Hey! This thing is still a Work in Progress. Files, instructions, and other stuff might change!

BLV mgn12 mod for Anet A8 / AM8

by Blv, published

BLV mgn12 mod for Anet A8 / AM8 by Blv Oct 21, 2017


BLV mgn12 mod for Anet A8 / AM8

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

  • This upgrade compatible with pheneeny's AM8 mod with small changes. (Huge credit!)

  • Why mgn?
    The linear bearing and Delrin Wheel Gantry commonly used at most of low-mid 3d printers as a cheaper solution for linear motion. Its cheaper replacement for the expensive mgn rails BUT price is at the expense of accuracy and reliability. Well, linear guided rails (mgn rails) are much more rigid, extreme precise and smooth then linear bearing or Delrin. The linear rails lets 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 need to be perfectly aligned and straight.
else, it will give you a headache, so don't start this project without tons of patience.

  • Please notice:
    Unfortunately, few days after started building this model, I was injured at work.
    So, right now i am recovering from cornea erosion - long story..
    Basically, I meant publish all the files only after putting all together but a lot of community members was asking for STL files. Therefore, all the files needed to build it released here. I'll appreciate every thoughts or suggestion that you will share with me.
    Thank you guys :)

  • 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 more 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.).

  • 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

Build it at your own risk.

Latest video update
A quick peek at my project building progress.
sorry for all the exposed wires - i had to test it. first video after all axis's electronics had been connected. Next week i'll get the 400mm threaded rods and install the rest.
I had to reverse x-motor connector in this video beacuse mistakly i fixed the carriage screw on the back instead on the front (i fixed and uploaded the fixed x carriage).


17.11 added a new experimental carriage adapter for Anet A8 Original carriage
17.11 STEP file updated ! (can be edited with any CAD software exp: fusion360)
14.11 added X-motor cover+cable holder (infill 65%+)
05.11 added X-Carriage for E3D Chimera Hotend
02.11 new LED strip holder (compatible with regular 9.8mm strip width)
02.11 new rubber feet mount instead of the tapped method. (Print with 60% infill)
02.11 new improved X-Carriage (added on both sides cable holder)
28.10 BOM updated
27.10 added Heated bed Belt locker (belt_lock_infill80.stl) (infill 80%+)
26.10 fixed x-carriage (the belt holder holes are now on front - reveres x motor not needed any more)
23.10 BOM list updated (added solution for AM8 with 440mm z extrusion)
22.10 added Cad Source file due to community request (BLV Mgn12 mod.step).
22.10 added BOM file (pdf)
22.10 added printing orientation images

Quick video: It's alive :) the first axis test..

Choose your Style

Mod variations:

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 orignal 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 a 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 + Free style + 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.

Requirements & BOM


  1. Anet A8 printer > AM8
  2. Tools
  3. Technical ability
  4. spare time

BOM - parts you need

clarification: BOM includes AM8 BOM.

  • 7 x Mgn12H Carriage (4 for Y-axis, 1 for X-axis, 2 for Z axis)
  • 3 x 2040 extrusion 313mm (for top, front, back)
  • 4 x 2040 extrusion 364mm (Y-axis)
  • 1 x 2020 extrusion 420mm (x-axis)
  • 2 x 608zz bearing (optional: if you intend using the top threaded rod holders)
  • 16 x HBLFSNF5 Corner Bracket
  • 150 x M5X10 Button Head Socket Cap Screw
  • 8 x M5x10 Socket Head Cap Screw
  • 6 x M5x16 Socket Head Cap Screw
  • 4 x M3X20 Socket Head Cap Screw
  • 60 x M3X8 Socket Head Cap Screw
  • 1 x M4X30 hex head (y-tensioner button)
  • 6 x M3X20 screw
  • 1 x M3X32 screw
  • 20 x M4X10 screw
  • 160 x M5 T-nut or M5x.8 Square Nut
  • 40 x M3 T-nut
  • 4 x M3 nut
  • 13 x M3 Washer
  • 1 x M3 nylock
  • 20 x M4 nut
  • 20 x M4 washer
  • 6 x Rubber Feet
  • 2 x GT2 16T idler (3mm bore)
  • 1 x 5 meters GT2 reinforced fiberglass belt 6mm wide pitch 2mm
  • 1 x PC4-M6 OD4mm (optional: if using greg's geard extruder)

for option 1 (original AM8 size):

  • 2 x 2040 extrusion 440mm (z axis)
  • 3 x Mgn12 350mm rail (x & z axis)
  • 2 x Mgn12 400mm rail (y axis)

for option 2 (extended z height):

  • 4 x Mgn12 400mm rail
  • 1 x Mgn12 360mm or 350mm rail
  • 2 x 2040 extrusion 500mm (z axis)
  • 2 x Threaded Rods 400mm

