I’ve a flat steel plate on my printer

I’ve made the experimental MGN12H one, no issues except at the max positive position, the block goes off the rails beyond the wiper exposing one ball. But in this position the gear is also hit, so maybe we need some end stop there before this happens. Anyways this position can be easily avoided, so I don’t think translating the blocks more to the center is worth it. But there is some risk involved of losing a ball when bumping into that position by accident. Luckily, the max negative doesn’t go off the rails. Apart from that small issue they are great, and even though the print isn’t the most accurate or stiff (PETG), I was able to get the Y within 0,02. Im using some older type spacers that are a lot wider and flexible that make it possible to finetune the bed by tightening the screw, much like you would turn it by hand on an older Ender. Tomorrow I’ll square my X and Z and then run some tests. Soon I’ll print it again from a different material, I did get some slight binding in the rails when tightened because my print isn’t perfect. So far I’m pretty satisfied with the results, great design!

I remixed the the LENEAR RAILS--flat--PLATE ADAPTER. Have a go and let us know: https://www.printables.com/model/907683-lh-rh-needitmakeit-lenear-rails-flat-plate-adapter

I couldn't find the MGN12C carriages so I opted for the 12H version, the "experimental" plate adapters fit great and the front and rear rail adapters are perfect only small hiccup was the particular 12H carriages I got had too short of a thread for the M3x8 screws that were meant to secure the carriage to the plate so I had to use washers on all four carriages to lift the whole bed up, leveled and auto z offset after the mod and now it prints great, zero Y wobble also a side note for anyone printing this in PETG-CF (might be applicable to other filaments but that's what I used), my rear adapter plate fell over mid print on my first attempt and turned into spaghetti, so I'd definitely recommend a raft for the front and rear adapter pieces overall very happy with the results, thank you Mike for this great design and for making it publically available for free, props to you for such a generous move!

Really like your mod and also the fact that it is supporting on a wider span the plate. Going to start making your parts and get necessary materials. Tks for helping us with issues that Creality shouldn't have created at the beginning ;) Will do follow up on the project soon ***UPDATE*** Did your MOD with the MGN 12H too and we have a small few little tweaking to do on the bed plate supports as i couldn't fit it on. I had to grind out some material to fit the plate on them but nothing major. Other issue was my screws M3 that were sticking out to much on top so i grinded the holes a bit deeper to fit the screws (could be because of screws it-self tho). As far it goes, WOW !!! The bed is super nice, sturdy and super smooth on the rails, even more quiet i would say !!! All i did after re-assembling it all,was an Auto-Leveling, printed a bed test and it came out right on the spot first shot (except for small part that didn't stick lol) !!! So .... thanks a lot for the STL's and your time to fine tune our KE that definitely should come out of the box with the bed rails instead of the wobbly tube bearings !!! Creality ...take notes for the future ;)

It would also be great to replace the rollers on the Z-axis with a linear rod with LM8UU linear bearings, so that the movement up and down is like in Prusa

So after doing this mod, omg the bed is rock solid. However after just 2 days of printing 2 out if the 4 carriers already started to seize and made the bed jump out of alignment mid print. I assume it has to do with the factory lube or the quality of the carriers themselves. Cleaned the whole thing and hopefully it will print for a little bit longer. Great mod with good quality parts.

Thank you for your work!

Great upgrade and made the instructions easy to follow along with! In case anyone is having issues after the build. For some reason my y offset was different from before the upgrade which kept giving me bed adhesion issues and trouble with my first layers. Once I corrected my y offset the issue was resolved and now I'm back to printing. Thanks for the upgrade and I'm looking forward to more upgrades to this machine.