Vertical Banding Revisited

[KAS]

What filament is that drunkenmugsy? looks rough like carbon fiber?

[drunkenmugsy]

What filament is that drunkenmugsy? looks rough like carbon fiber?

Makershed ABS I got on sale recently.

[drunkenmugsy]

What filament is that drunkenmugsy? looks rough like carbon fiber?

Makershed ABS I got on sale recently. Might be due to humidity. I have had it out for a couple weeks with no protection just printing when I get the chance.

[Jimustanguitar]

So... My belts were looser from the last round of modifications that I normally like, and I was suspicious that this had something to do with my print quality on the bandaid piece. Tightened the belts, reset my Z0, and bam - The print was absolutely identical. I couldn't tell a difference at all :/ I'll have to try a different slicer as the next test.

[KAS]

The original on the right was printed at #define MOTOR_CURRENT {155,155,155,165,0}
The left was printed the exact same print settings, #define MOTOR_CURRENT {130,130,130,165,0}
At that low of current I'm sure I would see issues towards the perimeter, although nothing noticed at the center.

The banding is muted, not as sharp. Specifically on the center section. My only theory is the current is creating a stronger magnetic force causing the armature to snap every step. This might be why the banding smooths out when printing at higher speeds.

Anyways, It made a difference enough to want to explore .9 degree steppers and/or/with 1/32 microstepping. I don't think the Rambo 1.3 supports?(could be wrong).
Guess I'll order a few 400 step motors and wait for the GLCD to come in before installing the Smoothieboard.


The other options I would like try is running the belt smooth side down over the top pulley. Or looking for a finer tooth/belt combo.

[JFettig]

You could get some pololu drv8825 drivers and wire them to the Rambo.

I'll do a before and after with Rambo vs linuxcnc at some point. I do want to see how that compares.

[Jimustanguitar]

You could get some pololu drv8825 drivers and wire them to the Rambo.

http://cabristor.blogspot.tw/2015/02/dr ... steps.html
Make sure that you wire them up with the correct capacitance on the power side. The TI whitepapers for the drivers specify a few nuances that I think get left out on the reprap boards.

[3D-Print]

Interesting.

It does seem like the effect of each "step" of the steppers is the mechanical issue at play. However, I was also wondering the impact of the controller and each stepper. For example, do each of the X, Y and Z-steppers move at the same time or are there timing offsets for each which can smooth the movement of the print head? I could also see a place for a dynamic stepper timing which would be dependent upon the speed and position of each stepper which is variable in different regions of the print bed?

[jdurand]

I was just at the [big 3D printer sales/service company] today which is about an hour's drive from here. I had a medium long chat with with one of their tech guys who runs the machines about the banding. I pointed out the banding on the Polyjet print we got from them as well as one of the big prints they have on display from one of the other printers. The best we came up between us was the stepper motor microstepping being inaccurate (a known problem with microstepping). It's the only thing in common between the various big printers they have and our smaller ones.

[geneb]

Doesn't the PolyJet use servos?

g.

[3D-Print]

After I tightened the belts and cheapskates I reprinted and compared. It is much better but still present.

[3D-Print]

I reprinted using Cura. I dont think this is really any different!!

[bvandiepenbos]

if it really is micro-stepping inconsistencies then maybe the way to go is FULL steps with 400 step motors and belts and pulleys gear reduction to increase resolution. Something I have been wanting to try.

[3D-Print]

if it really is micro-stepping inconsistencies then maybe the way to go is FULL steps with 400 step motors and belts and pulleys gear reduction to increase resolution. Something I have been wanting to try.

I agree I would try as well!!!

[stonewater]

I wanted to bump this as I think it is very important, I was pondering this, and I wanted to throw this out there, I do think this is related to a problem I was having a few months ago with ALL of my prints, namely the printer would print in steps, stopping and leaving material and then continuing on. a reload of a clean configuration file solved it. here is a pic of what it looked like

if I did a print it showed the same thing is the radius of all the prints, this is the perimeter of a print. it would show extreme vertical banding which this produced obviously in the print

at first I thought this may be a problem with my extruder stepper not stopping its extruding when the head stopped, but working thru it with JJ seemed to suggest it was actually how the Rambo was interpreting the slice data as it did not matter which slicer I used. the hot end would stop and start as it made a radius, not on the straight sections of the print though.

Tom C

[KAS]

if it really is micro-stepping inconsistencies then maybe the way to go is FULL steps with 400 step motors and belts and pulleys gear reduction to increase resolution. Something I have been wanting to try.

The 400 step motors came in today, just waiting on the 16 tooth pulleys before the install. I'll try those on the Rambo first before I convert over to the smoothieboard.

I will say that putting on the Trick trucks and Arms made a huge difference over stock. Not so much for the banding, just the quality and repeatability of the prints.

[Jimustanguitar]

The 400 step motors came in today, just waiting on the 16 tooth pulleys before the install.

What motors did you end up with?

[KAS]

I purchased these: https://www.sparkfun.com/products/10846

I realized after I unpacked it they don't have the flat section on the shaft. After I test them, I'll most likely mill or file a flat section for the set screw.

[KAS]

400 step motors installed with 16 tooth pulleys. Just finished the calibration and a quick test to make sure my config was correct.

Starting the banding test now.

[bot]

I'm very excited to see your results. What are the steps/mm now for each tower?

[KAS]

(steps * microstepping) / (teeth * pitch)
(400 * 16)/ (16 * 2) = 200 steps per mm

This is by far my best print to date.

[Jimustanguitar]

That is an amazing looking print, nice!

I still see the banding, albeit very slight. Does it look better or worse in person?

Also, what's the machine sound like with everything stepping at twice the speed?

[KAS]

It looks better than the camera shows. It sounds a little quieter but I haven't printed any thing large yet.

[bot]

That is super awesome. I hope the Rambo doesn't hiccup with the added steps on larger prints. (Are you still running a rambo?)

[3D-Print]

Awesome. That looks great!!! I agree it will be interesting to see a larger print.

So it really does appear to be the steppers..... such that each step results in an amplified yet slight non-linear movement at the end of the arms. As expected, such non-linear movement, or vertical banding, would be impacted by calibration and print speed clearly as noted in this thread.

KAS, how much of the improvement do you think was due the steppers vs. the 16 tooth pulley size? With the standard pulley, how close can you get to 200 steps/mm without getting into trouble by adjusting the microsteps or etc? Just personally, not sure about those adjustments.