Symptom of Heat Cartridge Slow Failure?



  • I keep bumping up my print temperature and it seems the cartridge has trouble staying at temperature even though auto-tuning was done at 260C.

    I'm printing PLA at 215C (which seems too hot) to prevent delamination, but I suspect my heater causes the temperature to fall during a print such that even a 205C print falls enough to delaminate standard PLA.

    I thought I may have misclicked a recent print that delaminated, but recently it happened at 215C, so my guess is the heater slowly fails but the machine manages to finish the print - just hot enough to extrude PLA. In raising the print temperature, I may be adjusting for a failing heat cartridge.

    Could there be another part going bad that I'm overlooking or does this sound like a heater cartridge failure?



  • @saffi If the heater is struggling to maintain the temperature, it will show in the Duet Web Control Panel. So the first thing to check is run a print and observe what the actual temperature is.



  • I did observe it dropping while printing, it was struggling to stay above 213C and never crossed 215C and then dropped down to 210C before pausing due to heater fault. I ordered a new E3D premium heater cartridge and I'll see if that helps.

    I'm kind of interested in seeing if it changes the glossy / matte texture of a specific print effect that seems to show up when I alter slicer settings mid-print.



  • @saffi A couple of things. Is that temperature drop with the part cooling fan running? Does it help if you turn the fan off? If so, then it might be that there is too much air flow over the nozzle and fitting a silicone sock might help if you haven't already got one. The only other thing I can think of to check is the supply voltage. Does that look healthy in DWC? If not it could be that your power supply is struggling. If it's OK then I guess the only thing left is the cartridge itself.



  • @deckingman said in Symptom of Heat Cartridge Slow Failure?:

    fitting a silicone sock

    this could be it, I can't remember if I tuned it with or without the silicone sock, but I'll retune the hotend with the sock removed and then try printing again with the sock added for extra insulation.

    Also, is there a way to tell the hotend to use a little more power when keeping temperature just to avoid temperature drops due to fluctuations like having fans at 100% or having the silicone sock removed?



  • @saffi Ideally you should tune the heater in the same conditions as you would be using it. Tuning it opposite to how it would be used in practice means it would be using an inaccurate model of it's performance.

    Try tuning it with the sock on and the part cooling fan running at the speed you'd normally use while printing. That should give you the most accurate thermal model and best performance.

    Also keep in mind that if you're printing with a very high flow of plastic, it will also cool the hot end as the heat is taken away by the plastic.



  • I have completed "draft versions" of 2 Hypercube Evolutions both with a range of modifications to meet my ideas of useful improvements. All parts are in PLA. Now time to finalise by replacing all parts with PETG and hope the PLA near the Hot End doesn't warp. Lots of failed parts so far as PETG tuning progresses.

    Whilst doing a Pressure Advance tuning the other day (large thanks to the author of the Python Script - I need to learn this language), using transparent PETG, at 240 (nominal advised range of 230 to 240) I noticed that during the high speed segments the plastic was going opaque indicating a lower temperature - the slow speed segments were clear. It appears the temperature gradient between the thermistor and the bore of the nozzle is an issue.

    I am using E3D volcano with 0.6 nozzle. At high flow ( 25 mm3/sec) the power is 7 watts. I started a spreadsheet to estimate the temperature gradient in the nozzle (the heat block a second order issue) - it is still a work-in-progress. It appears that the temperature gradient is large and any precision in PID control of the block temperature (that is excellent mostly within +/- 0.2) is less important than understanding plastic temperature control at varying flow rates, and precision is unachievable nor necessary.

    I guess others must have grappled with this issue - I have not enquired yet.

    In the meantime I am using 250 for this PETG as it prints clear at high flow but am wondering that at low flow rates it might overheat and/or not print well ???? A more thoughtful fan speed regime probably.

    My thought is a Temperature Advance parameter in M307 would be useful. Calibrated using clear plastic and for example a trivial variation of the Pressure Advance script.

    Any suggestions appreciated whilst I do all the reprinting.



  • @garis I've observed that the unwanted opacity with PETG that you described is not caused by temperature fluctuations, its caused by too much speed. My Ormerod (.5 nozzle) and Delta (.4 nozzle) both begin to exhibit this issue above 35 mm/s and it gets worse as speed increases. When sliced at 30 mm/s there is no opacity.


  • administrators

    @garis said in Symptom of Heat Cartridge Slow Failure?:

    My thought is a Temperature Advance parameter in M307 would be useful. Calibrated using clear plastic and for example a trivial variation of the Pressure Advance script.

    Feedforward power adjustment to anticipate changes in extruder power needed when the fan is turned on or the extrusion rate is increased has been on the firmware wishlist for some time. So far it's not been a sufficiently high priority item to be implemented.



  • Well, I retuned the hotend and it seems to be working fine so far on 12 hour prints.

    I may simply add tuning the hotend to a weekly or monthly schedule as regular printer maintenance.

    The problem seemed to be the hotend slowly drifting down in temperature, so perhaps there's an unknown factor (like an aging but still working heater cartridge) that the tuning from a few months ago did not experience.

    I'll post if anything changes. I plan on putting one of the new premium heater cartridges from E3D in the old one's place anyway, so perhaps those will be more reliable. I had to four wire most of my wiring on my PT100 after some strange readings, but once upgraded it hasn't skipped a beat, so the extra $10 for a premium heater cartridge may be a good investment.


  • administrators

    Have you checked that the screws in the E0 or E1 terminal block and the VIN terminal block are still tight?



  • @dc42 said in Symptom of Heat Cartridge Slow Failure?:

    Have you checked that the screws in the E0 or E1 terminal block and the VIN terminal block are still tight?

    No, but I will definitely add that to my troubleshooting list. I could imagine with the printer rattling during several weeks of printing they could loosen.


 

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