Bambu Lab AMS Roller Mod

There are three different sized rollers included. The 10mm seems to offer the best clearance for my 203mm spools. I haven't actually tested the 11mm version but it may work for you.

The rollers are split into two for easier printing and installation. The small raised part rides on the inner bearing races. 

I have included the step file if you need to make changes but be aware that there is a .5mm taper on the stock rollers. The inner diameter of the rollers on my machine works well at 3.1mm for a fairly easy press fit.

You'll need some 3x80mm steel rods and a file. Make sure you clean up the seams of the print so everything is as smooth as possible. A scraper will probably work well to wedge under the roller for removal. You can re-use the stock bearings, just be careful to not lose them as they will slide right off and there are holes inside the AMS where they can disappear. Make sure the steel rods are straight and make sure the roller spins freely after install. Check clearances before you completely close the AMS lid. Check the clearances all around the spool to make sure it's not rubbing on anything and check periodically while printing for your first couple prints. I used a piece of purge scrap to check clearance under the spools. A foam crafting sheet on top of your spool works well to give you an idea of how much clearance you have inside with the lid closed. Starting on slot one or four with a light shining from the opposite side can also help.

It might be worth printing this with nylon or something more wear resistant. Or just keep an eye on it during your regular maintenance and verify the clearances occasionally. 

I have not tested this with cardboard spools.

With the smaller rollers installed some of your spools may not ride on the rollers properly and you will probably run into issues unless you reinstall the stock rollers.

Some older AMS revisions seem to have a weak point around the bearing holders and I've seen them crack but that's nothing to do with this mod. Just something to be aware of. This mod isn't difficult to install and the stock roller isn't hard to remove so you shouldn't have to worry about breaking it but I don't know what the reason for those failures were so just be careful.