I'm building a fixed gantry CNC mill with 40"x18"x12" (X,Y,Z) travel. Budget is around $6500.
1. Machine rigidity
Can anyone with a non-DIY 3 axis mill like a tormach or HAAS help me out here please?
I am wondering how rigid these machines are so I know what I am getting into when building my own. That is how many Newtons of force required per micron of deflection or something along those lines.
I know people have measured bridgeports by sticking a dial indicator on the spindle and putting it with a bungee cord with force gauge. (they were reporting about 30N/micron)
Right now my machine frame is sitting at about 60N/micron in all directions (based on Inventor FEA and manual calculations for sanity check). Add in deflection of ballscrews and stuff and it's probably down to 50.
2. Spindle
Is it a good idea to use spindle cartridges taken from tormachs and driving it with a DC motor? I want to cut steel at a reasonable rate and those 10000rpm spindle motors on ebay don't seem like the right choice.
3. How much thrust (pushing) force do I need in each axis?
I already bought 2 ball screws. The one for X axis can handle 22kN and the one for Z can do 15kN (I know they are huge and overkill but they were pretty cheap and really nice NSK C2 precision ground screws).
I want to know how strong the motors need to be (I will be using steppers for now). I know most HAAS can do 15kN but I doubt I need that much.
4. small 5 axis trunnion (future upgrade)
I know very few DIY cnc mills are 5 axis but just how crazy is this? It looks pretty straightforward to me mechanically but I know there is definitely a lot more to it than I know, otherwise everyone would be doing it. Pretty sure fusion and mach 4 can do 5 axis just fine?
5. What would it take to cut grade 6 titanium alloy?
I know titanium and DIY don't usually come in the same sentence, but what would it take to cut it? Probably won't be doing any production runs on this thing but I imagine adaptive toolpath with very light cuts while blasting it coolant can probably make a dent. I mean people were able to make shapeoko cut aluminium.
Thanks