Gears & It's Manufacturing

Gears

It is defined as, "machine element used to transmit power". To meet device conditions, you need to design a:

• Robust Construction
• Reliable Performance 
• High Efficiency
• Economy
• Long Life

Factors which decrease the wear and tear of a gear are:

• Noise produced during working
• High load carrying capacity
• Constant velocity ratio

Manufacturing of Gears

Several processing operations are done for the manufacturing gears, which are as:

1. Performing of Blank (with or without)  ↠  important part of gears.
2. Annealing of Blank (Forged or Cast steel)
3. Machining of Gear Blank
4. Producing Teeth or Machining of Teeth
5. Finishing of Teeth (by shearing, grinding)  ↠  if required
6. Full or Surface Hardening of Machined Gear  ↠  case hardening 
7. Inspection and Testing of Finished Gears

Manufacturing process involves following categories:

1. Forming  ↠  shaping of plastic deformation in which volume remains constant (approx.) before and after the process. E.g.: Direct casting, rolling, powder metallurgy, injection molding, drawing, extrusion, stamping, forging, etc.
2. Machining  ↠  shaping of parts by removing material (involves roughing, finishing operation). E.g.: Cutting, Shaping, Planning, Slotting, Broaching, Milling, Grinding, Hobbing, etc.

Forming Methods for Gear Manufacturing

Following are the methods for forming gears:

1. Sand Casting  ↠  cast tooth are produced by melting and pouring into the mold cavity.
2. Die Casting  ↠  casted tooth are produced by injecting material into mold cavity using high pressure.
3. Investment Casting  ↠  tooth shape is obtained by melting pattern wax.
4. Rolling  ↠  deformation process in which thickness is reduced by compression forces exerted by two opposing rolls.
5. Powder Metallurgy  ↠  pressing of metal powder in dies final shape.
6. Injection Molding  ↠  producing teeth by injecting molten material into a mold.
7. Cold Drawing  ↠  forming teeth from steel rods by drawing (pulling) them through hardened dies.
8. Extrusion  ↠  shaping of teeth by pushing rod through a die having gear shape.
9. Stamping  ↠  a cutting process in which sheet metal is placed between portions of die which removes the gear from the sheet.
10. Forging  ↠  material shaping process by the application of localized compressive forces with power hammers, presses.

Machining Methods for Gear Manufacturing

Gears are manufactured in several routes:

1. Blanks are performed through machining, finishing and then teeth are produced.
2. Full Gears with teeth are made by different processes and then finished by further machining and grinding.
3. Accurate gears in finished form are directly produced by Near-Net-Shape process like rolling, plastic molding, powder metallurgy.

Machining methods for gear manufacturing are:

1. Forming (or Form-Cutting or Copying or Profiling Method)  ↠  teeth profiles is obtained as the replica of the form of cutting tool (milling, shear cutting, teeth cutting).
2. Generation  ↠  complicated tooth profile is provided by much simpler form cutting tool (edges) through rolling type, tool-work motion (Hobbing, gear shaping).

Note:

• Gear Ratio
• Gear Hardening & Tempering

References:

• Material from Class Lectures + Book named Fundamentals of Modern Manufacturing Materials, Processes and Systems by Groover + My knowledge. 
• Photoshoped pics are developed. 
• Some pics and GIF from Google.  
• Videos from YouTube (Engineering Sights).