Bed temp cutting out.

[Vandal968]

My bed temp sensor is cutting out while printing. If you monitor the print from Octoprint or from the LCD, the bed temp falls to either 4c or 0c for an instant while in certain positions. My bed temperature plot looks like a straight horizontal line with deep V's every minute or two. I'm assuming a wiring problem rather than a bad sensor. Anyone seen this before? Any pointers?

cheers,
c

[ednisley]

I'm assuming a wiring problem rather than a bad sensor.

Verily it is written: Hell hath no fury like that of an unjustified assumption. [grin]

Replace. The. Thermistor. Now.

If that doesn't solve the problem, then worry about the cable.

The overwhelming majority of similar problems boil down to a failing thermistor.

[Vandal968]

As much as I love my M2, I HATE the MakerGear webstore. I don't see the thermistor for the bed anywhere. Does it use the same one as the hot-end?

https://www.makergear.com/collections/p ... thermistor

Along the same lines, I've got a 3B hotend that's never going back in, can I steal the thermistor from that?

cheers, and thanks again Ed.

cheers,
c

[Vandal968]

Found some really good pictures of it here:

http://www.rcdon.com/html/makergear_m2_project4.html

So, now I know what I'm looking for.

cheers,
c

[ednisley]

can I steal the thermistor from that?

Nope, they're different animals. Same resistance inside entirely different packages.

Best to call MG and let them sort out the what-you-have versus the what-you-need…

[Vandal968]

I called MakerGear, the guy said probably not thermistor, sounds like wiring. Told me to put a meter on it an flex the wire, I decided to just flex the wire with the machine on and watch the readout. It's a little tricky to isolate, because when you move the wire in one place it tends to move in other places as well. It looks like the thermistor harness has failed where it is tied to the Y-axis stepper. This makes sense from a fatigue standpoint, since it's held rigidly at one point with an aircraft tie and is moving around a lot just beyond it. Before I replace the wire, I wanted to see how others are routing their wires and if there is a "best" way to do this. It looks like on the Rev E. machines the HBP harness runs differently than on mine with a nice big gentle arc. Does anyone know if there's a flexible "stick" in there or something which makes it loop like that? Any recommendations on this?

https://cdn.shopify.com/s/files/1/0030/ ... 1476716198

I also saw this, which seems like a good idea, although it's not where mine failed:

http://www.rcdon.com/assets/images/Make ... _9-000.jpg

cheers,
c

[Jules]

Jim had a trick for securing the wire at the edge of the spider that I used on my older model......

viewtopic.php?f=7&t=1712

[ednisley]

which seems like a good idea

The wire hanger is attached to the spider supporting the platform, which means the cable exerts forces that will tilt the platform and affect the print quality. It's much worse with spring-mounted platforms, but even platforms attached directly to the stage are surprisingly bendy: that's a long lever arm out there on the corner!

Anchoring the cable directly to the Y axis stage directs the forces to a (somewhat more) rigid structure where they won't do anything nasty.