Hi All,

I am a third year mechatronics student in Melbourne, Australia (nearly 30, however, so definitely a mature age student). After being interested in CNC for a while, and having built several CNC routers, I have decided to design (and hopefully build) a small CNC mill. Depending on approval from my university, I might also turn this design process into my final year project next year. I would like to work in the machine tool design field after university, so this kind of project might be one that gets me a foot in the door.

The basic goals of my mill design are:

  • X, Y, Z travel of 400 mm x 280 mm x 280 mm (15 in x 11 in x 11 in)
  • 2.0 - 2.5 kW BT30 spindle (2.7 - 3.4 HP)
  • 15 - 20 m/min rapid speeds (590 - 787 in/min)

The structural elements of my machine will be made from cast iron and I will employ servos, linear rails and ball screws on each axis.

The first steps I will be taking in my design process are:

  • layout out a rough design of the cast iron elements of the mill to get an idea of the mass of each major moving element;
  • undertake a "first pass" selection of the linear rails and ball screws;
  • calculate the power requirements to accelerate the mass;
  • select suitable servos;
  • calculate the rated linear force available from the selected servos (and define this as the maximum cutting force of the mill);
  • find the deflection of each major moving element under the above calculated linear force; and
  • update the design on the cast iron elements to minimise deflection.

Below is an image of the beginnings of my rough design. Currently it's around 300kg (660 lb).

Attachment 236354

Any comments would be greatly appreciated!