Page 74 - Injection Molding Advanced Troubleshooting Guide

58 7 Venting

Figure 7.7 Pin vent with ring relief

Porous steel or sintered vents are also an option with difficult part details and
backfill areas. It is important to follow proper instructions with machining and
cleaning, and to have the proper relief channels to reduce plugging of the pores.
Porous metal inserts must be kept clean to ensure proper venting and inserts may
need to be removed for cleaning or replacement on a regular schedule. One other
consideration with backfill areas is using a stationary pin and sleeve with ring
vents if porous steel is not preferred.
Vent inserts should be designed whenever possible for removal and cleaning in the
molding machine. Vent land on inserts should be a maximum of 0.040″ and vent
depth at maximum depths based on the material and process to reduce buildup.
Also bear in mind that venting can and should be added to lifters and slides when-
ever possible.

„ „7.2„ Alternate Venting

If additional venting assistance is required a vacuum venting system can be added
to a mold to allow the gas to be drawn out of the mold. This can allow for the best
overall venting possible in a mold. In most cases it is recommended to seal the
mold with gaskets and route all vent channels to the vacuum line. In some cases
adding a vacuum to a mold even without gaskets will lead to improved venting.