Gear Manufacturing for production engineers.pdf

Pdf explaining gear manufacturing useful for engineering students.

1. Gear Manufacturing

2. Fundamentals of Gear
* Gears are machinery components used to transmit motion and power between
rotating shafts.

+ The transmission of rotational motion is achieved between meshing gears by
teeth located around their respective circumferences.

* The teeth have a special curved shape called an involute, which minimizes
friction and wear between contacting teeth of meshing gears.

3. Gear Teeth Profiles (Forms) —
There are mainly two types of teeth profiles:
+ Involute >
It is a curve traced by a fixed point present on a
tangent which is passing through several points present
on the base circle.
+ Cycloidal
A cycloid is a curve traced by a fixed point on LT circumference of. a a circle which

rolls without slipping on a straight line.
Epi-cycloid — when circle rolls over an IVA HD
external circle EX) as o E AS)

Hypo-cycloid - when circle rolls over
an internal circle

Ca |

4. Source: https://commons.wikimedia.org/wiki/ileSpur_gears_animation.gif

we ©

Involute Gear Cycloidal Gear
Teeth are weaker Teeth are strong

Easier to manufacture Difficult to manufacture due to hypo and epi-cycloid profiles

Cheap Costly
Motion and heavy load transfer preferably motion

For classroom education purpose only (use unmodified, non-
‘commercial and non-sharable outside the Institute)

5. Types of Gears

Worm Gear Helical Gear Double Helical Gear

N (Herringbone Gear)

Spiral Bevel Gear Miter Gear Straight Bevel Gear

EN

Rack and Pinion

InternalGear

6. Gear Manufacturing Procedure
boring
Operation

Gear finishing

Heat Treatment Sur Peening

Induction Hardening
Carburizing
Carbo-Nitriding

ier SA psec ay ee am ==] Sasa Y
pepe pee tedio

Distribution

Cleaning

7. Gear Materials

+ AISI — American Iron & Steel Ins. Tbe? Recommended steel for various applications and gear types

+» SAE- Society of Auto. Eng.
« JIS- Japanese Industrial Std.

Among the through-hardening steels in wide
use are 1040, 1060, 4140, and 4340. These
steels can also be effectively case hardened
by induction heating.

Among the carburizing steels used
in gears are 1018, 1524, 4026, 4118,
4320, 4620, 4820, 8620, and 9310

EC

ng

Te

Ditterentats

Automotive
Heavy tm

Drives

Industrial
Traciaccesory

Engines
Heavy tuck

Equipment

Earth moving
E

Automotive
Transmisions
Automotive
Heavy Truck
Marine
OmThighway
Tractor

Hypo, spiaseaight bevel
Hyp, ira bevel

Helical. spur rack and pinion, worm
rossi elcl bial

Crosed as lca, sur, worm

Spira bevel. ero
Face internal, prallt
Heil, hringbone, mie,

Hell eicl conca, sprl bevel
Helical: internal, piralaig eve, spar
Herringbone, neral spur

2.0510

he Institute)

8. Gear Manufacturing Methods
Basic Four Types of Machining Methods
« Form milling
* Gear hobbing
* Gear shaping
* Gear broaching

« Form milling : The machining operation is classified as forming because the
shape of the cutter determines the geometry of the gear teeth.

* production rates are slow because each tooth space is created one at a time
and the gear blank must be indexed.

* The advantage of form milling over gear hobbing is that the milling cutter is
much less expensive.

9. Gear Hobbing: Gear hobbing is also a milling operation, but the cutter is called
as hob.
+ Hob is much more complex tool and therefore, much more expensive than a form milling.

* Special milling machines called hobbing machines are required to accomplish the relative
speed and feed motions between the cutter and the gear blank.

+ In addition to rotary motions of the hob and the workpiece, a straight-line

motion is also required to feed the hob relative to the
gear blank throughout its thickness.

+ Several teeth are cut simultaneously in hobbing, which
allows for higher production rates than form milling.

