CNC bootstraps and other war stories

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While some folks like engage in exercising their digestive system over the end of year celebrations, genetic fractals likes to line up a project that will provide ample excuse to get away from the in-laws that descend on my house at this time.

This year I’ve built a CNC router. A bootstrap to be precise.

I’ve been playing with 3D printers for a few years to manufacture my 3D fractals but I’ve been forced to use third party printers at great expense. That lovely tree below cost 2500 USD to print for a 30 cm x 30 cm x 30 cm size! I didn’t pay that but someone did.

ShadowTree

So, there is a imperative to get my own tools. Rather than build a home 3D printer, I decided to build its cousin, a CNC router. Although routers can’t create 3D objects with as much flexibility as 3D printers, they have the lovely ability to use any material; typically wood, aluminium, acrylic etc. Unlike manual routers, CNC routers can also vary the 3rd dimension and therefore you can cut 3D shapes as viewed ‘from above’. Below is an example of typical CNC art. The wall shows the 3D cutting capabilities. The chair and dog are also cut with CNC.

cnc art

The technology is otherwise very similar. You could easily convert a CNC router into a 3D printer. All you would need to do is to replace the cutting spindle by a 3D extruder and use slightly different control software.

I did a bit of research and ordered a minimum number of components like stepper motors, linear bearings and some electronics to drive it all.

Since this is a bootstrap, I used wood to construct the CNC router. The idea of a bootstrap is that you build a basic machine which you then use to cut more precise components, perhaps even in aluminium. As such the machine builds and improves itself.

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It took me a few weeks to assemble the components and build the CNC router in a couple of days.

There is a surprising variety of skills required. There is the mechanical and electronics design.  Construction of the device and the wiring of the electronics. I’m using an Arduino Mega and some Stepper motors (Nema 17) and drivers + power supply that I bought on eBay.

The eBay kit also came with a computer interface for MACH3  but that was based on a parallel connector DB25 that my laptop doesn’t have, and nor does any laptop younger than 10 years! MACH has good reasons to use this approach but frankly they should build a dedicated interface that gives them accurate hardware control programmable via USB. This message is for their benefit, not yours 🙂

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To get the thing to work requires quite a few IT components. You need a tool to draw the component at you want to cut. Right now I’m using MS Paint for simple shapes but once I’ve got it all to work, I will use more sophisticated 3D editing tools, including my own fractal generator software!

Using Inkscape I then convert the image to a vector graphics format. This I then load into http://jscut.org/jscut.html to create a G-Code file. This is quite cool. It calculates how the router should cut the material, taking into account the facilities of the CNC router, material, tool size etc.

Lastly, I use the GRBL set of software tools that will send the G-Code instructions to the Arduino board which has been connected to the stepper drivers. You can see this in the colorful wires above.

Needless to say, it took a bit of fiddling to get all this to work, to get the wires right, to get the software set up but … it works!

hello

There are two ways to look at this first CNC carved piece of wood:

This is an example of a CNC router project fail. There is nothing right about this! The cutting depth varies; there is massive backlash everywhere. Nothing traces correctly… Only a cursory look at my CNC ‘design’ will show you why the CNC router failed. The use of tie-wraps, cheap linear bearings, aluminium rods, wood – it is all wrong

or

 This is a message from another universe! Letters that were typed in MS Paint have found their way through a massive labyrinth of software, apps, cables, controllers, wires, drivers, steppers, bits of wood and steel and aluminium onto a piece of wood. I never expected it to really work but it does. I can even read the message.

This is only the bootstrap. The rest is easy; I only have to replace the wobbly bits and this CNC router will be great.

And since this was cut on 1 January 2016, I have 366 to fix it all.

How great is that!

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