Bavarian 700x900 IE Build(

First of all I want to thank Ryan for the great work he has done!

Here are some pictures and information of my 700x900 IE build.

X- Y-Axis: 25mmx1.5mm stainless steel tube
Outer frame: 25mm solid steel rod (cheaper and more precise than tube, weight doesn’t matter here)

  1. Alignment
    My x- y- axis are not exact square in their “normal” position but can be easily squared by hand. But also square axis can inadvertently become misaligned by touching. So this is my solution: I raised the timeout to inactivate the steppers, put 2x2 clamps over the axis to hold them square and move the axis back and forth 0.1mm with lcd commands. Then I can remove the clamps and the axis stay square. If I find out how to activate the steppers when powering up, I don’t would have to move 0.1mm.

  2. Height Alignment
    I put 4 nuts with inserts in the bottom of the legs and adjust the height with 4 bolts, then slide the printed parts down.

  3. Z- Bearing
    Added second z-bearing to take the upwards z-force from the stepper

  4. Belt Tensioner
    See imanges

  5. Spindle
    Built my own spindle from 40$ brushless RC- Motor

  6. Power Supply
    Built 12V (Ramps) 24V (Spindle) 56A 1300W power supply from 12V server power supply (8€ each, ebay)

  7. Tool Holder

Build different tool holders for self made spindle and Kress spindle, both 43mm bottom mount diameter. I will have to rebuild them for the new middle. :frowning:

more images (don’t know how to upload more than 4 images)

more images

and more …

and more …

Nice work and attention to detail!


What, how have I missed this thread? So nice, I am jealous of everything. Even your shop!

Any details on your outrunner spindle? How are you converting it to, I’m guessing er11, from the regular shaft? I would love to try that out but could never find an elegant coupler system. The motor and the ESC should be easy enough, I have used them in a few projects but the shaft conversion? This is what I wanted to do from day one and kind of gave up on it because the dewalt was so cheap and easy. The downside is it is heavy, awkward to mount, and loud.

Hello Ryan,

I used a C12-ER11A-100L cut to length and cut a 12x1.25mm thread on the end, pressed/glued (Loctite) the connection rod into the end of ERA11 (a little more than 8mm diameter and turned it to 8mm after installation)

The bearing case is turned from 25mm Aluminium.

The biggest problems I had with the bearings. First I used IBU 7201 12x32x10 mm, but they get very hot after a few minutes at 30k rpm. Then I used noname(china?) bearings 61801ZZ /12x21x5mm, still very hot. Now I use FAG 61801ZZ bearings which stay cooler. Nevertheless I redesigned the printed parts to route the cooling air of the built-in fan of the brushless motor over the bearing case. The brushless motor sucks the air into the bottom holes and over the bearing case and blows it out at the top.

Don’t have much hours on it at the moment, so I can’t say anything about durability of it.


  1. 1 Upper case printed part ABS
  2. 1 Lower case printed part ABS
  3. 1 Bearing case turned part 25mm Alu
  4. 2 Bearing FAG 61801ZZ
  5. 1 Collet chuck holder C12-ER11A-100L (cut to length)
  6. 1 Connection rod Steel 8mm
  7. 1     Nut self locking                 M12x1,25
  8. 1 Flexible coupler 8mm to 6mm
  9. 1 Brushless Motor Turnigy 600 H3763 Brushless outrunner 1330kv

Can give you the step files if you like.


So about the same as what I saw before. A lot of custom work. You did a great job. I would love to hear how it holds up after some time under its belt. I just ran the dewalt all day and it is still surprising me, but so obnoxiously loud, but not as loud as my vacuum…So for now I’ll stick with it.

At one point there was a motor you could press out the shaft and press in the collect shaft but I can’t find it anymore. With that you just needed to add a bearing near the tool end to offset the lateral forces.

Hi Franz,

richtig gute arbeit!

ich möchte auch mir eine mpcnc bauen, aber ich bin zu geizig bei der auswahl der materialien für die achsen. was kostet der spaß? ich hab fast alles bis auf die kupplung nema 17 (z-achse) und rohre für die achsen.

Hast du probleme mit Vibration ?

hast du gesehn das stahlrohr in zoll maßen 1€ pro meter kostet?

viele Grüße

Hi Franz,

really good work!

I also want to build a mpcnc, but I’m too stingy with the selection of materials for the axes. what is the cost for this fun? I almost have everything but the clutch nema 17 (z-axis) and pipes for the axes.

Do you have problems with vibration?

Best wishes

That flex coupler in your Z axis doesn’t give you issues?

No it doesn’t until now. Are there any known issues with this flex coupler. I cut a M8 thread in the lower half to mount the threaded rod. As I said before, I installed a second bearing to take all Z-forces from stepper and coupler.

I used 25mm massive steel rods for the outer frame (~35€ for 6m) and 25mmx1,5mm stainless steel tubes (~25€ for 4m) I think this is worth the money for such a nice machine!

I would think it would want to stretch when moving the z axis. It may be only a small amount but could still mess up a job.

My z axis is supportet by dual ball bearings, absolutely stiff in z-direction and no z-forces on the stepper or coupler. The coupler and stepper doesn’t have to hold the z-axis.

Fantastic work!

Id like to make some similar upgrades to my machine, starting with the spindle.

How is the spindle holding up after 6 months use?

Have you tried cutting aluminium with it?
If so how did it go?

Nice looking build! I like the alignment clamp idea too.

Be careful with motor selection, You are looking for low speed high torque. So in this case a low kv outrunner. The other option is to gear it. Big mills usually start down in the 400rpm range, the dewalt 660 is at 30,000, that is too high so most of us slow it down with a speed controller and that sacrifices some power.


my spindle is working fine until now. I have processed mainly carbon plates up to 3.5mm with 0.9mm to 3.0mm end mills, with spindle speeds of 20k to 30k rpm. My brushless outrunner has 1330kv, so with 24V I reach up to 30k rpm.

In the meantime I worked on my MPCNC

  • wired the x- and y- steppers in series and modified the Ramps to 24V. Max save Z-speed with M8 thread is 15mm/s (did not increase x- an y- because 195mm/s in more than enough)

  • did some stiffness improvements (see images)

    • new middle Z
    • strut on steppers
    • struts on legs
    • steel inlay gt2 belts
  • aded a dust extraction system via the two middle z-axis pipes

Dust Extraction in action

still don’t know how to add more images at once, so here the images of my “dust extraction system”