Metal CNC Project

[Mcgyver]

oh man, i can't sell anyone on my hydraulic fluid capstan idea....guess i'm going it have to build the sucker and see for myself. I believe (until proven wrong) that hydraulics might prove to be the holy grail of linear movement.

Don't to quick to discard a servo set up. Bigger mills would likely use servos instead of steppers, so all i'm doing is saying move from a encoder on the back of a servo (driving a ball screw) to a linear encoder telling a motor on a pump how fast to go.

Whether anyone including myself ever builds the fluid capstan aside, servo/encoder set ups are mainstream, so a linear encoder shouldn't be too much of stretch

speaking of stretch, that's the problem with chain. I suppose you could preload it, but there are so many little bearing contacts, each with its own clearance that it might be tough to keep it an accurate length as the forces on it change. dare I say, maybe with a linear encoder? ie just use the chain to move the thing as a component of it linear accuracy. or maybe in a capstan arrangement so that you could preload in both directions?

[lerman]

Originally Posted by tonofsteel Alright, so I have learned alot so far. I have been looking into this for awhile, and although there are many engineering challenges to creating a CNC mill that can work on steel I think I am up to it. This semester at school we had to create a microprocessor from scratch, and do a AES encryption implementation. Probably many people here do not know alot about those two subjects, but like you, I had no idea how to do it just a few months ago. So with a bit of information, and alot of hard work I think I can come up with something thats workable, mabye not to my ideal specs, but it will be fun. So, in my current moment of over optimism I want to attempt this. I have been down the "take the cheap way out" road many times (ie drill press mill) and I know that its a recipie for disaster. I am going to make all frame pieces, and all bearing holders, etc myself. I just need to know what are the requirements for the steppers, the linear rods, and the ballscrew. What diameters are required for this application? As well the linear shafts will not be end supported, they will be mounted on rails, what diameter do those have to be? I like the idea of buying a milling machine, that is of an older vintage, and that would serve my purposes perfectly. However I live in Saskatchewan, Canada, which is also known as the "gap". To those unfamiliar, we do not have technology here, and we do not have access to cheap parts. For me to buy a milling machine of that vintage off e-bay, or from an auction would cost at least as much as the mill is worth in shipping. I might as well build my own and gain the experience. As well, if i mess up on this attempt, the ballscrews, steppers, etc. will be good for the next time around. So all the smart people here, what parts do I need in what sizes? The frames, and other supporting structures will be designed to the best specs I can using information from some fellow mechanical engineers. As they do not have the experience that all of you have, I want to know your input for the critical expensive components, and the rest will be built over-spec what they would need to be, just to be sure. So please, what parts in what size/diameter/power to handle a max load of steel at max dimensions of 2ft x 2ft @ 100 to 200 lbs. (high end extremly generous)

Don't give up on the used machine idea. I bought a used Bridgeport clone for $250 from a used equipment dealer. Try thinking outside the box as far as transportation is concerned. I wound up taking my machine home in a dump truck and unloading it with a bucket loader. In my case, shipping was free because a friend with a dump truck owed me a favor.

Someone suggested that you could use a small car trailer -- try renting one.

Think of it as an adventure -- drive a few hundred miles, get the seller to load it onto a trailer, drive a few hundred miles back and then unload the thing.

Good luck.

Ken

[tonofsteel]

Alright, I am interested. If i can find a good used mill for 250 to 1000 dollars and then do improvements to it, I am sold. However, I am limited in which cities I can drive to. Winnepeg, Calgary, and Edmonton areas would be preferable.

So, who do I call, where do I look? I have not seen a "Mill Trader" here yet, so there isnt much listings that I can go browse. Any ideas? Also does anyone know of any mills available in the above places?

Thanks!