Tooling modifications for vacuum venting
A parting line installation consists of installing an “O” ring and a chimney around the cavities. The “O” ring is required to seal the mold and prevent ambient air from entering the cavities which assists in creating the vacuum.
The “O” ring can be glued in by using RTV (room temperature vulcanizing) silicone. A neoprene “O” ring can withstand temperatures up to 160 degrees F. Vyton up to 400 degrees F. “O” rings are available through various suppliers as outlined in the Thomas Register.
On long thin wall sections where there is an insert, it may be desirable to vent as close to the bottom of the insert as possible. This is illustrated in figure #6. Note: It is recommended that the insert walls in contact with the mold bases be coated with a fine coat of silicone, grease, or RTV silicone to prevent vacuum leakage.
Another method is to vent through the ejector pins of a mold. To obtain the maximum vacuum level, sealing of the ejector pins may be required. Vyton seals are recommended due to their durability and heat resistance. Contact our office for high temperature applications above 300 degrees F.