Ok need some conversation here. Been using my J1S mostly for PLA and low enclosure temperatures. But lately have been printing in PCTG (3dFuel) which runs 260C Nozzle and 80C Bed. Stuff is tough and makes great strong parts and prints better then PETG. When I print short prints I don’t hear servo noise. But when I print 12+ Hour prints (some 48 hour stuff) the servo’s are scorching hot and cannot even touch them and assume the heat is causing expansion in the servo motor shells and then I get noise and then shuddering between poles on the servo’s and then the finish get’s harmonic waves. See attached pictures. 42 hour print speaker enclosure. You can see the surface finish is much better at the bottom and after 30 hours of printing the finish get worse and when going around arc’s it’s skipping due to hot servo’s.
Running full time dehydrators/dryers and inline pre-heaters to preheat the filament before entering the enclosure. Only problem is this stuff sticks really good and you have to wait 2-3 hours after printing for it to cool so it will come off.
What’s is everyone doing to keep the servo motor cooler for long high temp materials?
1 Like
Dang that is great looking speaker boxes Very Impressive. I will need to print me some for my 12”s. I never thought about doing this, I bet it is better than wood since you can build flow chambers!!! You rock!!!
sorry for not answering your question since I dont have a J1S to know.
Scott
Are you sure what you’re hearing is from the stepper motors and not nozzle drag on the top layer?
It’s’ the motors. No Dragging or material buildup on the nozzle. Finished item is dimensionally correct and flat. Did not lift from the bed at all. The motors sound good for the first 6-12 hours and the finish on the corners is good. After 6-12 hours the motors really start to groan and make a sort of vibration grinding sound when it’s goes around corners (the fast x/y linear moves stacking up and when the motors are hot they make the noise, wish I recorded it but did not think about it at the time). It really shows up with combined x/y arc type moves. You cannot even touch the motors without getting burned. I’m running at 60-80mm/s movement speed..
If you look at the first picture behind the speaker magnet top left you can see the arc is smooth 2/3 of the way up from the bottom, then all of a sudden the corners have a rough edge. This rough edge is when the noise is happening. Same picture you can see the 3 back arc’s from left to right get better as the arc get’s larger. But still have the noise. The other pictures are close up shots of the surface finish with the vibration/noise. Straight lines are not showing the bumpy finish.
I run full sized CNC Mills/Lathes and it looks similar to overshoot/braking and then recovery of the servo motor which would cause the strange noise (Big machines have encoders to keep the step in check but these machines do not so it’s like the motor is struggling to hold the overshoot which then causes a buildup of heat. So I’m assuming heat is causing the steppers to loose steps and recover (swelling of the metal parts). I need to FLIR them tonight with my next part (PCTG about 4 hours run) to see what temp they are running at.
I added TL Smoother Diodes on my original Snappy for a similar issue and it runs much cooler and better finish. Don’t know which stepper drivers the J1S is using but dang they are getting hot….
Thanks.
1 Like
Just semantics, but these are steppers and not servos. 
It’s strange though. I have measured resonance that’s related to the stator period of the stepper motors on the J1. But I’ve not heard of heat related issues like this.
Are you taking any steps that would exacerbate heat at the motors? Print speeds/acceleration? Chamber temperature?
1 Like
Yeah agree steppers…. Get typing and mix industries….. Chamber 60-65C and bed is 80C (Chamber is a little less as I do have the top slightly raised open). Material is PCTG FANS 15 % Speed is 60-80mm/s. Need to check accelerations as this should still be stock (did not change those settings for the material). Started with PETG settings and adjusted for PCTG (Heat, Bed, Nozzle and fan).
I’ll get heat readings tonight from the motors. Last night they were hot and that was only 4 hours of run. This one has me stumped other than adding head sinks to the motor shells to reduce heat.
The noise only starts once everything gets really hot. Most of my PLA prints do not do this.
Thanks for assisting……
1 Like
Oh I don’t know how helpful I can be. But 60-65C in the chamber sounds very hot.
May need to find some of the folks who actively heat it to compare notes.
1 Like
I agree with @CadeFoster Great idea, those speaker boxes 
Reagrding your issue: I do not know if the original J1 Marlin can do this on the fly as RepRapFirmware does, but apart from cranking down acceleration values, it might be worth a try to reduce stepper currents with an M906 command.
Edit: If you do this often, adding water cooling to the steppers might solve your issue, even if the Y axis stepper is a bit tricky in that respect since it has a dual shaft.
1 Like
Thanks M, i’ll investigate further and check if that is possible.
1 Like
