Quote Originally Posted by FlyHighRC View Post
With ball screws and rails being the parts that judge the machines length what do you think of these? though these are quite a bit larger,would expect the machine tp be in the region of 1600x1200 which is pretty big but i got the room :)
Your heading into trouble already and doing the classic mistake new builders make by thinking it can't much more difficult to go larger.? Well your wrong it's whole differant ballgame. First and foremost your Budget is blown to bits.!!
Long and wide machines need larger ballscrews and more of them.! Strength needs to increase to keep ridgidty this adds weight This means larger motors, drives, PSU and more of them.! Longer cable chains more wire runs and the list goes on and the cost goes up fast.
Then you have the build it's self with rail alignment and getting on same plane which over longer wider distance requires careful prep and some knowledge which for a first time builder to take on is a risk and not something to do if your on a budget.

My suggestion is take a step back.! Build to your imidate needs not the future as they will 99% change when you actualy start using the CNC machine. You won't upgrade this machine too much from original you will 99% want to build another machine with all your new found needs.
If you build this machine correctly and use decent quality components and electronics you will most likely recover all your initial outlay and possible more. Cut corners and you'll regret it later and will make selling on harder.

Regards the rails then Stay away from round type rails all together because even the supported ones are not so great. Chai as started selling profiled linear rails and they are cheap enough to warrent not using round rail and they make world of differance to the machine and it's sell abilty. They make the diffrance between just average DIY and Great DIY/Professional. They will will certainly add more than there value to the selling price and make sell abilty far higher.