Page 56 - MetalForming September 2013

Tooling by Design
By Peter Ulintz
Press-Shop Maintenance
Tooling Technology
There are four types of mainte- nance that can be performed on stamping dies and pressroom equipment: reactive, preventive, pre- dictive and proactive. It is important to understand the differences between them, to avoid using the terms inter- changeably (or incorrectly) and to be able to assess the effectiveness of your maintenance operations.
Reactive Maintenance is nothing more than reacting to failed tooling or equipment by restoring its intended function. It is analogous to a tire on a car being very low on air. The owner observes the low-air condition and adds compressed air to the tire to restore its designed pressure level.
Many metalformers rely solely on this reactive maintenance—acceptable in limited circumstances, but gener- ally a costly way to operate. Break- downs are unpredictable, and labor and material resources may not readi- ly be available. You may have to pay premium rates for overtime and to expedite product to the customer. Downstream processes may be delayed, and tooling and equipment life will suffer.
An operation that solely relies on reactive maintenance generally expends
Peter Ulintz has worked in the metal stamping and tool and die indus- tries since 1978. He has been employed with the Anchor Manufacturing Group in Cleveland, OH, since 1989. His back- ground includes tool and die making, tool engi- neering, process engi-
neering, engineering management and product development. Peter speaks regularly at PMA semi- nars and conferences. He also is vice-president of the North American Deep Drawing Research Group.
Peter Ulintz pete.ulintz@toolingbydesign.com www.toolingbydesign.com
more labor and material resources than if they had a preventive-maintenance program in place.
Preventive Maintenance (PM) com- prises formal procedures and tasks that help prevent unplanned breakdowns and ensure that equipment and tooling
operate properly. To establish PM tasks and intervals, metalformers consult owner’s manuals, industry standards and guidebooks, and also must con- sider environmental conditions, equip- ment criticality, impact on safety and past experience.
Examples of PM tasks include changing lubricant, replacing con- sumable parts, and cleaning, adjusting, inspecting and testing equipment. In the automobile-tire analogy, PM might include checking and adjusting air pressure at each oil change.
A good PM program keeps equip- ment running in good condition and helps to extend the period between breakdowns. It also helps managers plan and budget for replacement parts, and schedule the necessary work at predictable and convenient times.
While PM is not the optimum main- tenance program, it does provide sev- eral advantages over a purely reactive
program. Performing preventive main- tenance extends the useful life of tool- ing and equipment. Tooling and equip- ment generally will run more efficiently when maintained properly. This trans- lates into cost savings. Preventative maintenance alone will not prevent catastrophic failures, but it will decrease the number and frequency of failures.
Adverse consequences of PM:
• Over-maintenance, where unnec- essary or ineffective maintenance is performed, such as adding air to a tire at every oil change when the tire does not require additional air.
• Under-maintenance, where fail- ure conditions are not identified or corrected in a timely manner, leading to the consequences described for reac- tive maintenance.
Predictive Maintenance (PdM)
improves on PM by using actual equip- ment-performance data for scheduling maintenance tasks. PdM tasks data will indicate deteriorating conditions or rate-of-decay. With this strategy, peri- odic or continuous monitoring detects the onset of wear or degradation. The information helps engineers predict potential problems and determine the best time for maintenance.
Today, most automobile tires include manufacturer-installed pres- sure sensors to sense when tire pres- sure falls below a critical level, or when the pressure differential between the tires exceeds a prescribed limit. The sensors send this data to a computer control, which illuminates a low-tire pressure indicator. In this way, the vehicle operator or mechanic can adjust tire pressure based on data rather than on a preset time interval, avoiding over- and under-mainte- nance.
PdM and PM represent very differ- ent strategies, even though many peo-
54 MetalForming/September 2013
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