Heater faults with numerous different heaters and thermistors

dc42

Does the temperature graph show a gradual deviation from the set temperature, or a sudden change?

Foden

@dc42 Hi dc42, it was a sudden change - currnelty into the test, 52 mins, with no fan or filament

Foden

@foden This is what it looks like so far https://imgur.com/a/ycVP0K4. When the fan is on there is a very slight tremor/wave in the hot end temp line

Foden

@foden Now past where it failed last time, will leave it until the end or it fails 32% to go yet

The hot end I'm using has a e3d v6 block and thermistor, with the thermistor at the back nearest the fan. I may tril rotating the unit 180o to see what that does

Foden

@foden completed print run without issue

Phaedrux

Silicone sock?

Foden

@phaedrux Yes, there's a silicone sock on the heater block

Phaedrux

Ah yes, sorry I missed that above.

If it were the fan you should be able to force a fault by heating up and then maxing the fan. If you can't force an error with worst case scenario I think it would be even harder to get a fault in normal operation. That would lead me to think a intermittent writing fault has developed.

I'd try with a new thermistor and writing. If it doesn't help, at least you have a spare.

Foden

@phaedrux I've gone through about 1/2 a dozen heaters and thermisters and several heat blocks all with the same issue. I have LOTS of spares now. If i have the fan at full speed it fails - the link is obvious now but it wasnt until deckingman and dc42 pointed it out.

My hot end assembly is a quick-removal type and I have tried 3 different versions of that, each with their own RJ45 pinvout board for cabling . It's definitely the fan cooling bouncing back onto the head/thermister.

Last test for today is running with fan at 35%, i rotated the hotend 90o and its holding up way better than before. I also up'd the print speed to 200% to stress everything else, loose cables, PSU etc - all good so far

Foden

@foden fan at 45%

Foden

@foden fan at 55% still holding temp

Foden

@foden hmmm, another thought struck me as I'm doing this test. My previous cooling,,that failed, was in steps of 25%. Now I'm doing it in 5% steps, possibly the fan fired up way too fast for the thermister to react? I'm at 75% currently - may try that tomorrow as I'm fed up of testing and its late

Foden

@foden last one tonight. Fan at 100% with hot end rotated 90%. I think he issue was fan related but not quite what we thought. Will test tomorrow with the same setup i have now, but think the fan was firing up too fast for the thermister/heater to cope. As i have the fan running now at 100% and the temp is holding perfectly

Phaedrux

How did you have the fan set when running a PID tune?

Foden

@phaedrux I think the fans where off, hot end and bed, when i was running autotune, which i see, now, would be another contributing factor

Will re-run autotine with fan on and see what happens

Foden

@foden Update - bed fan would be off when i was running the hot end autotune. Hot end fan comes on automatically at 45C

Foden

@foden Sooo, when previously running the H/E autotune without the bed fan i got a heater too powerful and dropped the power value. After Phedrux query i re-ran the autotune with the fan at 85% and on full power I did not get the over power warning. I had no idea the bed fan would have such an impact on the H/E. I don't have that issue with my Maker Select IIIP (almost completely rebuilt running on RAMPS 1.4)

I now need to design a shorter, or stronger fan duct that won't droop and make contact with the print. Trying a very short one just for now

Thanks again for all that read my ramblings and helped out!

Phaedrux

If you can, print your duct in ASA or polycarbonate. Quite a bit more heat resistant.

Foden

@phaedrux Thanks Phaedrux, haven't printed with either of those - will take a look

Phaedrux

@foden ASA is close to ABS. Polycarbonate is another beast altogether.