Spur Gear Manufacturing

Introduction to Spur Gear:

A Gear can be defined as a mechanical element used for transmitting power and rotary motion from one shaft to another by means of progressing engagement of projections called teeth.

Two or more gears working in tandem are called a transmission and can produce a mechanical advantage through a gear ratio and thus may be considered a simple machine

 Spur Gear Terminology:

•         Module: The size of tooth expressed mm of pitch diameter

                           M= Pitch Diameter/ No. of teeth

•         Helix Angle: It is the angle between Helix of tooth and centre axis of Gear

•         Pressure Angle: The direction of force created by a driving gear upon its mating gear .It is the angle between tangential to base circles and line perpendicular to tooth profile

•         Outside diameter: Diameter over the top of tooth

•         Root Diameter: Diameter of base of tooth

•         Addendum: The radial distance between pitch circle diameter and outside diameter

•         Dedendum: The radial distance between pitch circle diameter and root diameter

•         Pitch circle Diameter: The imaginary circle found at a point where  two gears meshes with each other

•         Base Circle diameter: The diameter of base cylinder from which the tooth profile starts

•         Clearance operating: The amount by which the dedendum operating in a given gear exceeds the addendum of the mating gear

•         Circular Pitch: The distance along the pitch circle between corresponding points on adjacent teeth

•         Whole depth: The total depth of tooth space

•         Working Depth: The depth of total engagement of teeth during mating

•         Face Width: The width of the tooth in an axial plane

•         Fillet Radius: The radius of the fillet curve at the base of the gear tooth.

•         Backlash: The space between tooth space and tooth thickness of mating gear

Selection of Gear Materials:

Material	Property	Application
•    Cast Iron •    Cast Steel •    Plain Carbon Steel •    Stainless Steel	•     Low cost, good machining •     Low cost, high strength •     Good machining, heat-treatable •     High corrosion resistant, nonmagnetic, non hardenable	•     Large size, moderate power rating, commercial gears •     Power gears ,medium rating •     Power Transmission applications •     Extreme corrosion, low power rating
•     Alluminum alloys •     Brass alloys •     Bronze alloys •     Sintered Powdered •     Titanium Alloy •     Nickel alloys	•     Light weight, non corrosive ,excellent machining •     Low cost ,non corrosive ,good machining •     Good compatibility with steel mates, low friction •     Low cost , low quality ,moderate strength •     High strength, moderate weight	•     Extreme light duty instrument gears •     Low cost commercial equipments •     Mates with steel power gears •     High production •     Special light weight height strength  equipment •     Special thermal applications
•     Nylon •     Teflon •     Fenolic Laminates	•     Low friction ,high water absorption •     Low friction ,no lubricant •     Quiet operation, high strength	•     Long life , no noise , low load •     Special low friction application •     Special applications

Inputs required in designing a gear: 

      1)      Gear Ratio

      2)      Input speed

      3)      Torque to be transmitted

      4)      Type of loading

      5)      Ambient condition

Design procedure for Spur Gear:

      1)      The load that would be exerted by the tooth during power transmission and pitch line velocity.

      2)      Decide the centre to centre distance between shafts.

      3)      Apply lewis equation

      4)      Calculate the dynamic load

      5)      Calculate the static tooth load

      6)      Calculate the wear tooth load

Gear manufacturing process:

A] For single piece:

Sr. No.	Operation performed	Machine used	Inspection process	Equipment used
1	Gear Blanking	Conventional Lathe machine	OD measurement Thickness measurement	Micrometer Vernier calliper
2	Teeth cutting	Milling machine	Measurement over teeth TTCE TCE Gear Profile	Flange type micrometer Dial Gauge Dial gauge Profile projector
3	Finishing operation	Conventional shaving machine	Measurement over teeth	Flange type micrometer
4	Heat Treatment	NA	NA	NA
5	ID Grinding	NA	NA	NA

B] For mass production:

Sr. No.	Operation performed	Machine used	Inspection process	Equipment used
1	Gear Blanking	CNC machine	OD measurement Thickness measurement	Micrometer Vernier calliper
2	Teeth cutting	CNC hobbing/shaping machine	Measurement over teeth TTCE TCE Gear Profile	Flange type micrometer Dial Gauge Dial gauge Involutes Profile tester
3	Finishing operation	CNC shaving machine	Measurement over teeth	Flange type micrometer
4	Heat Treatment	HT Furnace	Hardness inspection	Rockwell hardness tester
5	ID Grinding	Bore grinder	ID measurement	Air gauge

Material handling equipments:

      1)      Plastic bins

      2)      Trolley

      3)      Forklift

      4)      Pallets