So Ive had my 2x4' machine for a while and Im starting to really be frustrated with the limited work area. It seems everything people want me to work on for them is 3'x4' or something is just over 24, or is just plain huge (8'tall yard T-rex perhaps?) so im strongly considering converting my current machine into a garage consuming beast, while sticking to a budget. I will be cutting wood and plastic with the machine, sheet PVC in particular.
The way i built the machine is its a fixed gantry that sprawls over a 60" span with 1500mm THK HSR20 rails. The 24" table moves on 38" THK rails. My idea is to essentially lift up my current gantry and replace the current uprights that mount to my table, with ones that will roll on rails. Im currently using a chain drive for my long axis and have really had zero issues with it, so I would keep that, and look to Buildyourcnc.com for the rest of the inspiration. so I would follow his drive system for the gantry movement, with the motor placed in the center and use Chain as my drive system with v-bearings and angle as my linear slide. Id love to use THK again, but i just cant afford 1K in rails right now.
I've built an 8 x 4 machine after having a few 4 x 4's. I agree, people always want something cut just larger than your machine can handle.
Off the top of my head my machine cost around £1700 including motors, driver, frame, ballscrews etc.
All ali extrusion frame, BIG guide rails and ballscrews.
My only wish is that i put bigger motors on there, as they stall anything over 5000mm/min. But it's livable.
I can send you a list of suppliers I used for CNC parts, and ali supplies if you want. All u.k based.
They sell slightly differant things to what you need, but maybe you will change your design idea. Or maybe they have the things you need, im not sure.
I'll post a few pics of mine, too.