Print quality difference between bed ON and bed OFF

MoS-tekknix

Only a simple guess:

Try to monitor VIN in the WebInterface and how far it will drop.

And do a M122 in the print to print out the Statistics.

Take a closer look to;

[[language]]
Supply voltage: min 10.8, current 12.0, max 12.1, under voltage events: 0, over voltage events: 0

and

[[language]]
MaxReps: 4, StepErrors: 0, FreeDm: 218, MinFreeDm 146, MaxWait: 366839ms, Underruns: 9, 0

Cheers
MoS-tekknix

dc42

We've seen this before when the bed is running in bang-bang mode. Switching to PID has always solved it. If the PID is unstable, for example because you haven't run bed heater tuning, then the PID control could oscillate and produce the same symptom.

The cause is that the power voltage drops a little when the bed heater turns on, which reduces the hot end power. This is exacerbated if the wires between the PSU and the VIN terminal block are too thin.

In the next firmware version, on the Duet WiFi and Duet Ethernet the heater power will be compensated for changes in the supply voltage.

Persival

Thank you both for your answers.

I will check voltage drop.

I have autotuned bed at 15v PSU and 100% PWM, and M307 values come from there, but I will run it again at 12v and test at 12v.

Wires between PSU en Duet are 3.5mm and between Duet an bed are 4mm… but also will check wires and adjust blocks too.

I will report soon....

In the mean time.... a SRR may be help in this case? or will be the same ?

THX!!

MoS-tekknix

It may help if the PSU is not so culprint here. If this will drop down the same will be vaild with a SSR. The Wires should be thick enough.

dc42

You should run bed heater tuning at whatever PSU voltage you normally use. You can see whether the bed is operating in stable PID mode by watching the bed heater LED on the Duet, or on the bed if it has one. If it is running in PID mode then it should flicker but not flash on and off.

Persival

Did the adjustements.

-Retightened terminal blocks.

-Two new PID configurations tested:

PSU at 12v: Autotune runed for bed at 100% PWM, and default hotend PID settings
PSU at 15v: Autotune runed for bed at 90% PWM, and for hotend at 80% PWM

After print with test #1 settings:

Supply voltage: min 11.7, current 12.2, max 12.4, under voltage events: 0, over voltage events: 0

MaxReps: 4, StepErrors: 0, MaxWait: 484810ms, Underruns: 81, 0

After print with test #2 settings:

Supply voltage: min 14.0, current 15.0, max 15.4, under voltage events: 0, over voltage events: 0

MaxReps: 5, StepErrors: 0, MaxWait: 155000ms, Underruns: 0, 0

Printed part is OK on both tests.

Two Questions:

On test #2 voltage min was 14v over 15v… is it an acceptable drop? or could be better and more stable with a better quality PSU?
Cant find VIN monitor on web interface. I measured voltage externally. Can I add it to Web interface ? or maybe VIN monitor was added to a latest release?

MoS-tekknix

Hi,

the Voltage-Drops seems to be fine and i high quality PSU will not change it.

The "bigger" 1V drop of the Second-Test belongs to the Bed-Heater. Even with a 12V and 24V original Meanwell - PSU (both around 650Watt) i've noticed drops up to 1.2Volts. This has changed to max 0.3V drop after using SSR's for the HeaterBed

Additional you should find VIN in WebIf if you look up right

But if you meassure the Drop to on the PSU directly i assume this clone of Meanwell is more bad designed

Persival

Thank you!

Dont have a VIN in web.
Web Interface Version: 1.15a

I will update it anyway.

I measured votage with multimeter from Duet VIN terminal blocks.

MoS-tekknix

Puh, it will be a great idea to update…

Persival

I know, I know…jajaja... its the default coming with duet, only a couple of month ago buyed, I must to upgrade all the combo.

Thanks David, Thanks MoS.

Problem solved. Great result.

https://drive.google.com/open?id=0B9oEoHHZpMfITzZlV3VwMHd3dXc
https://drive.google.com/open?id=0B9oEoHHZpMfIc1dkc3JlSE5CajA