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Sunday 3 March 2019

CNC proof of concept design - Shapecut part 2

Continuing with my conversion of the ancient Shapecut Oxy Gas cutting machine, I have started to assemble a tiny CNC engraving machine to use to test the control electronics.

I purchased a low cost CNC machine from Amazon. There are many similar machines that use Arduino's to control them. I am only using the mechanical assembly and the stepper motors for my proof of concept.

It was a bit of a challenge finding the assembly instructions from the download link provided with the CNC machine. I eventually selected the compressed, .rar, file I found in one of the folders. The written instructions were OK but have a few mistakes.

In some photo's the moving bed is shown the wrong way round, it is also attached the wrong way round so the vertical frame cannot mount far enough back on the horizontal frame. I still need to swap mine round. I didn't notice the video instructions until after I had finished. The video shows a different way to assemble it.

For what I need it for this machine will be fine.

The plan is to use an Ethernet motion controller to connect, via a breakout board, to stepper drivers. For the purposes of the proof of concept I am using low cost, £8, stepper motor drivers. The final machine would need much more powerful drivers and stepper motors.

Common-Anode circuit

I've drawn up a circuit schematic to ensure I understand what parts and connections I need.

In the process I have found out that there are various wire colours for different types of stepper motors. I found the following handy reference article:

My test set up will use a 24V power supply for the tiny NEMA 17 steppers supplied with the engraving machine. The final solution is likely to be NEMA 34 stepper motors each requiring up to 6Amps and I'd run those at 60V. For that installation, I'd use one power supply for the X axis and a another one to power the Y and Z axes.

The next job is to put the electronics together.


Shapecut Series:
Part 1 - Magic Eye to CNC
Part 2 - CNC proof of concept design
Part 3 - CNC controller enclosure


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