Hot end will not heat up...

[scrubngbubles]

Hello everyone,

I just finished my Rostock Max V2 stock build about a day or two ago. I was able to successfully calibrate it and got up to the point where I extruded some filament and was about to start my first print. After starting the first print I noticed the hot end wouldn't come up to temperature and hovered around 218 degrees out of the target 228. After having the temperature hover for approx. 40 minutes I cancelled the print and attempted to re calibrate with PID Autotune. Those calibrations all failed and the hot end would not get past room temperature (approx. 23 degrees).

I noticed that the hot end would not heat up even if told to heat up. For example, I ran a test where I attempted to pre heat the hot end through matter control after watching the hot end temperature cool down. Even though I had hit the preheat button the hot end temperature would continue to decrease. Even after reaching room temperature It would not heat up regardless of the type of command sent to it (Pre-heat, PID Autotune, Print, etc.).

I did do some searching on the forums for similar issues and attempted some troubleshooting suggestions from those.
Here's what I did:
- I checked all three fuses on the Rambo board and all fuses are good
- I checked the thermistor resistance and received a reading of around 105k ohms. I'm not exactly sure if that means it's below spec and broken or if it's fine, but to me seeing a resistance value in that range indicated that the thermistor was most likely not the cause. I could be wrong though...
- I checked the continuity of the connections from the Rambo board to the hot end via the terminal screws on the Rambo board and the connections at the hot end. No problems there.
- I re uploaded the firmware to the Rambo board. I then performed another PID Autotune calibration. This failed due to a time out and the temperature of the hot end never went past room temperature.

Not really sure what else I can do before I start replacing parts. Also not sure what parts to replace. After all these checks my guess would be replace the Rambo board, but that seems a little extreme and I wanna make sure I have checked everything I can before I replace it.

Any help would be greatly appreciated.

Thank you,
-Mike

[RocketMagnet]

I'm a tad confused, are you saying it wont heat up at all or when it starts cooling down from a higher temp it wont reheat?

If it's the latter i'd disconnect your Printer from the computer and try preheating then cooling then preheating again from the Printer UI itself to rule out MatterControl.

I had some issues with weird behaviour with MC and it locking into cooling/heating cycles as cancelling mid code running didn't/doesn't cancel the last command like Repetier Host does. I found if I interrupted the current command (stop the print) I had to disconnect MC from the printer or it would just continue heating or cooling.. not sure if this has been fixed with the latest version of MC? Not sure how MC works but cancelling doesn't seem tell the printer it's cancelled like Repetier does so it continues doing what it was doing.

[scrubngbubles]

Sorry, I should have been a little more clear. At first it would not heat up after cooling down. Now it does not heat up at all.

I also emailed tech support and they suggested checking the thermistor. This was my first time using rtv so my hope is that the initial installation of the thermistor messed the heating process up and a re-seating will fix the problem. I'm still waiting on the rtv to finish curing, but after that I plan on isolating the printer and attempting to heat via the lcd control. I also plan on checking the voltage coming out of the Rambo board to make sure that the board is not the problem.

I'll keep the thread posted. (I think that was a pun?)

Thanks,
-Mike

[scrubngbubles]

So I reseated the thermistor and it seems to be working fine.

Another suggestion I got from tech support was to check the LED lights. He said there should be two red LED's that light up located directly under the HEAT 0 and HEAT 1 inputs. The HEAT 0 LED does not light up and I detected no voltage from that port after heating. I did notice that HEAT 1 lights up and provides the proper voltage.

What I would like to try to do is use the HEAT 1 port for the first print. My guess is that this board has modular heating inputs to allow for multiple extruders. If that's the case then I should be able to change up the inputs and change something in software and have Matter Control do everything it was doing for HEAT 0 to HEAT 1.

I changed the ports on the board and put the extruder to HEAT 1 and attempted to preheat the hot end via the LCD. For this initial test all I wanted to do was confirm the hot end and thermistor worked. The test was successful and thankfully I stopped the command before things got out of control. My guess is that the PID loop controlling the heating is still set to sense HEAT 0 and reading from T0. I want to change this to HEAT 1 and keep T0.

I did some searching on both the forums and the firmware website and noticed the "pins.h" file can be configured to remap arduino pins. I do have experience with Arduino and am a programmer so my initial thought was change the values. I tried changing some pins values around and haven't really come up with anything substantial.

The latest development I made was the smoking of my hot end at approx. 250 C (a cool yet slightly terrifying expierience) and the potential realization that maybe a new Rambo board might be my solution. I also want to upgrade to an E3D V6 hot end. I'm not too big a fan of the rtv. If possible I would like to print the mount parts for the E3d V6 with the current hot end so I can be prepared to install it if I decide to get it.

If anyone has any information on remapping pins or any more advice that'd be great.

Thanks and Happy Holidays,
-Mike

[RocketMagnet]

So it does start heating up to touch but the temp doesn't register?

Check the thermistor is correctly seated in the correct thermistor port on the Rambo, but saying this i'm pretty sure an unplugged thermistors (or dead) is obvious by the error it throws to the LCD for that specific temp readout.

If your thermistor comes loose from the hot end it can be dangerous as its possible to overheat as its under measuring so the heaters go on full.
I think there is some logic now that detects this situation but the best thing is to ensure its in well and wrap some Kapton tape around it also to help.. plenty guides on here on hotend builds.

I done some minor software mods last year that outputs if the heaters are running (% Load) and some XYZ position stuff to the LCD..
http://forum.seemecnc.com/viewtopic.php ... 4&start=25
http://forum.seemecnc.com/viewtopic.php?f=60&t=6989

With the % loads you can see if its at least trying to turn the heater on. Its really simple changes and as long as your confident in modding and uploading the code its easy to do.

As a total check i'd confirm the heating resistors are ok by measuring the Ohms over them combined (think it should be about 3.5 combined) I think a single is about 7 ish.
Yeah they should be fine but it is possible for them to die, would have to be both simultaneously for no heating at all and in my experience usually one goes and then your printer just cant attain running temps as its only working on one heater and measuring the Ohms confirms it.
I suppose if you really messed up the RTV on the heaters with lots of air space you could kill them pretty quickly.. but I doubt this.. did you get lots of white smoke (not just wisps of white smoke) from the heaters area on first heating?

<edit> this post should clearly come before your last one..

[scrubngbubles]

Well, I tried re-uploading the firmware and using HEAT 0 for the hot end an it worked. My guess is that I did something to the firmware the printer didn't like. As to what that is, I have no clue. But it works. Yay.
I do plan on posting a similar question to the google group for delta printers. I am still curious as to how to get the board to think it has one extruder on a different HEAT location. This could potentially save a board in case the initial ports are broken.
Thank you for the help...
-Mike