Apr 08 2011

Cutting Setup times

Published by at 1:09 pm under Uncategorized

When looking at changeovers from one job to the next there is a long set of arguments on how to fix it.  Ultimately it boils down to money.  Where your company’s money is best spent?

Here’s one way to do look at the problem.

Look at a molding operation as a cash generator. You sell marked up material, machine time and expertise converting it all into dollars per thousand pieces.  For the moment let’s not look at cost.  Suppose you have a purchase order for $5000 that translates into 25,000 parts.  Assume a 4 cavity tool and 20 second cycle.  With a little math that works out to $144 sales generated per production hour.  A simple analogy would be this is a taxi cab making $144/hour whether driving or idle.

If you included a setup charge of $200(?) you’ve allowed for about an hour and twenty minutes from the time you shut down the previous job to the time you’re producing acceptable parts on this new job.  This means if you don’t have acceptable new parts an hour and twenty minutes after you shut down the precious job, you are losing money.

That’s the theory.  Now let’s look at the Real World:

While probably not a complete list, here are the events in no particular order, that need to happen before you begin making money with the new mold:

1.    Unhook, blowout, and drain the water lines from the previous mold.
2.    Spray with preservative, do all appropriate paperwork for maintenance etc.
3.    Pull the mold from the press
4.    Store (?) knockout rods, hoses etc.
5.    Put the mold in storage.
6.    Drain (remove) the hopper containing the material for the previous job.
7.    Purge the machine’s injection unit.
8.    Hang the new mold in the press with the appropriate length knockout rods
9.    Hook up the cooling systems, power up the electrical system on the mold if necessary.
10.    Reset the machine’s settings – pressures, time, distances, speeds, and temperatures.
11.    Bring the mold up to temperature
12.    Hookup or fill the material hopper with the new material
13.    Dry the material per the specifications
14.    Fill the machine’s injection unit with new material
15.    Check the new material for proper temperature, adjust accordingly
16.    Have an adequate supply of packaging material at the press site
17.    Have the process, quality control, packaging, and secondary finishing documentation at the press.
18.    Clean off mold preservative from mold face.
19.    Start up the new mold.
20.    Adjust the settings until good parts are produced, at or faster than the quoted cycle.
21.    Get approval from Quality to begin production.
22.    Have an operator available when required.

Some of the steps must be done in sequence.  Some only must be achieved before actual production begins.  All of these steps are time, personnel and equipment/material dependent:

The setup team must do the setup.  You must have the people available. If they are pulled away to troubleshoot other machines, relieve operators during breaks etc. your setup stalls. If the setup happens during a shift change, there will be a further delay (unless somebody is paying overtime) when the new setup team has first checked production and then will resume the setup. All this delay time is billed off to the setup at $144/hr. Another personnel cost is having no operator available.  Equipment and material factors can be as simple as having the overhead crane unavailable to pull and hang the molds.  How much time did it take to bring the new material; boxes, skids, tape machines, labels etc to the press site?  Do you have all the paperwork at the press site?  How long was the wait time for QC to release the job to production?

The first step is to analyze the problem. Hire a ‘Joey’ or ‘Suzy’ – the infamous underpaid/overworked student intern.  Have them set up a spreadsheet using the items above.  Record each of the steps in terms of time – from the time one job was shut down, to the time the next job was in production.  Remember the Hawthorne Effect:  When you are observing people doing something, the very fact that you’re looking at them will change their behavior. To eliminate the ‘I’m watching you’ factor, record at least ten setups.

Put the data in a spreadsheet, do the calculation on how much the job should be generating per hour to give each component a cost per hour basis.  Remember the same machine might generate fifty dollars in sales per hour on one job and three times or even half that on the next job.

After a lot of keyboard thumping and spreadsheeting, have the computer merge all the data into one master spreadsheet.  Now sort the data and draw a Pareto Chart that orders the most expensive component to the least expensive. What you’ll see is usually an eye opener.

You’ll see two trends:  (1) Some jobs are ‘stinkers’ and have difficult setups and (2) some components are generically expensive. Have Joey or Suzy classify each step into the classic Operations Research categories:

MAN – most of the components in long setup times have to do with the availability of people.  Some shops only do changeovers on first shift.  Unless you can schedule all the runs to complete during the day your taxi cab is idling at our $144/hour overnight waiting for the setup team.  Scheduling operators, material handlers and inspectors for the job is just as important as hanging the mold.

METHOD – Train your people.  Most operators can do the first few steps of troubleshooting simply by comparing the required settings to the current settings on the machines. This keeps the setup team doing setups, and not troubleshooting.  Make sure the mold is ready to run with no blocked off cavities, dings from the previous run have been fixed, no wires are pinched etc. Having to pull the mold before you begin the run because maintenance wasn’t done is inexcusable. Before a new job is scheduled, pre-stage the materials.  Make sure getting the old mold put into storage, the new mold available, material, boxes, skids, and paperwork are all easily accomplished before you begin.  Make sure the inspector’s first priority is to be there to approve the parts when ready.

EQUIPMENT – a quick change mold system only shortens the ‘clamp up time’.  It is a waste of money if you spend time hooking up waterlines or going to the tool crib to make up new hoses.  If you spend the money to put manifolds on your mold there is only one ‘in’ and one ‘out’ to hook up on each mold half. Hookups can account for 20-30 minutes of setup time; different waterline hookup patterns also account for a lot of dimensional variation run to run.  Manifolds eliminate both problems.  Portable material hoppers with detachable mini machine hoppers allow you to pre-dry the material and in only a few minutes change materials.  Extra water and electrical hookups allow you to bring the mold up to temperature before you hang the mold.

The rule of PARETO analysis is to work on what costs the most first and ignore everything else. A practical goal is to cut that particular item’s impact in halve. When you’ve done your work properly on the costliest cause, redo the study.  If there’s something obvious in the ‘Stinkers’ fix it first, then look at the overall data. In many cases there is a spillover effect and something that was third or fourth place originally will now become first. Go work on that. When you get to where the elimination of the most expensive item costs more than the benefit you’ll receive; stop. It isn’t practical to continue.

With small run shops, setups comprise a significant portion of the overall run.  Here is where, if you can put it into the tooling cost, the quick changes systems make financial sense.  Other shops will tell you if the setup takes less than 5% of the run time, it doesn’t matter.  The answer to here is yes and no.  Yes – the portion of idle time can usually be buried in the part pricing.  No – this is leaving money on the table.  When you’ve lost several hours of potential money generating production time, you’ll never get it back.

There’s no such thing as an acceptable loss.

* * * * * * * *

For the Techno-Geeks and Gadget-Engineers this isn’t about new technology.  It’s about money.  Spend money so that you can maximize profits.  Technology constantly innovates. What is not practical now might be feasible in the future.  Keep informed on what can make your setups shorter.  There’s always something that can give you less idle time.

Your Choice

— Bill Tobin

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