ABEN 198 - Machine Design for AB Production

rational design

empirical design

industrial design

CLASSIFICATIONS OF DESIGN

Rational Design

carried out using mathematical formula and other engineering principles.

Empirical Design

based upon empirical formula derived from existing practices and past experiences.

Industrial Design

involves consideration like aesthetics, ergonomics, and production aspect.

original design

adaptive design

development design

CLASSIFICATIONS OF DESIGN

Original Design

does not exist before and it is only done by few dedicated designer who have personal qualities of a sufficiently high order. This also requires a lots of research, experimental activities, and creative brain

Adaptive Design

more concerned of the adoption of existing designs. This does not demand special knowledge or skills. Problems can be solved with ordinary training.

Development Design

begins with an existing design but the final result may quietly differ from the initial product.

pure metal

single element that are not combined with any other chemical element

they are too soft, low in strength, or low in some other desired property to be used in any commercial applications

alloy

mixture of two or more metals to produce new metal.

example are stainless steel, bronze, etc.

Iron

pure ferrite

pig iron

cast iron

two types of iron

Pig iron

produced from ore of hematite or magnetite in the blast furnace by melting with limestone andcoke.

Cast Iron

with carbon content of 1.7 to 6/7%. They are low cost, good casting property, high compressive strength, high wearing resistance, brittle and lower tensile strength.

Steel

molten steel that is cast into an ingot and then rolled, forged, hammered, pressed, or machined into desired shape.

Structural steel, steel bars and cylinder, and steel plate

are commonly used as machine elements and frame.

Soft-Centered Steel

durable to shock because the center layer is deformable and has higher wear resistance than hard steel at the outer side. They are usually used for moldboard and shear of a plow.

Low-Carbon Steel

with carbon content not exceeding 0.25%

Medium-Carbon Steel

contains 0.25 to 0.50% carbon. They are usually used in making structural and machinery steel.

High-Carbon Steel

carbon content is above 0.50%. They are usually used in the manufacture of spring and tool steel.

Mild Steel (MS)

contains carbon of 0.15 to 0.25%. They are malleable and easy to cut and weld

Cold-Rolled Steel (CRS)

Medium carbon steel which are used for parts and components of machines requiring greater strength and hardness, such as shafting and connecting rods.

Stainless Steel (SS)

• 1% Ni, 11-14% Cr, 0.6% Mn, 0.6% Si. They have high resistance to corrosion and oxidation.

• They are used for valves, nozzles, and dairy machines.

Sheet

• piece of metal which has been rolled into a sheet of 3/16 in. or less in thickness.

Strips

long sheet of metal that is less than 12in. wide.

Plate

• metal with thickness over 3/16 in.

• Commonly available size is 4' wide x 8' long.

• Thickness are given in terms of mm or in inch.

Metal Bars

• made of different shapes and are usually available in standard length of 20 ft. or 6 m.

• They are purchased in terms of quantity, shape, size, and kind of metal used.

Tubular Product

• include all hollow metal shapes such as pipes and tubes.

• They are available in round, square, and rectangular shapes.

• Specifications are given in terms of shape, schedule number, size, and length

Non-Ferrous

includes all the metals such as copper, aluminum, magnesium, and zin c in which iron is not present in large amount.

RUBBER

• material obtained from rubber tree.

• Capable to withstand extreme deformability with more or less complete recovery upon removal of deforming force

plastics

• Large group of materials consisting of combination of carbon and oxygen, hydrogen, nitrogen, and other organic and organic elements.

• Non-metallic material that can be molded into shape.

• They are light in weight, resistance to deterioration by moisture, low elastic and thermal conductivity, and good color range

thermoplastics and thermosets

classification of plastics

FIBERS

The oldest engineering material that includes jute, flax, and hemp

Usually used for engineered products such as rope, cordage, nets, water hose, and containers.

GLASS

A non-crystalline or amorphous solid

are made from silica, lime, and sodium carbonate.

shaft

A rotating member of a machine that is usually of circular cross-section used to transmit power and motion.

