HI TEAM ... i have good experience in build cnc with sizes (1m*1.5m)....but now !!!! i want to build cnc with ( 4m*2m working area ) ,to cut wood and plastic and some aluminum . the speed i want for rapid is about (7000mm/min) maximum fade rate about (5000/min) so i want good accuracy and rigidity my spindle is 24000 RPM i knew that is long travel on Y axis (4m) do i need long ball screw ? or other like rack and pinion ? what description i want ? what stepper or servo motor need? what description i want ? because i know some problems with long ball screw .... no problem with cost ($) ....all i need the rigidity and accuracy does Rotating Ballnut design good idea ? any advice please
Rack and pinion isn't a terrible plan, as long as you don't need ultra-accuracy. Really long screws can start to get whippy without support, it's a tricky proposition. You might end up needing NEMA 34 motors depending on your final weight. Rotating ballnut is pretty much always a good plan- if you need the accuracy over rack and pinion, go that route. I'd go fixed gantry for rigidity and build a fully supported 8m long bed under it for the table to go on. I'd build it primarily from steel rectangle tube with some aluminum parts and backfill all the hollow bits with at least sand, maybe concrete. Then add your V-Slot or other rail on top of that.
I would use Rack and Pinion here. It is plenty accurate enough for almost any purpose, especially with a belt reduction. Not only would ballscrews be extremely expensive at that length, you will never be able to get the speeds you want with them at that length. I switched from a lead screw to rack and pinion for my 1m x 1m system and am extremely happy with the results. Take a look at the CNC Router Parts rack and pinion system. That is the one I used and it integrated pretty well with C-Beam V-slot rails.
thanks for your replay team .... my question what is the specification for rack and pinion i want for my long cnc ?
