Banding in prints...???

just for fun, put your thin wall print next to your z threaded rod and see if the bumps line up. If they do, then you know the problem is in your rod.

@brnrd

I got a new set of calipers and printed some thin wall cubes, which do show the same banding even after recalibrating all 4 axis including E_steps. I'm at a loss and looking back at all my old prints I've done, this banding has always been there even with a Wades extruder, original 8mm lead screws, etc. Wondering if this could be a Firmware issue?? I've never printed anything with Marlin...I'm really at a loss here!!! Very frustrating

BTW: my ave. measured wall thickness is 0.43 and Slic3r says 0.37...I've played with extrusion multiplier, but it doesn't change the banding...

Here are some pics:



[i44.photobucket.com]

I also just tried one without retract and it is somewhat less apparent, but still there especially around corners...Ideas are greatly appreciated...

The bumps do line up with the thread pattern...so what's the solution...finer thread pattern? It's not a wobble issue if it is related to Z-axis is the thread itself!

I've been playing with tons of setting in Slic3r and I can definitely make it less apparent by playing with nozzle size...going down to 0.3 mm makes it better, so maybe my E_steps are not correct??

Can we see what your X-ends and Z-axis looks like?

Also, have you autotuned your hotend?

if you measure and mark off 50mm of filament does extruding 50mm bring you to that mark on the filament?

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- akhlut

Just remember - Iterate, Iterate, Iterate!

[myhomelessmind.blogspot.com]

Here are pics of my X ends and Z axis:









My E-steps give me exactly 50mm now, but still have banding??

I haven't autotuned my hotend as Repetier doesn't have this function...guess I could load Marlin and autotune if you think that will help...

And yes I do have an extra stepper Motor on my X-end to even the weight out...also didn't help!

I've been going through much the same process in the last week. I think it all has to do with the rods being bent and the rest of the z-drive system not allowing the x carriage to move independently from the wobble.

I started out with a makergear prusa with a lower z bearing, a solid motor coupler, and at least one bent z rod. I changed to a flexible coupling and it helped a lot. The coupling came from coiled tubing, so it was not 100% straight when I put it on. After a few days that straightened out, but there was still some wobble. I removed the lower rod constraint and now I am really happy with how little banding I have.

I think that provided your x and y axis are both square, tight and true then this problem is 100% caused by your z rod. I suspect that you changed from one set of bent rods to another set of bent rods. In lieu of getting straighter rods, my other thought is to get -smaller- threaded rods. I recently bought 3 feet of 10-24 and if my recent changes didn't get rid of my wobble then I was goign to put it in. The theory is that threaded rod pulls up and down, and wobble moves left and right. Smaller diameter threaded rod will not have enough force to be able to bend the smooth rod or flex the x-end. I _just_ uploaded this to thingi, in case you feel like tresting this theory. [www.thingiverse.com]

A wide photot of your machine would help me get an understanding of your hardware.

I just reloaded and saw (A) that you are not using acme rod, and ( that you have bottom constraints on it. pull up on your motors and x axis, pop those bearings out of their holders, put everything back together unconstrained and do a test print. I bet you'll be in much better shape.

The theory goes: If the top and bottom are fixed and the rod is anything but 100000% straight, then it has to wobble in the middle. Take the bottom bearing out and that end will probably have visible wobble in it. Better there, than in the print.

Maybe its my eyes. The smooth Z-rods and the drive screws in the second image don't look parallel. Probably just optics. Can you measure the distance between the tops then the bottoms of the Z-smooth rods? I wonder if they are parallel or not.

The bearings in the lower blocks - can you easily remove them?

Are you running without the anti-backlash Z nuts?

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- akhlut

Just remember - Iterate, Iterate, Iterate!

[myhomelessmind.blogspot.com]

Thanks for the advice...These are 1/4 ACME threaded leadscrews from McCarr Master...I previously had 8mm threaded rods. I thought lead screws would help, but they haven't. I know they are not straight, but there is plenty of room for the rods to move around in the 8mm bearing at the bottom. My motors are unbolted and free to wobble and I have flexible tubing at the top connecting my motors to the leadscrews. I took out the top X-end nuts, no change. Then I added the X-isolators of thingiverse to the bottom nut...still no change at all. I understand what you're saying, but I'm still not convinced that this is my leadscrews...the banding goes all the way around the print...

I will try without the bottom bearings, but as I remember they're in there tight!!

Do you have Z lift turned on?

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@ Sublime: No Z lift

@ akhlut: my Z rods are parallel, I just measured them, must be the angle of the picture.

I'm printing something now, then I'll try to take out the bottom bearings.

The banding looks more like a result of the layer thickness changing with z height. When the layer thickness is thinner than desired, the extruded filament becomes wider and when it's thicker, the filament comes out thinner. Thus, your walls bugles out periodically. I think that your z axis has a couple of problems that can be causing this.

1. Your coupler is a flexible tubing. This allows the z lead screw to go up and down. You should consider using Nophead's coupler design.

2. The bottom constraint bearing is a bad idea. You seem to be relying on this piece to support the lead screw. But this printed piece is not solid enough to support the x carriage. Also, installing bottom constraint on a Prusa makes worsens z wobble by increasing the effect of bent z threaded rods on the x carriage itself. The end of the threaded rods should be free so that the ends wobble instead of the middle. You should remove these printed plastic pieces and use a longer threaded rod to attach to the z smooth rods per Prusa's design.

It's a Miracle!!!! Thanks to all who helped me,...the banding is GONE!!!







It was due to Z-wobble as many of you fine folks thought. So instead of removing my bottom contraint bearings, I loosened the bottom nuts so the rod end is now free to move and what do you know...you guys were right!! Sorry for doubting you guys, but after no change when switching to acme leadscrews and completely decoupling my X-axis I was stumped. I've learned many things since getting my printer 3 months ago, but 3D printing is a bumpy road...highs and lows...success and failures...wish my wife could only understand!!

Hope this helps any other Reprappers!! Keep printing!

magicald, well done. can you take a picture of the bit you changed for me please. some of these terms are still flying over my head.
roger.

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Prusa 'Explorer' (3dStuffMaker), GEN6, J-head Mk III-B, Bowden Extruder, Marlin 1.0.0 RC2, Repitier-Host V0.84 and Slic3r 0.9.8, PLA. Live at Victoria, Australia.