RAMPS 1.4 power connector was melting

[alpha]

Today my GND port on the RAMPS 1.4 board started getting very hot and the green plastic melted. Now the plug and socket are fused... I think it's the lava bed - because this is last thing I "played" with - but I'm not sure? I thought there are fuses on the RAMPS, any idea why it's starts melting first before shutting down. Also it looks like the solder on the GND pin was a little black... I did a test with both extruders but the cable started getting warm again and I turned it off. Is the connector bad?

[SystemsGuy]

There's a thread somewhere with folks claiming that the fact that the heatbed cable wiggles back and forth caused the solder joint to fail and melted the connector...

I'll see if I can dig the details up tomorrow..

[cvoinescu]

Let me put it this way. You can start a fire with much less than 1 A, if you size your wire just "right". The fuse is 11 A. That is a respectable amount of current, and it needs to be treated with respect. The wire, the connector and the PCB traces must all be carefully sized. It helps a lot to have a ferrule on the wire, to make sure that the connector makes firm contact with as many strands as possible. Without a ferrule, if the screw pinches only some of the strands, they'll take all the current and heat up considerably. The contacts then oxidize and the strands get increasingly insulated from each other by the oxide, so the wire heats more, and eventually starts melting things. You'll have to replace the connector, reinforce the copper trace by removing the solder resist and loading it with solder, cut an inch or so off the end of the wire, strip and crimp a ferrule, then assemble and tighten very firmly. If you don't have a ferrule, you can twist the strands together and solder them, using plenty of flux to ensure the solder wets all the strands. Generally, it is not recommended to have wires with solder on them in screw connectors, but it may be better than nothing at all.

[kbob]

It helps a lot to have a ferrule on the wire, to make sure that the connector makes firm contact with as many strands as possible. Without a ferrule, if the screw pinches only some of the strands, they'll take all the current and heat up considerably. The contacts then oxidize and the strands get increasingly insulated from each other by the oxide, so the wire heats more, and eventually starts melting things. You'll have to replace the connector, reinforce the copper trace by removing the solder resist and loading it with solder, cut an inch or so off the end of the wire, strip and crimp a ferrule, then assemble and tighten very firmly. If you don't have a ferrule, you can twist the strands together and solder them, using plenty of flux to ensure the solder wets all the strands. Generally, it is not recommended to have wires with solder on them in screw connectors, but it may be better than nothing at all.

What are these ferrules? Can you show me a picture?

Thanks.

[cvoinescu]

To be honest, I'm at a loss as to where you would be able to buy some. I see them all the time -- any extension cord sold here (UK) would have them at both ends of the cord, and many factory-made electronics that rely on screw terminals have them on the wires. I'm pretty sure they're brass. The type I'm talking about is a tube with a zig-zag seam, which is crimped around the stripped end of the wire to squeeze all the copper strands together. Much like your bootlace ends, which have similar plastic or metal tubes at the ends to keep them from fraying. Those are called ferrules too.

The only type that seems easily available is something like this (to give a random link that came up), which is a metal tube with a plastic insulating collar. They're better than nothing, and offer some stress relief too, but I'd really like to find the ones used industrially.