Newbie- Help with first router design please! =]

[MynamesKenny19]

Hi guys, Im Kenny and I can honestly tell you I've never had or built a CNC Router before. But i'd like to =] I have to do an elective project for class at college and I need and want a machine of my own and CNC caught my eye.
A router table has the work area that i require and a CNC machine would be a lot faster than cranking handwheels, so I figured why not? My current budget to build the "machine" part is $200, but I can get more as I need it. At class, I have a full machine shop that I can use, several mills and lathes, saws and drill presses, a wire EDM, and lots of grinders and all the lil goodies that go with everything else. Sorry for all of my jib jab, let me get to the point:


In your opinion and within my budget, what should I make the structural part of the machine out of? Aluminum, steel, or MDF?

Im going to have a movable gantry to get the biggest workpiece possible, so what should I do for driving the axes?

Steppers with direct drive to ACME, Ball screws, or standard 1/4-20? Or....
Steppers with sprocket/pulley and chain or belt drive?
Steppers for X and Y, one of the 3 screw types for Z axis?

Travels that I hope to get are 2 ft x 4 ft.

The size of the machine i would like to make really depends on my budget and what I'd like to make. Mostly i'd be working with aluminum and sometimes wood. Budget is around $200 right now, but I still have to finangle the electronics into the budget which sucks.
But all Im worried about is making the machine first and getting good accuracy.
Accuracy tolerance in 2 ft I hope to be +/- .002 at most. I'm not sure if I worded that right.

[PG Signs]

You are going to need a lot more budget! Take a look at the drawings ofr this machine and this will give you an idea of what it takes to build a router. They couls be easily scaled down to the size you are looking at but I would make no smaller than a 4X4 table. http://www.mechmate.com/
Jimmy

[jsheerin]

It's going to be tough on that budget. I would say go with MDF for structure because it's cheap, but if most of what you want to do is cut aluminum I'd have reservations about doing that. Acme screws with anti-backlash nuts like from dumpstercnc.com would give you better performance than threaded rod but may not be within your budget. I'd say ball screws are definitely out of your budget unless you find some really cheaply somewhere (think in a dumpster or university salvage yard). Just the electronics for a machine that size will likely break your budget without doing some salvaging... Really for that budget, I think that will be your primary challenge - finding your materials for extremely cheap / free.

[ger21]

The acme screws and nuts will cost about $200. Go for direct drive and use either 1/2-8 2 start acme or 1/2-10 5 start, and nuts from www.dumpstercnc.com

[MynamesKenny19]

Alright, thanks guys! I can get all of the materials for the structural part for free, mainly steel and a few sheets of aluminum about 1/2 inch by 2ft by 2ft.
The steel, I can get in LOTS of sizes for free.

I don't see myself needing anything 4x4 in size as I'll be building airgun, paintball gun, and RC car parts mosty and a couple gun stocks. I' don't really want the Y travel to be much more than 2 feet if possibe mainly for bill of materials such as acme or ball screws and then also for rigidity/accuracy.

My small insignificant $400 bdget is for the mechanical part only, that what I have to work with for the metal tuff. The electronics, I have $350 to spend on them. That's another reason why I don't want/need a BIG machine like the 4x4 or 4x8's cuz they need bigger steppers and longer screws right? Too spendy.


So with all that said, what do you guys think of steel for base and everything else except for the gantry? I want to keep the gantry as light as possiblebut everything else heavy for stability and added mass.

[ger21]

Re-reading your first post, and the last about making paintball gun parts, you're going in the wrong direction. Building your own router, on a small budget, will most likely not give you the rigidity you'll need to regularly cut aluminum. You really should be buying a manual mill and convert it to CNC. Building a router will be throwing money away, imo.

[JLFINN]

surplus center in Lincoln Ne. used to have a control with stepper motors of somesort(www.surpluscenter.com) that was cheap. Don't know if they are big enough for what you are doing . I tend to agree that a router isn't your answer, maybe look at some of the combo mill lathe imports if your parts are small.

[MynamesKenny19]

Originally Posted by ger21 Re-reading your first post, and the last about making paintball gun parts, you're going in the wrong direction. Building your own router, on a small budget, will most likely not give you the rigidity you'll need to regularly cut aluminum. You really should be buying a manual mill and convert it to CNC. Building a router will be throwing money away, imo.

What about something like WidgitMaster's Midi Router? That thing has the travels I need and looks pretty sturdy/solid....Think I can make something like that, but out of steel and then buy ball screws/nuts instead of ACME???

I dont need anything big, but when I said 2ft x 4ft, I dont NEED that size, it just sounded kinda good. I have all the steel I need to make a Midi Router so thats all free, I just need to get the screws and rails and then electronics.

So the only things i need to buy are ball screws/nuts and rails, plus fasteners.
Electronics come later. Anybody know if i can buy a big length of ball screw to cut to size? Yes, I'm pretty sure that I sound like an idiot to you guys lol
Oh, can;t afford to buya mill then CNC it, too spendy, plus I need to make sumthing for my elective project for class, thats my main objective.

[jsheerin]

No, you don't sound like an idiot. We've all be were you are now. There's a lot of stuff to take in. However having done an independent study course when I was in school, I'd say you might be a bit behind the eight ball. I had my project all researched and planned out ahead of time. When the class rolled around I just had to do it which was plenty of work as is. If you have to do all the research first, get ready to devote a lot of time to it.

You can buy a length of ball screw and cut it up, but just be aware that typically ballscrews have a hardened surface that is very tough to cut. So typically you'd grind that off (like with an angle grinder) and then turn a bearing journal and cut threads on the end. Also be aware that it can be tough to hold a ball screw in a lathe to turn the end of it. And yet another thing is that typically the thrust bearing blocks cost more than the ball screws and nuts if you're buying nice stuff. One option for you if you can't find surplus is to buy something from Chai on ebay (linearmotionbearings2008) and get him to machine it for you. But for a small travel router like Widgitmaster's, you could probably find some stuff on ebay that would work. You could also build your own bearing blocks pretty easily if you had access to a mill. Look at Ahren's design on cncrouterparts.com for some ideas. It's basically a radial bearing in a block with a thrust bearing on either side using the outsides of the block as bearing surfaces.

[jalessi]

Kenny,

Roton 5/8 X .200 left hand is the most economical.

http://www.roton.com/Mating_Componen...family=7159321

Jeff...

[jalessi]

Automation Overstock has good pricing on surplus linear rail.

http://www.automation-overstock.com/...ies.asp?cat=14

[jalessi]

You may want to look around your neck of the woods for a company that recycles iron, they may have some old CNC machinery that you can strip parts from.