Pulling a vacuum on potting compoud
Patrick, Thu May 02 2019, 06:57AMmy 2 part silicone has a viscosity greater than honey but much less than peanut butter.
does a vacuum decrease the effective viscosity such that it can flow into tiny voids ? nad in between 36 awg wire windings?
see here:
and :
Re: Pulling a vacuum on potting compoud
klugesmith, Thu May 02 2019, 02:52PM
No. Not that I've potted any windings myself, or watched it done.
Vacuuming the mixing pot can get rid of most tiny bubbles.
Vacuuming the potting pot won't affect resin viscosity, surface tension, or wire-wetting properties. It can prevent tiny bubbles from forming as resin soaks into the windings, if resin is poured in a vacuum.
Best way to reduce the viscosity is to heat the resin, and deal with the reduction in working time.
Why is important for resin to penetrate coils of fine wire, except to improve tolerance to vibration?
klugesmith, Thu May 02 2019, 02:52PM
No. Not that I've potted any windings myself, or watched it done.
Vacuuming the mixing pot can get rid of most tiny bubbles.
Vacuuming the potting pot won't affect resin viscosity, surface tension, or wire-wetting properties. It can prevent tiny bubbles from forming as resin soaks into the windings, if resin is poured in a vacuum.
Best way to reduce the viscosity is to heat the resin, and deal with the reduction in working time.
Why is important for resin to penetrate coils of fine wire, except to improve tolerance to vibration?
Re: Pulling a vacuum on potting compoud
Sulaiman, Thu May 02 2019, 04:03PM
I think that the viscosity would not change,
but the lack of air may prevent the forming of a skin on the potting compound as it penetrates voids, stopping due to surface tension.
I'd probably give the coil a few dips in polyurethane varnish or similar, with drying after each dip.
Clean up excess polyurethane then pot the assembly as required.
Sulaiman, Thu May 02 2019, 04:03PM
I think that the viscosity would not change,
but the lack of air may prevent the forming of a skin on the potting compound as it penetrates voids, stopping due to surface tension.
I'd probably give the coil a few dips in polyurethane varnish or similar, with drying after each dip.
Clean up excess polyurethane then pot the assembly as required.
Re: Pulling a vacuum on potting compoud
Patrick, Thu May 02 2019, 05:01PM
material seen here.
Patrick, Thu May 02 2019, 05:01PM
klugesmith wrote ...
Why is important for resin to penetrate coils of fine wire, except to improve tolerance to vibration?
Doesnt corona kill insulation ? isnt potting used by flyback makers in TV's ?Why is important for resin to penetrate coils of fine wire, except to improve tolerance to vibration?
material seen here.Re: Pulling a vacuum on potting compoud
2Spoons, Thu May 02 2019, 09:44PM
Yes, but for potting transformers one would usually use something really runny if you want winding penetration.
2Spoons, Thu May 02 2019, 09:44PM
Yes, but for potting transformers one would usually use something really runny if you want winding penetration.
Re: Pulling a vacuum on potting compoud
Patrick, Fri May 03 2019, 04:35PM
ok ill use thin epoxy, then ive just about finished my vacuum/pressure vessel.
Patrick, Fri May 03 2019, 04:35PM
ok ill use thin epoxy, then ive just about finished my vacuum/pressure vessel.
Re: Pulling a vacuum on potting compoud
Avalanche, Sun May 05 2019, 11:04AM
'Vacuum impregnation' is certainly a thing in the industry, I've seen it done with electric motor stators but with much thicker wire.
For fine wire I guess you'd need to use some type of varnish with a viscosity more like water.
Avalanche, Sun May 05 2019, 11:04AM
'Vacuum impregnation' is certainly a thing in the industry, I've seen it done with electric motor stators but with much thicker wire.
For fine wire I guess you'd need to use some type of varnish with a viscosity more like water.
Re: Pulling a vacuum on potting compoud
2Spoons, Mon May 06 2019, 12:17AM
Ideally you'd use a heat set epoxy - pull vacuum, add epoxy, release vacuum, wait a day or two for full penetration, then bake.
2Spoons, Mon May 06 2019, 12:17AM
Ideally you'd use a heat set epoxy - pull vacuum, add epoxy, release vacuum, wait a day or two for full penetration, then bake.
Re: Pulling a vacuum on potting compoud
hen918, Tue Jun 11 2019, 07:55PM
I have had a lot of good experience with this for waterproofing electronics. The breakdown voltage isn't too bad either, and the viscosity is on par with water, and the lowest I could find for an OK price, it's pretty cheap and easy to find. It has a nice hard-rubber consistency after curing, but will crumble if heated with a hot-air gun.
hen918, Tue Jun 11 2019, 07:55PM
I have had a lot of good experience with this
for waterproofing electronics. The breakdown voltage isn't too bad either, and the viscosity is on par with water, and the lowest I could find for an OK price, it's pretty cheap and easy to find. It has a nice hard-rubber consistency after curing, but will crumble if heated with a hot-air gun.Print this page