Turning can be broken-down into a number of basic cutting operations and in effect, there are basically four such operations, these are:
1. Longitudinal turning (Fig. 16a),
2. Facing (Fig. 16b),
3. Taper turning – not shown,
4. Profiling – not shown.
briefly reviewed.
In its most simple form, turning generates cylindrical
forms using a single-point tool (Fig. 1.16a). Here, a tool
is fed along the Z-axis slideway of the lathe (CNC), or
a turning centre, while the headstock rotates the workpiece
(i.e. the part is held in either: a chuck, on a mandrel,
face-plate, or between centres – when overhang
is too long), machining the component and thereby
generating a circular and cylindrical form of consistent
diameter to the turned part . Facing is another basic
machining operation that is undertaken (Fig. 16b) and
in this case, the tool is fed across the X-axis slideway
while the part rotates, again, generating a flat face to
the part, or a sharp corner at a shoulder, alternatively it
can be cutting the partial, or finished part to length (i.e
facing-off) . Taper turning can be utilised to produce
short, or long tapers having either a fast taper (i.e. with
a large included angle), or slow taper (i.e. having a
small included angle – often a ‘self-holding taper’ , such
as a Morse taper). There are many different operations
that can be achieved on a CNC lathe/turning centre,
including: forming , while others such as drilling, boring,
screw-cutting, of internal features, and forming
and screw-cutting of external features, to name just a
few of the traditional operations undertaken.
With the advent of mill/turn centres, by having
CNC control of the headstock and rotational, or
‘driven-/live-tooling’ to the machine’s turret, this allows
prismatic features to be produced (i.e. flats, slots,
splines, keyways, etc.), as well as drilled and tapped
holes across and at angles to the major axis of the workpiece,
or off-axis. Even this explanation of mill/turn
centres is far from complete, with regard to today’s
sophisticated machine tools. As machine tool builders
today, can offer a vast array of machine configurations,
including: co-axial spindles (ie twin synchronised inline
headstocks), fitted with twin turrets with X- and
Y-axes simultaneous, but separate control, having programmable
steadies (i.e. for supporting long slender
workpieces), plus part-catchers , or overhead gantries
for either component load/unload capacity, to multiaxes
robots feeding the machine tool. This type of machine
tool exists and has multi-axes CNC controllers
to enable the machine’s down-time to be drastically
reduced and in this manner achieving high productive
output virtually continuously.
