how gears are manufactured

GEAR MANUFACTURING

Gears can be manufactured by various process that can be classified under the following  3 process 

1. Gear milling
2. Gear generating
3. Gear molding

a) Gear Milling:

•  This is one of the initial and best known and metal removal process for making gears. 
• This method requires the usage of a milling machine
•  It is also to be noted that this method can produce nearly all types of gears.
•  The method involves the use of a form cutter, which is passed through the gear blank to create the tooth gap. 
• This method is right now used only for the manufacture of gears requiring very less dimensional accuracy. 
• Surface finish  is good.

b)GEAR GENERATING:

• In the generating process ,teeth are formed in series of passes by a generating tool shaped like a mating gear.
• Either hobs or shapers can be used.

1. Hobbing:

•  Gear Hobbing is a continuous generating process in which the tooth flanks of the constantly moving work piece are formed by equally spaced cutting edges of the hob.
•  The main advantage of this process is its versatility to produce a variety of gears including Spur, Helical, Worm Wheels, Serrations, Splines, etc. 
• The main advantage of the method is the higher productivity rate of the gears.
• Hobbing closely controls tooth spacing,lead and profile.
  

     

2.SHAPING:

•  Gear shaping is a generating process.
• The cutter used is virtually a gear provided with cutting edges. 
• The tool is rotated at the required velocity ratio relative to the gear to be manufactured and any one manufactured gear tooth space is formed by one complete cutter tooth. 
• This method can be used to produce cluster gears, internal gears, racks, etc with ease, which may not have the possibility to be manufactured in gear hobbing.
• Using a shaper ,teeth may be generated with either a pinion cutter  or a rack cutter.
  

3.GEAR MOLDING:

Mass production of gears can be achieved by molding. 

• Injection molding:It produces light weight gears of thermoplastic material.
• Die casting:It is a similar process using molten metal.Zinc, brass, aluminium,and magnesium gears are made by this process.
• Sintering: It is used in small , heavy-duty gears for instruments and pumps.Iron and brass are mostly used for this process.
• Investment casting: It produces medium-duty iron and steel gears for rough applications.