• Circular Shaft (Round)

• Non-Circular Shaft (Hexagonal)

classification of shaft according to cross-sectional shape

• Solid Shaft

• Hollow Shaft

classification of shaft according to cross-sectional area

• Main shaft

• Line shaft

classification of shaft according to function

Line shaft

A continuous shaft with an input in one location and have several outputs on the same shaft

Universal Joint and Flexible Shafts

direct drive transmission system used to transmit power to a misaligned shaft

Cam

• device that produces intermittent motion or a specific motion to a member called follower.

• Disc with a lobe on one side and when rotate produces intermittent motion

AISI 1020 (Cold Rolled Steel)

Standard shafts used for agricultural machines usually have a steel designation of

304 or 316.

Stainless steel shaft that is usually used for special purpose has to have a steel designation of

Keys

are used to prevent relative movement of rotating members and the shafts or spindles to which they are mounted.

parallel keys

keys whose longitudinal sides are parallel with each other

Taper key

keys with tapered longitudinal section

Woodruff key

keys with a semi circular cross-section

AISI 1020.

Materials used for key should have a designation of

393 Mpa.

Tensile strength for key should be

BOLTS AND NUTS

threaded fastener intended to be mated with nut

They are used to hold machine parts together.

• Set screw

• Cap screw

• Log screw

• Wood screw

Classification of screws

RIVETS

• low-cost permanent fasteners well suited to automatic assembly operation.

• Tubular rivet,

• Blind rivet

Classifications of rivets

WASHERS

• used on the end either beneath the head of the bolt or beneath the nut.

• They are used primarily as a seat to distribute load in a fastener system

• Flat or plain washer

• Lock washer

▪ Internal tooth

▪ External tooth

▪ Helical spring tooth

classification of washers

PINS

• inexpensive and effective fastener and are used when loading is in shear.

• They are commonly used to fasten shaft in some control linkages.

• hollow spring pin

• tapered Pin

• cotter pin

• "hair " pin.

Classifications are:

RETAINING RINGS

used to provide a removable shoulder to accurately locate, retain, or lock components on shaft or in bores and housing

Bearing

permits relative motion of two parts in one or two directions with minimum friction while resisting motion in the direction of applied load

Plain or Journal Bearing

Anti-Friction or Rolling Bearing

Classification of Bearings

Plain or Journal Bearing

Loads are passed through the surfaces of the parts by sliding contact or separated by lubricants

Bearing that develops a hydrodynamic pressure to carry the loads and separate the bearing elements in order to minimize friction

Anti-Friction or Rolling Bearing

Loads are passed through the surfaces of the parts by rolling contact. It carries the load from a rotating shaft on balls or other types of rollers

Bearing that utilizes the rolling action of a number of balls or other elements between two rings in order to reduce the friction and prolong their lives.

• Radial Bearings

• Thrust Bearing

• Combination of Radial and Thrust Bearings

Classification of Bearings

According to the Direction of Applied Load

• Ball Bearing

• Roller Bearing

• Spherical Bearing

• Tapered Bearing

• Needle Bearing

Classification of Bearings

According to the Rolling Element

• Pillow Block Bearing

• Flange Bearing

• Square flange

• Rhombus flange

• Take-Up Unit

Classification of Bearings

According to the Type of Casing

Single-Row Deep-Groove Ball Bearings

• This is the common type of rolling bearing.

• The raceway grooves on both the inner and outer rings have circular area of slightly larger radius than that of the balls.

• In addition to radial load, thrust load can be imposed in either direction.

• Applicable for high-speed application.

• Low power loss characteristics

Single-Row Angular Contact Bearings

• Capable of taking radial and thrust loads in one direction.

• Contact angles available are 15, 30, and 40 deg. Larger contact angle, higher thrust load capability. Highspeed operation requires low contact angle

Self-Aligning Ball Bearings

• Inner ring has two raceways. • Only minor angular misalignment of the shaft in relation to the bearing housing is allowed.

• This type of bearing with tapered bore is often mounted using an adapter sleeve.

Cylindrical Roller Bearings

• The rollers are in linear contact with the raceway.

• Has large radial load capacity and is suitable for use in high speeds.

Needle Roller Bearings

• Has large number of long rollers with length-to-diameter ratio of 3 to 10.

• Suitable for condition where there is limited space.

Tapered Roller Bearings

• Capable of taking both radial and thrust loads in one direction

Spherical Roller Bearings

• It is a self-aligning type of bearing due to its shape that is spherical.

