First part cut on the New CNC (Roland mdx-20)

I spent a little time today calibrating the desktop CNC mill I’m refurbishing.   A little writeup is available on my site if people are interested.   This CNC will be mainly used to make PCB’s for radio projects 😉


I spent a little time today in between IT Tasks at work tuning the little desktop CNC I acquired recently. One of the first objectives is to replace the spindle which has an unusual collect design with a more generic ER11 collet so I can use all the small PCB and milling bits I have rather than searching for bits with a 6mm shaft. As part of this upgrade I’ll be moving from the standard 10W DC motor to a brushless RC motor with a little more torque and a lot more speed which is essential when working with small bits.

First up was calibratiIMG_20150612_200817ng the axes, and it turns out the web site I found earlier with the gearing ratio’s on the roland was either incorrect or the one I have is different as all measurements were out by approximately 25%.

A lot of tuning later I have the following (recorded for prosperity):

Step Angle: 3.75 degrees/step
Travel per revolution: 2.36mm (a resolution of 0.02mm)

So the resolution isn’t as good as I’m used to, but sufficient for everything I’ll be using this mill for. There was a little backlash on both the X&Y Axis, which I’ve managed to resolve by tightening the draw wires. I’m really happy I could fix this as the TinyG controller doesn’t actually support backlash compensation.


The tuning took a lot longer than it should have as I kept trying to fix the 0.02mm backlash I was seeing without realising that was the resolution of the cnc… Doh!

With the mill all tuned and adjusted, it was time to follow the age old tradition where the first part cut on the CNC should be a part ‘for’ the CNC. In this case in Wax rather than Delrin so I can verify the sizesIMG_20150613_164822 and offsets, good thing too as one of the mounting holes is off by 1.75mm.

This also lead to a little bit of Yak shaving where I needed to render the slab of machine wax down to sizes suitable for this mill. I have a nice little pile of wax ingots now, and still have another batch of wIMG_20150613_164440ax to render down tomorrow.