View Factor Orientation (or View factor or shape factor) plays an important role in radiation heat transfer. View factor is defined as, "fraction of radiation leaving surface 'i' and strike 'j' ". Summation Rule (View Factor) If there is are similar surfaces 'i' and 'j' , then: Blackbody Radiation Exchange Radiation Exchange between Opaque, Diffuse, Gray surfaces in an Enclosure 1. Opaque 2. Surfaces 3. Two surface enclosure Radiation Shield It is used to protect surfaces from radiation act like a reflective surface. References: Material from Class Lectures + Book named Fundamentals of Heat and Mass Transfer by Theodore L. Bergman + My knowledge. Photoshoped pics are developed. Some pics and GIF from Google. Videos from YouTube ( Engineering Sights ).
Several processing operations are done for the manufacturing gears, which are as:
Performing of Blank (with or without) ↠ important part of gears.
Annealing of Blank (Forged or Cast steel)
Machining of Gear Blank
Producing Teeth or Machining of Teeth
Finishing of Teeth (by shearing, grinding) ↠ if required
Full or Surface Hardening of Machined Gear ↠ case hardening
Inspection and Testing of Finished Gears
Manufacturing process involves following categories:
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.
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:
Sand Casting ↠ cast tooth are produced by melting and pouring into the mold cavity.
Die Casting ↠ casted tooth are produced by injecting material into mold cavity using high pressure.
Rolling ↠ deformation process in which thickness is reduced by compression forces exerted by two opposing rolls.
Powder Metallurgy ↠ pressing of metal powder in dies final shape.
Injection Molding ↠ producing teeth by injecting molten material into a mold.
Cold Drawing ↠ forming teeth from steel rods by drawing (pulling) them through hardened dies.
Extrusion ↠ shaping of teeth by pushing rod through a die having gear shape.
Stamping ↠ a cutting process in which sheet metal is placed between portions of die which removes the gear from the sheet.
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:
Blanks are performed through machining, finishing and then teeth are produced.
Full Gears with teeth are made by different processes and then finished by further machining and grinding.
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:
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).
Generation ↠ complicated tooth profile is provided by much simpler form cutting tool (edges) through rolling type, tool-work motion (Hobbing, gear shaping).
Solid Mechanics OR Mechanics of Materials OR Strength of Materials: It is the study of mechanics of body i.e. forces and their effects on deformable solids under different loading conditions. Deformable Body Mechanics: It is the study of non-rigid solid structures which deform under load. Deformation/Distortion ⇾ change of shape and size OR have some relative displacement or rotation of particles. It happens when we apply combined load. Rigid Body Motion ⇾ Translation or rotation of particles but having constant distance between particles. Since deformation occur at particular load. Below this load, every body is considered as rigid body . Types of Load: Point Load ⇾ Load apply on a single point i.e. concentrated load. Uniformly Distributed Load (UDL) ⇾ Load remains uniform throughout an area of element like beam. Varying Distributed Load (VDL) ⇾ Load varies with length with constant rate. Moment ⇾ It measures the tend...
Gear Forming by Machining Formation of gear through machining consists of following methods: Form Milling by Disc Cutter Form Milling by End Mill Cutter Shaper, Planner and Slotter Broaching 1. Form Milling by Disc Cutter It is defined as, " Tooth is cut one by one by plunging the rotating cutter into the blank " . Each gear needs a separate cutter. 8 - 10 standard cutters are available for producing 12 - 120 teeth gears. Used for big spur gears of large pitch. 2. Form Milling by End Mill Cutter It includes the cutting of tooth at a time and then indexed for the next tooth space for cutting. For a small volume production of low precision gears. Set of 10 cutters ↠ 12 - 120 teeth gears . Used for teeth of large gears/module. To reduce cost, same cutter is often used for multiple sized gears resulting in profile errors . Characteristics: Use of Hardened stainless steels (HSS) form milling cutters. Use of Ordinary milling machines. Low production rate (need of indexing...
Gear Generation by Machining Tooth profile is provided by much simpler form cutting tool through hobbing, gear shaping. It involves the following methods: Gear Hobbing Gear Shaping 1. Gear Hobbing It is defined as, " a machining process in which gear teeth are progressively generated by a series of cuts with a helical cutting tool " . Most accurate machining process. Used for gears production because it has excellent surface finish. Continuous Indexing Process ↠ in which both cutting tool and workpiece rotate in constant relationship while hob is being fed into work. Feed Directions The direction of feed during hobbing operation depends upon the type of gear to be cut. Following are the types of feed directions: Axial Feeding ↠ cutting spur and helical gears (Hob axis is parallel to Blank axis). Radial Feeding ↠ for bevel gears (Hob axis is perpendicular to Blank axis). Tangential Feeding ↠ for worm, straight, spiral...
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