1 Topic by metaldrgn (edited by metaldrgn 2015-04-22 16:25:30)

  • metaldrgn
  • Member
  • Offline
  • Registered: 2013-06-22
  • Posts: 151

Topic: Vertical striping (not Z-wobble) possible solution

So now that I've upgraded my hotend and z-rod, there's another problem that I haven't really seen people address and that's the vertical banding issue. Vertical lines running up and down the model. I believe it's a limitation of the extruder in it's current configuration.

Correct me if I'm wrong, but it should be 3000 steps per revolution. My calibrated steps/mm are 108. The excel doc I did my math on is on the other computer and I can post it later, but basically with 1.74mm filament coming into the extruder and exiting at 0.4mm that comes out to roughly 8 steps per extruded mm. That's straight down and will be even less depending on layer height. I measured one of skirts and found it was around ~1.2mm per step or so it looked @0.2mm layer height. That is where I believe the vertical striping is coming from.

I've seen some geared NEMA 17 motors (or whatever version) with a variety of ratios. The problem , if any, would be backlash with retraction and reextrusion. It would require a new mount shims and would probably restrict Y-axis limits. Printed gearing could be made, but the backlash problem, glass transition temps, and faster wear would be my biggest concerns.

Any thoughts?

2 Reply by AZERATE

  • AZERATE
  • AZERATE
  • PRINTiT
  • Offline
  • From: Chicago
  • Registered: 2013-11-28
  • Posts: 2,077

Re: Vertical striping (not Z-wobble) possible solution

A picture would really help on this.
If it is a straight seam, it is because you did not click for random start points in Slic3r
Pic would still help though

Printit Mason and Printit Horizon printers
Multiple SD2s- Bulldog XL, E3D v5/v6/Lite6, Volcano, Hobb Goblin, Titan, .9 motor, Lawsy carriages, direct Y drive, fishing line...the list goes on
Filawinder and Filastruder #1870.....worth every penny!

3 Reply by metaldrgn

  • metaldrgn
  • Member
  • Offline
  • Registered: 2013-06-22
  • Posts: 151

Re: Vertical striping (not Z-wobble) possible solution

I don't have a model readily available, but as you it's similar to what 2n2r5 had(http://www.soliforum.com/topic/2727/fix … -consumer/).

http://2n2r5.com/pictures/printer/m5_upgrade/frogs_green_close_up.jpg

4 Reply by grob (edited by grob 2015-04-23 04:27:08)

  • grob
  • grob
  • Member
  • Offline
  • From: Sydney, Australia
  • Registered: 2014-01-02
  • Posts: 900

Re: Vertical striping (not Z-wobble) possible solution

Is the pattern dead vertical like 2n2r5 or is it angled?

If it's vertical, it's more likely to be a belt or harmonic (ringing) issue.

Extruder pulsing is periodic with respect to filament volume, but has no particular phase relationship with the layers so you usually see a diagonal pattern. It is already known about (sorry!) - usually referred to as "moire". I follow your calculation, and get about 3.8mm of perimeter per extruder whole-step: so the pulsing would be either 3.8mm or maybe the next harmonic of 1.7mm period. All pretty rough, depends on your layer height / wall thickness settings of course.

Best way to see if you can clean it up would be tuning the E stepper driver Vref by ear - usually if you overdrive the motor it will make the pattern more pronounced, so you may have to compromise between avoiding skipped steps and this.

Using a 32x microstep driver (DRV8825) or swapping out for a (heavier!) 0.9 degree stepper will also make the pattern fine enough to disappear.

A geared stepper should also have a similar (even perhaps better) improvement, but for the size/weight I'd probably advise using a bowden feed rather than trying to fit that... Backlash is not an issue, you'd only have to increase retraction to compensate - which is already a pretty fuzzy parameter! Note the 1:5ish gear ratio is probably more than enough, much more and you'll be sacrificing your maximum speed.

SD3. Mk2b + glass, heated enclosure, GT2 belts, direct drive y shaft, linear bearings, bowden-feed E3D v5 w/ 0.9° stepper
Smoothieboard via Octoprint on RPi

5 Reply by metaldrgn

  • metaldrgn
  • Member
  • Offline
  • Registered: 2013-06-22
  • Posts: 151

Re: Vertical striping (not Z-wobble) possible solution

It isn't always vertical. It isn't so noticeable at smaller layer heights which you would think it would be, but there could be other reasons for that.

