Need advice on hobby CNC machine

[pandelume]

I'm looking to build a small CNC router or mill for hobby use, and to be frank I'm not sure which machine to purchase plans for or whether I should bother with plans at all. Here are a few specifics: I'd like to have basically a small multipurpose machine, capable of 1/4" or larger ply (1/4" single pass), plastics, and aluminum. It would also be nice to be able to do hobby PCB milling. I'm figuring the PCB milling and the ability to handle aliminum are going to be the difficult specs, requiring a pretty stiff and accurate machine. Cutting envelope would be something like 1' x 2' x 4".

So I ask: bilge brain trust, do you have any suggestions, advice, pithy anecdotes, or dire warnings of which I should take heed?

[paladin]

about 6-7K in a do it yourself system.

[pandelume]

6-7k would be over my budget - I was thinking of something more modest. With that number, how would you break down the various costs? From what I've seen on the internet a fancy spindle could easily eat up a couple of thousand if you let it. Do you suppose 3-axis motion control (steppers, linear rail, endstops, and lead screws) will cost ~4k for a 1' x 2' envelope? Are there reasonable alternatives to a custom spindle?

[John of Phoenix]

This might help if you haven't seen it yet. Has its own builder's forum too. http://buildyourcnc.com/latest.aspx
They have kits from $1500 to $3000.


I'd always thought of CNC routers being used for repetitive operations - mass production of parts to sell.
I'm curious... what would one make with a hobby CNC router?

[JBreeze]

A couple of woodenboat examples I read about for 4 x 8 ft. hobby machines:

1) The CAD drawings can somehow be used by the CNC to cut the nested plywood parts for a stitch and glue boat....the designer provided the data to the hobbyist (no lofting)!

2) Other have used the CAD stuff to CNC cut the molds for everything from the small craft such as kayaks and canoes to large sportfishers.....sounds nicer and more accurate than cutting pencil lines with a jigsaw. Even a 2' x 2' is probably good enough for the small craft.

[John Meachen]

Take a look at www.cnczone.com .There is no larger forum dedicated to cnc hobby machines.I have been known to visit the site myself.

[TerryLL]

If you could live with less automation, you can put together a fairly high-class pattern router system for about $800. Making the patterns is a chore, but if you're producing multiples in large numbers it might be an option. If doing one-off, then probably not.

[pandelume]

For clarification: what got me started thinking about this was using a CNC machine to cut the strakes and building jig for a small lapstrake ply boat, as discussed in this thread:
http://forum.woodenboat.com/showthre...his-a-bad-idea
Of course, a 1'x2' machine wouldn't be able to handle that, but unlike a large machine (or for that matter the boat in question) a small machine will fit in my garage and still allow room to turn around. I don't have a specific project in mind for the small machine, per se, but I've often wished I could make accurate hole patterns when doing other projects. I'm also starting to get interested in hobby electronics, and my results with etching copperclad have been abortive - I figured it might be easier to route the traces (well, once I have the machine it might be easier). From there is was only a small step to figuring that building a small machine would net me a lot of experience and I'd end up with a useful tool.

Edited to add: thanks for the links, John and John. I had run across cnczone before - a lot of interesting info there - but not buildyourcnc.

[stoneyreef]

You can build a bolt together for less than 3k with .005 in accuracy and easily does aluminum. Will post more later tonight when I get home.

[Bob Cleek]

I'm with Chuck. The cost and technical complications are WAY beyond the value in time savings and accuracy for boatbuilding purposes. You can learn most all you need to carry in your head about lofting in about ten minutes if you took high school geometry and mechanical drawing. If not, make it maybe a half an hour. The finer points, you can look up as you encounter them in a good book. Vaites' "Lofting" is as good a book on lofting as I've ever seen, and I've pretty much seen 'em all. The accuracy of CNC is pretty much wasted on wood. Your .005" tolerance isn't going to matter much when a big piece of boat timber can move plus or minus a quarter inch or more just with changes in ambient humidity.

[paladin]

I've built a couple of machines. You need stability and that means welding a very stiff table to handle the moving parts, and from there things get really interesting.

[Paul Pless]

Cutting envelope would be something like 1' x 2' x 4".

Why not just buy a used nc controlled bridgeport? Typical price for a decent one at a reseller is $2500.00. I've been following them at auctions that sell for as little as $200.00.

[Milo Christensen]

Paul, what in Hell are you going to do with a Bridgeport?

[TimH]

I need a bridgeport. They are expensive around here.

[stoneyreef]

Check out http://www.joescnc.com

You can build the hybrid any size you want, get 1500 ipm rapids with .005 in accuracy and you can get a machine for about 3k if you go high end with a welded steel base.

The support forum is fantastic. Many people build 2X2, 4x4 or 4X8. One is even building a 12X4

Easily will mill aluminum if you take your time in building the carriages and glue them up square and strong. Running a gecko g540 and 425 oz hobby cnc steppers you have more than enough power.

The only tools you need to build it is a drill press and common hand tools.

[stoneyreef]

The problem with a used bridgeport is that they are used, and some parts are worn and the manual machinist knows his machine intimately and accounts for the wear. So you really need to know what you are looking at to buy a used bridgeport.

[pandelume]

Thanks for the suggestions everyone. I think a bridgeport is out of the question for now, as much for space constraints as anything else. Stoneyreef, have you built one of joescnc's hybrid machines?

Anyone have an opinion of the designs here?: http://www.crankorgan.com/phoenix.htm (Warning: the proprietor's prose is a bit of a trip). some of these have similarities to Joe's CNC 2006 and the JGRO machine (both open source for personal use), which are both quite popular, so perhaps they might be worth a shot.

I was thinking more of a benchtop machine, rather than a freestanding one with a dedicated table - would it be a mistake to go that route?

[StevenBauer]

The Shark Pro Plus is $3800. 25" x 25" x 5" Pretty cool.

http://www.rockler.com/product.cfm?p...376&filter=cnc




Steven

[paladin]

I have the plans here somewhere for the table for up to a 6 x 8 size table and the info to stretch it to12 x 8 table and also the software. Timm and I had visions of doing the 33 foot blackhawk entirely on tabbing it together. I have a lapstrake 10 foot dink laid out the same way. We could make kits from them,

[Deadwood]

After a few years of starting and stopping building my own CNC, I bought one from a guy in Toronto. Here is a link to his thread on CNCZone.

http://www.cnczone.com/forums/showthread.php?t=109757

I am now helping him out a bit by running a forum for him.