Tuning for smooth extrusion

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.

Phaedrux

So it was just a case of low x and Y jerk?

gnydick

@phaedrux seems to be

gnydick

So, I've tuned and upgraded my printer mechanics. It now prints BEAUTIFULLY. The layers are ridiculously identical. But I'm having a couple problems. Notice the two circled defects.

The circles I print are all oblong or misshaped, though identical at all layers.

The other area has a kink in the transition from the top radius to the vertical tangent edge. Again, identical at all layers.

I can't seem to figure out how all straight lines are phenomenally consistent, but curves are so badly rendered.

I printed a large cube with pressure advance slightly changed every 5mm and picked a setting that yielded the best overall square profile.

SupraGuy

Every time I've seen oblong circles, it's been a case of backlash in a movement axis. This was what finally did in my I3, when I could no longer get rid of backlash in the Y axis, I took it out of service.

They're consistent layer for layer because the printer always goes around the circle in the same direction, usually anticlockwise around the perimeter. This means that it will still always start the straight line in the same place, but curves or changes in direction will be out, usually delayed along the axis that has the backlash problem.

gnydick

@supraguy That makes sense, but I don't think that's the case here. I'm going to print super slow to see if it still happens.

gnydick

In the mean time, does reducing jerk help this?

Phaedrux

@gnydick it might make it worse. The lower the jerk the longer the pause at a direction change which can lead to more plastic oozing out where you don't want it.

What speed settings are you using in firmware and in the slicer?

gnydick

@phaedrux

M201 X1000 Y1000 Z135 E250:250 ; accleration
M203 X24000 Y24000 Z2400 E5000:5000 ; velocity
M566 X300 Y300 Z20 E300:300 ; jerk

My printer is really rigid. The extruder is mounted to two linear rails, 6+ inches apart, perpendicular to each other, one over the extruder, one way behind. There really is no way for reasonably speed configured print to cause vibrations like this.

This configuration is what I have now after working through the weird overshot corners.

I took high speed video to figure that out, and saw that the carriage did indeed swing due to momentum, but now, there is no swinging, Even at a small scale. And I'm still getting results like in the photo.

I don't get it. My prusa mk2 can print 150mm/sec with almost no artifacting. I know they're different designs, but my duet based printer is leagues above in terms of rigidity and geometry.

I just don't get it.

Phaedrux

300mm/min is quite low for jerk. And your max acceleration is pretty conservative as well, so I don't think your issue is there.

I suspect something is loose mechanically. If you grip the nozzle and wiggle it does the carriage have any play?

What are your slicer speed settings?

gnydick

@phaedrux

Everything is tight as can be.

Actually, I just realized those are my current settings, I dialed it all back to get better results.

They were...
jerk: 1200, then 600, still problem
accel: I think was 2500 max and kept bumping it down.

Speed was and is set to

Max: 100
Perim: 60
Extern perim: 40
Travel: 80
Infill: 60
etc.

So now, the prints are better, but slow, as there generally isn't enough distance to reach top speed.

I'm used to my prusa that whizzes back and forth with acceleration between 4000-5000 and jerk is high as well, just don't remember.

Oh, and this is the printer from another post where I showed a 3mm diameter circle printed at a real world 150mm/sec with crazy jerk and acceleration. That was a demonstration print after fixing my carriage momentum problems.

gnydick

I should also add, that I use a Flexion extruder. It has extremely good bite. It doesn't slip under acceleration like most conventional extruders do.