(04 ME 33) Manufacturing Processes

MANUFACTURING PROCESSES

Presented By:Muhammad Idrees 04-ME-33

INTRODUCTIONBasically manufacturing is value adding activity where the conversion of materials into products adds value to original material.Thus the objective of a company engaged in manufacturing is to add value and do so in most efficient manner, using the least amount of time, material, money, space and manpower.To minimize waste and maximize efficiency we need a well designed and efficient manufacturing system.

MANUFACTURING PROCESSA manufacturing process converts unfinished materials into finished products often using a machine tool e.g. injection molding, progressive stamping, welding.

Manufacturing process is all that by which we convert Stuff into Things

CLASSIFICATION

CASTING

IT IS SUITED WHEN:

The part is very large and of complex shape.The component has internal cavity.The material of component is difficult to machine.The metal used is expensive and so there is to be little waste. The component has irregular curved surfaces.

IMPORTANT FACTORS IN CASTING OPERATION

The flow of the molten metal into the mold cavityHeat transfer during solidification and cooling of the metal in the mold (The metal grain sizes are smaller near the mold than in the center)Influence of the type of mold materialSolidification of the metal from its molten state

STEPS IN SAND CASTINGFigure Outline of production steps in a typical sand-casting operation.

SAND CASTING

SCHEMATIC ILLUSTRATION OF INVESMENT CASTING 1. WAX INJECTION : Wax replicas of the desired castings are produced by injection molding. These replicas are called patterns. 2. ASSEMBLY : The patterns are attached to a central wax stick, called a sprue, to form a casting cluster or assembly.3. SHELL BUILDING : The shell is built by immersing the assembly in a liquid ceramic slurry and then into a bed of extremely fine sand. Up to eight layers may be applied in this manner. 4. DEWAX : Once the ceramic is dry, the wax is melted out, creating a negative impression of the assembly within the shell.

5. CONVENTIONAL CASTING In the conventional process, the shell is filled with molten metal by gravity pouring. As the metal cools, the parts and gates, sprue and pouring cup become one solid casting.

6. KNOCKOUT When the metal has cooled and solidified, the ceramic shell is broken off by vibration or water blasting.7. CUT OFF The parts are cut away from the central sprue using a high speed friction saw. 8. FINISHED CASTINGS After minor finishing operations, the metal castings--identical to the original wax patterns--are ready for shipment to the customer.

DIE CASTINGExample of permanent-mold castingMolten metal is forced into the die cavity at pressures ranging from .7MPa 700MPaParts made from here range from:Hand toolsToysAppliance componentsThere are two basic types of die casting machinesHot-chamber - involves the use of a piston to push molten metal in to the die cavityCold-chamber molten metal is poured in to the injection chamber & the shot chamber is not heated

HOT CHAMBER DIE CASTING1. The die is closed and the piston rises, opening the port and allowing molten metal to fill the cylinder.

2. The plunger moves down and seals the port pushing the molten metal through the gooseneck and nozzle into the die cavity, where it is held under pressure until it solidifies.

3. The die opens and the cores, if any, retract. The casting remains in only one die, the ejector side. The plunger returns, allowing residual molten metal to flow back through the nozzle and gooseneck. 4. Ejector pins push the casting out of the ejector die. As the plunger uncovers the filling hole, molten metal flows through the inlet to refill the gooseneck, as in step (1).

COLD DIE CASTING PROCESS1. The die is closed and the molten metal is ladled into the cold-chamber shot sleeve.2. The plunger pushes the molten metal into the die cavity where it is held under pressure until solidification.

3. The die opens and the plunger advances, to ensure that the casting remains in the ejector die. Cores, if any, retract.

4. Ejector pins push the casting out of the ejector die and the plunger returns to its original position.

PRESSURE CASTINGFigure (a) The bottom-pressure casting process utilizes graphite molds for the production of steel railroad wheels. Source: The Griffin Wheel Division of Amsted Industries Incorporated. (b) Gravity-pouring method of casting a railroad wheel. Note that the pouring basin also serves as a riser. Railroad wheels can also be manufactured by forging.

