Pegasus 12 Melted Wire at Power Supply

[Jhlewis10]

Hour 6 of a 7 hr PLA print and no heat to the bed.

Investigation shows, melted negative 16 AWG wire from the power supply to the relay. I used 16 AWG per the kit instructions. That connector is fused to that terminal now.

Causes? Solutions?

I think I am going be running my thermal camera on things for a while after I fix this issue.

[Jhlewis10]

If I knew anything about electronics before building this I would have known that 16 AWG is too thin. The build instructions do not specify, but show using the speaker wire that was referenced in the parts needed. Which was 16 awg. Literally following instructions can get you in trouble.

Colin says I can double up the two ramps power wires and fan on a connector then have the heat bed on its own.

Picking up some 12 or 10 AWG on way home from work and will see if it works.

[printbus]

Suggestions...

Yeah, #16 is too light for a 12-inch bed.

Consider using crimp lugs on the wires going to the power supply screw terminals. I view this as fundamentally required if you're trying to terminate more than one wire at a screw. Otherwise it's hard to ensure you're clamping each wire properly.

Make sure there is *no* bits of insulation being clamped along with the wire.

If you nick or break off any of the wire strands when stripping the wire, cut off the stripped end and try again. Every missing strand puts more current on the remaining strands.

Don't tin the bare ends of stranded wire if you did before. The solder tinning will creep under pressure and degrade the connection over time.

It's always a good idea to go back and retighten screw terminals after a few days as a minimum. A periodic recheck every few months isn't a bad idea.

If you have the frame mounted relay, watch for problems there as well. Several people have had terminal block meltdowns on the frame mounted relay. Wiring going from the relay to the heat bed should have a strain relief of some kind on it. You want flexing to occur throughout the wire, not at termination ends. Also, consider wedging some sort of card stock under the terminal block; my assessment indicated that by design the terminal block rests up off the board just a bit. That's not a problem for normal terminal block use, but can be an issue for our printers. Wire movement at the terminal block will push and pull on the terminal block and put a small amount of strain on the solder points for the terminal block. Over thousands and thousands of in-and-out bed movements, this repeated strain can degrade the solder connections on the terminal block and lead to overheating. Card stock under the terminal block helps keep the terminal block from rocking back and forth.

[Jhlewis10]

Thanks for the great tips!

[Jhlewis10]

All back and working fine. Checks temps while running a print with my thermal camera and all wiring/relay are good.

Thanks.

[BLKKROW]

All back and working fine. Checks temps while running a print with my thermal camera and all wiring/relay are good.

Thanks.

I use 14 AWG silicone wire. The silicone wires can tolerate higher temperatures, similar to: https://hobbyking.com/en_us/turnigy-...wg-1m-red.html. They are also highly flexible which helps with the heated bed as it cycles a lot.