Can I use a negative pressure advance value?

Arminas

Hello,

jay_s_uk

@Arminas i suppose the question is what are you trying to do and why do you think a negative value is a good idea?

Arminas

@jay_s_uk just wondering what are the side limits of the value. Is it, let's say, from 0 to 1 or there are not actual limits?

jay_s_uk

@Arminas i don't believe there are any limits.
A negative value would lead to more material being deposited at corners than normal

Arminas

@Arminas So the higher the value = the less material deposited on the direction change? And also the more flexible filament the higher value should be set?

deckingman

@Arminas Suggest you read this to develop your understanding of the mechanisms at play https://docs.duet3d.com/en/User_manual/Tuning/Pressure_advance

dc42

@Arminas said in Can I use a negative pressure advance value?:

Hello,

Can I use a negative pressure advance value?

No. RRF 3.5 will reject a negative pressure advance constant. RRF 3.4.x might accept it but I suspect that it woold make extrusion go seriously wrong.

Arminas

@dc42 Okay, thanks. I have an issue with TPU corners, but PA does not help at all no matter I increase or decrease the value.

SJI

@Arminas
I predominantly print tpu.
I have my config with no PA, direct drive, 90A tpu. 45mm/s print speed, with retractions

What is the shore A?
Do you have bulging corners?
What's the print speed?
What's the extruder?

Arminas

@SJI Direct drive BMG with e3d v6, 0.4 nozzle. TPU95 HF, 50 mm/s. Yes, I have bulging corners.

dc42

@Arminas for information, direct drive extruders normally need a very low PA value, normally less than 0.1.

deckingman

@dc42 said in Can I use a negative pressure advance value?:

@Arminas for information, direct drive extruders normally need a very low PA value, normally less than 0.1.

I can add a couple of data points to that. For a Bondtech Lgx Ace/Mosquito combination and 0.5mm nozzle, PET-G needs 0.06, ABS and PLA both need 0.04 and TPU-HF95 needs none at all.