Temperature problems

I'm completely at a loss as to what's wrong/how to fix it.

Printing misc objects with PLA on the Ormerod 2.

The problem:
At some time interval from the beginning of print, the Ormerod 2 just quits and stops. Stopping the print and trying to extrude manually works just fine, so no idea why it stopped. From troubleshooting online, the reason it stops is the temperature is too low for extrusion and arises raising the temp a few degrees until the problem goes away. The problem does not go away, but it does allow the print to go longer before quitting. Eventually following this routine, the starting temperature is all the way up around 215 degrees which is definitely too hot, but it still eventually stops looking like the temperature is too low. (And this can gum up the print head too)

Additional:
Loading the material extrudes fine at 170 degrees (A little low, but the prints are set at 182, the temp I calculated on my Mendel as optimal for this reel of material).
I've replaced literally everything in the path trying to figure out what part is bad, if any. Several hot-ends (Both mono and dual-color quick-sets), entire new extruder motors/assemblies, 0.6 duet, 0.8.5 duet, different firmwares (Found a repeatable crash-bug in 1.11), managed to improve the accuracy of the bed leveling while I was trying to figure all this out...

Truly, I'm at a loss what's wrong.

Any suggestions what to try next would be very welcome! Thanks!

I believe the firmware will stop extruding once the temperature hits 160 to prevent damage to the hotend. Since 170 is quite close to that, maybe it's briefly dipping below the cutoff temperature? This can be overridden by enabling "cold" extrusions with the M302 command, though that's usually only done during maintenance.

Is the measured temp actually dropping under 170? If so, do you have a part cooling fan that might be cooling the heating block?

How did you calculate the optimal temperature? Normally this is done by a test print.

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Slicer: Simplify3D 4.0; sometimes CraftWare 1.14 or Cura 2.7
Delta with Duet-WiFi, FW: 1.20.1RC2; mini-sensor board by dc42 for auto-leveling
Ormerod common modifications: Mini-sensor board by dc42, aluminum X-arm, 0.4 mm nozzle E3D like, 2nd fan, Z stepper nut M5 x 15, Herringbone gears, Z-axis bearing at top, spring loaded extruder with pneumatic fitting, Y belt axis tensioner
Ormerod 2: FW: 1.19-dc42 on Duet-WiFi. own build, modifications: GT2-belts, silicone heat-bed, different motors and so on. Printed parts: bed support, (PSU holder) and Y-feet.
Ormerod 1: FW: 1.15c-dc42 on 1k Duet-Board. Modifications: Aluminium bed-support, (nearly) all parts reprinted in PLA/ ABS, and so on.

Quote
0x0000
I believe the firmware will stop extruding once the temperature hits 160 to prevent damage to the hotend. Since 170 is quite close to that, maybe it's briefly dipping below the cutoff temperature? This can be overridden by enabling "cold" extrusions with the M302 command, though that's usually only done during maintenance.

The heart of the problem is that the board + firmware believes that the temperature isn't dropping, but it is. So it's reading incorrectly. I have no idea what the too-cold threshold for this material when the print fails is. It would be amazingly difficult, I would think, for the heat loss from extrusion to overcome the capability of the block heater... Although it would be awesome to be able to extrude at that kind of speed!

Quote
achaz
Is the measured temp actually dropping under 170? If so, do you have a part cooling fan that might be cooling the heating block?

The measured temperature stays steady at the requested temperature, according to the firmware. The only way I "know" the temperature is being lost is from how the extrusion is occurring - too hot, it flows/drops out of the hot-end like water to too cold - where it bunches up and has bad extrusion (There were several example pictures online of this which matched what was happening to me), and then it finally jams up being too cold to extrude (The extruder avoids damage at this point by carving a little hole in the material at the gear, so it can't grip anymore)

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Treito
How did you calculate the optimal temperature? Normally this is done by a test print.

That's exactly how I did it. 25x25x100 hollow cube that scales in temperature, and then measure when found the right one. The reading will likely change from printer to printer, but using a value known for one printer makes a good starting-point for the other.

But it's the best idea to reprint this tower.

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Slicer: Simplify3D 4.0; sometimes CraftWare 1.14 or Cura 2.7
Delta with Duet-WiFi, FW: 1.20.1RC2; mini-sensor board by dc42 for auto-leveling
Ormerod common modifications: Mini-sensor board by dc42, aluminum X-arm, 0.4 mm nozzle E3D like, 2nd fan, Z stepper nut M5 x 15, Herringbone gears, Z-axis bearing at top, spring loaded extruder with pneumatic fitting, Y belt axis tensioner
Ormerod 2: FW: 1.19-dc42 on Duet-WiFi. own build, modifications: GT2-belts, silicone heat-bed, different motors and so on. Printed parts: bed support, (PSU holder) and Y-feet.
Ormerod 1: FW: 1.15c-dc42 on 1k Duet-Board. Modifications: Aluminium bed-support, (nearly) all parts reprinted in PLA/ ABS, and so on.

Quote
Treito
But it's the best idea to reprint this tower.

I agree, but in order to reprint the tower, I need to first be able to complete a print that large. I am not able to at this point due to the temperature problems.

Are you really certain that the relationship ship between the displayed and actual temperature is changing? That is not impossible if your Duet or thermistor is faulty, but is certainly unusual. Can you check using a multimeter with thermocouple probe? Are the thermistor leads secured so that the thermistor cannot move within the heater block?

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

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dc42
Are you really certain that the relationship ship between the displayed and actual temperature is changing? That is not impossible if your Duet or thermistor is faulty, but is certainly unusual. Can you check using a multimeter with thermocouple probe? Are the thermistor leads secured so that the thermistor cannot move within the heater block?

I do have a multimeter with thermocouple probe, but I have not been able to deduce how to attach it securely while a print is underway to determine this conclusively. I've tried securing it with kapton tape, but it just falls off.

My "certainty" (used loosely, as I'm only 90% sure) lies in inferential relationships based on the results I'm getting that this web-page claims means my extrusion is "too cold" [www.matterhackers.com]
Looking at the print, it goes from liquidy extrusion (too hot), to normal, to too-cold.. The change is visible in the print.

Perhaps try the following quick & simple test:- remove the filament and unclip the Bowden tube from the extruder, then feed your thermocouple probe down the Bowden tube till it hits the nozzle. Tape the free end of the Bowden tube and thermistor wires to the side of the extruder or X-arm so that the thermocouple is not dislodged by the carriage movement. Run your print job in the normal way. Obviously the extruder will not be feeding any filament, but otherwise the printer should behave the same as it does while printing. Monitor the temperature on both the digital thermometer and the temperature reported by the Duet. If the thermocouple reading and Duet temperature reading do not stay in step, it indicates a fault somewhere in the thermistor measuring mechanism and we can try narrowing it down further.

This is also useful to show how accurate the Duet's temperature measurement is. You can add calibration commands to your config.g file to get the Duet readings accurate over the operating range of your hotend.

Dave

Edited 1 time(s). Last edit at 05/03/2016 07:57AM by dmould.