Solidoodle 3 Aluminium bed Z Banding

The main problem is with how the threaded rod is manufactured...some better than others.... it leads to uneven repetitive error, there are several ways to mitigate this and make it less noticeable... one is to use a taller nut or multiple nuts which averages out the error.

The problem for me is that I went around a few hardware stores, and there aren't any imperial nut sizes on the shelves here in my part of the UK. I've so far seen a bag of those well nuts for $23 + postage online, which is a hefty bill. Which is why I want to be pretty sure any solution I try will work, as it will mean ordering whatever I need. M3 screws fit the holes in the aluminium bed, so I can fit a few of them to hold a well nut in place.

I think I need to keep shopping around.

If your lead screw is bent, I'd be looking at using a felxible coupling between the motor and shaft....and while your at it...just get rid of that screw and get a metric one... 1" long brass standoff can be used for the nut

The other problem with trying to swap the lead screw (on the aluminium bed) would be that the 5/16" nut is part of the bed. How would you swap it without getting an angle grinder onto that part of the bed? There are fittings that shrink screw sizes, for example, that you can screw into an M8 hole to leave an M6 thread hole, but I think you'd have a job finding one that goes from imperial to metric.

I think the anti backlash mod is the one to try, but if I'm spending that much, I may as well look for a proper 5/16" anti-backlash nut. If anyone sees a site that ships to the UK, please let me know, as I'm still looking!

I have found a 5/16" nut, at least. Only 85 times the cost of the M8 nuts I bought recently! Perhaps I can cobble together something with that...

Since the idea is to pre-load the thread, maybe a spring washer would work. Just screw the spring washer down with the nut, then fit something to the nut that stops it rotating by fixing it to the M3 screw holes.

I've heard ABS anti-backlash designs have too much flexibility, but I have some metal sheeting, so perhaps I could cut something suitable out of that...

For the Well nuts? What search term are you using? "5/16 well nut" doesn't give anything under £14.19 ($21.53) with postage.
"5/16 backlash" gives me no hits at all.

ok so I have replaced my bed and lead screw myself, I have even fabricated my own stepper and lead screw setup and that is not the problem.

this is the problem with 90% of the banding.

the firmware is incorrect where is say "default steps per unit". furthermore when you slice you stl file in whatever program you're using you're probably making your layer height to .3 or something to this effect. the issue with putting a nice rounded number like .3 is your stepper motor would need to take 42.523033309709426 steps to give you exactly a .3 layer height, but your stepper cannot do this. So you need to slice at a layer height optimum for your lead screw and your stepper motor. this will rid you of banding.

for example a layer height of .13 should actually be set to 0.1270 for an exact number of steps at 18 so now every time your motor steps to a 0.1270 layer height it ends at a full step. see the stepper will end at a full step anyway leaving you with more or less layer height every so many layers giving you a consistent banding making you think its the screw.

no one wants to do the math