CENTRIFUGAL CASTING

FORMING PROCESSES

GENERAL FEATURESMaterials are processed in solid state.No need to handle molten material.No deal with complexities of solidification.Material is not wasted as there is no cutting process.Plasticity, the ability to flow as solid without deterioration of properties, is the property that supports these processes.Only Ductile materials are processed.

FORMING PROCESSIt is suited when:The part is to be formed from sheet metalThe part has no internal cavities.Long lengths of constant cross section are required.Seamless cup-shaped objects or cans are required.The component is to be made from material in wire or bar form.

FORMING PROCESSES ACCORDING TO MATERIAL TEMPERATURE

HOT WORKING PROCESSDeformation made in this process involves materials of Low surface area to thickness ratio. When metals are plastically deformed at temperature sufficiently above their re-crystallization temperature, the process is called hot working. Deformation and Re-crystallization occur simultaneously.Material is worked above its both Re-crystallization temperature and 0.6 times of its melting temperature.

COLD WORKING PROCESSWhen metals are plastically deformed at temperature below their re-crystallization temperature, the process is called cold working. Deformation processes under conditions where Recovery processes are not active.Working temperature is usually less than 0.3 times the work piece melting temperature.

WORM WORKING PROCESS Deformation processes under conditions of Transition i.e working temperature is between 0.3 and 0.6 times the work piece melting temperature.

ROLL FORGING OPERATIONFIGURE Schematic illustration of a roll forging (cross-rolling) operation. Tapered leaf springs and knives can be made by this process with specially designed rolls. Source: After J. Holub.

FLAT AND SHAPE ROLLING OPERATION

STAGES IN SHAPE ROLLING

RING ROLLINGFIGURE (a) Schematic illustration of a ring-rolling operation. Reducing the thickness results in an increase in the parts diameter. (b) Examples of cross-sections that can be formed by ring rolling.

THREAD ROLLING PROCESSFIGURE Thread-rolling processes: (a) flat dies and (b) two-roller dies. These processes are used extensively in making threaded fasteners at high rates of production.

EXTRUSION FIGURE Extrusion and examples of products made by sectioning off extrusions. Source: Kaiser Aluminum.FIGURE Schematic illustration of three different types of metal flow in direct extrusion.

TYPES OF EXTRUSIONFIGURE Types of extrusion. (a) direct; (b) indirect; (c) hydrostatic; (d) impact.

EXTRUSION OF COMPLICATED SHAPESFIGURE (a) An extruded 6063-T6 aluminum ladder lock for aluminum extension ladders. This part is 8 mm (5/16in.) thick and is sawed from the extrusion. (See Fig. (b) Components of various dies for extruding intricate hollow shapes. Source for (b)

DRAWINGFIGURE Variables in drawing round rod or wire.

TUBE DRAWINGFIGURE Various methods of tube drawing.

SWAGINGFIGURE Schematic illustration of the swaging process: (a) side view and (b) front view. (c) Schematic illustration of roller arrangement, curvature on the four radial hammers (that give motion to the dies), and the radial movement of a hammer as it rotates over the rolls.FIGURE Reduction of outer and inner diameters of tubes by swaging. (a) Free sinking without a mandrel. The ends of solid bars and wire are tapered (pointing) by this process in order to feed the material into the conical die. (b) Sinking on a mandrel. Coaxial tubes of different materials can also be swaged in one operation.

CROSS-SECTIONS PRODUCED BY SWAGINGFIGURE (a) Typical cross-sections produced by swaging tube blanks with a constant wall thickness on shaped mandrels. Rifling of small gun barrels can also be made by swaging, using a specially shaped mandrel. The formed tube is then removed by slipping it out of the mandrel. (b) These parts can also be made by swaging.

FORMING PROCESSES FOR ROCKET CASINGFIGURE The forming processes involves in the manufacture of solid rocket casings for the U.S. Space Shuttle.

