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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.

This is a kickass tip! I bet it reduces the noise from the hot-end fan too!

Yes PC builders have been doing this for ages - in fact it's the first tip you read when people talk about whisper quiet builds Very cool idea, thanks for letting me know I'll probably try it!

I would not have thought of the fans as a source of vibrations but after reading your comments it makes perfect sense.
Thanks for the tip!

Yeah, I've been wondering about it for a while, especially after noticing the change after moving to dual extruder.

It's pretty straightforward to figure out if it's a factor. My build plate was really vibrating.
After the switch to 7v, the fans do not contribute vibrations to the build plate.
It gets broadcast down to the build plate through mag arms, through the nice tight cheapskates, down the extrusions, and onto the build surface.

I've been running at 7v for a few days now with no issues. The hot end before the heat break is now a little warm, but now so much quieter and reduced vertical banding and moire in prints.

I tried the same "fingertip" experiment while the printer was printing, and I still feel vibrations, I'm wondering if the 0.9 steppers will help to smooth that out...

Interesting. I wonder if you could use some kind of rubber mount for the fan to decouple the vibrations as well.

Out of balance at high rpm is out of balance at low rpm. Try balancing your fan.

Loosely mount your fan by one corner and put a piece of mirror/CD/tinfoil on the opposite side. Shine a laser pointer on the reflective object and watch the dot that hits the wall (preferably a fair distance away). Turn the fan on and see if the dot gets bigger (vibration). If it does move a small pieces of tape around on the ends of the fan blades until the laser do doesn't get bigger (or its small enough to make you happy).