Other - Hot Rolling - Stamping - Powder Metallurgy
Gear
Gear
milling
Hobbing
Gear Broaching
- Extrusion
Gear Shaping
Sand Casting
- Coining
Die Casting
Gear Generation: Gear teeth are obtained due to relative movement between gear blank and cutter. Profile is not dependent on shape of cutting tool Proper setting of tool is required Internal profile can be easily obtained. Better finishing can be obtained. Pitch of involute gear should be same for proper meshing. •
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Gear Forming: Tool is having negative shape than tool profile to be cut. Gear milling, Gear shaping, Gear Slotting etc. are gear forming processes. processes. Accuracy depends on tooth profile. It is not suitable for internal i nternal profile. Difficult to make complex form tools. •
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GEAR MILLING:
Disk type form milling cutter is used. Gear blank is mounted on mandrel. Form cutter is rotated and table is reciprocated. Cutter is moved to radial direction to provide depth. Gear blank is indexed to make another tooth. Gear milling can also be done with end mill cutter. •
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GEAR MILLING:
Advantages: Economical All kind of gears can be cut. Preferable for small batch size. Roughing and finishing both can be done. • • • •
Disadvantages: More milling cutters are reqd. More time is spent in indexing. Not preferable for mass production. Limited for course pitch. Variation in shape of tooth. These gears are used for slow drive. • • •
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GEAR BROACHING: Broaching tool is used in vertical broaching machine. Speedy and accurate process. Tooth space is produced in single stroke More blanks can be mounted at a time. Blank is indexed after producing each tooth.
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Advantages: Finished gears can be obtained. Advisable for small gears. Advisable for internal gears. High production rate. Good accuracy. accuracy. Economical
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Disadvantages: Costly tool External gears are difficult to make. Different broaching tools are reqd. for gear having diff. modules. Not preferable for bevel gears.
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GEAR SHAPING(By forming method):
Tool having shape of tooth space is mounted on ram of shaper. Blank is mounted on two centers and tool is reciprocated. Indexing mechanism is used to rotate blank. More time is spent due to indexing. Teeth are not accurate. Preferable for spur gears. •
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GEAR HOBBING:
It is gear generating ge nerating method. Fast and accurate. Hob(like worm cutter) is rotary tool on which single or multi start threads are cut. Each thread is having shape of involute tooth. Gear blank is mounted on table. Relative motion between tool and work piece is obtained by gear train. Gear blank is moved up to desired depth. Hob is moved in axial direction of blank. •
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GEAR HOBBING:
Advantages: Set up time is less. High production rate. Accurate gears. No need of indexing. Worm gear, spline, rachets, helical gears etc can be made. •
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Disadvantages: Internal gears can be cut. Difficult to cut bevel gears. Not advisable for blanks having flanges. •
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GEAR SHAPING ( GENERA GE NERATING TING METHOD): Cutter is one kind of gear having cutting edge. Pinion or rack type cutter can be used. Gear blank and cutter are rotated with adjusted velocity ratio. One gear tooth is generated by one cutter tooth. Cutter is axially reciprocated with 50 stroke/min. Reciprocating Reciprocating movement is dependent on face width. Cutter is also reciprocated in radial direction to provide full depth mean while blank remains steady. •
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GEAR SHAPING ( GENERA GE NERATING TING METHOD):
Rack type cutter is also used, in which blank is rotated and cutter is provided longitudinal motion.
Advantages: Spur, helical, rack, internal gears can be manufactured. Cutter is universal for same pitch and it does not depend on numbers of teeth. Advisable for mass production Disadvantages: Production rate is low compared to hobbing Helical guide is required for helical gear. Low rigidity. rigidity. Sufficient undercut are required. • •
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GEAR FINISHING METHODS: Gear shaving: - Rack type - Rotary type -In rack type, shaving tool is kept below gear and reciprocated. -Grooves are made on cutter. -In rotary type, grooves are made on gear shaped cutter.
GEAR FINISHING METHODS: Gear Grinding: 1.) Form grinding -Involute shaped grinding disk is used to finish each teeth one by one. -Indexing mechanism is used to rotate blank. -Sometimes two disk wheels are used to reduce time. 2.) Generation Grinding -Spiral, bevel gears are grinded by this method. -Grinding wheel is also moved in tooth space. 3.) Grinding by threaded wheel -Similar to hobbing -Grinding wheel is having helical threads.
