Friday, 1 March 2013

CNC Mill Build - Enclosure

After finally getting the mill running it became obvious that I was nowhere near done.

Firstly, in their current position the electronics didn't give the machine enough room to move freely, so they would have to be relocated.

Also my current method of using drawing pins to hold down material wasn't going to be a permanent solution.

The first problem is easily fixable, I collected a bunch of connectors, then got out my calipers, cracked open Vectorworks* and began designing an enclosure. 
I cut all the pieces out of 3mm MDF and when assembled they looked like this.

From the front all you see is the name and power switch.

One side features a cut out for a fan.

The back has all the connections, A/C power in, parallel signals from the computer and five molex connectors, one for each motor and one for the limit switches.

I designed the box to be low profile so it would fit in the sliding drawer under my desk.

Here it's nice and out of the way but easily accessible if I need to fiddle with it.

Under the hood, you can see the power supply takes up most of the space. Main power is routed through the illuminated switch at the front. The 24V supply then gives power to the motors, it also drives a tiny 5V regulator for the logic power supply and the motor is supplied by a slightly larger 12V regulator (you can see it glued to wall on the right)

I found some little fuse holders and intend to put a small fuse in after the switch. There's also room at the back for adding more connections, for things like spindle control and an emergency stop button.

Being the first real thing I've made with my machine this taught me a lot. Firstly my machine is pretty damn accurate. 
The pieces just fit, I was expecting to have to sand things, but they actually fit great and I measured the pieces to be well within 0.2mm of what I intended, that's nowhere near what some CNC machines can achieve but with MDF it's more accuracy than I'll ever need.

Another thing to note is, always measure your material. I should have remembered this from when I designed stuff for laser cutting, but my 3mm MDF turned out to be 3.2mm, so my box joints aren't quite flush.

A lot of time designing this was spent on the engraving. The majority of fonts these days are solid blocks, you can turn them into outlines with a vector program, but the best results are achieved from single line fonts. You can see that the axis labels I engraved on the back of the box are a bit chunky, I didn't like that so I spent a while manually creating single line letters for my title font.

This was tedious but I'm happy with how the final thing came out.

The M6 for short

I'd like to make the lettering black so it pops more, but I can't think of a good way to do this, hand painting would be tricky, and detract from the nice clean finish.
The easiest solution is to mill all the way through a material and place black behind it.

I also installed a hold down table. Essentially this just involved sinking a bunch of t-nuts into the back of my board in a grid. I now have a grid of points where I can bolt things down to the table.

Above you can see me marking out holes, and a couple of nuts ready to insert.
The grid is now finished, I'll snap a proper picture next time I'm using it.

I've actually found that for most materials  double sided tape is a better solution, most of the time the clamping bolts just get in the way.

I've been happy with this set up for the past few weeks, I've had a go at milling a phone dock, pcbs, and at the moment I'm milling maps out of cork. :D

One thing I haven't really tried is milling plastic, I've got some chunks of acrylic on the way so that's next on my to do list.

*Vectorworks is my CAD program of choice, mainly because it's what I used during my architecture degree. However it seems that I'm in the minority using this program. Most people use AutoCad or SketchUp, or for simple 2D work, Inkscape.
Supposedly AutoCad was designed by engineers and Vectorworks by architects.
I've got a copy of Illustrator, but most of the time I get frustrated with the alien pen tool, give up and switch back to Vectorworks. 

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