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by: Sin Yong Tan

130

2

2

# ME324_Quiz_3_Study_Guide_or_Cheat_Sheet ME 324

Marketplace > Iowa State University > Mechanical Engineering > ME 324 > ME324_Quiz_3_Study_Guide_or_Cheat_Sheet
Sin Yong Tan
ISU
GPA 3.92

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Study guide that mainly focus on the theories on the materials. Only 3 main equations (C-rule, bernoullis and mass continuity) are included in this study guide. Good luck in Quiz 3!
COURSE
Manufacturing Engineering
PROF.
Dr. Chao Hu
TYPE
Study Guide
PAGES
2
WORDS
CONCEPTS
Manufacturing Engineering
KARMA
50 ?

## Popular in Mechanical Engineering

This 2 page Study Guide was uploaded by Sin Yong Tan on Sunday February 21, 2016. The Study Guide belongs to ME 324 at Iowa State University taught by Dr. Chao Hu in Spring 2016. Since its upload, it has received 130 views. For similar materials see Manufacturing Engineering in Mechanical Engineering at Iowa State University.

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Date Created: 02/21/16
Casting: Molten metalforce by gravitysolidify to the shape in cavity. It’s a process, but also the name of the part. Pros: Complex shape, external + internal, net shape, large part, mass produce Cons: limit mechanical properties, poor sur.fin. & dim. Accuracy, hot molten safety, envi. prob. Expendable: sand, plaster + binder Permanent: metal / ceramic refractory mat. Mold cavity : external Core: internal design Gating system: pouring cup(reduce turbulence & splash), downsprue, runner, main cavity Riser: Reservoir in the mold which is a source of liquid metal to compensate solidification shrinkage. PourLiquid Shrinkage(minimal effect)Solidification shrink(riser)thermal shrink(oversize: pattern shrinkage allowance) Solidification s.: reduction in volume per unit weight of metal Directional solidification: most distant freeze first, use C-rule design casting, orientation & riser. Put lower V/A away from riser Chills - internal or external heat sinks that cause rapid freezing in casting. External chill induce rapid freezing  avoid shrinkage cavity External Chills: placed in mold against the wall. Internal Chills: pushed into cores or the mold wall Expendable: complex but more time spent on making mold than cast Permanent: high production rate, but limited geometry (needa open) Sand casting step: make pattern and core, pin tghpour molten metal to sand moldsolidifybreak mold, remove castingclean and inspect(remove rise and gating syst.)heat treat/machining Shell molding: A match-plate or cope-drag metal pattern is heated and placed over a box containing sand mixed with thermosetting resinBox is inverted so that sand and resin fall onto the hot pattern, causing a layer of the mixture to partially cure on the surface to form a hard shellbox is repositioned so that loose uncured particles drop awaysand shell is heated in oven for several minutes to complete curingshell mold is stripped from the pattern; Pros: better sur.fin.& dim. acc, collapsibility minimize crack, mass production Cons: metal pattern more exp, difficult to justify small quantity Evaporative pattern: polystyrene patterndip in refractory slurryflask with unbonded sandVibrate&compactpourcool &remove sand Use metal mold/die to mass produce poly. pattern + divide into segment for complex shape&combine using hot-melt glue + full mold process: Green sand is compacted around the pattern and gating system Pros: x nid remove pattern, Simplifies and speeds mold-making, because two mold halves are not required as in a conventional green-sand mold Cons: new pattern for each casting + Economic justification of the process is highly dependent on cost of producing patterns Lost-Foam Casting: polystyrene beadsexpanded polystyrene pellets three foam pattern segmentsassembled and dipped polystyrene patternfinished metal casting (metal duplicate of the polystyrene pattern) Investment Casting (lost wax process): Wax patternattach to sprue to form pattern tree refractoryinvert, heat,melt waxpreheat cavity, pour & solidifybreak mold (Invest: refer to refractory coating) Pros: very complex&intricacy, good sur.fin&dim.acc, reuse wax, no machining required Cons: many steps + expensive Permanent mold casting: Basic permanent mold process: preheat + coated  put core + close mold pour & solidify Pros: good dim.& sur.fin, cold moldfaster coolingfiner grain structurestronger casting, reuseable mold Cons: for metal with low melting pt, high mold cost (used for mass prod. only) Die casting: inject molten metal to casting under HIGH PRESSURE. Pressure is maintained during solidification. Product is called DIEs. Hot chamber die-casting: high production rate Simple steps: lift plunger, metal flow in, plunger force metal to chamber, maintain pressure when cool Cold-chamber die casting: pull ram, pour, push ram&force metal into die, maintain pressure (Cold not as fast as hot) Hot: zinc, tin, lead, and magnesium Cold: Al, brass, & Mg alloys sur.fin, rapid coolingfiner grain &strong cast Pros: mass prod, good dim. acc& Cons: low melt.pt metal only, geometry must be removable frm mold Centrifugal casting: Mold rotated at high spd, centrifugal force distributes molten metal to outer regions of die cavity True centrifugal casting: Molten metal poured into rotating mold to produce tubular part (pipes, tubes, bushings, and rings). Outside shape of casting can be round, octagonal,hexagonal, etc , but inside shape is (theoretically) perfectly round, due to radially symmetric forces Semicentrifugal casting: Centrifugal force is used to produce solid castings rather than tubular parts. Molds are designed with risers at center to supply feed metal. Density of metal in final casting is greater in outer sections than at center of rotation. Often used on parts in which center of casting is machined away (wheels&pulley), thus eliminating the portion where quality is lowest. Centrifuge Casting: Mold is designed with part cavities located away from axis of rotation, so that molten metal poured into mold is distributed to these cavities by centrifugal force. Used for smaller parts. Radial symmetry of part is not required as in othercentrifugal casting methods Cold shots(gas bubles): Metal splatters during pouring and solid globules form and become entrapped in casting General defects: Misrun: solidify b4 complete filled Cold shut: flow tgh but lack fusion due to Shrinkage Cavity: premature freezing Hot tears: casting cannot shrink freely. Exothermic (heat-producing) compounds may be used (as exothermic padding) to control cooling at critical sections to avoid hot tearing. Casting design rule: (1) Use radii/fillets to avoid corners. (2) Deep cavities should be on one side of the casting where possible. (3) Wall sections should be uniform. (4) Ribs&/fillets improve bosses. (5) Slopping bosses can be designed for straight die parting to simplify die design. (6) Side cores can be eliminated with hole designs. Sand casting defects: Sand blow: release of mold gas Pin holes(porosity): Formation of many small gas cavities at or slightly below surface of casting Penetration: penetrate to sand mold, causing Surface to contain sand grain Mold shift: A step in cast product at parting line caused by sidewise relative displacement of cope and drag

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