Tuning for smooth extrusion

gnydick

I suspect the ripples on the surface of my print are due to extrusion pulses. My printer has been upgraded to all linear rails. everything is smooth and slick as melted butter with PTFE mixed in. My prints just have ripples in all directions.

Is there any advice for determining if it is the extruder and if so, how to tune it?

Phaedrux

Can you post some pictures of the problem? And details of your print settings?

LHelge

What type of extruder are you using? Is it geared? If so, are the gears running smooth?

I have similar issues with a Zesty nimble, which is an issue that has been known for some time. (https://forum.zesty.tech/t/surface-effects-like-ripples-etc/186) It doesn't bother me much since i mainly print functional parts, bu I could see how some would be bothered by it.

gnydick

@lhelge

I'm using flexion extruders. They're not geared.

burtoogle

If the extruder isn't geared, the steps/mm value is going to be quite low and, therefore, the resolution of the extruder is going to be low. I think this can cause quality issues, especially when using relative extrusion and made even worse if using 2.85mm filament.

bot

Increase your extrusion axis resolution dramatically and see if it goes away. Gear it down 3-5 times more than you are now.

gnydick

@burtoogle my steps/mm are 183. It's not geared just like my prusa isn't geared, and my prusa prints literally perfect surfaces.

gnydick

@bot said in Tuning for smooth extrusion:

what do you mean by that? What is axis resolution?

bot

Try using absolute extruder positioning rather than relative positioning.

I just mean your E steps/mm. X axis, Y axis, Z axis, E(xtrusion) axis -- at least in my mind.

With relative E positioning, you get underextrusion when steps/mm are low.

gnydick

I turned on absolute extrusion and it started expelling really fast a lot of filament into big blogs every time there was a retraction.

adavidm

@gnydick

Did you re-slice the file using absolute extrusion too? If not then you need to.

gnydick

@adavidm yes, I did. Turns out, the duet wiki says not to use absolute as it's prone to compounding of rounding errors.

gnydick

This photo shows a low poly model. There are two contiguous faces outlined. The edge between them, surrounded by the intersection of the squares is protruding from the part. The angle between the faces is very shallow. All of the edges on the model stick outb like that. Does that kind of artifact mean pressure advance is too low or too high?

dc42

@gnydick said in Tuning for smooth extrusion:

This photo shows a low poly model. There are two contiguous faces outlined. The edge between them, surrounded by the intersection of the squares is protruding from the part. The angle between the faces is very shallow. All of the edges on the model stick outb like that. Does that kind of artifact mean pressure advance is too low or too high?

XY jerk may be set too low, and pressure advance is probably too low as well.

gnydick

@dc42 I tried all sorts of values and nothing worked. I was running around 100mm/sec actual speed. I cut it in half and it looks like the ripples have gone away, or at least reduced.

How do you think the speed is affecting it?

dc42

Using high speeds usually excites resonances more than using low speeds does. This effect shows up particularly well on flat surfaces downstream of sharp corners, such as when printing cubes and similar parts.

gnydick

I was really tired, I kept lowering jerk instead of increasing it, so it kept getting worse.

gnydick

Thanks for the help

dc42

Glad to help! Is the problem solved?

gnydick

@dc42 it's definitely much better.