CNC Haps: started a new Y axis, and Toner Transfer fun!

Long time no write...

I've been busy recently working on more CNC fun-ness.

In particular, I'm trying a form of building a CNC axis with OSB (Oriented Strand Board, AKA chipboard, used for house sheathing).

Ugly, horrible wood, but unbelievably cheap: $8CAD per 4x8 sheet, 3/4 inch thick.

I'll take some pictures at some point (I'm in my pyjamas and my camera is upstairs!), but my scheme is to try to build an axis (and, if that works out, a whole machine) based on adjustable, simple construction using only OSB, 2x4 scrap, and wood screws. I'm using found printer bearings and linear slides (cheat), but my final design will probably use skate bearings and pipe of some sort.

So far, I've built an axis and carriage that slides nice and smooth, and mounted a hardware store coupling nut underneath (one of those long nuts). With a hand drill and a piece of threaded rod, it runs nicely.

My goal thus far (and still) is to build a DC gearmotor-based servo setup with feedback loop control. My current prototype is using a partially disassembled optical mouse wired to my Arduino. It reads changes in position accurately, but loses some ticks over long runs. It may not be accurate enough for my needs. We'll see. I still have to try improving the mousing surface (I figured just putting paper down for the mouse to run on. OSB is a pretty terrible mousing surface! :-) )

Next steps are to mount a drill motor and chuck, cut a piece of threaded rod to length, and use a bit of white plastic cutting board at the other end of the threaded rod for a bearing. Based on this, I'll write a little Arduino sketch that drives the thing around, and see how it all goes. Should be fun. :-)

I found a good source of skate bearings. Used rollerblades. At a church bazaar I was at this weekend, I got a pair of inline skates for $1. Each skate had 8 bearings, so each bearing cost me 6 1/4 cents. :-) I wish I'd picked up a few more pair. You can sometimes get them for free, too. Nobody wants old dirty nasty inline skates. Except me! :-) ABEC-1 bearings, nothing too great, but they spin nice, and should be good enough for my junkbot.

Finally, I'm sold on the wonders of toner transfer PCBs. I tried it twice tonight (the first one turned out backwards, and I didn't iron it quite enough), and the second time came out as close to perfect as I can imagine. I'm going to try the hydrochloric acid/hydrogen peroxide scheme talked about on the Net for etching -- trip to the hardware store in my future.

For reference, I've got an HP LaserJet 4mp - nice workhorse of a printer. I use generic brand Staples (Canada) HP compatible toner cartridges. I am using this week's Wal Mart flyer (glossy, thin, low quality paper) to print on. Scrub the board with a green scrubby, put the printed (reversed) circuit on the board, set a clothes iron real hot, and just press the heck out of it. Soak in an inch or so of soapy water, rub the paper a bit, then slowly remove. Then scrub the result with your fingertips.

I'm going to make 3 DC motor drivers based on the LM18200T. Simple circuits, just some female headers, a few components, and the IC. I've got some heat sinks I've ripped out of old electronics that should fit the 18200s.

Cool stuff. I'm enjoying it.

Oh yeah -- also, I discovered the joys of Active Electronics! They've got a retail outlet here in Ottawa, and it's awesome.