extruder temperature stability I am having a problem with my extruder recovering from the fans starting up. The fans start on layer 3. There is no issue with temp on layer 1 and 2. As soon as the fans start, the temp drops about 10° and stays there for about 60 sec. - long enough to cause a fault and stop printing. I set it back to only 50% and that seemed to work, sort of. I then reran my PID calibrations for extruder and bed. Now even at 50% it will trip out. My fans are not pointing at the nozzle. If I turn fans off as it is retreating, it will recover. The I turn fans back on at 35% then advance and it again drops but recovers faster and everything is solid for the hole print. I mean, with the fans on the temp curve is flat. I can increase to 70% and it still is good. It is the first recovery that it too much for it. Why? What to do about it? Marlin 2.0, Repetier Host thanks https://reprap.org/forum/read.php?1,866035,866035#msg-866035 Tue, 09 Jun 2026 17:27:47 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?1,866035,866124#msg-866124 Re: extruder temperature stability https://reprap.org/forum/read.php?1,866035,866124#msg-866124 DSC08391.JPG
I cut a silicon trivet and made a little wind break, just incase, I doubt it would help in your case, you possibly dont need part cooling, when i used mine it was on 10% any less it would stop, but lately once bed adhesion got the ellnet hold i dont need part cooling for PLA, but it does help to have more than one part on the bed allowing enough time for each layer to cool.]]> MechaBits General Mon, 20 Jan 2020 12:05:56 -0500 https://reprap.org/forum/read.php?1,866035,866106#msg-866106 Re: extruder temperature stability https://reprap.org/forum/read.php?1,866035,866106#msg-866106
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ruggb
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MechaBits
Do you need these fans, sounds like your talking part cooling.
Yes, they are the part cooling fans.
I guess the best short term solution is socks.
I like the Repetier firmware solution, but that involves another learning curve.

To fully isolate the hotend, just leaving the nozzle free of course, is not a short term solution, it is the way to do.

You are not the first one having this kind of issue with fan used to cool parts.

If you had posted picture of your set up, it would have saved a lot of guesswork.]]> MKSA General Mon, 20 Jan 2020 05:48:54 -0500 https://reprap.org/forum/read.php?1,866035,866082#msg-866082 Re: extruder temperature stability https://reprap.org/forum/read.php?1,866035,866082#msg-866082
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dc42
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ruggb
What is puzzling me is the fact that if I bring the fan speed up slowly, at 50-70% the temp curve is flat for the rest of the print. It is the initial shock that it doesn't handle.

You can have sensitive PID parameters that react quickly to changes in load such as increasing extrusion speed or turning the fan on. But if you use those PID parameters during initial heating, you will get a large overshoot, which is undesirable. So in most 3D printer firmwares, the PID parameters are a compromise.

However, in RepRapFirmware the tuning process fits the heater behaviour to a FOPDT model, and calculates two sets of PID parameters from that. The slow-and-gentle set is used during initial heating, and the fast-and-sensitive set is used when the temperature is within 5C of target. This provides better temperature maintenance while avoiding a large overshoot during initial heating.

No other firmware that I know of uses this approach. It's still not perfect, so I plan to add feed-forward terms too.

Interesting, thanks. I may look into that. It will be another learning curve as I am using Marlin now.
I am still waiting for Repetier to fix a script offset issue. My #1 script name appears as the tooltip on the #2 script button. and so on...2 on 3, 3 on 4, 4 on 5]]> ruggb General Sun, 19 Jan 2020 20:09:37 -0500 https://reprap.org/forum/read.php?1,866035,866081#msg-866081 Re: extruder temperature stability https://reprap.org/forum/read.php?1,866035,866081#msg-866081
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MechaBits
Do you need these fans, sounds like your talking part cooling.
Yes, they are the part cooling fans.
I guess the best short term solution is socks.
I like the Repetier firmware solution, but that involves another learning curve.]]> ruggb General Sun, 19 Jan 2020 20:05:42 -0500 https://reprap.org/forum/read.php?1,866035,866076#msg-866076 Re: extruder temperature stability https://reprap.org/forum/read.php?1,866035,866076#msg-866076
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ruggb
What is puzzling me is the fact that if I bring the fan speed up slowly, at 50-70% the temp curve is flat for the rest of the print. It is the initial shock that it doesn't handle.

You can have sensitive PID parameters that react quickly to changes in load such as increasing extrusion speed or turning the fan on. But if you use those PID parameters during initial heating, you will get a large overshoot, which is undesirable. So in most 3D printer firmwares, the PID parameters are a compromise.

However, in RepRapFirmware the tuning process fits the heater behaviour to a FOPDT model, and calculates two sets of PID parameters from that. The slow-and-gentle set is used during initial heating, and the fast-and-sensitive set is used when the temperature is within 5C of target. This provides better temperature maintenance while avoiding a large overshoot during initial heating.

No other firmware that I know of uses this approach. It's still not perfect, so I plan to add feed-forward terms too.]]> dc42 General Sun, 19 Jan 2020 16:05:03 -0500 https://reprap.org/forum/read.php?1,866035,866071#msg-866071 Re: extruder temperature stability https://reprap.org/forum/read.php?1,866035,866071#msg-866071 MechaBits General Sun, 19 Jan 2020 14:34:15 -0500 https://reprap.org/forum/read.php?1,866035,866061#msg-866061 Re: extruder temperature stability https://reprap.org/forum/read.php?1,866035,866061#msg-866061 It is obvious the fan is causing the problem. The shrouds are formed to direct the air under, in front of and behind the nozzle/block.

When I tune the PID should I have the fans running?

I looked at those socks long ago and totally forgot about them. That is probably the solution. Thanks.]]> ruggb General Sun, 19 Jan 2020 08:10:50 -0500 https://reprap.org/forum/read.php?1,866035,866047#msg-866047 Re: extruder temperature stability https://reprap.org/forum/read.php?1,866035,866047#msg-866047 dc42 General Sun, 19 Jan 2020 02:26:12 -0500 https://reprap.org/forum/read.php?1,866035,866044#msg-866044 Re: extruder temperature stability https://reprap.org/forum/read.php?1,866035,866044#msg-866044 How much power does the heater use?]]> the_digital_dentist General Sun, 19 Jan 2020 01:27:02 -0500 https://reprap.org/forum/read.php?1,866035,866038#msg-866038 Re: extruder temperature stability https://reprap.org/forum/read.php?1,866035,866038#msg-866038 ruggb General Sat, 18 Jan 2020 18:54:58 -0500 https://reprap.org/forum/read.php?1,866035,866036#msg-866036 Re: extruder temperature stability https://reprap.org/forum/read.php?1,866035,866036#msg-866036 the_digital_dentist General Sat, 18 Jan 2020 15:40:46 -0500 https://reprap.org/forum/read.php?1,866035,866035#msg-866035 extruder temperature stability https://reprap.org/forum/read.php?1,866035,866035#msg-866035 As soon as the fans start, the temp drops about 10° and stays there for about 60 sec. - long enough to cause a fault and stop printing. I set it back to only 50% and that seemed to work, sort of.

I then reran my PID calibrations for extruder and bed. Now even at 50% it will trip out. My fans are not pointing at the nozzle. If I turn fans off as it is retreating, it will recover. The I turn fans back on at 35% then advance and it again drops but recovers faster and everything is solid for the hole print. I mean, with the fans on the temp curve is flat. I can increase to 70% and it still is good. It is the first recovery that it too much for it.

Why? What to do about it?
Marlin 2.0, Repetier Host

thanks]]> ruggb General Sat, 18 Jan 2020 14:37:57 -0500