417 Exam
53 flashcards · Other · by Dylan Matwe
What are factors impacing surface integreity
Strain hardening Cracks formed in low speedcutting Phase transition due to high temp (mettalurgical) Residual stress
Disvt of casting
Porosity caused by gas & contimainants Dimensional control is difficult Shrinkage due to solidifcation Poor surface texture Poor grain size (non uniform) Safety Hazard
Adv of casting metals
Work for some metals that are dfifficult to machine Large castings minimize metal scraps Complex shapes Any metal Mass production
What is a rise
A source of liquid metal to compensate shrinkage
What makes up the gating system in a mold
Cup, Spruce, Runner
What is a mold
Cope (Upper) and Drag (Bottom)
What is a Flask
Container for casting
What is dressing
Conditioning worn grains by producing new edges (like a grinding wheel)
What are the abrasive types
Alumium Oxide - Cheap + Hard Silicon Carbide - Good friablity CBN (Cubic Boron Nitride) - Self-sharpenign Diamond
Reasons for grinding
Convectional machining can't provide required accuracy Workpiece material is too hardy or too brittle Fine surface finish is required
Types of abrasive machining
Grinding, honing, lapping, buffing
How to avoid chatter?
Improve the stiffness of the workpiece-holding device Modify tool and cutter geometry cuttting fluids Change machine parameters (feed, speed, depth)_ Higher stiffness of the tool or damping capcity
What are the results of chatter
Poor surface finish Loud noise :( Premature chipping, tool breakage and wear Damage to machine
What can be done to avoid poor surface integrity factors
Careful selection and matinence of cutting tools and control of process conditions or post processign
What are the causes of chatter
Type of chips produced Inhomogeneities Surface Condition Fritcion at the tool-chip interface
What is chatter
Uncontrolled vibration due to the interaction between tool and workpiece
What is Sand Casting
Negative is made in sand and then filled with material
Patterns in sand casting
Used to mold the sand mixture into the shape of the casting
Cores in sand casting
Achieves the internal surface of the part
Chaplet
Metla supports that are used to anchor the chore of the part
What is Shell Casting
A mounted patern is heated, coated with a parting agent and clamped. A coating is formed that is and then it is cast. Has a very high dimensional accuracy
Evaporative Pattern Caqsting
Foam is used which evaporates when the hot metal touches it
What is hot chamber die casting?
The injection system is submerged under the molten metals
What is cold chamber die casting
External melting container, not in the injector
Categories of casting defects:
Metallic projections Flash Swells Rough Surface Cavities Blowholes Pinholes Shrinkage cavities Discontinuities Cracks, Cold or hot tearing Cold shunts Defective surface Surface folds laps scars oxide scales adhering sand layers Incomplete Casting Misruns incorrect dimensions or shape Improper shrinkage deformed parts, pattern mounting error Inclusions Oxygen slag FoD
Cold shot defect definition & solution
Splattering of metal created metal globules Sol: Modifying pouring procudes, adjusting gating system
Shrinkage Cavity def & sol
Due to denisty difference between solid and liquid Design gating system with a proper riser Increase local heat dissipation using chills Reduce casting temp
Misrun def & sol
Molten metal doesn't completely fill mold due to lack of fluidity Improve mold design and gating system
Sandblow definition and solution
Big voids beneath the surface, caused by mold gase and low permeabilty of mold Should dry out modls and core before use, increase gas permeabilty of sand modl and cores
Cold shunt definition and solution
Stream of metal from 2 gates solidify before thy can combines Need more fluidity and better gating system, increasing heat as well
Excessive metal casting defect
Casued by high velocity of molten metal which erodes the molding sand away fix with better gating system, and better mold design with more binder
Hot tear casting defect
Cracks appear to form in a branched patern caused by weak metal unable to resist tension during the cooling process fix by improving collapsibilty of mold, or removing parts immediatly after solidification
What is fusion welding
Arc Welding (AW) Resistance welding (RW) Oxyfuel welding (OFW) Laser Electrobeam
What is solid state welding
Has no melting, no fillers, no liquird Diffusion welding Friciton welding Ultrasonic welding
What is SMAW welding
Shielded metal arc welding consumable electroc
What is GMAW or MIG
Metal inert Gas Welding, uses a gas for welding Faster than SMAW
What is GTAW or TIG welding
Tungsten inert gas welding
What is wetting in brazing
When the metal is turned into a liquid
Aloyying and spreading
Determines the strength of the joint from No melting of the base occurs, just alloying of the filler metal
Pros of brazing
Any metals can be joined, very thin, no heat affected zone
Cons of brazing
Low strength, low service temp, color mismastchj
different between soldering and brazing
Soldering is a lower temperature
Charictaristics of thermoplastic
Reversible, weaker than thermosets, increase temp weakens
Charictaristics of thermosets
Non-Reversible Curing reaction Stronger
Vulcanization
Invented by goodyear curing of rubbers to allow them to resist sunlight and UV light
FDM printer
Normal 3d printing
SLA printer
Resing 3d printer
SLS printerin
Selective lasre sintering Metallic powders are melted into one parts
Powder Metallurgy
Make complex parts by compacting metal powders in dies and sintering them (heating without melting) to net- or near-net-shape products
What does the springback factor mean?
K_s = 1, no spring back (completely plastic) K_s = 0, full recovery (comply elastic)
PM List of Processes
Atomization Blending Compatction Sintering Finishing
What are the main parts of an injection molding machine
Screw Barrel Heating Clamp Hopper Molds
In injection molding, what are the essential die elements
Spruce, runners, gates, ejectors, core and cavity