UM2 50W heater PIDs and power budget

[rotorhead 1]

I have an ultimaker 2 With Tinker firmware 17.10.1 and have just fitted a 50Watt heating element.

I moved the head to the middle of the bed, almost touching it and with the fans on and then ran a PID auto-tune using the firmware. This gave me p23.4 i1.2 d30.4 but I am still getting a 10 degree overshoot, 8 degree undershoot and therefore a very oscillating temperature for the first few minutes. Searching the internet and people are suggesting figures ranging quite significantly from 5.6 0.35 23 to 12 0.75 55.

Is there another way of working this out or has anyone else found a solution that works? I feel like it should perform better but maybe not?

 

I've also looked at the power budget. Default was 175W total 150W bed and 25W heater. Presumably I need to increase the heater to 50W but do I also need to increase the total or is this a fixed value based upon the 220W power brick?

[tinkergnome 927]

2 hours ago, rotorhead said:

then ran a PID auto-tune using the firmware

 

Don't use this... Marlin auto-tune does not work - it never has 🤷‍♂️

 

2 hours ago, rotorhead said:

Is there another way of working this out or has anyone else found a solution that works? I feel like it should perform better

 

I would like to be wrong, but articles that are useful in practice (for this specific task) are very rare...

Here is a nice write-up that may help (especially the "Troubleshooting" section):

 

https://forum.seemecnc.com/forum/viewtopic.php?f=36&t=11440&p=106976

 

 

3 hours ago, rotorhead said:

do I also need to increase the total or is this a fixed value based upon the 220W power brick?

 

no!, yes! 🙂

 

BTW: The absolute values do not count, the ratio between them is the key. Here is the shortest (but complete) explanation from the originator:

 

 

[rotorhead 1]

On 8/12/2020 at 9:22 PM, tinkergnome said:

no!, yes! 🙂

 

BTW: The absolute values do not count, the ratio between them is the key. Here is the shortest (but complete) explanation from the originator:

So in which case and as I understand it, I need 175 150 50 and it's absolutely fine that the sum of the parts do not add up to the total?

Presumably the 220-175 difference is so that there is some allocation for the steppers and main board?

 

On 8/12/2020 at 9:22 PM, tinkergnome said:

I would like to be wrong, but articles that are useful in practice (for this specific task) are very rare...

Here is a nice write-up that may help (especially the "Troubleshooting" section):

 

https://forum.seemecnc.com/forum/viewtopic.php?f=36&t=11440&p=106976

 

I have also really struggled to find any decent information on this for the UM2 but you are correct about that article being very good. I have just followed through the process as described there with the cooling fans on full, nozzle  almost touching the build plate and in the XY centre and with the bed set to 50 degrees. There was no material in the head however and I was only heating to 100 degrees (for speed.)

After about an hour of tinkering, I ended up at a set of PID values that were disappointingly close to the default values for the 30W heater!

My trial and error got me to P:13 I:0.4 D:50

and 35W default is P:12 I:0.75 D:55

and actually this looks slightly better!

The autotune suggested 23 1.2 55

 

I will start some prints and continue to fine tune for real world use and then update this thread for anyone else needing this.

 

I did some screen shots and copied the PID values on to some of them for reference.

Edited August 14, 2020 by rotorhead

[tinkergnome 927]

4 hours ago, rotorhead said:

So in which case and as I understand it, I need 175 150 50 and it's absolutely fine that the sum of the parts do not add up to the total?

Presumably the 220-175 difference is so that there is some allocation for the steppers and main board?

 

yes (to both questions).
All these numbers are only guesses, estimates and averages anyway. 🙂

As long as you use the default PSU and everything runs stable - just leave it at this.

 

Good luck with the PID tuning!