Newbie diy cnc, could use some tips

[Banana Jack]

So it's now summertime, which means it's now time to get started. First things first: I'm new to this site and a newbie to machining in general, but I've been reading up on cnc as much as possible recently to prepare for my planned summer project. I've been reading all the plans for diy cnc machines, all that good stuff. And I was hoping you guys could help me with this project.
My goal is to make a (functional) desktop (about 12" x 12" x 4" or 30cm x 30cm x 10cm milling area)3-axis cnc machine, myself, for... not super expensive. The cheaper the better, but I couldn't see myself spending more than $250 total for the machine. of course, if it's a part that I just can't live without, i'll shell out the cash for it, but...I'm not rich. I'm going to go off my my own ideas, not someone else's plans that i may or may not have to pay for. I don't have much personally in the way of tools, but I have a neighbor with a complete machine shop I could visit if I needed. This is mainly for RC, so I would like the machine to be able to be fairly accurate.
and...I'd like to machine as tough a material as possible. I'd be mainly doing plastics and aluminum, but also some carbon fiber every once in a while. I would also LIKE/like to be able to do steel, but if that's not possible, I'm not too worried about it. (Steel wouldn't be for rc, so it wouldn't need to be as accurate.)
I won't be running a huge business with this or anything, so speed isn't a big deal. (it would be nice, but...you know.)

So first - should I make a first-try cnc machine and then use that to make the real deal? Or just go right into the real deal?
And what do you suggest I use for the frame?

[brtech]

There is a great line about specs, quality and cost that you can fix 2, but the third is dependent on the values of the other two.

You can't get anywhere close to $250 for a machine that can accurately cut wood, let alone aluminum or steel.

If you were a really talented machinist who can make parts really accurately from blank steel, you can trade a whole lot of your time for cost. Other than that, you either make the frame from 8020 extrusions, in which case you can get a strong frame with decent accuracy, or you make it mostly out of MDF, in which case it is cheap, but not very strong and accurate.

Even with MDF, most people report spending north of $1000 on a complete CNC.

Keep reading, and keep saving your money. There are lots of build logs of folks who have built something with your specs.

[amishx64]

I couldn't see myself spending more than $250 total for the machine....I'd be mainly doing plastics and aluminum, but also some carbon fiber every once in a while. I would also LIKE/like to be able to do steel, but if that's not possible, I'm not too worried about it. (Steel wouldn't be for rc, so it wouldn't need to be as accurate.)

You'll need to spend about $250 for the router that cuts material like aluminum. If you are doing steel, you'll need a real spindle.

I started with just about the same intentions as you not very long ago. I tried to make my machine out of stuff I could make or had lying around. Needless to say it didn't really work out quite like that. I ended up spending much more in order to get something that would be able to do what I wanted. Go ahead and take a look at my build log in my signature below. I think that if you try to do this you'll end up a lot like me, and if that is so, you'll blow your first $100 on trying out plans and cheap linear motion ideas.

Save your money and put together some serious plans complete with dimensions or you'll be kicking yourself later like me for wasting your time and money.

Best of luck to you.

- amishx64

(P.S. Drawer slides are no good.)

[Banana Jack]

ok well, first off i'm gonna say i'm not worried about the rest of the parts right now. I'm just worried about the machine. No controller, and no motors. I just want it to slide back and forth. that's what my $250 would be going toward.

and ok, if that's not enough then no go on the $250. then, i don't care how much it costs. This project might take longer than expected though. I only get a paycheck every two weeks.
But can it really be that expensive? This here says it is capable of machining metal. (doesn't say what kind. aluminum possibly?)
http://www.harborfreight.com/two-spe...ine-44991.html
I considered...am considering...simply getting this. There, first goal accomplished. Next would be get some motors, motor mounts, so on and so on...but that stuff isn't gonna cost more than $200. So that makes $760 at most.

And amish-i went to your link, and straight to the end because i'm getting kicked off right now, i'll come back to it later...but it looks like after all that, you're still going with some plastic/wood stuff. With goals of cutting aluminum? Is it stiff enough?

and what are 8020 extrusions? Is that just a type of aluminum rails?

[amishx64]

and ok, if that's not enough then no go on the $250. then, i don't care how much it costs. This project might take longer than expected though.

Ah, that's the spirit!

The harbor freight one would not be bad if you were trying to do some soft metals (up to aluminum), but there are lots of unknowns about this product, but maybe you can find the info elsewhere. You need to know:

1. How much backlash, and is the amount acceptable for what you are trying to do.
2. How rigid is the entire machine, i.e. no wiggly parts.
3. How long will this machine last you. Meaning, once you get this machine up and running, and you find that it doesn't have the specs to mill a certain type (steel) or size of material, how long will you want to keep it around until you upgrade.
4. Will you be happy with the cutting area: X:8" Y:4" Z:8-1/8" ?

