Jul 07 2007

The Crown Jewels Experiment

Published by at 5:25 pm under Uncategorized

Regrind has always been a Ghost in the Attic to most designers.  However the fact is that if you don’t burn, hydrolyze, or color shift the material it can make acceptable parts after several heat histories.  The Quality and Compliance geeks in the medical industry have a further fear of regrind having to do with the dreaded ‘Lot Traceability’.  Traceability is easily overcome by immediately using your regrind in the same lot you are currently molding.

Molders both like and dislike regrind.  If you run your business properly you look for a part that can use all your regrind.  In this manner you charge your original customer for the regrind you couldn’t use in this first place, then your second customer as though you’d just purchased the resin specifically for him.  Molders also don’t like regrind:  If the sprue and runner weight exceeds the regrind allowance you have material left over.  If you can’t mold it elsewhere it now becomes a problem in disposal.  While the tree-huggers might scream about selling your regrind to a recycle company, in some cases the cost of shipping to the re-cycle company exceeds the value of the plastic.  Until we find a lot more uses for engineering grade resin regrind, this will stay a major headache to the molders.

The obvious solution to the regrind problem is to use all of it.  In this manner literally a thousand pounds of material go into the process and nearly a thousand pounds of material are sold as finished goods.  BUT, how do we convince the buyer/designer that the parts are good?  You convince your customer by doing a Crown Jewels Experiment.  This comes from the idea that you are so confident of the outcome; you’d be willing to bet the crown jewels on the experiment.

There’s an interesting concept in the legal community: It’s called the Affirmative Defense.  What it means is that ‘there never was anything wrong in the first place’.  In our application of this principle you start with is the assumption that using all your regrind will produce acceptable / saleable parts.  Your customer will work on the assumption that the presence of an excess amount of regrind is derogatory to the product.

First get a reasonable sample of parts produced to your customer’s specification for regrind. Depending on the calculations you’ve made to consume all the regrind this product produces in each run, manufacture a sample of those parts with this new percentage of regrind. OR to prove the worst case scenario mold parts out of 100% regrind.

Second, you’ll be mixing the samples together but NOT in any specific or equal proportions.  Once you’ve done that, sequentially identify each part.

Third, give your customer entire sample of good and experimental parts and ask him to segregate the parts built to his specifications and separate out the parts where you’ve used regrind.  If you want to assist your customer, say: “There are up to X% parts in this sample that are made from Z% regrind.  If excess regrind makes inferior parts, you can easily segregate all of the excess regrind parts from the ones built to your requirements.”  Along with this challenge mumble the cost savings he will enjoy if regrind doesn’t cause problems.

Naturally you’d be the fool if you didn’t already know the outcome of this challenge.   In the vast majority of cases with a robust process and good material control; the parts will be indistinguishable regardless of the percentage of regrind.  Keep in mind that regrind cycles will have little effect on the mechanical properties of the resin if you don’t burn it or run it with entrapped moisture.  However the dyes used to color part, specifically the pastel dyes, will shift under heat.  You have to be careful that  your color doesn’t change.

This same technique can be applied when ‘discussing’ cosmetic or dimensional defects. However this time you don’t use the QC or Design folks:  This version of the CROWN JEWELS experiment makes the assumption that whatever the designer or the inspectors are quibbling about is really no concern of the end use customer.  Here you set up the experiment the same way, randomly mixing ‘good’ parts and the supposed ‘bad’ parts.  Go to your customer’s cafeteria and set them out with a small ballot and something akin to a ballot box so that the employees can vote if they can pick out the parts you’re interested in.  As above don’t tell them how many ‘defectives’ or ‘good’ parts are in the sample. If you don’t think you’ll get enough volunteers, “Pay” the customer’s employees with a free lunch sized bag of chips, an ice cream cone or something for voting.  This time simply count the ballots against what you’ve identified as good or bad parts.

Customers suffer from two common mental diseases:  The first is called “The Downstream Syndrome”.  This is where the inspector or someone on the line is unsure if they can spot a defect but they are supremely confident they can spot a perfect part.  So as not to make the mistake of putting bad parts into their manufacturing system (downstream from the receiving dock) they simply keep raising the quality standards unnecessarily.  The second mental defect is called “The Hawkeye’s Syndrome”.  Suppose you are making televisions.  Do you think an end use customer would purchase and personally use dozens of them?  Of course not!  Most people view the purchase of one television as a major dent in the budget.  But the inspector for the molding department sees the cases and bezels come off the machines at a rate of hundreds per hour all year.  Very quickly the inspector literally develops the vision of a hawk who can see a potential meal from a half a mile away.  The inspector can look at a skid of parts and immediately point to a defect without even doing an inspection.  Again we’re not looking with the Eyes of the End Use Consumer who will actually buy the TV.  With the criteria being (1) find the supposed defect and (2) would this particular defect cause you NOT to buy the product because you think it has inferior workmanship; a Crown Jewels Experiment in the cafeteria will again settle the disputes

Do Crown Jewels experiments help your customer?  Yes, but only indirectly.  What you really did was help yourself.  Your material requirements will be less and you’ll no longer have to worry about throwing out useable parts or filling up your warehouse with regrind hoping for someplace to use it.  For your customer give him a nibble of your good fortune with a small cost reduction.


This article is virtual. If you’re afraid of the customer’s buyer, or your manager’s wrath for even suggesting such heresy; you can print it out and use it to scare away salesmen or inspectors. This might also be a project for the Quest-for-Continuing-Quality-/-Cost Reduction-Black-Belt-Ninja-Number-Geeks – the latest incarnation of the Quality-Is-Free-5S-12-Sigma zealots.  Just think of the PowerPoint presentations, graphs, charts and meetings something like this might generate even without any real work being done!  Even worse, this kind of a project might even succeed and thereby confuse management!   OR, you can use it yourself, pass it along to someone else, or delete it for fear someone might see the cost savings potential and improve your company’s profits.

Your choice.

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