Molten Terminal Duet

[Waycer]

Hello, the red wire connecting the heatbed to the Duet loosen himself from the therminal and it burnt as shown on the photo below. How can I fix that ?
[img]https://img11.hostingpics.net/pics/904534IMG20170919151013.jpg[/img]
Thank you

[Xenocrates]

Easiest way would be to order replacement terminals ( these ones, probably), then desolder it and solder on the replacements. Plus use ferrules on the wire (And definitely not solder), to give it a better surface to grip on.

[Waycer]

Okay, I'll do that then ! Thank you for your quick answer !

[Tincho85]

Why did it melt? Are you runing the onyx at 24v?
Edit. Oh ive just read that one wire was loose.

[Xenocrates]

{snark} Because it's a thermoplastic. No fancy Thermoset resins here. Nosirree. {/snark}

More seriously, there's not a lot of beef there, so most people don't feel good torquing it very much (I have seen this sort of connector tightened with one of the pen size screwdrivers, and that's not kosher given the torque specs usually used for electrical), plus especially on the heated bed terminal, it sees a wide difference in load profiles at times, so thermal expansion and contraction (plus creep), can cause them to loosen. It's even worse with soldered wires, or AL wire. Really, a good crimped lug to eliminate the creep and the correct installation torque saves a lot of trouble, but to be sure it's done right takes another 60-120$ in tools, which many people don't like, and in some cases would never know about. See the problems in the US with Al household wiring for more historical context, and to realize you aren't alone in having issues like this.

[geneb]

bootlace crimps help too.

g.

[dc42]

bootlace crimps help too.

g.

Yes, which is why we supply some with every Duet WiFi and Duet Ethernet.

We're looking at alternatives to screw terminals for the next generation, but it's hard to find any other type of high-current connector that is within budget.

[geneb]

You could use screw terminals with spade lug connectors.

The only issue with the bootlace connectors is that to properly crimp them, you need a four point crimping tool - they're cheap though - $12-ish on Amazon.

g.

[rootboy]

...See the problems in the US with Al household wiring for more historical context, and to realize you aren't alone in having issues like this.

Well, actually, the vast majority of the problems with AL wiring was with wire sizes of #10 and smaller. Just about every house wired from the '80's on has AL for the service and the electric range. Hot tubs usually have AL feeders to them, as well as feeders for detached garages and workshops. Panel interiors are almost always made out of AL.

Commercial is almost exclusively wired in AL for the services.

Most of my customers from those days neither cared, nor wanted to spring for the extra money it would take to use CU. Don't get me wrong, I'm no fan of AL wiring, and I'd rather run CU any day. But it isn't the boogeyman that people make it out to be.

Where you got into trouble in houses was with the constant insertion/removal cycles of plugs into outlets that loosened things up. That and the occasional doofus that tried to connect AL to CU directly without using an approved AL-CU connector (you will eventually end up with burnt up connections and possibly a fire).

And I guess in the interest of completeness, the proper procedure (as of the mid-eighties when I transitioned over to engineering) is:

1) Strip your wire carefully, without nicking it (don't sweat small nicks, but if you took your knife and cut a ring into the insulation to the point that you cut halfway through the outer conductors, you are asking for trouble).
2) Wire brush it.
3) Use No-Lox or some other anti-oxidation grease.
4) Use an approved connector. It will be silver in color and have AL-CU stamped on it.
5) Tighten down the wire firmly. Like it owed you money or something. Then take the wire and bend it back and forth a few times and let it cool off. Now tighten it again (you should get 1/2 - 1 full turn depending on the wire gauge).

Mike Holt's forum is the place to go for how it's done these days: https://www.mikeholt.com/

[Jrjones]

IMO you are asking for trouble with that much exposed wire on the VIN terminals. You should not see any exposed wire from the terminals.

Best method is crimping ferrules and tightening the connectors properly. I use the same type of connectors (and ferrules) on mobile equipment and have never had them come loose.