For classroom education purpose only (use unmodified, non-
commercial and non-sharable outside the Instit

10. Gear shaping

+ In gear shaping, a reciprocating cutting tool motion is used rather than a
rotational motion as in form milling and gear hobbing.

* the cutter has the general shape of a gear, with cutting teeth on one side.

* The axes of the cutter and the gear blank are parallel and the action is similar to
a pair of conjugate gears except that the reciprocation of the cutter is gradually
creating the form of the matching teeth in its mating component.

11. Gear broaching
+ It involves short production cycle times and high tooling cost.
+ It is therefore economical only for high volumes.

* Good dimensional accuracy and fine surface finish are also features of gear
broaching.

+ The process can be applied for both external gears (the conventional gear) and
internal gears.

+ Here the cross section of the tool consists of a series of gear-shaped cutting
teeth of increasing size to form the gear.

12. Gear Shaving:

+ It involves the use of a gear-shaped cutter that is meshed and rotated with the
gear.

+ Cutting action results from reciprocation of the cutter during rotation.

+ Each tooth of the gear-shaped cutter has multiple cutting edges along its width,
producing very small chips and removing very little metal from the surface of
each gear tooth.

13. Other Gear Manufacturing Processes
Casting Methods :

+ Sand casting : cast iron gears for low speed farming machinery. Accuracy and
finish is not very important.

Crane

Source:
ns: //snappygost.com/s/Pq=bestofsá3Arust20pipesá20dirtyX20factoryX20
‘machine %20scratch#7237640711714549cadbedi(72afe20064dd121{,0,1046.

14. * Die casting : mass manufacturing of low melting point metal (Al, Mg, Zn, Cu)
gears for low loads and moderate speed instruments (cameras, toys etc.)

Movable Movable

sonar, rene sat ra
Nez
Elector pa vr Ejector
ps / pins
Pungor £

Cay © = +

Pot

Chamber

a Ñ @
—
a
— es Cold Chamber die casting process
o w

le cai Source: Groover, MP, “Fundamentals of Modem Manufacturing’ John Wiley & Sons
Hot Chamber die casting process . d

15. * Investment casting/Lost wax method: near-net shaped small to medium size
gears with high accuracy and surface finish for heavy loads and stresses.

O gf
|
wax [i 0

0) e 0

4

Source: hitps:/in.Pnterest.com/pn/302515299957109662/

16. + Shell mould casting : small gears are produced in batches. The accuracy and
surface finish lies in between sand casting and investment casting.

«
Source: Groover, M.P., Fundamentals of Modern Manufacturing, John Wiley & Sons.

17. Other Gear Manufacturing Processes... continued

Gear rolling process:

« External steel gears (straight or helical teeth) of small to medium size.

* Teeth are formed by cold rolling (deformation) using flat or circular dies.
+ High surface finish and strong teeth are formed by material flow.

flat die (rack type)

Source: Module 7, Scre

methods, Version 2, ME, IT Kharagpur

18. Powder metallurgy : Neat-net shaped high quality gears (spur).
Blanking: Sheet metal operation is done to produce metallic gears from thin
sheets. These gears are used in watches, tovs, meters etc.

Strip scrap)

ft tun gan

Plastic molding : small to medium size plastic gears are formed by injection
molding. These gears are less noisy and used under light loads such as toys,
electrical equipment etc. Fenster — Hea

corto sem

19. Extrusion : small to medium size high quality external gears are produced by
extrusion process. Gears of required width are cut from the extruded bar having

desired numbers of teeth.
Wire Electro-Discharge Machining (Wire EDM): High precision gears
+ Non-conventional machining process which uses a conductive tool (electrode)

and dielectric medium (de-ionized water, kerosene). High temperature sparks
of high frequency are generated between the gap which melt the workpiece.

Y ar

Work

À Se ow otalecie tu cuting pan

Cary created
Brenner,

Source: Module 7, Screw threads and gear manufacturing methods, Version 2, ME, IT Kharagpur