MakerGear Forum

Hi Everyone,

I know there are a ton of topics on this subject, but it's tough to piece them all together to see what actually worked and what didn't - so my apologies for creating another one.

Problem: Temperature fluctuation on the hotend +/- 7 degrees C when set in the controls. A little more extreme when printing (~+/- 15).

Model: Single extruder - not sure which revision (Purchased in Feb 2016).
Slicer: Simplify3D

What we've tried:
-Replacing thermistor
-Replacing V4 Heater Cartridge
-Removing the wire bundles from the harness, measured each temp related one back to the Rambo board (while moving it around) and they were all ~1 Ohm or less.

Not sure how to upload pics, but here are the links to the pics of the Consol and the printer - sort of taken apart..

https://ibb.co/6DjpVJm
https://ibb.co/CVcprBf

You can see the fluctuation in the extruder temp. It's slight, but it won't allow a good first layer, causing the entire print to fail. You'll see in the 2nd pic we have the hot end out of the bracket, but that was just for testing purposes. New thermistor measures 130K Ohms.

We have successfully used these settings and made this print probably 500 times - so I don't think the settings are to blame. We just upgraded to the newest version of Simplify3D - but we were having some issues prior to that. We print via USB cord.

That's about all I can think of. Hoping someone can help. Thanks in advance for suggestions and assistance.

SnakebiteSnaps wrote: ↑

Wed Feb 20, 2019 3:11 am

Problem: Temperature fluctuation on the hotend +/- 7 degrees C when set in the controls. A little more extreme when printing (~+/- 15).

Slow cycling like that indicates the hot end's PID loop coefficients don't match reality.

Preheat the extruder to maybe 200 °C, run a PID calibration (M303), store the results in EEPROM (M500), and that should do the trick.

PID coefficients depend on the hot end's physical condition, so you should re-do the calibration whenever anything changes on the hot end. Even removing & reinstalling the same hardware will change the contact points between, say, the thermistor and its hole in the hot end.

A dab of good heatsink compound on the thermistor should stabilize its contact with the hot end, although that will change the reported temperature and PID coefficients. Probably doesn't make any real difference, but I felt better:

https://softsolder.com/2018/08/24/maker ... libration/

So Ed, I have 3 hotend one with .25, .35 and .5 nozzle.. Sounds like I should run a pid cal when I set my starting height each time I switch?
Is that the entire process, set to 200C, let it stabilize, enter M303 on the console then M500?
Thanks!
Doug

airscapes wrote: ↑

Wed Feb 20, 2019 10:29 pm

run a pid cal when I set my starting height each time I switch?

Assuming you swap entire hot ends (*), including their thermistor & heater, then you can calibrate each one, write down its PID values, manually set 'em with M301 when you install it, then use M500 to store 'em in EEPROM.

set to 200C, let it stabilize, enter M303 on the console then M500

Yup. In principle, you could calibrate from a cold start, but IMO it's more realistic to let the hardware stabilize.

(*) Because you bend those fragile thermistor wires every time you swap hot ends, keep a couple thermistors on hand. You'll need 'em.

Yep, think I have one.. I bought both when the wire broke on the heater.
The other nice thing about 3 complete hot ends is I can always swap a nozzle if something fails in one of them. Found it faster and easier to switch the complete end rather than change the nozzle..

@Ed
Hey this was the result of the auto PID
Recv: bias: 57 d: 57 min: 147.80 max: 152.42
Recv: Ku: 31.43 Tu: 30.47
Recv: Classic PID
Recv: Kp: 18.86
Recv: Ki: 1.24
Recv: Kd: 71.83
Recv: PID Autotune finished! Put the last Kp, Ki and Kd constants from above into Configuration.h

I then ran M500 but it did not say setting saved or anything like after doing a M206 . When I use this hotend I just calibrate how to I enter this data into the console??

I had the temp set to 150 as it failed and said too hot at 200

Oh.. think I broke it!
Send: M500
[...]
No response from printer after 3 consecutive communication timeouts, considering it dead. Configure long running commands or increase communication timeout if that happens regularly on specific commands or long moves.
Changing monitoring state from "Operational" to "Offline (Error: Too many consecutive timeouts, printer still connected and alive?)"
Connection closed, closing down monitor

Wait.. maybe I got I ran M301 P18.64 I1.24 D71.83 and M500 which saved..

airscapes wrote: ↑

Sat Mar 02, 2019 11:34 pm

increase communication timeout if that happens regularly on specific commands

Programming EEPROM goes slowly; I haven't seen a timeout, but I suppose it depends on the Marlin flavor and surely the moon phase.

Apparently feeding the parameters returned by M303 into M301 is required before the M500, again modulo flavor & phase.

Once you figure out the sequence, just do those things!

AFAICT, there is no doc for any of this and what works for one person at one time serves as a hint for another person at another time. So it goes.

Yup! All good temp stable now when printing no bouncy bouncy..
Thanks Ed!