gears machining

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7/27/2019 Gears Machining http://slidepdf.com/reader/full/gears-machining 1/47 1 GEARS MACHINING GEAR TYPES Cylindrical gears: - spur - helical Bevel gears: - straight - curved (spiral) Worm wheels and worms

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7/27/2019 Gears Machining

http://slidepdf.com/reader/full/gears-machining 1/47

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GEARS MACHININGGEAR TYPES

• Cylindrical gears:

- spur

- helical

• Bevel gears:

- straight

- curved (spiral)

• Worm wheels and worms

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Involute tooth profile

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Spur and helical gears cutting

METHODS:• form milling  – using a cutter  (with the same

edge profile as the shape of the tooth space)

and a dividing device• hobbing  – using a hob and a generating

process for creating a tooth profile 

• shaping  – using a shaper cutter  and agenerating process for creating a tooth profile 

• broaching

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Gear machining – form milling

(single gear tooth cutter)

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Gear machining – form milling

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Gear milling  – tollerances and

surface finish

Type of cut IT Ra

Form milling

 – shape mill9  – 11 3,2 - 6,3

End milling 8 - 9 3,2 - 6,3

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Gear machining - hobbing

• Hob  – a tool designed as a worm shaped

cutter , which acts by the cutting as a worm

cooperating with the machined gear wheel

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Hobbing cutter

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Gear hobbing

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Gear hobbing

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Gear hobbing machine tool

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Gear hobbing machine tool

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Gear hobbing – kinematic schema

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Gear machining - shaping

• circular  shapercutter → 

rack shaper cutter↓ 

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Gear shaping – a circular cutter

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Gear shaping – a circular cutter

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Gear shaping – the principle

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Gear shaping – a rack cutter

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Gear shaper with the rack cutter

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Tollerances and surface finish

Type of cut IT Ra

Hobbing 5 - 7 0,8  – 3,2

Shaping  – 

circular cutter 5 –

 6 0,8 –

 1,6

Shaping  – 

rack cutter4 - 5 0,8  – 1,6

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Broaching

• Very productive method

• Broach has the shape of gear

Ideal for internal gears – Tooth gaps one after another

 – All gaps simultaneously

Desc.:1  – elongated body, 2  – teeth, 3  – 

gullets, 4  – teeth gaps, 5  – axis, 6  – 

follower end, 7  – pull end, 10  – 

outside shape of broach

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Broaching

• From a premachined hole a final gear is made

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Broaching

Type of cut IT Ra

Roughing 5  – 6 0,8  – 1,6

Finishing 4 - 5 0,8  – 1,6

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Spur and helical gears finishing

METHODS:

• shaving  – for gears without heat treatment

• grinding  – mostly for gears after heat

treatment 

- form grinding

- involute - generating grinding

• lapping

• teeth rounding  – creating a shape of tooth

(in the direction parallely to the axis of

rotation) to make changing gears easier

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GEAR WHEELS SHAVING

A gear wheel being shaved is

run in contact with a

shaving cutter

Shaving cutter   – HSS tool;

teeth with serrations, whichare acting in the shaving 

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GEAR WHEELS SHAVINGThe gear and the cutter  are run in mesh with their

axes crossed at a small angle. During the rotation thegear  is reciprocated longitudinally across the cutter .

This „shaving“ process causes very fine chips are cut

from the tooth surface (process requires less than 1

minute)

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Form gear grinding

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Form splining grinding

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Involute-generating grinding

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Involute-generating grinder

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Gear finishing  – tollerances and surface finish

Type of cut IT Ra

Shaving 5 - 6 0,4  – 0,8

Form grinding 5  – 7 0,2  – 1,6

Involute-generating grinding

with straight-sided grinding

wheels

2 - 4 0,2  – 0,4

Involute-generating grinding

with a worm grinding wheels3 - 5 0,2 - 0,8

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Gear lapping• On finished, shaved and hardened gears.

• The gear runs in contact with one or more cast

iron lapping gears

• Flow of oil with abrasive is used

• Improves surface quality at low costs then

grinding

• Ra = 0,1  – 0,2

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Teeth rounding

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Teeth rounding

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Straight bevel gears cutting

METHODS:• form milling  – using a cutter  (with the same

form as the tooth face) and creating first one,than the opposite face flank of the tooth

•involute-generating milling

 – using twocutters representing one tooth of a rack and a

generating process for creating a tooth profile 

• shaping  – using a shaping rack tool and a

generating process for creating a tooth profile • broaching  – using rotational broach

Straight bevel gears

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Straight bevel gears

involute-generating milling

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Straight bevel gears - shaping

St i ht b l b hi

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Straight bevel gears - broaching

St i ht b l b hi

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Straight bevel gears - broaching

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Curved bevel gears cutting

METHODS:

• Gleason  – teeth curved in the form of

circle• Oerlikon  – teeth curved in the form of

epicycloid

• Klingelnberg  – teeth curved in the

form of involute

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Gleason method

Tool is a composition of a

round body and cutting

tools. The can be

adjusted separatelly.

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C d b l O lik

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Curved bevel gears - Oerlikon

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Worms and worm gears

Worms  – produced by turning or form milling

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Worms and worm gears

Worm gears  – produced by hobbing

Worm hob has a small diameter

In feed machining