MakerGear Forum

Came home to a stopped printer that had kicked out a MAXTEMP Error. Revision E with a V4 hotend. I was printing a long PETG print at 245C.
Rebooted and all seems functional. Is this a sign of future problems? Any ideas what would cause this? IIRC, the V4 is rated to over 300C, so it should have been well within range.

EDIT:
Printer is working, but thought I would add an Octoprint screenshot showing that the temp is fluctuating a great deal.

I would check your thermocouple to see if it has any issue(wires) or connection. Usually when a thermocouple goes bad it reads low.

Its not likely that he is running a thermocouple to sense his temp. Its more likely to be a thermistor.

Thermistors read low when there is a disconnection, so if I had to guess I would say that your maxtemp setting in your firmware is 250 or 255C and you had a bit of an overshoot with your temp and it triggered the maxtemp shutdown.

turn on your printer, set the temp to 260c and see if you get the maxtemp error again at a certain temp.

EDIT

Is your v4 original? as in did it come with your printer?

if so, then your temp probe id in the firmware is probably correct and you just need to do a PID autotune and input the values it spits out, into your firmware.

steve220 wrote:showing that the temp is fluctuating

Order a new thermistor. When the package arrives, install it.

Until then, do not change any firmware / software / slicer / configuration settings, so as to save yourself a world of hurt while restoring the previous values after the replacement thermistor solves the problem.

Search the forum (*) for "thermistor maxtemp mintemp" and you'll find many, many similar discussions. On rare occasions the cable between the thermistor and the RAMBo board fails, but that's not how to bet.

What's wrong: the fine wires at the thermistor bead are disintegrating. It's pretty much the weakest link in the chain and there's no repair or workaround, other than replacing the thermistor.

(*) Using your favorite search engine with "site:forum.makergear.com thermistor", not the useless forum search box in the upper right corner of your screen, for best results.

Thanks everyone for the input. The thermistor pulled out really easily, meaning the set screw had likely come loose. I tightened that down and all seems right with the world now. Just finished the 13 hour print that had thrown the error previously. Here is a printout of the temperature screen from Octoprint showing no more wild fluxuations:
I'll order another thermistor to have on hand just in case it acts up again.

Farr0wn3d wrote:Its not likely that he is running a thermocouple to sense his temp. Its more likely to be a thermistor.

Thermistors read low when there is a disconnection, so if I had to guess I would say that your maxtemp setting in your firmware is 250 or 255C and you had a bit of an overshoot with your temp and it triggered the maxtemp shutdown.

turn on your printer, set the temp to 260c and see if you get the maxtemp error again at a certain temp.

EDIT

Is your v4 original? as in did it come with your printer?

if so, then your temp probe id in the firmware is probably correct and you just need to do a PID autotune and input the values it spits out, into your firmware.

Oops yeah, thermister. I had thermocouple on my mind, at the time I was writing my response.

Well, may have spoken too soon. The temp fluctuation issue came back, so I changed the entire hot end (including another new thermistor). Thankfully, I have not gotten another MAXTEMP error, just the temp fluctuations. Thoughts on where to look next? Here is another screenshot showing the temp after the new hotend.

steve220 wrote:Thoughts on where to look next?

Further along the thermistor cable: "On rare occasions the cable between the thermistor and the RAMBo board fails …."

Try tugging & pushing at all the obvious places where a free length of cable bends abruptly at a fixed object: the connectors, the extruder, the frame, the electronics box, whatever. Watch the temperature graph as you wiggle the cable, because any variation means you've found the problem.

Here's what a USB cable looks like after a zillion flexes against a hard anchor:
https://softsolder.com/2011/10/20/flex- ... met-cable/



To do a thorough job, you must extract the wires from the braided sheath and examine each one individually; nobody wants to do that, but sometimes ya gotta do what ya gotta do.

Good hunting!

Thanks Ed,
That's what I was hoping to avoid
That's exactly what happened with my nozzle heater wire in this thread:
viewtopic.php?f=7&t=5217

As usual, you were right on the money. I jiggled the wire at the same spot the heater wire had broken and that IDed the problem. I should have checked, but I couldn't believe the same thing had happened again (with a different wire). The good news is that after the first problem, MG had sent me a new wiring harness that I never bothered to install. Took about 30 minutes to swap the harness out and the issue appears resolved. I'll fix the bad wire when I get a moment so I can still have a spare harness on hand.

I have to admit I'm now a little worried about the wiring flexing at that spot (topmost zip tie on the print head harness). Two wires have now broken due to the flexing there. Any advice anyone has about mitigating that would be appreciated.

Here's a new temp printout.
Of course, I thought I had it licked before, so I'm hoping this fix lasts.

steve220 wrote: Two wires have now broken due to the flexing there

Well, after a while, you'll run out of wires … [grin]

The simplest improvement: cut the offending cable tie to let more of the braided sheath move around and reduce the stress previously concentrated at the cable tie. The sheath still bends at the next cable tie, but the wires should move less and last longer.

Industrial applications use what's called a drag chain to support the wires in a (more or less) gentle curve as the machinery moves back & forth:
https://www.amazon.com/s/ref=nb_sb_noss ... drag+chain

Several folks have fitted drag chains to the X and Y axes of their M2s, although I think the surgery also requires installing longer and, ideally, more flexible wires.