Originally Posted by
Bear5k
Due to the wonders of eBay, my machine that is under construction (well, design, really) is using the Bosch Rexroth 4590 "heavy" (4590H) aluminum profiles for the base, plus equivalent profiles from Misumi USA for the gantry because I really like how easy it is to order machining services from them, and they are offering a 30% rebate (up to $150) off of my first order. For linear motion, I am using THK SR30 linear rails and an NSK 25-10 ball screw (this latter piece is a "maybe" while I wait to get a decent quote for machining a custom ball nut housing/bracket).
While the SR30 rails and the 4590H are pleasant "finds" from eBay, they also work really, really well together (on paper). The SR30 rail takes an M8 socket head screw, and Bosch makes a 1m long "super nut" that comes pre-tapped for M8 screws in the exact spacing that is required by the THK SR30 rail. This should be a really strong connection. Since I lack many of the machine tool toys that others here have, I'm pretty excited by how this will come together (note: I'm waiting on the critical nut bracket before getting serious on assembly -- and documentation).
Other people use things like cold-rolled steel (CRS) and aluminum carriages with skate bearings for linear motion, while yet others do things with steel pipe. There are a bunch of options, though the linear guides are pretty much at the top of the heap for quality -- and expense.
There is an old adage in racing: Speed costs. How fast do you want to pay? For a homebrew CNC, the same is basically true about the various component options. If you want higher accuracy? $$. If you want easier assembly, $$. The question is really what your goals are, what your capabilities are and what your time is worth.
And a whole lot of reading. :cheers:
Bear