2. WHAT IS MILLING?
Milling is the process of cutting away material
by feeding a workpiece past a rotating multiple
tooth cutter. The cutting action of the many
teeth around the milling cutter provides a fast
method of machining The machined surface
may be flat,angular, or curved The surface may
also be milled to any combination of shapes.
The machine for holding the workpiece,
rotating the cutter, feeding it is known as
the Milling machine.
3. Types of Milling CuttersTypes of Milling CuttersTypes of Milling CuttersTypes of Milling CuttersTypes of Milling Cutters
Types of Milling Cutters
4. Gears can be manufactured by most of manufacturing processes
discussed so far (casting, forging,
extrusion, powder metallurgy, blanking). But as a rule, machining
is applied to achieve the final
dimensions, shape and surface finish in the gear. The initial
operations that produce a semifinishing part
ready for gear machining as referred to as blanking operations;
the starting product in gear machining
is called a gear blank.
Two principal methods of gear manufacturing include
Πgear forming, and
gear generation.
GEAR
MANUFACTURING
5. In gear form cutting, the cutting edge of the cutting tool
has a shape identical with the shape of the
space between the gear teeth.
Gear forming
Two machining operations, milling and broaching can
be employed to form cut gear teeth.
Form milling-
In form milling, the cutter called a form cutter travels
axially along the length of the gear tooth at
the appropriate depth to produce the gear tooth. After
each tooth is cut, the cutter is withdrawn, the
gear blank is rotated (indexed), and the cutter proceeds
to cut another tooth. The process continues
until all teeth are cut.
Each cutter is designed to cut a range of tooth numbers. The
precision of the form-cut tooth profile
depends on the accuracy of the cutter and the machine and its
stiffness.
6. Form cutters for
finishing cutting
(Left) and
for rough cuts
(Right).
Dividing head (Left),
and footstock (Right)
used to
index the gear blank in
form milling.
8. The demand for greener energy and concerns about
climate change are making wind energy increasingly
topical.Indeed, wind power is a rare bird in today’s
unforgiving economic climate. While the 30 percent
growth rate of recent years has diminished to 18–22
percent, long-term growth still remains strong.The
main challenge in the wind power industry – how
to keep pace with demand – is very different
and much more positive than the challenges facing
many other fields. In wind energy, the focus
is on increasing productivity and fulfilling the stringent
quality requirements.
Increase Productivity in Gear Milling OperIncrease Productivity in Gear Milling Opera
9. The gearbox, the link between
the rotor, the main shaft and
the generator, is one of the most
critical components in a wind
turbine. A typical gearbox
contains several geared parts
such as the ring gear, planetary
gear, sun gear and slow gear
wheel.
In addition, wind turbines include
various rings with gears such as
slewing rings, a type of
component consisting of a gear
and a bearing to control the pitch
angle of the blades and to orient
the nacelle appropriately in
relation to the wind.
10. New Technological Possibilities of Universal
Gear Milling Machines
The calculation of the hob tooth profile requires the use of difficult
mathematical formulas and graphical checks. Even with the best
calculations, it will frequently be necessary to undertake numerous
adjustments during the cutting process in order to achieve the
desired result.
The second aspect of the milling machine that we discovered in
May 2005 — 100 to 120 years from the time the universal gear-
milling process was introduced — involves changing the places of
the cutting tool (hob) and the blank.
This “reversible MLG method” will be of interest to those who
already have knowledge of the hobbing process. Therefore, I will
not go into detail about the actual cutting process or the techniques
required for manufacturing hobs and broaches.
11. The hob that is created will be custom-matched to the shaft; a
shaft of a different size will require its own custom hobs.
First step: Instead of installing a hob on the mandrel in the
gear-milling machine’s spindle, I mount a blank (usually soft
tool steel) with the same O.D. and length as the actual hob.
Then, I turn the blank to match the helix of the desired size of
the hob. I mount a blank above the broach.
Second step: The broach that is required looks like a straight-
sided spline broach for splined holes (round internal, push-
type.) The dimensions of the broach must match those of the
desired spline shaft. The cutting rake and back angles should
match those of the standard straight-sided spline broaches.
Unlike a standard broach that is tapered, this broach must be
made with a constant outside diameter for its full length. When
producing the relief for the edges, be certain to provide enough
room for chip clearance between the teeth. The completed
broach is installed on the milling machine’s table, in the same
manner that a workpiece would be installed.
