For the longest time, I’ve wanted to start tinkering with CNC milling and routing. But despite the number of well-documented homebuilt CNC machines out there, I could never quite get the momentum to start building one. So I decided to fast-track my entry into DIY CNC by starting with a kit.
I chose the micRo, a tabletop CNC robot kit from Lumenlab (the base price is $999). I wanted something small enough to be stowed under the workbench when not in use, but stout enough to cut aluminum and hard plastic.
The micRo looked great (in a NASA sort of way) with its white technical plastic connecting block construction and shiny aluminum base, and, although diminutive, the working area is about 12″×10″×4″, which is big enough to be quite useful to the broad-spectrum hobbyist. I couldn’t resist.
Anatomy of a Gantry Robot
Traditional milling machines are configured sort of like a drill press with a stationary spindle mount, and have a movable X-Y table such that the workpiece is moved around below the cutter. The micRo, on the other hand, like most (but not all) DIY CNC machines, is of the “gantry crane” design, whereby the work is stationary and the tool holder moves around on 3 axes, bringing the cutting tool to work the piece.
Building the Machine
The kit came with all the parts I needed to build the machine: bed, ways, leadscrews, collars, bearings, stepper motors, power supply, machined structural blocks, all fasteners, stepper driver boards, DB-25 parallel port breakout, spindle, and spindle mount. The only things I had to procure were the wiring and enclosure for the driver boards, and an old PC.
Note: Lumenlab has since changed its offerings a bit, and is now selling an assembled machine controller rather than discrete electronics boards and components. But if you prefer to roll your own controller, you can still purchase the DIY machine kit by itself, and use stepper drivers from one of the many vendors who offer CNC drivers and driver kits. A PC with a parallel port, running the free and open source EMC2, makes a fine CNC controller.
The basic machine assembly went pretty effortlessly, with almost no opportunity for mistakes. Documentation and assembly instructions reside on the Lumenlab website, and the companion forums are full of helpful tips from other CNC machine builders.
Once you get the machine all bolted together, you need to use a framing square to make sure that the X ways are perfectly parallel, and that the y-axis carrier (gantry) is perpendicular to the x-axis. This is referred to as tramming the machine.
The optional spindle kit for the micRo is a flexible shaft, hanging grinding tool, and a set of mounts for attaching the toolholder/chuck to the Z blocks. It worked well for me, though you could easily mount a Dremel, or other type of rotary tool, if you choose. The spindle had more than enough power to cut through hard plastic without bogging down.
Running a Job
There are two fundamental software steps to preparing a job for a CNC machine. First you have to draft the part in a CAD (computer-aided design) program. Next, you use CAM (computer-aided machining) software to interpret the model and generate the appropriate tool path for the machine to follow. CNC tool paths are written in a language known as G-code. The machine controller software then uses the G-code as a map, and drives the tool around appropriately to carve the piece.
I have a confession to make: I’m not really up to speed with CAD just yet, but I did find a cool CAM program called Image to G-Code, which converts a grayscale image into a cutting depth map. I fed a photograph of a skull, along with the size of my material and cutting tool, into the software, and it generated the proper G-code to mill the photo into a translucent material. I machined the image into a sheet of white Corian acrylic, and when held up to the light, it looks like the original picture!
I’ve got some CAD learning to do before I can start making robot parts, but let me just say that this desktop CNC tinkering feels good, and I’m really glad I started with a kit.
Resources
Image to G-Code program: makezine.com/go/gcode
GeckoDrive (good CNC drivers): geckodrive.com
EMC machine controller software: makezine.com/go/emc
Lumenlab: lumenlab.com
My build photos: makezine.com/go/lodefinkcnc
Note: Lumenlab has since changed its offerings a bit, and is now selling an assembled machine controller rather than discrete electronics boards and components. But if you prefer to roll your own controller, you can still purchase the DIY machine kit by itself, and use stepper drivers from one of the many vendors who offer CNC drivers and driver kits. A PC with a parallel port, running the free and open source EMC2, makes a fine CNC controller.
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