Posts made by imqqmi

Thank you David, hopefully allowing high jerk for travel moves will resolve the issue.

I'll try and source a 3mm bowden tube. In the mean time I'll turn off the pressure advance feature for now. I just printed a floppy cleaning kit someone asked for but the filament lost traction for about 10 layers before picking it up again due to the extreme back and forth motion of the extruder motor, especially with narrow infills like 2-5mm wide.

Especially the turn tool got out with under extruded layers, it was easy to snap them in two parts. I've reprinted it without PA and came out fine.

No change or improvement in the pressure advance department unfortunately. The same k value is indicated.

I've tried a bigger print. The infill makes the extruder go back and forth with quite a bit of noise, clacking back and forth.

I'm not sure this is the way to go for me at least. Does the noise improve at lower k values? It wears the filament down too, with the PA calibration the extruder lost grip on the filament. Luckily it was near the end of the print but it wouldn't be good for other long prints to fail half way.

I may try an older firmware to see if the travel/extrusion move jerk is back on how it performs.

I've adjusted jerk to 1000mm/s from 600mm/s and started skipping steps. I upped the motor current to 1800mA (was 800mA) and stopped skipping steps. It makes a heck of a racket when doing infill. And the gap is still there unfortunately. But the speed is about the same now as without pressure advance.

I'll try doing the pressure advance calibration again since the backlash may have changed since tightening the gears, there's no play in them now.

I've increased acceleration, velocity and jerk (slightly) but it doesn't seem to improve much. The left most seems to be the best. At the top you can see the outer perimeter near the hole isn't as thin as the other two. I'll try bumping up jerk as you suggest, its at 600mm/min, I'll try 2400mm/min.

The bowden tube diameter is about 3.1 to 3.2mm when I scan a cross section and measure it in photoshop. With the calipers it's between 3 and 3.1mm. The ABS filament is about 2.85 to 2.90mm (brand: RRW Dutch ABS).

The push fit connectors don't show any motion. I use 3d printed clips to secure it in place. There's a bit of wiggle room between the extruder gears though. I've attempted to tighten them but ended up with skipping steps. That was before the duet upgrade so I could try it again. The drivers provide much more power to the stepper motors.

Bowden connector on the x carriage:

Bowden connector on the extruder side, there's no play in the tube nor any movement when printing/retracting un retracting:

Here's the same test with setting k= 2 to 6. The third layer looked good to me, which corresponds to k=2.24. I have this set in the config.g file now.

I've reprinted the 20x20x2 slab. To the left is the 2.24 newly printed, and compared with the 0.2 one printed earlier. A clear improvement and the blob on the top is almost gone. Instead there's now a hole, probably due to the pressure not being able to come back up quickly enough. The infill cornering is improved as well, I can now set the infill/perimeter overlap higher to fix this. There's a print speed penalty though as the acceleration is now adjusted to the speed/acceleration the extruder can handle. I will tune that further first and see how it will perform. I did notice that the infill looked different, in the center it seems wider and flatter and near the perimeter it's narrower and rounder. Coming into the corner looks different than coming out of the corner. The left one looks more consistent apart from the blobs at the end of each infill cornering.

I've looked in my failed prints bin and found a couple of marlin 1.1.9 prints, but I'm not sure what settings and what stage of calibration it was. I had to calibrate motor current at some point, not sure if it was before or after motor calibration. My guess is the left one is pre motor calibration and the right one post motor calibration looking at the extrusion line spacing, left is irregular and right is more regular. I don't know if jerk was changed either. At least I've gotten rid of the corner blob that is still present in the print below.

Here's the pressure advance calibration test with the settings K=0.4 to 2.0. 2.0 isn't high enough, so next test print will be 2.0 to 6.0. Is my bowden setup that bad? Maybe the teflon tube is a bit too wide?

Thanks for the script! Please note, to use the gcode you should use relative extrusions using M83, otherwise nothing is extruded. I think slic3r uses absolute extrusion M82. If you copy/paste startup gcode this could affect the print.

