Page 107 - Injection Molding Advanced Troubleshooting Guide

92 10 Purging

Figure 10.1 Example of degraded purge

„ „10.2„ Purging Method Example

This is an example of a simple step-by-step purging procedure.
1. Prior to shut down, verify that the new material is the correct material, dried,
and ready to be used.
2. Shut off material feed based on number of remaining shots to be molded.
3. Drain hopper of any extra material.
4. Back barrel away from mold after completing required quantity of parts.
5. Begin using inject forward and screw rotate to purge the material through the
barrel, and purge until barrel is empty. Increase injection velocity to purge some
high-velocity shots to try to increase the cleaning action.
6. Clean all hoppers and material feed lines of previous material.
7. If using purging compound begin feeding into the machine at this point. Follow
the purging compound recommendations for quantity, back pressure, and any
specific methodology.
8. Using screw rotate and inject forward to purge the purging compound com-
pletely out of the barrel. Vary the back pressure from low to high as well as the
injection speed to increase agitation while purging.