for Anet A8/ Prusa I3

BLV mgn12 3D Printer mod


The main purpose of this project is converting your Anet A8 into an incredible 3d printer, using MGN12 rails fixed on an aluminum extrusion frame.

This upgrade compatible with Pheneeny's AM8 mod with small changes.

It will completely change your printer making it way more reliable, accurate and fast.



The linear bearing and Delrin Wheel Gantry commonly used at most of the low-mid 3d printers as a cheaper solution for linear motion. Its cheaper replacement for the expensive mgn rails BUT the price is at the expense of accuracy and reliability. Well, linear guided rails (mgn rails) are much more rigid, extremely precise and smooth then linear bearing or Delrin. The linear rails let you print with higher speed - shorting print time without compromising print quality. The fact rails are fixed to frame prevents unwanted motion related to bent threaded rods or other axis's motion. There seems to be a good reason why they are mostly used with high-end 3d printers.
So, I found cheap Chinese mgn rails at Aliexpress and thought to myself why not?





​fixing the mgn rails can be very frustrating. it needs to be perfectly aligned and straight.
else, it will give you a headache, so don't start this project without tons of patience.

  • design flexibility and Source file
    I'm sharing with you the source file of this project in order to improve the design and make it even better. you will find the STEP file inside the project zip.
    Please follow the item license (under the Creative Commons - Attribution - Non-Commercial - Share-Alike.).

  • If you are using the STEP file, please don't forget to mark it as a Remix :)

  • Also made for this project a Build plate for simplify3d

Please notice you may need to re-center bed coordinates via marlin configuration
or change Z extrusion position to center the hotbed

Seeing all of these great community members uploading photos and remixes worth all of the long hours that I have put into this project :)
I will appreciate if you could please upload an "I made one" photos :)



Choose your style

You have the ability to choose your own style:

  1. Anet A8 converted to AM8 (original height: 440mm) + BLV mgn12 mod:
    If you are already a proud owner of an AM8 printer and don't want to change the original height, you will have to get a 350mm rails instead of 400mm.

  2. Anet A8 converted to AM8 + Higher Z-axis (height: 500mm) + BLV mgn12 mod:
    First, you will have to build an AM8 with small changes:

    • instead of: 2x440mm 2040 extrusion > replace with: 2x500mm 2040 extrusion or bigger.

    • instead of: 2x340mm 2040 extrusion > replace with: 4x364mm 2040 extrusion

    • get a longer threaded rods 400mm.
      obviously, you don't need to print all AM8 parts but some (more info at printing info section)


  3. Anet AM8 + Freestyle + BLV mgn12 mod:
    As I mentioned, the design is flexible and includes separated parts that can be fitted to your wish. if you want custom size printer with a bigger bed or higher Z-axis, please choose wisely your own extrusion size and attached the modular parts to your desired extrusion.




Anet A8 3D Printer


Technical ability 

AM8 upgrade

Spare Time

budget (mid)



clarification: BOM includes AM8 BOM



Choose Size

​for option 1 - original AM8 size:

for option 2 - extended z height:







Part to print from this BLV mgn12 mod project:
print all except those optional parts:

  • Y mount motor - (print this part only if you don't have the AM8 Y motor mount)

  • Top z holders - (aka anti z-wobble) (holders may limit Z height and they are not really needed)

  • Caliper Holder - (print only if you have a digital metal caliper)

  • LCD case and brackets - (print it only if you have a RepRap Discount LCD 12864 only, else use the original AM8 LCD case and brackets)

Part to print from AM8:

  • 1 x 1_LCD_Base_Left (only if you are planning to use the original Anet A8 LCD)

  • 1 x 1_LCD_Base_Right (only if you are planning to use the original Anet A8 LCD)

  • 1 x 1_LCD_Case_Top (only if you are planning to use the original Anet A8 LCD)

  • 1 x 1_PSU_Mount (for Original Anet PSU)

  • 1 x 1_Wire_Holder

  • 2 x 2_Bottom_Tee_Plate

  • 2 x 2_Top_Corner_Plate

  • 4 x 4_Bottom_Corner_Plate

  • 1 x Anet_Board_Mount__With_Fan (don't print if you choose the electronics box)

  • 1 x Anet_Board_Mount_No_Fan (don't print if you choose the electronics box)

Material and Infill

Inside the zip file, you will find a PDF file named: BLV mgn12 mod.pdf
which contains full spec of the Parts (name, material to print with and infill percentage).

Printing orientation

Highly important: I added 4 pictures showing the printing orientation of the prats.
the printing orientation is very important because it contributes to the strength of the items.

make sure before printing that its calibrated since the dimension precision are crucial!


  1. AM8 modAssemble the frame extrusion according to pheneeny's at the AM8 mod files, you will find also the prefect guide pheneeny made for assembly.

  2. Assemble the BLV mgn12 mod according to assembly instructions found in this project zip file. its a pdf file named: BLV mgn12 mod.pdf. the file contains a sketch with all
    the main parts.


  3. I made an assembly video in order to explain how to assemble: Bed adapters, X-axis components, Cube carriage, and V6 carriage. In this video, I mentioned a 5010 blower fan but I was wrong- I meant for 5015 fan.
    Please notice you may need to re-center the hotend/bed coordinates via marlin configuration.



MGN12H rails & Carriages extra info

Well, I used cheap Chinese mgn12H rails from Aliexpress cost 18$ each.
After buying from 4 different Aliexpress sellers i found the best rails sold here, at "CNA Mechanical Parts Store" store.
I even not needed to clean the rails! The block is sliding smoothly without the need to clean it. Wonderful rails, highly recommended!

Please be careful and DO NOT buy rails from: "RDC Official Store" nor "linkcnc Store" at Aliexpress. "linkcnc Store" sold me an awful rail which was used, damaged and shorter then what I ordered. even after cleaning and lubricating it was still stuck and jammed "RDC Official Store" started to ship mgn blocks with non mgn standard size, so i can no longer recommend on him.

Cleaning and lubricating

notice that the mgn rails you'll get will not be smooth as it should be.
at the factory, they lubricate it with a protecting oil that needs to be cleaned away. There are some videos on YouTube showing how to clean the carriage with WD-40.
Don't forget after cleaning both rails and carriage to lubricate it with sewing machine oil or Teflon silicone grease.
As for smoothness: Please ignore the method for testing smoothness by tilting the rail - it's wrong! You want it to be smooth but not too much.
Also, since its miniature rails, please don't use too thick grease for lubrication.

Cleaning mgn12H carriage video
it's a pretty good video. just use a container in order not to lose steel balls
note: after assembling all steel balls, you will be left with empty space of one steel ball.

fixing the mgn rails can be very frustrating. it needs to be perfectly aligned and straight. else, it will give you a headache, so don't start this project without tons of patience.


BLV mgn Cube - 3D Printer by BLV  (Ben Levi) is licensed under the Creative Commons - Attribution - Non-Commercial - Share Alike license.




Special Thanks to:

  • I want to give heartfelt thanks to my lovely wife for encouraging and supporting me throughout the project.

  • Huge thanks and appreciation for Peter (Blurolls store) for mass supporting this project and Tim from for supporting this project and many more!

  • This great community for making this place my second home :) Thank you!

There are no conditions other than the license terms.
You don't have to, but if you insist a small donation will be greatly appreciated.

Thank you :)