Cheap CNC, eh? ;)

[Zippi]

Hi Folks!

Just found this site tonight, I think I'll fit right in... LOL!

My project: A cheap CNC machine built using materials from Home Depot (don't laugh... ok, laugh... ). The goal of this project was to start familiarizing myself with hands-on CNC experience without a big investment (with a perk of kicking out some nifty Christmas gifts for a large and extended family..). I plan on at least two more "useable" CNC machines that will be more of an investment (three, perhaps? LOL), and wanted to start familiarizing myself with practical experience before taking the "plunge".

My background: I have a degree in electronics, worked w/ linear motion years ago, satelite tracking systems. I write software for a living now. I have a small mill and small lathe I've purchased in the past couple of years (7x12 lathe, mini-mill). I have always enjoyed building / making things, and I find myself leaning more towards the tangible as of late (software being more of a "virtual" creation).

The Machine:

4 - 50 oz/in steppers driven by a custom (read home-brewed) driver using half-stepping code on PIC 16F84A's (code from www.dakeng.com for the two PIC chips), running IRF-740 MOSFET's using a really messy logic-to-gate driver stage. Plain Jane, no chopper, 3 axis' worth of drivers. Steppers are ~12v, using 12v Radio Shack 25a (overkill) power supply (again, no chopper drive here).

Machine Structure is made entirely of 3/4" birch plywood (two sheets of 2' x 4' required). Major panels: 7. Minor ply pieces (motor mounts, nut brackets), 8.

Custom machined stuff: screw ends (4) machined, couplers (4) machined, nut carriers (4) machined.

Screws: (ok, laugh all 'ya want) 1/4" x 20 threaded brass rod (translate, SLOW!). Nuts: 1/4" x 20 steel (not pre-loaded, angled to reduce play).

Slides: (Ok, laugh really hard) ball bearing keyboard drawer slides (3 pair).

Tool: Dremel, on Dremel router mount stripped from router attachment mounted using steel 6" L-brackets (currently need to be re-drilled to get more X axis motion).

Primary design layout, "Play as you go"(tm).

Not counting the motors, controller, or dremel, the cost is around a hundred bucks (the slides being the most costly part).

The x axis moves the work, the z axis is powered by 2 of the 4 steppers and carries the y axis (no counterweights).

The machine is presently undergoing testing / tweaking.

So far, I have successfully machined 1/16" into a piece of birch ply (hey, I had leftovers!), and engraved MDF using 3/32" and 1/32" Dremel engraving bits. I am using TurboCNC on a dedicated 200mhz PC (using an IOMega 4 port KVM switch to use my keyboard / vid / mouse between the two). NC files generated from DeskArt and DeskEngrave. I haven't yet attempted to route deeper than 1/16", but the machine seems stable enough to take at least a 1/8" cut (and the feed rate is so slow, I can't imagine it having a problem there, or even deeper, perhaps).

At present, there is "slight" warpage in the table on the X-axis (with a funky spot of about .012" out 1 inch in from one edge). I think I'll just have the machine mill a "skew plate" for mounting work. I have room to adjust skew elsewhere (shims, slotted plates in the slides).

About the electronics, one could substitute something much less complicated with the same results - per-pin gating of an IRL series MOSFET would do just as well (half-stepping is pointless on a system this slow w/ 20 TPI threads).

It's really ugly, but I'm surprised with the results!!! Can imagine a few neat projects this machine should be able to do.....

Not built to last, not built to impress, only built to learn on.

I can post pictures if anyone wants to see a machine built in a day (really, it's that straightforward). Can also post pictures of engravings..

Take Care,
Paul

[chuckknigh]

Why would we laugh? It sounds like you just built what we refer to as a "first machine." And, it sounds like a fun machine!

Lots of us use 1/4" (or so) allthread, and smallish steppers. BTW, since you're obviously a tech geek, the HPLJ I, II, and III printers each contain a single 100 oz-in stepper motor...if you're interested in upgrading your motors. They're commonly available surplus, and at thrift stores, for next to nothing.

Congratulations! It's relatively unusual that anyone actually completely finish a machine -- you're in an elite group. Welcome to the group!

Please, post your pictures... I'm sure we'd all be interested in seeing your creation!

-- Chuck Knight

[Zippi]

Hey Chuck, Thanks for the info Re Steppers, and Thanks for the Welcome!

Elite, eh? WAHOOOOOO!!!!!!

Ok, ok... Pictures....

Comments / opinions welcome! (ball screws / 600 oz / in steppers / Geckodrives in mind for Mill conversion... Estimating around $1000 to $1200 for the conversion... I'll do some searches and post any questions about pricing when I'm closer to ready for that endeavor... )

EDIT - BTW- Tim and Chris are my sons.....

[High Seas]

Zippi- Way Cool- Ya, "Just DID IT!" (appologies to Nike - or whoever)
How about using an end mill - or squared off router bit to surface the work top and not build the shim plate? I had to do that and got everithing back in 'plane.'

Looks like a lotta home made Christmas thingies! Cheers - Jim

[ynneb]

Welcome Zippi, We dont laugh at any ideas here. In fact we love out of the square thinking. I am constantly surprized at some of the unique ideas that are posted here.
Your contributions will be a great asset to the forum, and I hope youll learn a bit from us too.

Edit: If you recon your machine is ugly then take a look at mine. http://cnczone.com/forums/attachment...achmentid=2241