Additional electronics BOM

  • 1 x e3d v6 hotend or Clone

What & How to print

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

  • Y mount motor - (print this part only if you dont 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 planing to use the original Anet A8 lcd)
  • 1 x 1_LCD_Base_Right (only if you are planing to use the original Anet A8 lcd)
  • 1 x 1_LCD_Case_Top (only if you are planing 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 (dont print if you choose the electronics box)
  • 1 x Anet_Board_Mount_No_Fan (dont print if you choose the electronics box)

Material and Infill

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

Printing orientation

Highly important: i added 4 pictures showing 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 !

view original size: open it in a new windows and save the image or use the pdf file inside the zip files

Assembly instructions

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

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

Please notice you may need re-center the hotend/bed coordinates via marlin configuration.

Additional Parts

Additional Optional Parts

MGN12 rails & Carriages extra info

MGN Rails

Well, i used a cheap Chinese mgn12 rails from aliexpress cost 20$ each.
The store i bought it from named: "Mellow" via aliexpress. Before that i bought from other store named: "linkcnc Store" and the rails was awful! it was a used rails, damaged and shorter then what i ordered. They ware so awful, that even after cleaning and lubricating it was still stuck and jammed.

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 need to be cleaned away.
There are some videos on YouTube showing how to clean the carriage with WD-40.
don't forget that after cleaning both rails and carriage, you will have to lubricate it with sewing machine oil.
As for smoothness: Please ignore the method for testing smoothness but tilting the rail - its wrong! You want it to be smooth but not too much.
Also, since its a miniature rails, please don't use thick grease to lubricate.

Adittional links

Cleaning mgn12 carriage video:
Although the video in russian language which i don't understand - its 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.

Rails installation:


  • fixing the rail can very frustrating, you will have to re adjust it a few times until the rail will be leveled and straight.
  • the mgn bed adapters needs to be fixes with screws to the heated bead carriage - screws must be tighten in cross like in anet a8 manual.
  • take your time an adjust until it will be even from both sides then the motion will be smooth.
    its very tricky and need a lot of patience.

Small demonstration video

Note: The motor in the video is incompatible. it was installed only for taking the video and testing the weight.

view original size: open it in a new windows and save the image or use the pdf file inside the zip files

view original size: open it in a new windows and save the image or use the pdf file inside the zip files

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First of all, wow, thank you. You brought some serious game to the AM8. Thank you.

Question about the Y Axis extrusions. Pheneey uses 340mm and you have 364mm.

Am I overlooking something?

Thanks again for your contribution!

This Question was already asked (And I just discovered) by user Mycroftholmes on Oct. 22 and subsequently already answered by BLV. To save some scrolling, the short answer is Pheneey's design shorted the bed from the original Anet, and BLV's extrusions restore that loss. I'll delete this comment if people think it junks up the board or if I misinterpreted the answer given

Thank you my friend !
Please don't delete it, i think it can help others.

Good luck building it :-)

Comments deleted.

I realy like your Modification and want to rebuild it. I have only one Problem with the Mesures , because i got a Coocheer A8 with a 220x270 mm bed and 270 mm height print volume.
4 x 2040 extrusion 364mm (Y-axis) i will change to 4 x 2040 extrusion 414mm (Y-axis), because my print bed is longer than a usual at a anet A8?
I would be thankfull for help, to step on with that nice Build without cut or order wrong mesured profile parts.
Height will be ok, usual i can upgrade the linear rods later.

Theoretically it depends on the bed carriage more then the bed. I can try mesure it to see if you will need a 450mm mgn rails
Do you have any sketch and domension of the bed carriage

where in the USA are people getting the Mgn12H Carriages?

You can find mgn12 rails on amazon / aliexpress / ebay

So do I need 2 440mm extrusions even when not changeing size?

I just got my am8 frame and don't want to buy more extrusions unless nessesary I see you mention option 1 won't change size but still needs two extrusions in the bom

If you want to leave the original AM8, you just add two exteusion (on the Y-axis) for the y mgn rails + brackets. Rest of AM8 extrusions should be the same..

Comments deleted.

Nice, that's taken it to the next level.
thanks you

Very Nice! I don't have the time right now, but if I'd upgrade my A8, I'd do it your way.
Kudos for releasing the step files!

Another 3D-Printer working with linear rails is the cetus. You might look at the belt-management which i really like!

Thanks Thorax :)
I admire the clean setup of the cetus printer !
At first, i designed a belt system running inside the aluminium extrusion, but after couple
of hours i noticed the belt was to close to the extrusion core. Knowing that bigger wheels
such as 20T decreases the accuracy - led me to design an open lifted belt system..

my friend that excellent work, I mounted an original am8 and wanted to replace with MGN only the X axis, but I see that its parts of the X axis are attached to the Z axis what solution?

