Long-term care

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by Andrew McCarlie

Preventive maintenance will extend the life of your fabricating equipment investments


When sheet metal fabrication machines are first purchased, regular maintenance schedules and operator training are integral elements of the process.

Fast-forward three to five years and the enthusiasm for regular maintenance has often diminished.

Tight production deadlines often interfere with maintenance schedules, but both are interdependent upon one another.

A good example of this is the oil service interval required on hydraulic powered machines. Clean hydraulic oil of the correct composition is vital to the smooth operation of these machines. Failure to replace this oil at the manufacturer’s specified intervals, particularly when the working environment of the machines exceeds 100F/38C, will cause failure in the servo-hydraulic valves as well as other ancillary parts of the system, including the pump and associated hardware. This often results in lost production time and expensive part replacements.

Another area of regular maintenance often neglected is cleaning of air intake filters and the radiator for the hydraulic oil cooler and the air conditioning units on the main control cabinets. This can result in catastrophic overheating causing “over temperature” alarms and degrading the hydraulic oil due to failure of the hydraulic oil cooling unit and the air conditioning unit. Again, costly machine downtime is the end result.

Toolholders are also often neglected with long-term maintenance. They should be included in the weekly, monthly and yearly maintenance schedules. One obvious sign of holder wear is the excessive amount of tool sharpening required compared to when the machine was new.

An example is lift springs in toolholders, which, if not replaced during scheduled maintenance, will cause the machine to shut down with a “punch stuck in sheet” alarm. Regular inspections of the holders will pick up wear in the guide keys along with wear in the holder. These items will contribute to excessive tool wear and the need to sharpen tooling on an almost daily basis when holder wear is excessive. This is particularly important when using very small die clearances for punching material 1 mm (0.040 in.) and thinner.

Weekly maintenance should also include clearing slugs, dirt and grease from the turret area. Slugs can build up under the turret and get into places that can cause machine damage.

The clamps that hold the sheet while punching tend to be neglected in long-term machine maintenance. A small amount of time spent checking the functionality of the clamp sensors, clamp teeth, and clamp plates will prevent major problems from occurring during punching or cutting.

Another area of maintenance often neglected is the care and maintenance of the Multi-Tool punch cassettes. There is a documented service interval for them. The spring replacement is based on the number of spring cycles. For example, a MT20/24 cassette ends up with the highest number of hits due to its large tool capacity. They are often crucial to production, as in many cases their tool load is required in most products.

Failure of the punch cassette can cause significant downtime.

The old saying “for want of a nail the battle was lost” applies to the long-term commitment of following the PM schedule laid out in the machine manuals, along with the machine warnings in the later series of machines that indicate the machine is due for a service interval (similar to the maintenance message light in your car). SMT

Andrew McCarlie is an applications engineer with Prima Power North America Inc., Arlington Heights, IL

Prima Power North America Inc.

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