Until recently, milling machines had just three axes, X, Y, and Z. For someone facing the machine, X is where the work holding table moves left-right, Y is the table moving backward and forwards, and Z is it moving up and down. From many prismatic parts, (those with straight, square sides and surfaces,) this is enough “degrees of freedom” to machine any required features. However, parts that need non-orthogonal (not 90°) surfaces require additional setups.
5 axis milling addresses this problem. This adds two rotational axes to the three linear axes. Machine designs vary, but typically a 5-axis milling machine adds A and B axes. These provide rotation around the X and Y axes. Other machines add B and C rotational axes, (rotation around the Y and Z axes), and there are probably some somewhere with A and C axes.
The big advantage of 5-axis milling machines is that the cutting tool can reach five faces of a prismatic part. (The part is mounted on the sixth face.) Many 5-axis machines provide what’s called, “5-axis positional machining.” This means the axis rotates to a fixed position, and then the cutter starts removing metal. This is useful for applying chamfers or cutting grooves and dovetails, but it’s not full 5-axis machining.
Full 5-axis machining is where the rotational axis turns as the part is being machined. With this, the cutter can produce contoured surfaces, like those on a turbocharger impeller or fan blade.
All this additional capability, over 3 axis machines, doesn’t come cheap. In addition, programming 5-axis milling machines is complicated. However, for some parts, there are substantial benefits. These include:
- Fewer setups to produce complex shapes – because the cutting tool can reach more surfaces
- Less expense on fixtures
- Superior geometric precision between features otherwise produced in separate setups
- Ability to machine contours
- Improved surface finish – because the machine allows for shorter cutting tools that suffer less vibration
5-Axis Milling (1 Mill)
Max Travel: 21” x 16” x 19”
A,C Axis Travel: +30°/-110°, 360°
Max Weight on Table: 330 lbs