Slitters: Increasing speed: myth; Chapter 36
Estimating production runs based on actual field tests versus pie-in-sky dreams:In the last two posts we addressed the actual "run times" of a duplex slitter rewinder. The start-stop cycle time issues were calculated. In this post we will continue to explore these points in more detail.
This is the biggest mistake made by converting plants when bidding or estimating run times on any given converting job. A simple calculation mistake can lead to thousands of dollars in losses. This can also lead to future loss of business.
A client who was charged a dollar a roll for the last job is going to be extremely upset when you discover your mistake and now quote 2 dollars a roll for the same job. Had you done your homework the first time around, this mistake wouldn't have occured.
Knowing your production speeds, down to number of rolls produced per hour, on a given slitter rewinder is critical. We shall now continue with our time study.
Ramp speed:
How does one determine the best operating speed for any given grade of paper, film or foil?
This depends on several factors:
1) Lineral footage that has to be wound on the finished roll.
2) Properties of the material that is to be wound.
3) Grade of paper or film.
4) The thickness of the stock in question
5) Parent roll size and weight.
6) Other unique conditions.
These are not the only conditions, but this gives you an idea of what is involved.
Each grade of paper ( or plastic) has its' own unique properties. All these properties come into play during the rewinding cycle. The only way to determine the exact run times is an actual trial run. Ofcourse, if the plant has run a certain grade of paper in the past this becomes a moot point.
If you have never run a certain grade of paper before, don't assume that you can have the same production results.
The weight of the parent rolls will be different. The slitting knives will have to be readjusted for this new grade of paper. Core sizes may be different than what you are normally accustomed to. The job may call for a different rewind core diameter. You may not even have these different sized shafts in your plant.
The parent rolls may be seconds. They may be wound too tight or too loose. Crushed cores and other defects in the parent rolls may bring the plant to a complete stop. The job you thought was going to take 2 hours might end up being a 2 day nightmare.
If you, as the owner or the plant manager ignore all these points and go ahead and quote a price, you have to live with the results.
Standard operating procedures:
Every job that comes in has to have a master work sheet. This master work sheet doesn't have to look like the IRS tax return form. But try to address all the points listed above and then some. The form should be signed off by the estimator, the receiving manager and the machine operator before the quote is sent out to the customer.
This is Dr. Winder saying bye bye......Live long and prosper.
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