heated bed repair / don't use that metallic clamps

Topics around mechanical design, controller and electronics. Mods & hacks welcome.
theRenegade
Posts: 60
Joined: Tue May 03, 2016 11:58 am

heated bed repair / don't use that metallic clamps

Postby theRenegade » Sun Jun 19, 2016 1:00 pm

Lately I had to refit my printing plate and when securing it with the metallic clamps that came with the printer I saw some arcing from below the bed on the left side. There are warnings in the forum about that, now I will take care and use isolated clamps. 8-)

After that the bed temp was always sensed with 0° and I could only continue to print with slicing the parts for 0° bed temp (but it worked that way and I printed for some days like that).

Yesterday I removed the bed by unscrewing the 9 nuts from the long screws that fix the bed to the mount.
I measured the resistance of the thermistor wich is a common 100K NTC and it was not connected.
The NTC is connected to the small connectors SIG and GND Pins thru the copper traces that are routed to the outer left middle and from there to the center of the bed. I found the traces to the left scratched by the clamp and actually one of them was broken.

I decided to use a cable to get the connection back (those copper traces are quite weak, didn't want to work on them), the cables diameter has to be smaller than the height of the nuts that fix the bed screws (leveling issue).

The pics show how I did it. One of the pics shows the NTC (very small, below the letter 'N') and a hole next to it (below the letter 'C') wich allows easy repair with a thru hole glas bulb NTC (shown to the left) that is commonly available.

Resistance between SIG and GND is about 85-100K, depending on your room temperature, heater resistance (+ / -) on the large connector is about 3 ohms (I first feared that the heater was killed by that clamp).

Only issue I had was with the connectors that have been glued to the sockets by manufacturing. IMHO this is nonsense and provides potentially more damage when the bed has to be disconnected (and this will happen on any printer sooner or later) than just leave it as it is.
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Vicky@Raise3D
Posts: 6464
Joined: Fri Mar 25, 2016 3:54 am

Re: heated bed repair / don't use that metallic clamps

Postby Vicky@Raise3D » Mon Jun 20, 2016 2:14 am

I suggest you warp your clips with PTFE Coated Fiberglass with Silicone Adhesive tape to protect your heating bed with sharp cut from clips. Or add an insulation board under the heating bed. Though your fix the temperature sensor function, clips may do harm to heating wire in some cases. Please be careful.

theRenegade
Posts: 60
Joined: Tue May 03, 2016 11:58 am

Re: heated bed repair / don't use that metallic clamps

Postby theRenegade » Mon Jun 20, 2016 7:14 am

Vicky@Raise3D wrote:Though your fix the temperature sensor function, clips may do harm to heating wire in some cases. Please be careful.


Not mine, they are perfect :)
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Vicky@Raise3D
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Joined: Fri Mar 25, 2016 3:54 am

Re: heated bed repair / don't use that metallic clamps

Postby Vicky@Raise3D » Mon Jun 20, 2016 7:28 am

it's a good idea.

thebriceman
Posts: 18
Joined: Mon May 02, 2016 3:03 pm

Re: heated bed repair / don't use that metallic clamps

Postby thebriceman » Tue Jun 28, 2016 3:22 pm

I use the same clamps for mine.....


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