Goals


  • Mill aluminium moulds
  • Good surface finish in aluminium
  • Have a very damp machine
  • Get experience with casting composites
  • Have fun!



Requirements


  • Max deflection: 70N/?m
  • Positional accuracy over 100mm: 0.05 mm
  • Part flatness over 200mm: 0.03 mm
  • Vibration dampening properties
  • Must contain dust and chips
  • Benchtop machine



Specifications


  • Gantry clearance: 120mm
  • Part size: 300x600mm
  • 1.5 kW HF spindle



Features


  • Square linear rails and ball screws
  • Epoxy granite base
  • T-slot table



I have not specified a part accuracy, but I'm fairly certain that I can get the positional accuracy to be better than 0.05 mm. The goal with the tolerances is to be able to machine somewhat of a press fit in aluminium, and I'm fairly confident I can achieve that by using precision milled stock (0.01 mm flatness) to mount the linear rails onto. I think the flatness of the t-slot table and aluminium stock to mount the linear rails on, will be a little better than specified by the manufacturer, to give them some room for error. Therefore the machine will probably be a little more precise and increase my chance of milling "somewhat" of a press fit. The base of the machine will either be a thin t-slot table cast into epoxy granite, or just a solid piece of cast iron t-slot plate. The t-slot table will also have a flatness of 0.01 mm. The linear rails for the gantry will simply be mounted directly to the t-slot table.

I've specified a maximum stiffness of 70 N/?m for the whole machine, this means that the machine should not be able to deflect more than 0,001 mm from where it previously was, every time we apply 70 N.

Now there's still a lot for me to figure out, but for now I'll start designing the gantry for the machine. I'm still not sure weather or not I will use epoxy granite for the gantry or if it will be made of a composite consisting of fibers. - It depends on what I can get my hands on for cheap/free.

Any questions and input are always welcome