Guide for determing screw and motors?

[gasmasher]

I am making plans for my first CNC machine and want to make it desktop size capable of cutting plexi and plastic. I have read a bunch of threads here and am a bit confused on how to determine my drive screw and motor size. Is there some documentation or articles that I can read to get more information?

The plan is to use a rotozip or dremel as my router and I want a cutting bed of about 12" x 12" x 4". I intend to use a 1/4" motion shaft with ball bushing blocks (hopefully the terminology is correct) for support. I really just need to figure out what motors and screw I should target for my first build. Any help is appreciated.

[jsheerin]

See:
http://www.cnczone.com/forums/showthread.php?t=8129

[gasmasher]

That is perfect. Thanks for the link.

[shawnc515]

how much do you wan't to spend? and do you prefere ball screws or will acme screw do if you wan't ball screws prepare to spend a bit more (at least in my experenc).

ps: sorry about the bad spelling.

[shawnc515]

sorry did not see some one else reply wile i was typing.

[gasmasher]

I'm thankful for all replies.

I want to keep the budget for the entire build under $1K. I do plan to use ACME screws to save a bit, but will use a manufactured linear bearing. I'm thinking something like these:
Shaft
Ball bushings

I am still browsing around for shorter shafts since I am not making that large of a cutting bed and assume that I will not be able to cut the hardened steel rods to the desired length.

Here is a rough estimate of my spending plan:
$200 on linear bearings
$150 on screws and homemade backlash nuts
$400 on motors, controller, transformer and case - I like the hobbycnc 4 axis kit (using 2 motors on the X axis)
$100 misc. parts (big red switch, limit switches, wiring, etc..)

I already have roto tools (dremel and a generic roto cutter) and a command PC. I also have the materials to make up the body in plexi for the first revision.