Hi,
I’m interested in designing my own CNC machine. Ideally, I would like the machine to be able mill aluminium in 3D shapes with an accuracy of +/-0.001" which I know is optimistic, so I’m looking for a rigid design. At the moment I’m planning on using ball bearing linear rails and ball screws on all axis as well as using 2 ball screws for x-axis.
I would like a cutting area of 3’ x 2’ x 8” but I’m happy to sacrifice cutting area for accuracy.
I have a couple of questions.
1. Aluminium vs steel for build material? Pros and cons? From memory steel’s stiffness is 3 times stronger than aluminium which is better but I want to use aluminium as it’s easier to work with and doesn’t rust. I also question using aluminium structure with steel linear rails and ball screws; I’m effectively building a bi-metallic strip!
Now onto my main question. Look at design 1 and 2 below. Yes there are multiple differences, but consider the designs to be exactly the same with the following exceptions:
Design 1 has no gantry sides as such (sides are there for torsion support only, not to raise the y-axis). Gantry beam is directly mounted to x-axis linear blocks. Also the cutter bit of the router is always at or below the x-axis rails.
Design 2 has gantry sides. The cutter bit of the router is always above the x-axis rails.
What are the pros and cons of each design? I thought that design 1 would be better as the moment arm on the gantry sides from the cutting force is minimal.
Where’s the best place to position the ball screws in both designs?
One last question is it better to mount the x-axis linear rails on the top of the beam like design 1 or on the side like design 2?
Thanks!