Speed Based Pressure Advance

CCS86 · 10 Dec 2022, 18:38

Running pressure advance calibrations at different printing speeds shows the need for different ideal values, based on speed.

I haven't done enough testing yet to see what the shape of the speed vs PA curve is, but I think even a linear lookup would be an improvement over a single static value.

o_lampe · 11 Dec 2022, 08:09

@CCS86
Why is speed the most important factor? Isn't it acceleration , too?

CCS86 · 11 Dec 2022, 13:38

@o_lampe

Speed is very important because it has a very direct impact on the flow rate / nozzle pressure required for correct extrusion.

I haven't checked the impact acceleration has. But, the reality is that it is very uncommon to vary print move acceleration during a print. But, varied speeds are common.

o_lampe · 12 Dec 2022, 07:52

@CCS86 said in Speed Based Pressure Advance:

But, the reality is that it is very uncommon to vary print move acceleration during a print.

I agree, but it should be included as a constant at least.
AFAIK, the next FW-update come with dynamic acceleration. So, if it has an impact on PA, it gets complicated.

CCS86 · 13 Dec 2022, 03:38

@o_lampe said in Speed Based Pressure Advance:

@CCS86 said in Speed Based Pressure Advance:

But, the reality is that it is very uncommon to vary print move acceleration during a print.

I agree, but it should be included as a constant at least.
AFAIK, the next FW-update come with dynamic acceleration. So, if it has an impact on PA, it gets complicated.

If you think there is a relationship between PA value and acceleration, why don't you test it?

Each variable added makes everything more complicated and time consuming to develop and for every user to test and quantify. You can't justify that without proof of a real need. I have tested a range of speeds and can provide that data. Others have found the same.

OwenD · 13 Dec 2022, 07:20

@CCS86
Just curious...
Do your PA tests at various speeds include the use of non linear extrusion?
I would think that for PA to be consistent over a range of speeds that first the volume extruded would have to be consistent.

dc42 · 13 Dec 2022, 10:36

@CCS86 I agree. Nonlinear pressure advance is on the list to implement when we have time.

CCS86 · 13 Dec 2022, 14:03

@OwenD said in Speed Based Pressure Advance:

@CCS86
Just curious...
Do your PA tests at various speeds include the use of non linear extrusion?
I would think that for PA to be consistent over a range of speeds that first the volume extruded would have to be consistent.

I do not use non-linear extrusion. I tested for this and could never demonstrate the need for it within the range of volumetric flow rates that I use.