Archive for November, 2005

Nov 07 2005

News Flash

Published by under Uncategorized

The quality of a molded part depends on the process as defined by the mold.  Here’s actual proof.  Many folks who really don’t understand molding are requiring Cp and CpK’s not only for molds but also insist that each mold be qualified in EVERY press that it runs in.  Not only is this a very expensive qualification run that no-one wants to pay for, it kinda puts a cramp in the molder’s flexibility unless he’s polite enough not to tell anyone which machine the molds are in the current producing parts. 

It’s in my book QUALIFICATIONS STARTUPS AND TRYOUTS 2nd Edition, I teach it in my seminars, Rod Groleau teaches it in their Master Molding class at RJG Inc, John Bozelli says it during his demonstrations.  Maybe all three of us are nuts but it’s a fact: the ideal process for parts is MOLD DEPENDANT, not machine dependant.  “Show the plastic the same conditions; you’ll always get the same part regardless of the machine.”

Just to prove everything Gene Wells, Sr. Process Engineer at Nypro ( ran molds in different presses to see if all the noise THE GURUS (Us) was correct.  He sent me several process sheets.  Three molds, two machines each. Sure enough, the conditions to make a good part were only dependant on ‘what the plastic saw’.  It had nothing to do with which machine the mold was in.

What does this mean to the average molder and customer? Be happy when the mold is qualified in one machine. You need only  be shown that the tech can translate molding conditions from one machine to the next.  The parts produced will be identical in all machines.

Don’t believe me?  Contact Gene.

Think about it.

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