Polymer Processors -
Thermosoftening
Injection Moulding: Polymer in granular form, heated to molten state, injected through a nozzle under pressure into water cooled mould. Mould constructed of two parts which open and eject the component.
Blow Moulding: Compressed air blown in molten polymer tube that expands outward.
Extrusion: Granular polymer, heated to molten state. Forced though a die onto a conveyor belt to cool.
Thermoforming: Thermoplastic sheets heated on mould surface and take mould profile.
Thermosetting
Transfer Moulding: Heated in a container then transferred to a mould by hydraulic plunger where it is compressed and cured.
Compression Moulding: Thermoset in granular form is placed in mould and subjected to heat and pressure, melts and takes shape. Continued till cured.
Surface coating
Calendering
Ferrous Forming and Working Processors
HOT
Rolling: Metal is past between a gap in two rolls above recrystallisation temp. Improved ductility, removal of voids, improved mechanical properties, scale.
Forging: Compression of material between die surfaces.
Extrusion: Direct and indirect. Forcing hot metal billet through and maintaining cross section of die. Heatsinks, antennae, aluminium solid and hollow. Good surface quality/accuracy, but dedicated expensive equipment.
Drawing: Blank forced though a die hydraulically or mechanically, many times. Pipes.
COLD
Forging: Compressive forces causing plastic deformation resulting in improved strength due to grain flow. Upset bolt heads.
Impact Extrusion: Article formed by single blow, low strength metals only, cans.
Hydrostatic Extrusion: Fluid used to transmit pressure from ram to billet. Aluminium.
Drawing: Article pushed through die, then pulled through with tongs. Passes through successively smaller dies. Work hardens so needs annealing. Wire.
Rolling: Same as hot, below recrystallisation temp. Increased hardness/strength, reduced ductility, retention of residual stress, good surface finish.
POWDER FORMING
Making of powder. Pressing in mould. Sintering final product. Removing scale. No machining, minimal scrap, complex shapes, un-alloyable materials. Inferior strength, expensive dies to resist high pressure, powder materials expensive.
Heat Treatments
Annealing: Removal of work hardening and internal stresses, increase in ductility. Heat above recrystallisation temp, soak, cool under equilibrium. Cold worked metals.
Process annealing: Removal of work hardening stress, increase ductility. Heat to juts below LCT and cool. Cold worked LCS.
Normalising: Removal of work hardening effects and internal stresses with retention of fine grains. Heat into austenitic range, soak, air cool. Cold worked/machined L/MCS.
Tempering: Reduces brittleness in hardened steels by reverting martensite to pearlite. Heat to below LCT and cool slow. Structure depends on soaking time. Hardened steels.
Quench hardening: Achieves maximum hardness. Heat to austenitic range, soak, quench. M/HC and Tool Steels.
-Austempering: Hardens without developing martensite. Austenitise, quench to martensite region, soak till bainite transformation completed. HC/Tool Steels.
-Martempering: Avoids quench cracking when hardening. Austenitise, quench to martensite region, hold, then quench to room temp before bainite transformation. HCS/Tool Steels.
Surface Hardening: Hard skin with soft centre.
-Carburising
-Nitriding
-Selective Hardening
Casting Processors
Sand Casting: Temporary mould, made from sand and binders. Top half cope, bottom drag. Large grains, low strength., low cost for few casts, intricate easy patters, poor as-cast finish.
Shell Moulding: Similar to sand casting, but bound together by polymer material.
Permanent Casting: Metal mould, similar to sand casting, but mould can be used lots. Low cost when high number of casts, design changes costly, improved surface finish, faster cooling rate, small grains, better mechanical properties.
Die Casting: Injection of molten metal under pressure into metal mould/die. Low cost when high number of casts, design change costly, high initial cost, good surface finish,
Investment Casting: Was pattern made then sand/plaster are poured in for mould. Wax melts out leaving cavity for molten metal. Small accurate components.
Centrifugal Casting: Casting is spun about axis as molten metal is poured in. Dense hollow objects.
Continuous Casting: Molten steel poured from ladle into ‘tundish’ then to water cooled mould. Then exits in continuous strand where water cools it as it moves along to further processes. Low waste, fast.
Testing of Materials
NON DESTRUCTIVE
X-ray: Expose ray onto and through the specimen with a radioactively sensitive film set behind it to impose an image of the internal structure and flaws.
Gamma Ray: Same as X-ray, but portable.
Magnetic Particle: Iron fillings sifted on specimen and subjected to a magnetic field. Magnetic flux is locally distorted by the presence of discontinuity. Fast and effective for surface & subsurface defects in ferromagnetic materials of any shape.
Ultrasonic: High frequency sound waves and echo off the internal structure of the specimen. Recognises small defects and is estimates location & size of flaw.
Visual inspection: The basic principle is to examine the specimen with the eye. is Simple, quickly carried out and usually low in cost, experience sometimes needed.
Acoustic Emission: Similar to ultrasonic but listens for internal imperfections instead of probing.
Dye Penetrant: Wipe surface with a fluorescent dye. View with a ultraviolet light to allow surface flaws to become eminent.
Eddy current inspection:Inducing eddy currents into the specimen and observing the interaction between the article and the currents on a display screen. Well suited for the detection of service induced cracks, i.e. fatigue.
DESTRUCTIVE
Tension: Clamp sample at either end and apply uniaxial separating load. Load and extension plotted on graph.
Compression: Uniaxial load applied in compression. Fail in hourglass, shear plane or shear cone.
Transverse: Place specimen on two fulcrum supports applying load, measuring deflections
Notched Bar Impact
-Izod: Test piece held vertical, with notch facing specimen. Izod
-Charpy: Test piece held horizontal, with notch facing away.
Fatigue: Cyclic loads.
Hardness: Tests resistance of material to scratching, abrasion, indentation. Indenter pressed into a material with a known load then depth of indentation is measured.
-Brinell: Hardened steel/tungsten carbide, ball.
-Rockwell: Diamond cone, or hardened steel ball.
-Vickers: Diamond pyramid.
Shear
Ductility
Torsion
Erichsen Cupping Test
Bend Test