Page 29 - Injection Molding Advanced Troubleshooting Guide

10 1 Troubleshooting Methodology

ƒ Machine wear or damage
ƒ Mold wear or damage
Any change in the above factors may lead to a condition that exceeds the ability of
the molding process for producing quality parts.
When observation of the baseline data shows that the problem has always existed,
the main question is not “what changed?” but rather “what must be changed?”
There are many parts in manufacturing operations that have such small process
windows that they produce a steady stream of scrap. If the part has been steadily
producing scrap it is often more difficult to troubleshoot because the problem may
be rooted in several factors and not in a simple change. If observation shows that
the part has had defects since it was launched, all of the 4M’s must be reviewed in
depth for possible causes. A common situation found in troubleshooting is where a
process was established to work around another issue such as venting in a mold.
Rather than finding and correcting the root cause during process development, the
processor worked his/her magic and developed a process that produced “good”
parts. Sometimes it is only after the mold has had some run time in manufacturing
that the true ramifications of the narrowed process window are understood.
In many cases a troubleshooter will find that ongoing scrap problems are rooted in
processing around a mold, machine, or material concern. It cannot be stated
enough that molders must not process around problems but rather need to have
the problems fixed to maximize process windows and minimize scrap and cost.
Putting “Band-Aids” on a problem will not help establish a robust process; fix the
problem! To effectively resolve problems the technical groups must work together.
If the maintenance or tooling department will not fix the problems that are en-
countered the processor is left holding the bag and will have to process around a
root cause.

1.4.4„ STOP: Proceed

This is the step that everyone is anxious to get to because this is where actual
changes are tried. The problem that frequently occurs is that people will jump to
trying things without going through the systematic, thinking, and observing
phases of troubleshooting.
Jumping right into making changes can lead to damage to equipment or molds.
Figure 1.4 illustrates an example from someone who jumped to a solution. In this
case, the machine was producing short shots and losing cushion, so the technician
increased the shot size to add more plastic to the cavity during first-stage inject.
The problem here was not a shot size issue but rather where the plastic was going.
As the photo shows the hot runner manifold was leaking and was encapsulated in