Kyoujin Mk1 - Rack & Pinion Conversion

I’ve decided to migrate away from GT2 belts (as in primary method of movement) to a R&P / Lead screw configuration.

R&P on the X axis (3:1) and lead screws on the Y axis (2.77:1). Longer travel on Z.

I am still using the old waste board for now, but that will quickly get pulled out soon.

IMG_1245.m4v (9.9 MB)


Amazing work loving it !
Fantastic idea for tension system.

Yup loving this new setup. Super torquey. Rapids are very, very rapid. And also super rigid.

If you need dust collector I just did mine in 20 min this weekend for same gantry setup. Pic and link to project there:

Cool. I have something else in mind.
Plus it’s a Easel project. I use LinuxCNC.

Tool Offset Probe that I am working on for the new machine. The top was cut out with this machine the main body was cut out on my smaller/heavier duty machine.


Machine in action. (This is using my old machines wasteboard)

This new one is under construction.

Since my smaller machine made all the parts for Kyoujin- I figured it was fair that Kyoujin made a part for it.

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Judging by your profile pick and choice of name, I’m going to guess you like shingeki no kyoujin? :wink:

Awesome build by the way, looks amazingly professional :slight_smile:

May I please ask your estimated build cost?

I haven’t been on the forums here for a LONG time. Figure I should update the status of this machine

Now it’s closed looped. Finally got a VFD spindle for it. 2.2kw water cooled. Changed out the wasted board to PVC and did sheets vc one big sheet. This way I can just replace the ones that get really back vs the whole damn thing.

And for the smaller machine I changed the waste board out for MIC6


Looks awesome, lots of progress. Excuse my ignorance, but what do you mean by closed loop?

Open loop = no feedback. Tell it to move and you assume it moves. This is why you can lose steps and the machine not rectify it. Position is always an assumed position given the machine actually did what it was told to do. This is GRBL and Mach3.

Closed Loop = positional feedback. You tell it to move and an encoder/resolver tells you how much it moves, this data is fed back into the control loop and it uses it for the next motion command. The control system knows the reported position is the actual position and not an assumption. This allows the control system to kind of correct for lost steps or other issues. Theoretically, if you hit a clamp and can’t move, the Gcode wouldn’t keep telling the machine to move because the last command never finished (in a system that implements such control).

I’ve read some articles about open vs closed loop for CNC machines and opinions can vary. Since you are cutting as you move, if you cut off path, even if the machine corrects it, you still get a blemish on the part. Closed loop should allow for more accurate feed rates as the system can understand how the machine is moving and, in some systems, ramp up the power to move more inline with the commanded feed rate. also, my understanding is that only LinuxCNC runs closed loop for software based controllers. You basically have to be running at real time to be able to do efficient closed loop. At work, we have a closed loop system running at 1khz and it’s all embedded fpgas and dsp chips (not a CNC).


That’s a great explanation, thanks a lot. That’s very interesting.

Are you God?

How is the backlash on this system? If any how do you compensate for it

A couple of overdue updates.

Wireless Touch Probe (/w its own offset G59.3 and G30. So when it tool change is needed, it goes to G30 I change the tool and it checks the offset and goes back to work.)

Couple years back I got a DOT enclosure from a salvage yard and repurposed it.

Also redid and sealed the coolant setup for the VFD.

And switched the controller over to PathPilot.

This is nice cause now both machines use the same motion controller and I can use the same PostProcessor.
The only thing I need to grab is touchscreen. And both setups will be the same.


All axis have anti-backlash mechanisms. So if it does have any. It’s minimal.

Vacuum vises for days.

I love these. Makes fixturing so much easier. If you have the option of use them, use them. You can machine/route around the part without worrying about clamps being in the way. The otherside effect is since this machine was completely designed in Fusion 360, In the CAM I can use the center of the puck as my origin. Or any aspect of the machine for example, the threaded inserts in the wasteboard. Since the positions are known I can set each one it’s own offset (if the part is small enough) Then set G54, G55 for side one and G56 & G57 as side two.

Example of holding a large stock.

I finally now have a proper E-Stop that trips a relay which then drops the enable pin on the driver to low and sets the alarm pin on the VFD invert to high. This stops the motion instantaneously and the VFD shuts down and ‘brakes’ the spindle to a halt. (The VFD has an option for a braking resistor. Handy later when I build a tool changer)

The green button starts a job and the last button (mislabeled) turns the vacuum pump on & off.

Since I have a proper charge pump setup for active/e-stoped, i.e trigger the status LED to flash if a estop has occurred or an error like the gcode file is trying to extend beyond the limits of the machine.

These are pictures of the other mill making the vacuum vises (aka pucks)

That’s after making 18 of them. The one in the vise was the last one.


Once you go rack, You’ll never turn back.

Super fast, super torque’y. Love it.

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What pump do you use with your vacuum vises? Btw, they look like store bought. Well done.