CNC machining centers are machine tools that can perform multiple machining operations on a workpiece in a single setup under numerical control. They are classified as vertical, horizontal, or universal depending on the orientation of the machine spindle. Vertical machining centers have a vertically oriented spindle and are used for flat parts, while horizontal machining centers have a horizontally oriented spindle and are suitable for cube-shaped parts. CNC machining centers feature automatic tool changers, workpiece positioning systems, and automatic pallet changers to reduce non-productive time during machining operations.

1. CNC MACHINING
CENTERS
Submitted to
Salman
Jailani

2. CNC MACHINING CENTERS:
The machining centre, developed in the late 50’s
is a machine tool capable of multiple machining
operations on a work part in one setup under NC
program control.

3. Classification :
Machining centers are classified as vertical, horizontal, or
universal. The designation refers to the orientation of the
machine spindle.
1. A vertical machining centre has its spindle on a vertical
axis relative to the work table.
2. A vertical machining centre (VMC) is typically used for flat
work that requires tool access from top. E.g. mould and
die cavities, Large components of aircraft
3. A horizontal machining centre (HMC) is used for cube
shaped parts where tool access can be best achieved on
the sides of the cube.
4. A universal machining centre (UMC) has a work head that
swivels its spindle axis to any angle between horizontal
and vertical making this a very flexible machine tool. E.g.:
Aerofoil shapes, Curvilinear geometries.

4. The term “Multi tasking machine”
is used to include all of these machine tools that accomplish
multiple and often quite different types of operations. The
processes that might be available on a single multi tasking
machine include milling, drilling, tapping, grinding and
welding. Advantage of this new class of highly versatile
machine compared to more conventional CNC machine tolls
include:
 Fewer steps,
 Reduced part handling
Increased accuracy and repeatability because the parts
Faster delivery of parts in small lot sizes.

5. Features of CNC machining centers:
CNC machining centers are usually designed with features to
reduce non productive time.
The features are:
• Automatic tool changer :
The tools are contained in a storage unit that is integrated
with the machine tool. When a cutter needs to be changed,
the tool drum rotates to the proper position and an
automatic tool changer (ATC) operating under program
control, exchanges the tool in the spindle for the tool in the
tool storage unit. Capacities of tool storage unit commonly
range from 16 to 80 cutting tools.

6. • Automatic work part Positioned:
Many horizontal and vertical machining centers have the
capability to orient the work part relative to the spindle. This
is accomplished by means of a rotary table on which work
part is fixture. The table can be oriented at any angle about
a vertical axis to permit the cutting tool to access almost the
entire surface of the part in a single setup.
• Automatic pallet changer:
Machining centers are often equipped with two (or more)
separate pallets that can be presented to the cutting tool
using an automatic pallet changer. While machining is
performed with one pallet in position at the machine, the
other pallet is in a safe location away from the spindle. In
this location, the operator can unload the finished part and
then fixture the raw work part for next cycle.

9. Vertical Machining:
known as milling, relies on rotary
cutters to remove metal from a work
piece. Vertical machining occurs on a
vertical machining center (VMC),
which employs a spindle with a
vertical orientation. With a vertically
oriented spindle, tools stick straight
down from the tool holder, and often
cut across the top of a work piece.

10. Horizontal Machining:
A horizontal machining center (HMC) is a
machining center with its spindle in a horizontal
orientation. This machining center design favors
uninterrupted production work. One reason for
this is that the horizontal orientation encourages
chips to fall away, so they don’t have to be
cleared from the table. More significantly, the
horizontal design allows a two-pallet work changer
to be incorporated into a space-efficient machine.
To save time, work can be loaded on one pallet of
an horizontal machining center while machining
occurs on the other pallet.

12. Vertical and Horizontal Machining
Application:
Horizontal machining centers are
often used to mill grooves and slots.
It may also be used to shape flat
surfaces.
Vertical machining centers have
its spindle axis vertically oriented.
Its milling cutters are held in the
spindle and it rotates on its axis.

13. SOLUBLE OILS: Contain no petroleum or mineral oil ,
composed of
alkaline inorganic and organic compounds
SEMISYNTHETIC FLUIDS: Emulsion when mixed
with water
( LEAST EXPENSIVE )
SYNTHETIC FLUIDS: Combination of synthetic and
soluble oil fluids

14.  Lubricating during cutting process
 Cooling the workpiece at high cutting speeds
 Improving tool life,
 Improving surface finish
 Flushing away chips from the cutting zone
 Corrosion protection of the machined surface

15.  High Accuracy e.g. Aircraft parts
 Production rate is very high
 Complex surfaces need to be machined
 Flexibility in job change , automatic tool
settings
 More safe , higher productivity , better quality
 Less paper work , faster prototypeproduction

16.  Costly setup
 Skilled operators
 Computers , Programming knowledge required
 Maintenance is very difficult

17. Refrences.
Downloads/unit-7-CNC-
machining-centers.

18. Thank You.