Thank you mate :)
Since it is a modular design, you can try and use thaug29 2020 X-Axis 2020 mod.
Then try to add the X-axis parts from the mod i designed.

Anet A8/AM8 2020 X-Axis 2020 for E3D V6/Titan Aero
by thaug29

Entendi, obrigado!

Hello, for what groove you have make the parts 5 or 6 mm

All the parts that fixed to frame are 5mm (hole)
Some internal parts with m4 and m3 (not to the frame).
You can look for it at the am8 manual and the bom file.
As for the other m3 & m4 all the description its attached as pdf file.

Y Axis question: I currently have an AM8 and used the 364mm extrusions on the sides as per the AM8 variant. The two new 364mm extrusions are held in place by alum corner brackets?

Thank you

Yes, the two 364mm extrusions below the rails are held with corner brackets (two brackets each).

That's all I needed to know, thank you!

First of all: WOW, you put really much effort in this, not only for building it but also for documenting it well!
Thank you a lot for this, also for the hint on how to get the china mgn12 rails to properly work (will try that asap).
I want to build this from my own custom made prusa i3 and have recently ordered a mk42 bed, has anyone tried using it and will it fit and be usable in all its size?

Thank you :-)
The bed used in the project is 220X220, I dont think you will have problem using 250X210.
For 300mm bed: it will fit also but the hotend will not reach the edges unless X-axis size increased.

Whenever this thing is completed? I'm looking forward to it and i will definitely build one! <3 <3 <3
Thank you for build and share that with me and everyone!!!

I have built it already :-)
A few things left to do.. such as installing BLtouch, find center of bed, PID, calibrations and finding Best jerk / acc
Then i will post the results :)

Hi Blv,
You did a really great job here!!
And yes, a BLTouch would be really appreciated :)
In your file "BLV_mgn12_mod", green is for PLA and blue for ABS/PETG or it was just for the style?
Are pieces in STL files in the way they have to be printed?
thx :)

Thank you :)
The bltouch will be installed with fang fan (This fan has a built it sensor mount for bltouch and proximity).
You are right, all the parts colored green is for pla and blue for petg, but some parts can be changed according to user will.
I added now a few new parts:

  • new feet mount instead of the tapping method
  • led strip holder for top and x-axis
  • improved x-carriage

Right now i am working on adding higher version of mgn y-axis adapter.

Hi, thanks for this awesome piece of work. One question : In the BOM it says : 5 MGNH12H carriages but shouldn't that be 7 ? (4 for the bed, 1 for the X-axis and two for the Z-axis)
Thanks for clarifying !

Correct !
I thought i fixed it 3 days ago, but after saving i got "token invalid" on thingiverse site (too much edit time i guess)
any way i have corrected it now
Thank you very much body !!

Comments deleted.

Could you please advise the lengths for 2040 for the front, back and top of the printer. I could not see this on the BOM.

My friend
Its 313mm according to AM8 manual
as i wrote in section "Choose your Style" at the item description, first you will have to choose your style (Original AM8 OR extended Z height). then, since it's based on the AM8 you will have to download the AM8 manual from here.
i wrote. Dont forget to read the "what to print" section in order to know what to print from AM8 parts.

AM8 - Metal Frame for Anet A8

This is awesome, I am preparing to upgrade to AM8 soon.

Cool ;-)
It's a lot of work, but man.. what a difference !

Hello and thank you for sharing, I would have liked to know if a heatbed of 300x300 can be installed with the dimensions of the frame to 500mm?

Thanks :)
you will have to replace the 313mm (2040) extrusion and the X-axis (2020) extrusion.
if you will not do that, the V6 carriage will not cover the bed edges (Y-axis depends on the carriage size)

And on the y axis no change? I thought to extend 80mm both axes (frame and rails). The original bed is 220mm and the one I want adapted 300mm that's why 80mm.

It depends on the carriage you are going to use.
Give me a link to the bed carriage and i will calculate for you the Y rails/extrusion size :-)

I think I will cut a plate of aluminum 300 * 300 like the heated bed.

So will you leave the space between the mgn carriage the same?

I will use the mgn12h which will be fixed under the plate of aluminum then between the plate of aluminum and the heating bed, the springs and screws.

Yes, but before you need to calculate the Y rail length because the travel distance extended by 40mm each side.
The distance depends in the space between the carriage that holds the bed carriage. please tell me the space
between mgn carriage (rear<>front) then i will calculate what lenght of rail you will need for 300mm bed

In fact, I thought to take the distance proportional to that of the 220mm!

That makes sense :)

Oh yes! now here is a mod I like!


