Ignoring Conveyor PM Jeopardizes the Entire Pressroom
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In many metalforming facilities, press lines are interlocked to a main scrap conveyor, and if that main conveyor goes down the press lines automatically shut down as well. Even without interlocks, a conveyor shutdown will eventually lead to press downtime. Consider the typical JIT manufacturing scenario in the automotive industry. Should scrap backup cause a body-panel stamping operation to shut down during the morning shift, within 24 hr. the welding lines would likely go down, and then, shortly thereafter, final assembly would cease.
Additionally, excess scrap in stamping and forming operations can affect operator safety, while also putting tools, dies and other equipment at risk.
Imagine Losing $26,000/Min.
The dangers described above are not just hypothetical, as one auto manufacturer with integrated stamping in its main assembly facility can attest. The manufacturer, whose main scrap conveyor crashed and stayed down for two shifts, lost all vehicle production for one shift—it typically operates at a production rate of two vehicles/min. Add to that the cost of the plant’s payroll of $26,000/min. and suddenly maintaining the health of the humble scrap conveyor becomes a critical function.
Keeping scrap conveyors running efficiently starts with conveyor design, which presents an opportunity for new facilities and a challenge for many older plants. For example, one major manufacturer (let’s call it Manufacturer A) designed and installed an extremely long main conveyor with a good layout for operations but a poor layout for maintenance. More than 1000 ft. long, the conveyor runs the entire length of the plant, but the trench in which it sits provides less than 24 in. of clearance on each side.
The plant diligently performed its housekeeping chores and kept the trench clean and clear of material. However, eventually it decided to turn housekeeping responsibilities over to an outside service, whose employees lacked the plant personnel’s understanding of the importance of keeping the conveyor trench tidy—to them it was just another hole in the floor. Over time the trench filled with debris. Along with hindering efficient operation, the debris blocked inspection of the lower rails. As the rails finally wore out, the return strand of belt fell through the frame and became jammed. The press operator, thinking the conveyor was overloaded, continued to increase its speed and eventually caused a catastrophic conveyor failure. It took the plant three weeks to clear away the debris and repair the conveyor.
There Must be a Better Way
In many metalforming facilities, press lines are interlocked to a main scrap conveyor, and if that main conveyor goes down the press lines automatically shut down as well.
Conversely, consider Manufacturer B, a company that designed its stamping and scrap-handling systems with maintenance accessibility in mind, and now follows up with a program of complete inspection and lubrication of the main conveyor every six months. After more than 20 years of operating 24/7, its 800-ft.-long main conveyor still runs with the original belt, requiring only minor replacement belting sections, all due to the company’s robust maintenance program.
Whether or not you have the luxury of a fresh design, Manufacturer B’s course—regular and thorough inspection and maintenance—obviously is the way to go. Sure, conveyor manufacturers build their equipment to be tough, but let’s be realistic. These are mechanical systems subjected to high stress loads, extended duty cycles andeven occasional abuse. As a result, some components must eventually be replaced.
Consider Outsourcing Conveyor Maintenance
A metalformer might add conveyor maintenance to the task list of its maintenance staff, but this may not represent the optimum use of those valuable resources. And, the staff may be highly competent yet lack the specialized skills and expertise needed to keep a scrap conveyor running efficiently. Also, maintenance personnel typically focus on keeping the plant’s more expensive and highly visible production equipment up and running, pushing scrap flow well down their list of priorities. This is particularly true in more recent times, when many companies run lean on maintenance resources, and trained personnel are scarce.
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Further, many shops charge their facilities department, rather than production, with purchasing, operating and maintaining their scrap systems. Facilities personnel may not be focused on maintaining an efficient and lucrative production operation; rather, they might be more concerned with keeping the lights on and maintaining the climate-control system. The same holds true for metalformers who hire a scrap-hauling contractor to install and maintain the scrap system.
For many shops, the best solution is to let the conveyor vendor develop a complete preventive-maintenance (PM) agreement covering inspection and maintenance, and including a service component covering emergency repair and the availability and cost of spare parts.
Conveyors should undergo regularly scheduled PM every six months, and include key measurements of system performance as well as inspection of wear components. Cleaning the conveyor is a key element of any PM activity—removing excess material prolongs belt life and the service life of the bearings and reducer, and ensures that limit switches and other electronic sensors will perform as-designed.
Keep all conveyor components well lubricated and properly adjusted, including the belt chain, roller chain, bearings, take-up screw and reducer. Maintenance technicians also should make any needed adjustments to the conveyor-drive assembly, and should check and adjust (as needed) belt-chain tension. They also should inspect and repair all safety guarding.
Regularly scheduled PM sessions provide opportunities for the service provider to train the plant’s personnel in the essentials of system maintenance. This encourages the metalformer to take ownership of its conveying equipment, and will dramatically reduce the possibility of unplanned downtime. However, breakdowns do occur, and companies are therefore advised to establish PM agreements that include emergency repairs and parts.
Prepare for Downtime to Minimize the Damage
A service agreement allows the metalformer to preplan and budget for a service technician and for the needed replacement parts. Preplanning for conveyor service and parts saves time and money and shields critical maintenance items from budget-slashing routines. Write purchase orders for headshaft assemblies, drive assemblies and other critical components upfront.
Often, depending on life expectancy and delivery times, it makes sense to stock critical conveyor components. This practice can save hours—sometimes days—and allow a timely restart of production, rather than having to watch production grind to a halt and workers and presses standing idle. By stocking critical replacement parts, the metalformer also can avoid paying overtime and other added fees that pile up when forced to expedite the needed parts.
Unlike the typical emergency-repair situation, where the meter is running and the focus is on getting the service technician off the clock and out of the plant as quickly as possible, a service agreement enables the provider to perform some diagnostics on the malfunctioning part. Thus, instead of merely putting a band-aid on the problem and hoping for the best, the metalformer can gain greater insights into the actual strains on the conveying system, and help avert future trouble. It’s likely that a failure in one area of a conveyor indicates other potential problems; additional parts may need to be inspected, repaired, or replaced to keep from simply moving the problem to other, undiscovered areas of the conveyor or operation.
Ultimately that’s what preventive maintenance is all about—averting trouble and eliminating or minimizing the many costs that come in trouble’s wake. Stampers don’t neglect the maintenance of their most valuable presses, why would they neglect the maintenance of their scrap conveyors? Without the scrap conveyor, the most valuable presses aren’t worth much at all. MF
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See also: Mayfran International, Inc.
Related Enterprise Zones: Automation
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