Vertical Banding Revisited

[KAS]

My printers apart right now getting a good cleaning and doing a better job on the cable management. Installing the v27 belt tensioners, and I think I've decided to remove the dampers while I'm at it.

At least that way I have a base line on how it prints both ways.



[img]http://i482.photobucket.com/albums/rr189/Onuxis/20150215_204933.jpg[/img]



These were linked on the forums, but not sure who made them. Thank you who ever you are!

rostock max v2 belt tensioner v27.stl

(159.26 KiB) Downloaded 405 times

[JFettig]

I haven't really had much of any banding ever, never really did much of anything special. I never print PLA. I print from 20mm/s to 100mm/s and it doesn't really make a difference. I always print from the SD card(now trying octoprint).

Completely stock machine never had any issues, now dual extrusion, TL arms, etc. still no issues.

yes but what size nozzle are you using? A smaller nozzle dia increases the x-y resolution making the banding more apparent....

.5mm from seemecnc and now a .4mm from E3D. I have a .25mm nozzle but I don't have a need to install it right now.

[Tonkabot]

Die Swell ???

Differing or pulsing "pressures" on the filament would cause corresponding artifacts in the printed part... I may be using the wrong terminology, but I thought die swell was pressure's effect on extruded diameter... Sorry about that.

the delta axis (axii?)

Axes with a long E.

If the patterns stem from the extruder, then if we do something to change the speed of the extruder (like print thinner or thicker layers) the patterns would change [size].
That should be pretty easy to test.

I think these patterns all boil down to the fact that we are using steppers which are almost always going to have a 'notchyness' due to being steppers [ and that micro-stepping does not eliminate the notchyness]
If we upgrade to higher [native] resolution steppers like .9 instead of 1.8, or even try the exotics of .36 or .18 I think it the notchyness will be less visible.

If we use a smaller number of teeth on the stepper pulley, that will help. Maybe if we go to a finer pitch belt we can go to an even smaller number of teeth on the pulley

If we upgrade to geared steppers that would also increase the step resolution - however there will be added backlash thrown into the mix.

If we make the software run the steppers even more smoothly, that should also help. I think that the accelerations must be smooth for better print, and I am questioning how the accelerations are implemented. Also I think if we implement smooth accelerations [and curves] then the moves should be unsegmented and made as long as possible - and prints should be more artifact free.

I know of a memory intensive way to implement simultaneous smooth stepping on lots of steppers at once. It would be interesting to try it, although I am pretty sure non of the current boards can handle this technique. Maybe I should add that capability to my board I am designing. It would mean moving to a BGA cpu package that can do DDR memory. How does 256MB Ram sound?

[dunginhawk]

anything that fixes this banding issue sounds good to me

[KAS]

I love the idea and definitely support anything that improves our current feature limits and adds functionality. I'm just curious why some people say they don't have this issue on, I'm guessing stock or somewhat modified machines, while others obviously do. The ones that do have it are showing the pictures and trying various steps to correct it. Honestly, I'm not here to degrade anyone's product or abilities, I'm just trying to get what I own printing the best it can.

I'm in the middle of calibrating everything after a few changes. I should be up and running again in an hour for more testing without the dampers this time.

[DavidF]

anything that fixes this banding issue sounds good to me

Sandpaper???

[Broose]

Do cartesian printers with equivalent controllers get similar banding with curved surfaces? I would assume that cartesian systems do piecewise linear interpolation on curves, while deltas do piecewise curvilinear interpolation on straight lines.

[Tonkabot]

I see there are plenty of patents on 'my' idea of driving steppers using DMA. Fortunately some of them look old enough to have already expired. I didn't expect there not to be patents, it seems a fairly obvious way to deliver extremely accurate and high step rate data to steppers (or servos with step and direction interface).

You queue up all the 1's and 0's for step and direction into a big chunk of ram, and then use DMA to read the RAM out at some high rate (10,000 to 100,000 per second, if need be) directly into the step and direction inputs of stepper motors. DMA channels can feed the IO pins directly on most CPUs that have DMA channels (and IO pins )

The trick might be doing the actual queueing up in a timely manner. Although the processor won't be hampered with having to manually bit-bang.

[Tonkabot]

Do cartesian printers with equivalent controllers get similar banding with curved surfaces? I would assume that cartesian systems do piecewise linear interpolation on curves, while deltas do piecewise curvilinear interpolation on straight lines.

Cartesian printers get similar banding even on straight lines. If you have a straight line that is like 2 or 3 degrees off an axis the banding can be obvious.

I have a print here that was done on a stratasys printer and you can see that the cylinder is like a 40 sided polygon, but that was probably from the original model.

KAS found this old thread for cartesian vertical banding.

Interesting read. Different printer/style same issue: http://www.printrbottalk.com/forum/view ... =15&t=5721

[dunginhawk]

I have two printers, a rostock max v2 and a flashforge creator pro and i get NO banding on the FF at all.

[img]http://i1132.photobucket.com/albums/m562/dunginhawk/C2257739-DF37-43AD-B2B7-5F73471762E2_zpsjbe4dbbq.jpg[/img]

[Tonkabot]

It looks to me like there is banding, just not very pronounced.
Can you print an edge that is like 3 degrees off the X or Y axis?

