Electromagnet Chuck Rebuild - Proper Potting Compound to Use?

[tcom-frazzled]

I'm in the process of rebuilding a Walker 8x18 that had a coil go bad due to liquid intrusion. I have the chuck stripped apart and did the math to order the correct length of magnet wire to make new coils and will be winding and testing them this week. The one thing I noticed during the teardown was that the potting material previously used was stiff, but slightly pliable in its cured state, unlike a hard epoxy potting material would be. that made things pretty nice when it came to stripping the chuck and prepping it to receive the new coils because it was easier to dig out the potting than I was expecting. I'm trying to figure out exactly what that potting material was, but guessing it was a urethane based on the material properties.

Does anyone here happen to know what potting material is typically used in these chucks and possibly a source for it? I'd like to use the same material if possible so that the chuck can be serviced again in the future if necessary. Pouring it with typical epoxy would make it significantly more difficult and I'm not sure silicone would be the right choice.

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[joeavaerage]

Hi,
the most common potting compounds are epoxy, polyurethane or silicones.

The polyurethanes tend to be black in colour and while firm will yield say to fingernail pressure.

The brand I'm familiar with is Electrolube. It is an isocyanate hardened polyurethane. Typically its a mix in bag type so you don't introduce air bubbles when mixing.
To get the best results you need to use vacuum infusion.

https://nz.element14.com/electrolube...250g/dp/108786

Because of the vacuum infusion requirement a low viscosity epoxy potting compound is often a better choice if you don't have molds and vacuum gear.

Craig