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Distinguish between preventive and responsive maintenance. Preventive maintenance includes calibrating instruments and testing incoming raw materials. Responsive maintenance fixes what’s broken, of course, but should also include written records of such actions.

Allan Griff

November 18, 2017

5 Min Read
Extrusion line maintenance: If it ain’t broke, DO fix it

I won’t forget and won’t let you forget, either: There are no toxic plastics, but people want to think so because they are changeable/moldable and “chemical.” The science of chemistry, like all science, challenges belief in the impossible, which we all need to some degree. So we are scared of this “unknown” and don’t really want to know it well, lest we see the nontoxic truth.  

Now to maintenance of extrusion lines. Some of you are old enough to remember Bert Lance, Jimmy Carter’s banker friend and budget director, who popularized the expression, “if it ain’t broke, don’t fix it.” The folksy, ungrammatical structure appealed to the anti-intellectual sentiment popular at the time. It may be sound advice in banking and politics, but not in a factory, where staying alive means doing things to avoid both kinds of broke. 

We would all agree that you fix things that are broke(n), but even this isn’t so simple. There may be a choice between buying a new one or fixing the old one, which then depends not only on direct cost but also on delivery and installation time and whether it will affect production: Will it slow down production? Stop it? Reduce consistency? Change product properties? And then, whether it’s new or old, you need to consider the maker and features that you want, the payment terms and so forth. It’s like deciding when to buy another car—new or used, cash or loan, maker’s guarantees and expected service life.

Even fixing the old is not so clean. If your car fender gets loose, maybe after backing into something you can’t put the blame on, do you crawl under the car and wire it up until you need to go to the auto shop for something else and have it fixed while the car is on the lift anyway? Or do you get it to the shop ASAP and rent a car in the meantime, whatever it costs, so no one sees the damage? Maintaining an image should not be part of running a factory, but it often is, especially when sales are involved. It may be OK to care about the image, but admit it, and don’t look for technical reasons that don’t exist. That’s like blaming plastics for the reduced fish catch this year or next.

Separate preventive maintenance from responsive maintenance.

Preventive maintenance includes calibration of sensor instruments, following data trends (such as output per rpm) and looking for causes when something looks fishy, and testing incoming raw materials to ensure you’re getting what you think you’re getting. It may also include keeping spare heaters and sensors, and finding out where to get a new thrust bearing, just in case. 

Preventive maintenance means general cleanliness. Even if this doesn’t directly contribute to productivity, it makes the staff prouder of the equipment and pay more attention to its condition, like a farmer may do with a prize cow or pig. 

Responsive maintenance includes fixing what’s broken, of course, but should also include written records of such actions, like a ship’s log, so the people who sail in the same “waters” in the future have the benefit of past history.

Whodunit? Better, whoduzit? Assigning responsibility for maintenance is critical. The maintenance manager may also run the shop, or just have too much to do and may need (budgeted) help. Who fixes a lift-truck charging station that isn’t charging? Who gets called at 2 AM? Who measures screw and barrel when a screw is pulled for whatever reason? Who negotiates times for maintenance checks when all production stops, and is this known early enough to manage vacations?

And don’t forget frequency. How often should each thing be done: Weekly, monthly or quarterly? Fulfilling these needs may ensure their doing, and support the costs of doing it. How do we review past process data, which may be (should be) recorded and available for back search? And who looks at the numbers and decides to change the frequency? The original frequency may be too often or not often enough.   

I keep a list of specific things to do for extruder maintenance—it runs five pages and doesn’t even cover downstream considerations. This space is too small for such details, but every extrusion line should have such a list. The OEMs may have one for you, but edit it and make it meet your personnel and cost needs. It’s too easy for me to say, ”all maintenance work is justified as it keeps the plant running!” That doesn’t quote numbers, and my readers should already know my obsession with numbers, especially costs.

Last but not least, get the money people in on this. If they see firsthand what’s involved in keeping a plant producing, maybe they will feel more like team members instead of automatic nay sayers until something is really broke and maybe can’t even be fixed. 

Allan Griff is a veteran extrusion engineer, starting out in tech service for a major resin supplier, and working on his own now for many years as a consultant, expert witness in law cases and especially as an educator via webinars and seminars, both public and in-house. He wrote the first practical extrusion book back in the 1960s as well as the Plastics Extrusion Operating Manual, updated almost every year, and available in Spanish and French as well as English. Find out more on his website, www.griffex.com, or e-mail him at [email protected].

Griff will present live seminars in Houston on Dec. 15, Toronto on Jan. 11 and Chicago on Jan. 23. If you can’t attend these live events, he offers a Virtual Seminar, which can be seen at any time, any place. E-mail Griff at the address listed above for more information.

About the Author(s)

Allan Griff

Allan Griff is a veteran extrusion engineer, starting out in tech service for a major resin supplier, and working on his own now for many years as a consultant, expert witness in law cases, and especially as an educator via webinars and seminars, both public and in-house, and now in his virtual version. He wrote Plastics Extrusion Technology, the first practical extrusion book in the United States, as well as the Plastics Extrusion Operating Manual, updated almost every year, and available in Spanish and French as well as English. Find out more on his website, www.griffex.com, or e-mail him at [email protected].

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