When you get the electronics, consider them an investment. You'll want to buy good enough ones that will last you several years and a new machine upgrade or two. Others on the forum will say the same thing here too.

And amish-i went to your link, and straight to the end because i'm getting kicked off right now, i'll come back to it later...but it looks like after all that, you're still going with some plastic/wood stuff. With goals of cutting aluminum? Is it stiff enough?

I started with some cheap wood compound - MDF and found it insufficient. That is in the earlier pages of my build log that I wouldn't recommend anyone take after. I then moved on (recently) to the plastic-wood decking compound (Verdanda) and found it so much better in every aspect. I am using this now. Right now it is as solid as a rock, and very heavy. I would sooner choose the Verdanda over aluminum (in most cases) because of its machinability and its manageability. I mean, you can put screws in the stuff - you aren't stuck with bolts all the time and it is so much easier to cut to size - a standard miter saw will to the trick.

I am fully planning on milling aluminum and my machine should have no problem with that task. It is most certainly stiff enough, especially with the use of some 2x4 (wood) supports that you'll see in the next post. I am pretty confident that I could drop the machine 5 ft and it would still work fine.

and what are 8020 extrusions? Is that just a type of aluminum rails?

80/20 is pretty much just hollow aluminum tube. Many people have built their machines out of it and have had much success. I'd recommend looking into it. The problem with 80/20 for me was A) getting it (S&H) B) Price and C) machinability. Aluminum is pretty unforgiving, and once you mess up, the piece is pretty much scrap. Just my opinion.

Keep asking away.

- amishx64

[jsheerin]

I have that mill at work (actually I have the Grizzly version). It cuts aluminum fine. I have never tried steel but assume it would work if you went slow enough and took light enough cuts. There is significant backlash. Typically people who retrofit manual milling machines swap out the screws for ball screws. You might read some threads in the metal working diy machines forum for inspiration. Here's one good one of a mill from scratch:
80/20 mill build
Here's a cnc conversion of a mini mill:
http://biobug.org/machine-shop/mill/

[Banana Jack]

Awesome! It seems there's quite a few builds based on 8020 aluminum. I think I'll go with that myself. It looks real nice, and should make a nice stiff frame. As for the harbor freight, I was gonna just either deal with the 4" Y or modify it to be longer, if I could. But I'm not gonna worry about that anymore because I've decided on a ground-up build.

I am pretty confident that I could drop the machine 5 ft and it would still work fine.

That's pretty impressive, however, I'm not planning on abusing my machine...

You'll need to spend about $250 for the router that cuts material like aluminum. If you are doing steel, you'll need a real spindle.

OK, now I've decided on frame materials (I'll do the actual designing later) so I'll get to this part now. What do other people use? I've heard that I'll need a nice high speed spindle if I plan on cutting aluminum, let alone steel...so what should I be looking at?

[jsheerin]

I would go for the mini mill head for cutting aluminum. Most people use a router or Chinese 3 phase spindle with VFD in the 1.5kW to 2.2kW range for cutting wood and then also use it to cut aluminum. But if your primary use is cutting aluminum, I would go with the lower speed mini mill head. You can get it from Little Machine shop in various states. There are several threads in the router forum about this. Try searching on my user name.

[Crevice Reamer]

Hi B Jack. Welcome to the Zone!

NO router is going to cut steel. You would need a mill for that. The 44991 WILL cut steel, but don't buy that. THIS is a much more capable version with better motor and larger travels:

http://littlemachineshop.com/3900

There are also mods that can increase the travels even farther.

CR.

[Crevice Reamer]

On the other hand, if you want to go into hock, you could buy this CNCd & ready to go mill for $1700.00:

http://deepgroove1.com/cncmill.htm

CR.

[amishx64]

That's pretty impressive, however, I'm not planning on abusing my machine...

What do other people use? I've heard that I'll need a nice high speed spindle if I plan on cutting aluminum, let alone steel...so what should I be looking at?

Most people I see buy a Chinese spindle, sometimes water-cooled. that has a belt drive and a large DC (sometimes AC) motor. Sorry, but I don't know a whole lot about spindles, as I am not using one, but there are plenty of others that do. Someone may come along here and post something (nm I see jsheerin already has), but if they don't there are other places to ask and lots of posts about spindles others have bought already.

[jsheerin]

That is a bit confusing... When most people here say Chinese spindle, they mean a high speed spindle (~8000-22000rpm). These are typically water cooled, but you can also get air cooled models. There is no belt drive. It is a 3 phase AC motor with a chuck directly attached to the motor armature. You must use a VFD (variable frequency drive) to run it. This is used for cutting wood primarily, but can be used to cut aluminum with light cuts.

On the other hand there is a mini mill spindle (also made in China). This is a low speed device (typically 3000rpm and slower). This has a gear drive as standard but can be converted to a belt drive and can be purchased with a motor (typically DC I think) or fitted with a different motor of your choice.