Thank you :-)

Thank you this is brilliant.
I do have a few simple questions though that being if i was wanting to do this build without making it larger and with using the standard extruder carriage what i the parts that would be needed? I have seen that you listed a Mgn12 350mm rail instead of the 400 for the standard build size am I just missing the other parts that would be needed?

PS get better need good designers out there...

Well ,i worked on something, check the attached images to this post.
The weight is still an issue and i'm afraid you will have to get a longer extrusion instead of the 313mm.
since the Original Anet extruder is very wide compering to V6 it will not cover the edges.
the adapter i made is only a prototype and i am not sure about it.. on Sunday i will be at home and check
again the measurements.

Thank you :)
you will need the 350mm rails, But for the extruder - i will have to make wight and size simulation of the original carriage.
if it will fit there, i will design a mgn12 carriage to Anet original extruder adapter .

I will update you :)

Honestly this is really stunning work that you have provided to the community. I wish you a speedy recovery. Many thanks for releasing the STEP files.

Dear friend
i really appreciate that, thank you :)

First, I hope you recover soon.

This is AWESOME, thanks for creating this. I recently completed the Ranita AM8 that turned out great. After I finish my MksGen1.4/Bowden upgrade might have to do this!

One suggestion.

The original AM8 LCD mount uses the Anet LCD, that when mounted on the front, would still fit within a Ikea "Lack Table" enclosure, mounting the 12864 will cause the AM8 frame to no longer fit (too long). I recommend the "AM8 RAMPS Full Graphic LCD Smart Controller Mount" by PapaJohn88.



Thank you mate !
I appreciate your excellent suggestion and will add your recommendation to item description.
also i am very pleased to know that my work can be helpful to you :-)

Thanks for the reply.

From the look of the images, your solution seems to be not any wider than the "stock" a8? The "other" v-rail,slot, open-rail etc A8 solutions seem to be wider, so they would not fit in a "Ikea Lack table" enclosure. BRAVO!

Why did you change the vertical (Z) 2040 extrusion to 500mm from 440mm? Since I have already built my AM8 frame with 440mm Z will it work with 350mm rails?

Thanks for the note on a source for the rails, as I thinking of buying the rails form Aliexpess "Cheaper the better" I was thinking but maybe not? One seller (wuhushiyu Store) says in their listing "NOTE: We can cut in any length of rail. Just do not hesitate to tell us your request."

PS: Found the "link cnc store" as they seem to be the only one that offers 360mm rail. The pictures show rails scratched and worn etc.

Thank you :)
I have changed it to 500mm in order to increase printing volume height
The main reason i am answering only now is because i made some simulations with a 440mm extrusion (original AM8 size).
at the end i found that 350mm mgn12 rails can fit there pretty good (measured it with a 350mm threaded rods).
Also, the drawing/sketch of the simulation attached to this replay message.
The 350mm mgn12 rails will fit just fine to the X-axis rail without any problem
btw: I think you should avoid buying custom size rails, they will cut it horribly.

Thank you!

Again, good work!

Hello... I bought all pieces to make AM8 ranita versión... It is possible to make that one but with same high of ranita one and not 500 mm?

Yes, it is possible.
the z rails can be fixed to a bit smaller extrusion.
As long as you will make sure to fix it well to extrusion. even if a small part of the rail will hang on air - it will work just fine.

hi again , i have another question , i would like to know if you have de 3d files of the pieces maybe in solid works , i do that question because i can machining some pieces in a machining center for doing it in aluminium ,and from the stl files i cant take the measures.
best regards

Well, since you asked so nicely..
I have uploaded the full Step file which can be edited with most of CAD software.
Enjoy :-)

hi,the desing is awesome , bue i have few questions,
in the BLV mgn12 mod PDf . i see 2x364mm profiles and 3x313mm and i the pom pdf , says 4x364mm profiles can you say me what is the real one for 220x220 bed ?. and another question , if i want to do a 500x500mm i must just add the resting 280mm from the diference of 220 bed ?

You are right and i will explain it:
In the original AM8 BOM there are 2 Y-axis size 340mm which was wrong, since it was less then the original Anet A8 y-axis size. as a result the pause function didn't worked. So, Another user (ranita) suggested changing the Y-axis extrusion size to 364mm in order to gain back the lost 2cm. in conclusion, You will have to buy 4 x 364mm Y-axis extrusions. I apologize for the messy pdf, in this case i made there 2 images: the first 2 x 364mm extrusion is for the bed rails and from right you will see another sketch with another 2 x 364mm extrusions.
Yes, you will have no problem doing it with 500mm the measurements will be divided excluding the bed size (you may have need to change the bed coordinates in marlin) i will be glad to add the right measurement or code after you will finish it.