Normal temperature variation?

[mevander 0]

Hi.

What is a normal temperature variation while printing? I've been wondering about it a while but forgot to ask. When my fans are starting up I have +- 10C in variation and when they have stabilized at 100% I have +- 5 C. Sounds OK or too much?

 

[Dim3nsioneer 557]

I had +/-13°C with the standard PID settings after upgrading to Firmware 14.09.1.

After using the PID autotune feature and setting the PID factors accordingly I got +/-1°C.

 

[mevander 0]

We were discussing that the regulator seemed to be pretty badly tuned. Is there a description somewhere how I would go about changing the parameters?

 

[Dim3nsioneer 557]

Hmmm... there is not much I fear (maybe there is a tutorial somewhere I don't know of).

You need a terminal connection to the printer. You may look at http://reprap.org/wiki/G-code and check the commands M303 and M301/M304. I used Printrun/Pronterface as terminal app.

 

[mevander 0]

I guess this is the thing to try?

http://reprap.org/wiki/PID_Tuning

 

[yellowshark 153]

Once stabilised, maybe 5mins thereabouts after hitting target temp. then variation should be +/- 1 deg. What I have found is that if I need to change temp during a print then it is best to move to the new target in 1 or 2 deg steps. If you jump 5+ degs then it sets off a wilder variation.

 

[Dim3nsioneer 557]

Once stabilised, maybe 5mins thereabouts after hitting target temp. then variation should be +/- 1 deg. What I have found is that if I need to change temp during a print then it is best to move to the new target in 1 or 2 deg steps. If you jump 5+ degs then it sets off a wilder variation.

 

Next one who is going to like TweakAtZ 3.3....

 

[mevander 0]

Hmm, regardless of what goal temperature I set in the M303 command it never goes up to more than 155C. Is it OK to run the test at this lower temperature?

[Dim3nsioneer 557]

That's strange... it should go up to any allowed temperature, e.g. 'M303 S210 C10'... if it doesn't then maybe something is wrong with the temperature sensor. Or the heater. But the sensor would be more dangerous.

 

[mevander 0]

Maybe that can explain some of my weird results I've been getting lately. However, normally when printing the sensor updates the temperature every second or so and it seems to be more or less correct temperature at least (I've checked with a probe). For some reason my printer seems to be a drama queen ...

 

[mevander 0]

I updated the PID settings with the variables I got from running the test at 150C and the temperature during a 210C run is much more stable now at least. It seems to be fluctuating between 209 and 210 so that's a huge improvement.

 

[Dim3nsioneer 557]

May I ask what values you got? Mine were: Kp=16, Ki=1.5, Kd=42.5...

Just to see how big the variation between different UM2s is...

 

[mevander 0]

Sure, my initial values were 12.15, 1.00 and 37.02. My new values were 10.86, 0.7 and 42.37.

I was hoping that this would solve my problems with top surfaces that doesn't touch but it didn't unfortunately. At least the temperature is stable now ...

 

[Dim3nsioneer 557]

Ok, they are quite different. I was hoping the default values could be improved...

It might be an idea to define an option in the Maintenance menu for the PIDautotune...

 

[Daid 306]

Ok, they are quite different. I was hoping the default values could be improved...

It might be an idea to define an option in the Maintenance menu for the PIDautotune...

 

The problem is actually that the sample rate it too low. I spend the last week doing some tests on this and improving it, the latest git version is better at getting at stable temperatures now.

 

[Dim3nsioneer 557]

The problem is actually that the sample rate it too low. I spend the last week doing some tests on this and improving it, the latest git version is better at getting at stable temperatures now.

 

It's the one my UM2 uses now...