Reddit reviews LEZHI GT2 Timing Belt Torsion Spring for 3D Printer 6mm Width Belt Pack of 10

$6 fix, prime. https://www.amazon.com/gp/aw/d/B01E913IJK/

I would call this "ok" but not perfect. If you print in grey or black you might not notice it as much. This is about as good as my DIY printers ever did even after years of tweaking. My prusa does a bit better.

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Unfortunately there are a lot of things that could potentially cause these tiny layer shifts. It might not really be simple to diagnose. Some free things I would try:

• Double check that your Z axis is calibrated. I.e. when you request a 10cm move , the head really moves exactly 10cm. Do the same with the E axis (extruder).
  
• Maybe the nozzle is scraping against the print. Make sure the part cooling fan is blasting. You could try intentionally underextruding (extrusion multiplier 0.9) to see if it scrapes less.
  
• Belt tension is a complicated topic and people have different opinions. My strategy is a tighten them so they barely make a bass guitar sound when strummed. Then I add a belt tensioner spring like amzn.com/B01E913IJK (just an example, there are cheaper options I'm sure). That gives you some future-proofing because as the belt stretches with age, the spring takes up some of the slack.
  
• You can muck with the voltage sent to your steppers motors. There are usually small potentometers on the stepper driver chips on your motherboard. You can turn them with a tiny screwdriver to increase or decrease stepper voltage. Maybe a small increase will help. But do some reading about it first. The steppers could overheat and skip steps or burn out.

https://www.amazon.com/gp/aw/d/B01E913IJK/ref=ya_aw_oh_bia_dp?ie=UTF8&psc=1

Are you using the original Anet belts? If so, change them to softer, more flexible ones, like: RepRap Champion 5 Meter 6mm Width GT2 Timing Belt for Reprap Delta 3D Printer Kossel Rostock and while you're at it, change the idlers (pulleys) to something like BIQU GT2 20Teeth 3mm Bore Aluminum Timing Belt Idler Pulley for 3D Printer 6mm Width Timing Belt (Pack of 5pcs)

Also, changing the Y-belt mount helped me: Y-Belt holder

The above changes made a hell of a difference on my A6 (which is not too different from the A8).

I've also changed the linear ball bearings to Igus DryLin, but am not sure if they helped or not (at least the noise is greatly reduced and it doesn't sound like metal grinding on metal anymore).

Then, once everything is changed make sure that your belts are tight but not overtightened.

Maybe something like Mercurry GT2 Timing Belt Tensioner Torsion Spring For 3D Printer RepRa 6mm Width Belt Pack of 10 can help for the final tensioning.

My first thing I would look at is your belt tightness for the y axis. This looks rather consistent with that.

Installing the belts is much more of an art than a science. The belts are incredibly tough, and tbh you'd be more likely to bend the frame then break the belt.

I would get the belts relatively tight by hand (so not full strength but about 75%) with the tensioners all the way loose, then tighten them up, which you should see them tighten well. If the front plate bends at all back off.

The personally I like to also clip on belt tensioners like these:

Mercurry GT2 Timing Belt Torsion Spring For 3D Printer 6mm Width Belt Pack of 10 https://www.amazon.com/dp/B01E913IJK/ref=cm_sw_r_cp_apa_EgNWAb0MB6NJK

You want to put it directly next to where the belt ends meet, bc then it won't interfere with the movement of the bed.

Let me know if this is not the case!