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VIP stands for vacuum, inject,
pressurize. To produce a part using VIP molding, the mold is
placed in a chamber which is then evacuated. After full vacuum is
established, the urethane material is injected into the mold while
maintaining full vacuum. After the mold is filled, determined by
observing the mold through the viewing port, the vacuum is turned off
and the chamber is pressurized to 80 psi. The change from full vacuum to
full pressure takes place in a few seconds.
The VIP process yields very high quality void free
parts. By injecting the plastic into an evacuated mold, the problem of
trapped air in the mold is eliminated. When the still liquid urethane is
pressurized in the mold, any gas bubbles which are formed during the
curing process are compressed to micro size and do not affect the
strength or appearance of the part.
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Vacuum
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