<p>You should run the fan at what you expect it to be at the majority of the time it is printing.  If you tune at 100% fan and never use a fan then it will be too aggressive, if you tune at 0% fan and use the fan then you will struggle to maintain/reach temperature.</p>

CC BY-SA 3.0
2017-11-27T17:06:23.550Z
Thank you, that completely makes sense and I think is an important tidbit that all bazillion of these guides should mention.
Adam Plocher
CC BY-SA 3.0
2017-11-30T06:48:04.563Z
One last (possibly stupid) question: does it matter if there is filament in the printer when Auto-Tuning?
Adam Plocher
CC BY-SA 3.0
2017-11-30T12:12:52.203Z
Ideally I'd think you should extrude when you tune but I'm not sure if that is possible.  Having filament in might help but most of it is going to ooze out as it heats up anyway.
tjb1
CC BY-SA 3.0
2017-11-27T16:20:25.983Z
2017-11-27T16:20:25.983Z
tjb1
<p>I'm using an Anet A8 with Marlin 1.1.6.</p>

<p>I've read countless guides on PID auto-tuning and never saw that the fan needed to be on, but when I look at the Marlin source code's ANet A8 configuration (here: <a href="https://github.com/MarlinFirmware/Marlin/blob/1.1.x/Marlin/example_configurations/Anet/A8/Configuration.h" rel="nofollow noreferrer">example_configurations\ANet\A8\Configuration.h</a>) it states:</p>

<pre><code>  ...

  // ANET A8 Standard Extruder at 210 Degree Celsius and 100% Fan
  //(measured after M106 S255 with M303 E0 S210 C8)
  #define  DEFAULT_Kp 21.0
  #define  DEFAULT_Ki 1.25
  #define  DEFAULT_Kd 86.0

#endif // PIDTEMP
</code></pre>

<p>So, should activate the fan before running the auto-test if I wish to update the PID values in Marlin for my Anet A8?</p>

<marlin><anet-a8><cooling>
Should I be doing PID auto-tuning with my fan at 100% (Anet A8)
Adam Plocher
# Should I be doing PID auto-tuning with my fan at 100% (Anet A8)

(Asked by: username_0 on 2017-11-27)

I'm using an Anet A8 with Marlin 1.1.6.
I've read countless guides on PID auto-tuning and never saw that the fan needed to be on, but when I look at the Marlin source code's ANet A8 configuration (here: example_configurations\ANet\A8\Configuration.h) it states:
  ...

  // ANET A8 Standard Extruder at 210 Degree Celsius and 100% Fan
  //(measured after M106 S255 with M303 E0 S210 C8)
  #define  DEFAULT_Kp 21.0
  #define  DEFAULT_Ki 1.25
  #define  DEFAULT_Kd 86.0

#endif // PIDTEMP

So, should activate the fan before running the auto-test if I wish to update the PID values in Marlin for my Anet A8?

**Tags:** marlin, anet-a8, cooling

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## 1 answers

### Answer by username_1 on 2017-11-27. Score: 7 | Accepted answer

You should run the fan at what you expect it to be at the majority of the time it is printing. If you tune at 100% fan and never use a fan then it will be too aggressive, if you tune at 0% fan and use the fan then you will struggle to maintain/reach temperature.

> **Comments:**
> **username_0**: Thank you, that completely makes sense and I think is an important tidbit that all bazillion of these guides should mention.  
> **username_0**: One last (possibly stupid) question: does it matter if there is filament in the printer when Auto-Tuning?  
> **username_1**: Ideally I'd think you should extrude when you tune but I'm not sure if that is possible.  Having filament in might help but most of it is going to ooze out as it heats up anyway.  

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