• Can also take both radial and thrust loads.

Single-Direction Thrust Ball Bearing

• It is composed of a washer-like bearing rings with raceway grooves for the balls.

• This bearing is highly suitable for thrust load such as those in the auger of the vertical feed mixer

BELT-AND-PULLEY DRIVE

• the simplest method of transmitting power in agricultural machines.

• It is widely adopted in driving various production and postproduction parts of agricultural machines.

• Cost of transmitting power is very much lower compared with sprocket and chain and gear drives.

Flat Belt

V-Belt

Classifications of Belt-and-Pulley Drive

Flat Belt

• flexible material which is band on two or more pulleys where power is transmitted from driver to the driven pulley.

• Power transmission primarily depends on the friction between the belt and the pulley surfaces.

V-Belt

• transmission system consisting of an endless flexible belt that transmits power by contacting and gripping the sheaves which are keyed to the shaft of a driving and the driven machine.

Flat Belt

used to transmit rotary motion and power between two shafts which lie flat on the face of the corresponding pulley.

Narrow V-Belt

• belt with trapezoidal cross-section to transmit rotary motion to parallel shafts.

Double V- Belt

• V-belt with inverted V on top making it more suitable for multiple-sheave drive arrangement.

Cogged Belt

• V-belt with teeth design for a special kind of sheave to provide more gripping action to obtain higher efficiency hence minimizing belt slip

V-Ribbed Belt

• combines the features of a flat belt and a V-belt. It operates very efficiently and can run at a very high speed

Variable Speed Belt

• most common where there is a large center distance between shafts or were drive ratio must go beyond the commonly supplied drive

Idlers

• are grooved sheaves or flat pulley which do not serve to transmit power.

• Instead, they are used to tighten belt when it is not possible to move either shaft for belt installation and take-up.

SPROCKET AND CHAIN DRIVE

basically consists of an endless chain whose links engage the teeth of sprocket keyed to the shaft of the driving and the driven mechanisms

This kind of drive is used to transmit power and to synchronize motion or maintain a fixed-speed ratio between rotating shafts

Detachable Chain

Pintle Chain

Engineering Steel Chain

Inverted-Tooth or Silent Chain

Bead or Slider Chain

Roller Chain

Types of Chain

Pintle Chain

• They are used for slightly higher speed (up to about 450 fpm) and heavier loads. • They are made of individual cast ling having full round barrel end with offset sidebars.

inverted-Tooth or Silent Chain

They are high speed chains used predominantly for prime mover power take-off drive.

Bead or Slider Chain

They are used for manually controlled or slow-speed drives

Roller Chain

• This is the most important type for agricultural use. It is available either single- or multiple-strand type.

• Roller chain composed of roller, links, and pin links, alternately spaced throughout the length of the chain. The roller link consists of two sets of rollers and bushing, and two link plates, and the pin links consists of two pins and two link plates

GEARS

are tooth wheels used to transmit power and motion at a constant ratio from one rotating shaft to another by means of a positive contact of successively engaging teeth.

Spur Gear

• most common type of gear.

• Teeth are straight and parallel to shaft axis.

• Its advantages are simple, low cost, and easy to maintain.

• Drawbacks are: have less capacity and are noisier than other types

Helical Gear

• carry more load than the equivalent size spur gear.

• Operates more smoothly and quietly. • More costly than spur gears.

Worm Gear

• provides a maximum reduction ratio for a given center distance.

• They are quiet and smooth action.

• They are used only for speed reduction.

• Cannot back-drive at ratios greater than 20:1.

• Contact area is large hence load capacity is high. • • Shaft is almost always at right angles.

Straight Bevel Gear

• simplest type of gear for intersecting shaft.

• It is commonly used for shaft intersecting at right angle but can also be used for shaft mating at any angle.

• Gears are designed in pairs thus are not always interchangeable.

• Supporting shaft and bearings must be rigid to maintain proper tooth contact.

Hypoid Gear

• similar to spiral-bevel gears except that the shafts do not intersect.

• Operates more smoothly and more quietly and is stronger for a given ratio.

• Permits a very high drive ratios.

• Shaft angles usually 90 deg, but other angles are possible.

• Higher load capacity with the size and ratio of spiral bevel gear