How are you wiring your heated bed?

The back and forth motion of the bed, especially on big prints, combined with the thick wire needed to carry enough current for the heater has repeatedly broken all the connectors I've used. I'm using hard drive molex connectors, and each time the wire has fatigued right where it enters the pin in the connector and eventually loses connection. Also, I haven't found a good place to suspend the wire from where it doesn't get caught on the frame or drag on something, probably adding to the stress. What have you guys done to solve this?

You need solid strain relief to stop the cable bending at the connections. It needs the bend over a large radius to prevent the strands breaking and it catching fire. I have had two catch fire, one mains, one 12V.

I am just about to try ribbon cable. I have used it successfully for a mains driven bed where I used two for live and neutral and four for earth plus two thermistor. Thinner wire will bend through a much smaller radius without breaking. Putting lots of ways in parallel gives the current capability. It is also rated for 300V and 105C surprisingly.

For a Prusa PCB bed I plan to use ten in each direction plus two thermistor. I will blog it if it works.

Edited 1 time(s). Last edit at 11/30/2011 05:02PM by nophead.

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I run the wires from the solder points tot eh center of the bed, where a couple of strips of capton hold the wire in place. From the, to the edge, I put another piece of capton on top along the length. and a final piece perpendicular to the wire along the edge. From there, it is a free floating 7 inch loop of wire, and then into the RAMPS enclosure.

In the end I just replaced the molex connectors with screwdown terminals screwed to the side of the bed. Probably not any more resilient than a connector, but at least when it breaks its trivial to fix.

On the Prusa PCB heater, I just soldered a pair of 13 gauge stranded wires and ran them through a plastic loom that is tie-rapped to the lower part of the left side frame near. It's held up for at least 8 months so far.