[dunginhawk]

Yeah i didnt mean to say no banding, but 95% less than my rostock, and im completely willing to accept I may need to tune my printer even more to get it better. but circular prints are great, with little to no banding.
this picture really amplifies it too, so the tiniest bit of banding shows up on the left print, where the right looks worse than it is, although its pretty bad.

[Jimustanguitar]

I can see them a little bit in the photo. The plastic just has a different sheen to it.

Interestingly, FlashForge's website shows the same kind of ridges in their promo photos for the dreamer model:

[img]http://www.flashforge-usa.com/shop/medi ... b-nobg.jpg[/img]

[dunginhawk]

so yeah it is definatly more pronounced on the rounded parts.. im seeing the same thing... the first thing i printed was this coiled up thing with lots of angles, and its pretty pronounced there, but not on the flatter spots.
thats what leaves me to believe that its much more to with cartesian vs delta than anything else.
I own one of both and each behave exactly different.
Cartesian - good at straight lines and OK at circles
Delta - good at circles and OK at straight lines.

seems to play to each strength of their design.

[KAS]

Exact same print setting except I took off the Astrosyn dampers. I'll be honest in saying, I'll never put them back on.
Still have the banding, but the print quality is much improved from the original.

[img]http://i482.photobucket.com/albums/rr189/Onuxis/20150218_202421.jpg[/img]

[JFettig]

Can you guys feel your vertical banding?

I printed a part in black ABS yesterday and I can see a hint of vertical banding on flat surfaces that changes as speed changes(layer time cooling adjustments in software) but its not something I can feel.

Curved surfaces seem to have more pronounced vertical banding but I think that is largely the mesh

[KAS]

Yes I can feel mine. Some sections are better than others where I can't physically feel it but it can be seen and other sections you can feel the ripples.

I think I'm going to order a set of .9 degree steppers and see how well those work.

[dunginhawk]

my tricklaser arms shipped today. hopefully ill get em put on this week and run another round of tests... even if it cuts the banding in half ill be happy. I just want some quality prints on anything larger than 3x3in
Anything in the middle of my printer looks great. amazing results.
anything large is where it starts to get not as good

[JFettig]

I have been printing some black ABS lately, there is a little bit of banding however its quite difficult to see, definitely can't feel it.

[Tonkabot]

Exact same print setting except I took off the Astrosyn dampers. I'll be honest in saying, I'll never put them back on.
Still have the banding, but the print quality is much improved from the original.

I didn't expect the dampers to be as 'mushy' as they are. Maybe the cork dampers or some other dampers would be better...

I will eventually get some [more] .9 degree steppers (I actually have a few now, but I don't think I have 3 unused) and I'll take off the dampers when I put them on.
I am also going to find some pulleys with fewer teeth.

What is the top speed we can run before the current steppers start losing steps? I never print that fast now, but if I go to .9 degree steppers and fewer teeth on the pulley, I will be stepping at more than double the current rate. Maybe that will start getting near the max speed??

[3D-Print]

These were linked on the forums, but not sure who made them. Thank you who ever you are!

rostock max v2 belt tensioner v27.stl

These belt tensioner builds look awesome. Agree, thanks for posting.

[Polygonhell]

Exact same print setting except I took off the Astrosyn dampers. I'll be honest in saying, I'll never put them back on.
Still have the banding, but the print quality is much improved from the original.

I didn't expect the dampers to be as 'mushy' as they are. Maybe the cork dampers or some other dampers would be better...

I will eventually get some [more] .9 degree steppers (I actually have a few now, but I don't think I have 3 unused) and I'll take off the dampers when I put them on.
I am also going to find some pulleys with fewer teeth.

What is the top speed we can run before the current steppers start losing steps? I never print that fast now, but if I go to .9 degree steppers and fewer teeth on the pulley, I will be stepping at more than double the current rate. Maybe that will start getting near the max speed??

It's not the steppers that are the issue, it's the load on the CPU on the RAMBO, what will likely happen is that rather than skipping steps you'll get uneven motion, as the main thread starves the planning queue.

[3D-Print]

What speeds are you printing. My settings are: Infill 40 mm/s, inside perimeters 40 mm/s, outside perimeters 30 mm/s, and non print moves 300 mm/s.

I only notice this with black and on the vase image attached. I slowed my printing down after my first few prints and have never picked up the speed since that time. It makes since and if so the band would be closer together at the center of the bed than at a the edge with the idea that when the delta arms are at 45 degrees the movement with each step would be less than when they are at 30 degrees and most prominent when the print line is parallel to the delta arm in reference. Humm thinking twice about that one.

In the end you are thinking this is due to stepper degrees?

[KAS]

Is anyone running a geared extruder that has vertical banding? Curious if it correlates to the extruder steps. For those who don't have vertical banding, do you have a geared extruder or some other system that's changing the ratio?

[mhackney]

KAS, I mentioned this in my other post a few minutes ago but I don't see any difference with the geared stepper. But, what I see as vertical banding is MUCH less pronounced than the photos I see here. I will try to print some cubes in black PLA today to post comparisons. Black seems to be the best color to observe these.