Use "this one simple trick" to reduce vertical banding



  • Postby gestalt73 » Mon Jun 02, 2014 11:37 am

    (Sorry, couldn't resist the headline)

    So, you upgraded to an E3D-V5 or V6, and you're noticing vertical banding and moire patterns on your prints?

    Run your hotend fan(s) at 7V, and it should reduce or eliminate them.

    To see if this fix would work for you, try this simple experiment:

    with your hotend and build plate off, put a couple of fingers on your build plate. Is it vibrating? If you have vertical bands in your prints, it probably is, if you have magnetic arms and an E3D, then it definitely is. Your hotend fan(s) are sending vibrations up your arms, through the aluminum extrusions, and down to the build plate. When I installed my dual E3Ds, using bubbasnows mount with two fans, the moire patterns got worse.

    now, however you'd like, turn off your hotend fan, keeping everything else on, and try again. If your build plate stopped vibrating, you may benefit from this simple mod.

    So, where do you get 7V from your ATX PSU?

    You get it from the difference between a +12v line, and a +5v line.

    However you'd like, wire your fan positive (red) to a +12v (yellow) line, and your fan negative (black) to a +5v (red) line.

    I wouldn't do this with any type of high load device, but PC builders have been doing this for years to quiet down case fans. Driving a fan like this should not adversely impact your PSU. When I do this, the fins on my hot end aren't cold anymore, they're only a bit warm. I don't anticipate any cooling or jamming issues with ABS. Probably with PLA too. YMMV, so experiment a bit to see what works for you.

    While it does reduce airflow across the cooling fins a bit, it's still plenty to keep the your hotend cool after the heat break, and I can't feel any vibrations on the build plate anymore.

    I'm going to run a few parts like this shortly to verify, but this may be the root cause for the vertical banding and moire patterns we're seeing.

    Source: http://forum.seemecnc.com/viewtopic.php?t=5538



  • Are you familiar with this post? http://forums.reprap.org/read.php?178,763881 ?

    Nebbian did a lot of work there, and tracked it down (moire especially) to decay modes in drivers, which thankfully isn't a big problem on Duet (wifi/ethernet). There were also recommendations for layer heights to use to accentuate the effect and to eliminate it and mods for drivers where applicable.

    I am a bit dubious about fans being the cause unless one of the blades has broken off even then the pattern would be regular, and it rarely ever is. I had a WTF fan (http://www.wildturbofan.com/product-new) on my kossel XL at one point, at 7v (they're designed for RC cars so are run at 2S lipo 7.4v) it sounded like a jet engine, at any higher voltage I am quite sure it would generate enough vertical lift to fly, but no signs of any unwanted vertical lines (I actually ran it on 3v in the end - just to keep the noise down - no effect on the prints). Plus if you want 7v get an adjustable buck converter for £2 from ali/ebay.



  • I do not personally have a delta. just came across the post but from the comments people said the effect became greater when adding a second hotend with second fan and by doing his 7v hack it went away. I am not arguing, just was sharing something I found.



  • No worries I'm sure it's worth looking at to eliminate possible sources.



  • Reading your link i want to do some experimentation. I know what they are addressing has to do with deltas but i, at some point in the past read about a bug in Simplify3D that was overcome by changing layer height to 2.0001

    Even though i have a cartesan i want to see if theres any difference between changing the points where steps vs microsteps land on the layers


 

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