Thanks for the link, I'll check it out. It's not the exact same gcode but the same settings as with the test print. I didn't do any test prints on marlin 1.1.9, only actual prints of things I needed like an extruder holder for the e3d v6 (which is what the last image is of).

Thanks! Before your last comment I printed four test prints as shown below. Clearly the top and bottom is a big difference but at 1.6 the printer is slowing down as if a low acceleration is set. The extrusion stepper motor is doing some wacky back and forth motion on the infill too, though I must say the infill looked fine.
I'll try reducing retraction distance tomorrow. (please ignore the bent prints, I've pried them off while the bed was still fully heated, it didn't warp during print.)

Marlin 1.1.9 seems better controlled, yet doesn't use pressure advance:

Thanks, I wasn't aware of that option. I'll try this in config.g:
M572 D0 S0.2

The bowden tube is about 600mm.

Tony is right, I meant axis jerk, the nozzle stops moving an instant (or slows down) so the oozing creates a blob. And yes it's the option in slicer to prevent retraction if the axis moves less than a certain amount. It's called Minimum travel after retraction in the printer settings tab, Extruder section and it's set to 1mm (default: 2mm).

I agree, in this case (during short travel moves) the oozing is acceptable or preferred to stopping and continuing, when it will ooze even more.
It's basically a discontinuous extrusion move.

Oh, and when I said hidden seam, the Seam position option is set to Rear (on the Print settings tab, Layers and perimeters), I think this was an option introduced by Prusa. This is different from the default corner position where it will also do a between layer retraction.

Thank you! It will be great for beginners as well.

The documentation about centering the bed or setting the bed origin I mentioned that when you use the online configurator and setting an offset for z, the generator will create files for homing that prevents the z offset to be used.
https://duet3d.dozuki.com/Wiki/Centering_the_bed_or_setting_the_bed_origin

It would be great if an option can be added if m208 z is non zero the homing files will account for the z offset.

I've just upgraded to the duet 2 wifi and like it a lot. There's however an issue that cropped up and I've read this post that seems related:

https://forum.duet3d.com/topic/2416/support-separate-jerk-values-for-extrusion-and-travel-moves

When I use Slic3r Prusa Edition 1.40.1 and enable hidden seam the perimeter will start/end half way a straight line for example. I used a slab of 20x50x2mm.
There's a very short travel move from one perimeter to the next like the image below. The printer slows down during this move and deposits a blob that expands beyond the perimeter. The Marlin firmware didn't do this, it just used a jerk to continue at the same speed the perimeter was done (or so it would seem to me).

Is there any option I can use to enable jerk during these moves?

Here's a gcode snippet:
G1 X64.327 Y69.517 E7.13438
G1 X64.267 Y69.898 F4980.000 ;This is the travel move
G1 F3300
G1 X39.873 Y69.898 E7.52870
G1 X39.873 Y51.111 E7.83239

In config.g:
M566 X1800.00 Y1800.00 Z60.00 E420.00

Firmware Name: RepRapFirmware for Duet 2 WiFi/Ethernet
Firmware Electronics: Duet WiFi 1.02 or later
Firmware Version: 2.01(RTOS) (2018-07-26b2)
WiFi Server Version: 1.21
Web Interface Version: 1.21.2-dc42

You can see that the blob of the inner perimeters overlap the outer perimeter:

[edit]
This is one that I printed using marlin 1.1.9, though it's a different object but exactly the same 3d printer. What you can't see is that the blob doesn't come up as much as with the duet printed one. The brown 'smudge' is smaller.

[edit2]
Here another print of a 20x20x2 slab with the duet. I've set the jerk to 60mm/s. You can now better see that the blob sticks out at the top while the marlin version was almost flat, 0.1mm bump and thise one 0.66mm (measured with digital calipers). All images have boosted contrast, this is white ABS and scanned at 1200 dpi.