I can tell it isn't the belt harmonics because those are noticeable at hard edges.

Thanks I may try some of those ideas.

6 Reply by 2n2r5 (edited by 2n2r5 2015-05-18 18:57:58)

  • 2n2r5
  • 2n2r5
  • Member
  • Offline
  • From: Frederick, MD
  • Registered: 2013-05-09
  • Posts: 1,208

Re: Vertical striping (not Z-wobble) possible solution

It's a problem with skipping micro-stepping on one of your X/Y motors, probably. Try a calibration cube and see what side the vertical banding happens on.  Then you can attribute that to the X or Y motor and adjust your vref for that motor until it smooths out.

As was mentioned before, this could also be from your Extruder.

As always, check the guides on this site to find out the proper way to setup your printer.

SD3 w/ mods:
Glass bed with QU-BD heat pad upgrade, threadless ballscrew w/ 8mm smooth rod, spectra line belt replacement, lawsy MK5 extruder, Lawsy replacement carriage, E3D hotend, Ramps 1.4 w/ reprap discount controller, DRV8825 drivers, 12v 30A PS, Acrylic case, Overkill Y-idlers, Filament alarm, Extruder fan + more.

2n2r5's Website

7 Reply by metaldrgn

  • metaldrgn
  • Member
  • Offline
  • Registered: 2013-06-22
  • Posts: 151

Re: Vertical striping (not Z-wobble) possible solution

It's the extruder and I'll post pictures when I can. I've been busy and forgot about this. For some reason if you make the layer height finer it isn't so bad, but I have my theories about that. I think I am at the limits of the motor, but I will have to check the vref. A microstep driver may be what I do next.

8 Reply by metaldrgn (edited by metaldrgn 2015-05-26 04:18:19)

  • metaldrgn
  • Member
  • Offline
  • Registered: 2013-06-22
  • Posts: 151

Re: Vertical striping (not Z-wobble) possible solution

Ok so I haven't taken any pictures yet, I've been busy/lazy tongue. I did look more into the suggested solutions and it seems that micro stepping is out of the question because of the torque lost. Half stepping may work, but it still takes away ~30% of the torque (please correct me if I'm wrong). A geared stepper right now appears to be the best option and I was thinking exactly what Grob said and go 5:1 and maybe use half stepping or maybe even micro stepping to smooth it out even more since I would regain torque from the gearing although some would be lost from higher speeds.

Edit: I'm thinking 2x microstepping instead of halfstepping with the torque loss. I don't know what the torque loss would be with halfstepping.

9 Reply by metaldrgn (edited by metaldrgn 2015-05-26 04:19:28)

  • metaldrgn
  • Member
  • Offline
  • Registered: 2013-06-22
  • Posts: 151

Re: Vertical striping (not Z-wobble) possible solution

Here are some images of what I'm talking about These are just 1 layer skirts from Kisslicer so a little thicker than normal (200%?) @0.2mm height.

http://soliforum.com/i/?4CRPUIK.jpg
http://soliforum.com/i/?KdcKTcm.jpg

10 Reply by grob (edited by grob 2015-05-26 06:03:25)

  • grob
  • grob
  • Member
  • Offline
  • From: Sydney, Australia
  • Registered: 2014-01-02
  • Posts: 900

Re: Vertical striping (not Z-wobble) possible solution

Ok, halfstepping? That's pretty much just 2x microstepping haha!
I'll take you up on that offer to correct you over the microstepping and torque:
Here's a pretty fun article on microstepping and torque, which explains what the deal is quite well, but it's not as obvious as you might think at first: http://www.micromo.com/microstepping-my … -realities

tl;dr Increased microstepping does not reduce torque at all for movements larger than a whole step.

Torque will be reduced with higher actual / angular speeds though!

SD3. Mk2b + glass, heated enclosure, GT2 belts, direct drive y shaft, linear bearings, bowden-feed E3D v5 w/ 0.9° stepper
Smoothieboard via Octoprint on RPi