Call me Crazy!

[xclr82xtc]

I need a CNC machine! Pronto! obviously, i dont have the resources to go buy a 100k machine, so i have no choice but to build it. I do alot of hobby cad design in solidworks, and i have access to a machine shop that will make me anything i take them to cut. so i can design the machine on solidworks, no problem...my questions come into play when i start trying to figure out what size motors, controllers etc.

mechanically, its no sweat, electrically.... lol anyways, can anyone be of some help? looking to build one big enough to machine a 20l, 20w, 16h block of aluminum. (is 5 axis possible for the home builder????) also, i have a older GE 3 phase 15hp 8000rpm motor that im going to be using for the spindle...(good enough????)

i do alot of race motor parts, so im looking to design my stepper motors to have a gear down reduction system that i can use to make my steps go from .001 to .0005 (not all the time, only when extreme precision is needed) you guys think thats a good idea? or should i not waste my time with the extras? lol.


thanks again

[PixMan]

Happy to oblige....you ARE crazy!

There is no way I can think of that you would be able to build something capable of the things you need to do for less than you'd spend for a respectable used machine.

[DareBee]

CRAZY FO SO

Like PIX said ^

I build machinery.
I one-off custom that is comparable to an off-the-shelf will be 5 times the money.
You really think you can outdesign (in one shot) something that has been field proven and tweaked for 20 years?

All the best to you

You might as well build 5 or 10 because we will line up to buy them.

[xclr82xtc]

LOL no i know its gonna cost a little bit, but i can build the mechanical side of the machine for around 3 grand. (and the spindle is a BIG chunk of that) thats with all the mill works, motors, and everything...the money is gonna come in with the controllers. and im looking to spend another 3 grand there. (in other words i only got 6 k to play with, and i need the most machine for the least money. i already got a little head start, with the motor, some ball screws, and a table top (from a old table saw that i had milled flat) now i just gotta make it all work. someone point me in the right direction for controls! lol

btw..im not including tools, im just talking the machine..

[msomerville]

If your spindle falls within that $3000 range I would bet that it is not capable of cutting that aluminum for an extended period of time.
You are dreaming if you think you can build a reliable 5 axis machine.
No offense of course.

[DareBee]

Soo...
You are trying to tell us that a $100,000 machine has $6000 worth of material in it?

I am happy you are building within your budget to suit your needs but your comparison is ludicrous.

$6000 won't even buy the bearings for the spindle of a 100G machine.

[xclr82xtc]

jeez all the annimosity...maybe i should have posted in a differnt forum. all im trying to do is build a.machine that is Capable. i'm not talking about a vf3. . . I'm not talking high speed or 5 axis. . . I'm just trying to build something to have fun with. That and the ultimate goal is to use this mill. . . To build a better mill. guess I'll just have to go it on my own

[xclr82xtc]

what is if i.machine my own spindle? i would obviously get the best bearings i could afford and would save on the spindle cost just buying material and doing it myself

[awerby]

Just because people confirm your own stated opinion of yourself. Realize that you're talking about building a machine on the cheap that would outperform the $100k machines these guys are sweating to pay off.

The main thing that's problematic here is that 16" Z height on your billet. If you're talking about building a machine with that much Z-travel, that's pretty radical. Think about it this way - in order to reach the bottom of your billet with a tool, you'd have to have a 16"+ long endmill, and you'd need 32" of clearance to traverse over the top of it. I'm not saying that's impossible (although you'd need a pretty stout tool not to get severe deflection) but it would make for a somewhat unique design.

Reduce the max height to about half of that, and you've still got a longer Z-travel than most mills and routers while the mechanical forces working against you are a lot less. Unless you need to make a specific part that's really that high (in which case you might want to look at other ways of going about it) the project would be a lot simpler if you scaled it down a bit vertically.

As some people here have tried to hint, it's a lot easier to come up with a good used machine with a broken or obsolete controller than to build its equivalent from scratch. In this economy, older CNC mills with perfectly good ballscrews, slides and even motors are being dumped for about the price of the scrap metal they contain. If you can work within the envelope thus provided, you'll save a lot of time and money.

And no; putting gear reduction on your motors will not give you any added precision. The added backlash from the gear train will more than cancel out any theoretical improvement in resolution. As for controllers, since you're talking about using steppers, Mach3 and the Gecko G203V drives would probably be a good choice, for a lot less than the $3k you were looking to spend.


Andrew Werby
www.computersculpture.com

[keebler303]

Just another small dose of reality:

You should probably start small. Your mistakes are less expensive on a small machine, and trust me, there will be mistakes.

I have never seen a machine with that work envelope using stepper motors.

I can guarantee that you can't build a machine capable of machining aluminum that size for $6K, just no way you can even buy the raw materials for that, let alone put them together.

I see two options for your price range:

If you want to build your own and learn how its done, start small, look around this site and you will learn LOTS. It will give you a better perspective on what it costs and what kind of capabilities a machine with a certain construction has. Once you have a real list of parts, you will see that $6k will dry up pretty fast.

If you want to be machining serious metal right off the bat, you will save lots of money by buying a used machine. I'm not sure what $6k will get you, maybe a nice knee mill. 2HP, work envelope around 20x12x6. Would be a lot more realistic first step. I know there are a lot of nice VMC's going for around $15k on ebay and the like.

Start reading around here and you will get up to speed.

Good Luck
Matt

[Curtis_F]

Wow, someone who makes me look sane!

I'm relativly new to the whole "build your own machine" concept, but I do have some practical machining experience.

First off, that 15hp motor is powerful enough to rip off your arm without slowing down. To build a machine frame capible of handling it's torque is a major task. Don't try it unless you have a certified engineer perform finite element (stress/strain) analysis for whatever design you decided upon or you could kill yourself.

For a hobby machine using that motor you should plan on a horizontal mill setup where the motor and spindle are stationary with rigid support and not suspended in the air.

But really, do you need that much power? Are you going to build a spindle that can handle an 8" facing mill, or a 3" diameter end mill?

I reccomend designing the mill around what you need it to do rather than around that motor.

As to the question of a 5 axis home mill, sure it's possible. It's just a matter of finding (or making) a breakout board that has enough control functions. There may be breakout boards out there that can be used in parallel as well.


Cheers,

Curtis F.

[DareBee]

Sorry
I understand what you are saying, and wish you the best in your build.

You caught this flak by making it sound (in your original post) that you are building a machine to rival a 100k unit.

I suggest you start a new thread with a revised 1st paragraph, simply mentioning that you want to build a budget 5 axis machine and need help.
That will give you a nice clean slate, without all my crap on it