Some CNC machines can be extended to
utilize 4th axis capabilities. Typically, a machine that cuts using
a rotary table and tailstock uses a rotary axis as its 4th axis. Any
machine with 4th axis capabilities greatly increases its potential
work range for applications such as carving, scanning and indexing.
Indexing is the simplest function to use
on a 4th axis. Indexing is utilized for applications when multiple
operations are required on several different sides of a workpiece.
In these cases, the axis is usually defined as the A-axis. Within a
G-Code file, X-, Y- and Z-commands are provided for the machine's
three axes. At certain points in the file, rotary commands or “A”
commands are given to index or rotate the part into a new position.
A good example between each pocketing operation to rotate the part
at regular intervals, typically 90°.
Another type of 4th axis application is
sometimes called an axis swap. A toolpath for a flat part is
generated with the intent of carving it on a cylindrical surface.
This is done by swapping the X- or Y-axis for the rotary axis. Thus,
the original X-axis of the flat part is now going to be carved
around the workpiece in the rotary table. This is the equivalent of
wrapping the toolpath around a part instead of along the X- or
Y-axis.
The last 4th axis application is what is
referred to as true 4th axis machining. Toolpaths are generated
using all 4-axis commands: X, Y, Z and A. This utilizes the full
potential of the rotary table and allows the machine to create the
part in the most efficient and flexible way. There are, in fact,
several parts that cannot be made by swapping, but require true 4th
axis machining.
Geometrics
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