Design Thinker: Shapeoko2 CNC Miller

Carriage Assemblies
Three carriage assemblies…

So… at the end of my last entry on the Shapeoko2 CNC Milling Machine, I had four working motors! Woo! And at this point, I have three motor carriage assemblies.  See the picture? These are the platforms which will hold the left Y-axis motor, the X-axis motor, and the Z-axis motor.  What happens to the right Y-axis motor, I’m not sure at this point; the wiring diagrams, and the arrangement of tubes and wires and zip ties to attach everything have got me confused.

One of the hardest things about design, or about Making in general, is to know when to stop. Mistakes are always the result of stopping too late and giving the mind a chance to catch up.  I’m really excited by this project, and I’d love to be done tonight… but that’s not realistic.  I’m looking at the remaining directions, and I realize that this is silly.  Don’t move on yet; you have to think through the rest of the machine from here, because from here the directions start getting weird.

Carriage Assemblies
The Carriage plates, when they were just parts…

Because from this point out, I ‘ve got to be thinking about my own layout of the machine. Where are the wires going to go, so that they don’t droop into the machine?  Which motor is the left Y-axis motor, and which one is the right Y-axis motor?  Once I start attaching them to the carriage plates, how do I unwire them from the test build, and rewire them back together for the construction-build?

But I think I’ve made good progress for the first day.  I’ve got the carriage assemblies finished. That meant assembling a good number of bearing-housings and washers into wheels; and assembling wheels into wheel subassemblies, and then attaching the subassemblies to the carriage plates.  This was not an inconsiderable amount of work.

When I opened up the box that the kit came in late Friday, I was dismayed. There were dozens of little baggies of parts, each with a serial number.  I wasn’t sure quite what I was expecting, but this was not it.  Frankly, it was a little terrifying. But now that I’m into the construction of the machine, I’m no longer as uncertain that I will finish building it. The technical documentation is good, and the instructions are good, even if they’re now getting into questions of soldering and the technicalities of attaching the motors and the electronics to the build plate.

Carriage Assemblies
This link eventually will lead to a really cool image of the v-wheels, their washers and bearings, artistically knolled.

All of those smooth idler wheels and v-wheels, I built those today. As I did so, I had all kinds of questions answered, too, about how car wheels might be attached to the chassis, and how and what might be wrong with our 3D printer at school.

Because I have a sense, now, that a CNC machine works by translating digital code into 3-direction Cartesian movement, and then powering a router which scrapes against the raw material inside the operations envelope of the CNC machine.  It’s essentially a 3-axis framework hooked up to a Dremel tool, so you can give it precise commands about structure in a digital format, and ask it to ‘print’ the results.

The CNC milling machine is subtractive. It will eventually cut away the inessentials from a block of wood or plastic.  But Moira the 3D printer is additive.  It heats up plastic and lays down a ribbon of plastic which attaches to prior ribbons as it cools.  Even so, I now understand that it’s an X-axis motor or drive problem on my school’s 3D printer — it’s not a problem with the heating element inside the print head, and it’s not a problem with the Z-axis or the Y-axis.  And I have greater confidence that learning how to build this CNC machine will teach me how to repair Moira.

The cost of buying this machine, and the time I’ve spent building it, has already paid for itself.

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