Vertical banding

Attached is a pic. of a single wall 20x20x20 cube in PET. It's perfect in everyway except for the vertical striations. They are very slight variations in wall thickness which are not present when printing stretchy, opaque filament but show up clearly with stiffer, transparent stuff like PET.

The lines are suspiciously close to 2.5mm* apart, occur in X and Y axes and go away in Y if I pinch the belt onto the Y pulley during the print. Belt tension seems to be the problem therefore, even though the Brecoflex is still nice and twangy. I'm at max. belt tension in Y sadly, so I'll have to move the belt a few teeth in the anchor.

Before I start taking the thing to bits again I thought I'd ask for any thoughts as I'm not 100% certain about my diagnosis - could there be another reason? Erratic extruder perhaps?

*Holding the cube to the belt teeth there is "fair" but not perfect registration between teeth and striations.

Did you forget to attach it.

If it was extruder related they wouldn't line up vertically unless the perimeter was exactly the right length.

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[www.hydraraptor.blogspot.com]

Did you forget to attach it.
Yes

Perhaps stiffer belts are better....

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[www.hydraraptor.blogspot.com]

Ooooffff....

My modified Y ider allows more tightening. [www.thingiverse.com]

Hmm, I had something like this with my printer, I changed to a 20 tooth pulley from a 36 tooth pulley and it fixed the problem.

@threedyprinter,
I couldn't find anything wrong with your belts. I built them into a printer made up from current kit production and it seems to print fine. It got commandeered for the Popup 3D Printer Factory at the Manchester Mini Maker Faire this weekend. So if you happen to be near Manchester tomorrow you can see it printing for yourself.

When I get it back I will investigate it some more and also try Neptunier's belts and the Brecoflex ones.

I did have an odd experience with the Y belt on one of my machines a few days ago. It started riding out of the pulley at a particular spot and jumping a tooth. I twisted it over to examine the suspect patch and couldn't see anything wrong. When I let go of it, it then worked fine again. All I can think is that it had something stuck in a tooth and I dislodged it.

Edited 1 time(s). Last edit at 08/10/2013 03:15PM by nophead.

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[www.hydraraptor.blogspot.com]

@nophead
I twisted it over to examine the suspect patch and couldn't see anything wrong. When I let go of it, it then worked fine again. All I can think is that it had something stuck in a tooth and I dislodged it.
Precisely what I experienced; with both X and Y belts. It was too much of a coincidence to think that something had got stuck in the teeth, but I did wonder if the blacking indicated that the belts were grinding down rough patches on the new pulley teeth enough to clog them? A bit far fetched perhaps but the belts were pretty black when I first examined them.

When I get it back I will investigate it some more and also try Neptunier's belts and the Brecoflex ones.
I'm really keen to know how you get on with them. I have spent a lot of time this week with slicers and machine setup; the results have been encouraging but the vertical banding is still there unless I print perimeters very slowly (~10mm/s).

Have you tried reducing the acceleration? The firmware I distribute has it set to 4000 but I think 2000 works better.

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[www.hydraraptor.blogspot.com]

Yes, I always use 2000 now (set in the slicer, haven't touched Marlin), it makes everything much smoother but banding is still there if you look for it.

Info: At the moment I'm printing ABS at .2mm layer height. After 30 sec. in acetone vapour the banding and layering totally disappear; I defy anyone to tell the objects are not moulded.

Info: Printing with the rubbery FPE gives an absolutely perfect print - I would have settled for slight banding until I saw this quality. Plus the dimensions of a single .5mm walled, 20x20x20mm cube were exactly right. Jaw-dropping stuff!

Did you ever get this figured out? I have the same vertical banding in a delta printer and I have never been able to fix it. What kind of extruder/hot end are you running? I am running j-head with a geared extruder simlar to what makergear uses. Controller is rambo. As I have the same banding as you with Delta I think that rules out belts as a cause as you wouldn't see the same pattern.

Edited 2 time(s). Last edit at 02/01/2014 03:02PM by xnaron.