Vacuum time for high temp thermomolding

Vacuum time for high temp thermomolding

Cheryl Lewis

3/22/2006

We have been having a lively discussion in our clinic regarding how long a
thermoplastic molding needs to be left on vacuum as it is cooling.

I was taught that the vacuum should stay on for twice as long as it took the
material to heat up. I haven't seen this written anywhere but it seems
logical to me. I am curious what other clinics do.

To remove some extra variables, please assume a dry cast at room temperature
using 3/16th poly-prop or colene with a nylon over it as a wick. Also
assume the plastic is left on the cast overnight before cutting. We use
electrical tape around the pipe to ensure a good seal � if you have another
technique please let us know!

I always thought that the �2x time to heat up� rule of thumb allowed for
different thicknesses, materials (poly-pro vs colene vs. poly-eth) as well
as variations within material (ie. Different manufacturers). Of course the
overall goal is for a a nice tight device that doesn�t spring after cutting
off. What does everyone else think??

I am sure this discussion has been on the list before � I know it hasn�t
been for a while now and I am curious if ideas have changed or new tricks
are being used. I will post all responses with names.

Thanks in advance to all who respond!

Cheryl Lewis BSc. (HK), C.O.(c)
Clinical Orthotic Consultants of Windsor