The IDEAL Lead screw?

[Imacman]

Hi I am looking for some advice.. here is the situation.. I just got off the phone with an old friend and found out he is running a high end Threading company!.... He can make me any type of threaded rod I need and give me a great price on it...I am new to CNC and I am about to start building a CNC that will cut about 17" X 30" X 5" So my question is what would be the best Threaded rod to request from my friend? They use all types of materials. can some one give me the ideal specs for my situation & requirements?

[TarHeelTom]

I'm not an expert at all.

But to my understanding, the ideal leadscrew will always be a ball screw.

Probably not something your friend makes.

Tom

[Imacman]

Thanks,,, I know that ball screws are the best but very expensive.. I should have posted the URL to his business that may give people a better Idea. they are at www.threadall.com I guess my question is, based on my build size... what length of lead crew..what thickness...pitch, Turns per inch etc... and what material to make them out of. Thanks

Imacman

[KIMFAB]

I doubt that they make ball screws but it looks like they make Acme threaded rod. Get some that has a nice number of threads per inch or cm and put it together with some no backlash nuts.
Look around, there are plenty of designs here.

[Imacman]

yes thanks... that's the type of thing I need to know... If more or less threads is better...and how many... I'm looking for good accuracy... another question is how many starts on the ACME screw is best. In a nutshhell I will have him make me ACME screws... and I'm in a position to have them custom made to my own specs rather than the typical "take what I can Get" scenerio... so I'm trying to find out what are the best technical specs to have the screws made at for my particular build.

Thanks

Imac

[Drassk]

The 'your particular build' part is something you'll need to define a lot more fully than process area if you want to be able to figure out what sort of screw you'll need.

Figure out what sort of motors you'll use and how fast they'll turn
Figure out what sort of feedback you'll use and it's resolution relative to screw pitch
Figure out what sort of speed/resolution you need or can realistically achieve

Once you have that stuff figured out, then it's just math to figure out what'll give you the balance you want. A more 'accurate' screw (low pitch) is a slower screw. A lighter screw will be easier to move, but weaker. A screw with less backlash will have more friction.

If you can't figure out the above on your own, then the easiest thing to do is find a design you want to build and use what they used.