Find out how simple preventative maintenance can keep your presses running at peak levels and head off costly downtime and quality issues.
By Rick Fuqua
Be careful not to use a high pressure grease gun (large pump handle) and then pump with an extreme amount of force as this can sometimes create enough pressure as to distort a bushing to where the machine may not raise and lower freely without removing the grease fittings and relieving the excess pressure.
Other linkages, such and chains and belts, are often responsible for power transfer on presses. Most designers now use timing belts (Figure 5) more often than chains, but chains are still preferable in some instances. Chain wear is described as stretch. The chain becomes longer over time, and it is thought to be from the metal stretching. This does not really happen; instead, each of the holes in the length of the chain where the pins go through grow larger in diameter from wear, thereby lengthening the chain. If you can adjust chain tension, tighten it up. If not, make the necessary replacement. Belts, on the other hand, seem to hold their shape very well and tend to fail mainly from over tightening or from wear due to another mechanical problem.
A worn gearbox (Figure 6) may prevent optimum machine performance. In indexing applications, play in the gear-box may make smooth indexing or movement difficult—if not impossible. In applications where the printhead is lifted and lowered, the wear in the box may allow over or under travel, causing the machine to run roughly or inconsistently. In some cases, the gearbox may be too complex (planetary gears) to rebuild yourself; in other cases, simple boxes with a worm gear may use shims that can be removed to reduce the gap/play that takes place with the wear of the worm gear.
Getting fixed up
A monthly inspection of all knobs, handles, and broken parts is also worthwhile. The extra time spent working around these inconveniences is always more costly than the time, money, and effort needed to replace them. Because today’s machines use a lot of these, they are sometimes easy to overlook until you are setting a job up. If maintenance is performed by a non-operator, he may never notice these broken or missing items. Marking them with a fluorescent sticker or tape may be helpful in remembering what needs attention.
Everything that moves is subject to inspection. Even microadjustments are thought to be bad sometimes when only a lock nut is loose. Operators performing set ups for weeks without the use of a microadjustment may lose a lot of time that could be saved by spending two minutes with a wrench.
This article highlights many of the most common issues that simple maintenance can minimize or prevent. You should consult your equipment rep/tech or your press’s manual should a very specific problem arise. You goal is to keep your press operators in that role and not make them into part-time service techs. Learning even a small amount about your press and how to care for it will allow you to take care
of the things affordably.
Rick Fuqua is the owner of Real Performance Machinery, LLC. He has more than 14 years of experience in graphic arts and 14 years of experience working for screen-press manufacturers. Fuqua holds a teaching degree in graphic communications, a master’s degree in technology education, and 14 screen-printing-machinery patents ranging from complete machine designs of both oval and round presses to flash-cure units, pin registrations systems, and all-over-print platens.
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