RS at work wrote:

Jim Wilkins wrote:


What will you use for the self-powered remote control sealer?


I had several ideas here. My firat idea was to get a standard impulse
bag sealer, put it inside the chamber and just run the power wires
through glands in the sidewall. Once the desired level of vacuum was
drawn the power could be applied to the sealer.



Glands? Use feedthrough capacitors to prevent all air leaks.


In researching plastic sealing however I found a place that sells
parts and controlers. It seems that the state of the art is to
measure the temp of nichrome sealing element by measuring the current
that is being drawn so you do not over heat or underheat the bag you
want to seal. (The resistance changes as the temp rises)

This seems to be the way to go. but that opinion may change when I
price their controler. Optionally, one could mount the guts from the
off the shelf bag sealer outside the chamber and run the lower
voltage to the seal bar inside.

The bag is sealed between two pieces of silicone foam rubber and
several insulating and teflon strips to hold the melted plastic while
in resolidifies.

One thing for sure is that I am going to try an alternate cross
sectional geometry on the heating element. They sell one that has a
radius top edge to prevent the sealing bar from overheating the edge
of the band like the flat bands are prone to do.

Roger Shoaf


--
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