels should be serviced immediately.
7. Brakes/Tensioning Devices. Brakes are the simplest, but often the most overlooked, devices on a reel. If the brakes are subject to high temperatures, they must be cooled. The brake lining should be inspected weekly. The lining should be replaced when it falls below the minimum thickness indicated by the OEM.
On high-maintenance brakes that must be replaced constantly, modern tension brakes can be retrofitted to the existing reel. These tension brakes are cooled hydraulically, pneumatically, or with water systems.
The maintenance and upkeep of cradles and reels keep these capital investments a profit center that few consider. Often, presses, slitters, press brakes, or roll formers receive the attention and cost justification for upkeep and modernization. However, the coil payoff and uptake are the machinery without which the automatic coil-fed operation will not run. Returns on proper planning in procurement, installation, and upkeep of this machinery are as important as the material they handle.
Plant engineers must take seriously their role in company profit by caring for cradles and reels properly.