SPACE SHUTTLE LAUNCH

FIGURE The Space Shuttle Atlantis is launched by two strap-on solid rocket boosters. Source:NASA

MACHININGPROCESSES

WHAT IS MACHININGRemoving material from a workpiece In the form of chips.As in case of MECHANICAL machining processes. Without formation of chips.As in case of NON-TRADITIONAL machining processes.

TYPES OF NTM PROCESSESCHEMICALChemical reaction b/w a liquid reagent and the w/p results in etching.MECHANICALHigh velocity abrasive or liquid or their mixture removes material.THERMALHigh temperatures in very localized regions evaporate material.ELECTOCHEMICALMaterial removal is resulted by an electrolytic reaction at w/p surface.

WATER JET CUTTING

JOINING PROCESSES

TYPES OF JOINING PROCESSES

OXY FUEL WELDINGUses heat from combustion (fire) between oxygen and a fuel

Filler metal may or may not be usedWhat type of weld is made without filler metal?Autogenous weld

OXYACETYLENE WELDINGMost common fuel used is acetylene

Oxyacetylene welding is flexible

ARC WELDINGUses an electric arc to coalesce metals

Arc welding is the most common method of welding metals

Electricity travels from electrode to base metal to ground

SHEILDED METAL ARC WELDINGArc is protected by the electrode coating

Also called Stick Welding

GAS METAL ARC WELDINGShielding gas protects arc between wire electrode and weldUses argon gas

Also called MIG welding

GAS TUNGSTUN ARC WELDINGArc is protected by gas surrounding the electrodeUses tungsten gas

Also called TIG Welding

FLUX CORED ARC WELDINGElectrode contains a flux center

Flux prevents harmful substances from forming on the weld

SUBMERGED ARC WELDINGArc travels between bare electrode and weld.

SAW (Submerged Arc Welding) The electric current arcs beneath the flux powder. When the flux melts, the weld bead appears

PLASMA ARC WELDINGArc travels between the tungsten electrode and weld.

RESISTANCE WELDING

Uses heat and pressure to bond metals

MECHANICAL FASTENERS

MAJOR CLASSES OF MECHANICA ASSEMBLY

Methods that allow for disassembly Example: threaded fasteners Methods that create a permanent joint Example: rivets

THREADED FASTENERSDiscrete hardware components that have external or internal threads for assembly of partsMost important category of mechanical assemblyIn nearly all cases, threaded fasteners permit disassemblyCommon threaded fastener types are screws, bolts, and nuts

SELF TAPPNING SCREWSDesigned to form or cut threads in a preexisting hole into which it is being turnedAlso called a tapping screwFigure: Selftapping screws: threadforming, and threadcutting

RIVETSUnthreaded, headed pin used to join two or more parts by passing pin through holes in parts and forming a second head in the pin on the opposite sideWidely used fasteners for achieving a permanent mechanically fastened jointClearance hole into which rivet is inserted must be close to the diameter of the rivet

Figure Five basic rivet types, also shown in assembled configuration: (a) solid, (b) tubular, (c) semitubular, (d) bifurcated, and (e) compression

INTERFACE FITSAssembly methods based on mechanical interference between the two mating parts being joinedThe interference, either during assembly or after joining, holds the parts together Interference fit methods include: Press fittingShrink and expansion fitsSnap fitsRetaining rings

SNAP FITSJoining of two parts in which mating elements possess a temporary interference during assembly, but once assembled they interlockDuring assembly, one or both parts elastically deform to accommodate temporary interferenceUsually designed for slight interference after assemblyOriginally conceived as a method ideally suited for industrial robots

ADHESIVE BONDING

It is the permanent joining of metals(similar or dissimilar), ceramics and composites thru the use of heat and filler metal.

Melting temperature of filler metal necessarily is above 4500C but lower than those of base metals.BRAZING

SOLDERING It is brazing type of operation where filler metal has a melting temperature below 4500C.

SURFACEPROCESSES

SURFACE PROCESSFrom the definition of manufacturing processes, surface processes are not among the basic manufacturing processes. But they are integral to them.Surface processes are carried out once all manufacturing processing is completed, with the exception of heat treatments.They are also called as finishing processes