Manufacturing Process Mid Term
4. The principal components of an injection molding machine are which two of the following: (a) clamping unit, (b) hopper, (c) injection unit, (d) mold, and (e) part ejection unit?
Clamping unit Injection unit
The upper half of a sand-casting mold is called which of the following: (a) cope or (b) drag?
Cope
2. Which of the following pure metals is the best thermal conductor:
Copper
2. Which one of the following types of stress strain relationship best describes the behavior of most metals at room temperature:
Elastic and strain hardening
1. A machine tool is a term developed during the Industrial Revolution, where it referred to electric-driven machines.
False
1. Chromium is the predominant alloying element in all of the stainless steels.
False
1. General-purpose equipment is more flexible and adaptable to a variety of jobs. It is not commercially available for any manufacturing company to invest in.
False
1. The range of carbon percentages that defines an iron carbon alloy as a steel ranges from 2.51% to 3.12.
False 0.02%-2.11% carbon
The forward movement of polymer melt in an extruder barrel is resisted by drag flow, which is caused by the resistance to flow through the die orifice: (a) true or (b) false?
False Drag flow is the forward motion of the melt caused by the Archimedian screw principle in the barrel. The resistance to forward flow is called back pressure flow.
4. The press-and-blow process is best suited to the production of (narrow-necked) beverage bottles, while the blow-and-blow process is more appropriate for producing (wide-mouthed) jars: (a) true, or (b) false?
False It's the reverse.
2. Some manufacturing processes that produce very good or excellent surface finishes (Four possible answers:)
Honing Superfinishing Lapping Polishing
4. The function of the ejection system is which one of the following: (a) move polymer melt into the mold cavity, (b) open the mold halves after the cavity is filled, (c) remove the molded parts from the runner system after molding, or (d) separate the part from the cavity after molding?
Separate the part from the cavity after molding
Silica sand has which one of the following compositions: (a) Al2O3, (b) SiO, (c) SiO2, or (d) SiSO4?
SiO2
1. Besides high carbon content, what other alloying element is characteristic of the cast irons?
Silicon
2. In the heating of most metal alloys, melting begins at a certain temperature and concludes at a higher temperature. In these cases, which of the following temperatures marks the beginning of melting:
Solidus
2. Which of the following are the three basic types of static stresses to which a material can be subjected (three correct answers)
Tensile Shear Compression
4. Which of the following processes are generally limited to thermoplastic polymers (two best answers): (a) blow molding, (b) compression molding, (c) reaction
Thermoforming Blow molding
1. What do bauxite and corundum have in common?
They are both minerals of alumina
3. Total solidification time is defined as which one of the following: (a) time between pouring and complete solidification, (b) time between pouring and cooling to room temperature, (c) time between solidification and cooling to room temperature, or (d) time to give up the heat of fusion?
Time between pouring and complete solidification
1. An element which is traditionally alloyed with copper to form bronze
Tin
2. A tolerance is which one of the following:
Total permissible variation from a specified dimension
1. An examples of Capital good:
Trucks and busses
1. The four types of permanent joining processes used in assembly are: welding, brazing, soldering, and adhesive bonding.
True
2. A three‑point bending test provides a measure called the transverse rupture strength for these materials.
True
2. Under what circumstances does the strength coefficient have the same value as the yield strength?
When the material is perfectly plastic and does not strain harden.
1. An element which is traditionally alloyed with copper to form brass
Zinc
4. Typical glass melting temperatures are in which of the following ranges: (a) 400°C to 500°C, (b) 900°C to 1000°C, (c) 1500°C to 1600°C, or (d) 2000°C to 2200°C?
1500°C to 1600c
2. What is the difference between a bilateral tolerance and a unilateral tolerance?
A bilateral tolerance allows variation in both positive and negative directions.
What are some of the limitations and disadvantages of casting?
Answer. Disadvantages include (1) limitations on mechanical strength properties; (2) porosity; (3) poor dimensional accuracy; (4) safety hazards due to handling of hot metals; and (5) environmental problems.
What is flash in die casting?
Answer. Flash is a thin portion of metal at the exterior of a casting that results from molten metal being squeezed into the spaces between the die halves of the mold at the parting line, or into the clearances around the cores and ejector pins.
What are some of the general defects encountered in casting processes? Name and briefly describe three.
Answer. General defects include: (1) misruns, in which the casting solidifies before filling the mold cavity; (2) cold shuts, in which two portions of metal flow together but there is lack of fusion at the joint; (3) cold shots, where solid globules of cast metal become entrapped in the casting; (4) shrinkage cavity, which is a depression on the casting surface or an internal void in the casting caused by solidification shrinkage; (5) microporosity, which is a network of small voids throughout the casting caused by localized solidification shrinkage; and (6) hot tearing, which is a crack in the casting caused by a mold that does not yield to the metal during the early stages of solidification shrinkage.
What does heat of fusion mean in casting?
Answer. Heat of fusion is the amount of heat energy required to transform the metal from solid state to liquid state.
Which die-casting machines usually have a higher production rate, cold-chamber or hot-chamber, and why?
Answer. Hot-chamber machines are faster because cold-chamber die casting machines require molten metal to be ladled into the chamber from an external source. Ladling takes more time than injecting the molten metal into the die as in the hot-chamber operation.
What is the difference between true centrifugal casting and semicentrifugal casting?
Answer. In true centrifugal casting, a tubular mold is used and a tubular part is produced. In semicentrifugal casting, the shape is solid; an example is a railway wheel. The mold is rotated so
What are some of the operations required in sand casting after the casting is removed from the mold?
Answer. The operations include (1) trimming, in which the sprues, runners, risers, and flash are removed, (2) core removal, (3) surface cleaning, (4) inspection, (5) repair if needed, (6) heat treatment, and (7) machining.
Name the two basic categories of casting processes
Answer. The two categories are (1) expendable mold processes, and (2) permanent mold processes.
What is the difference between vacuum permanent-mold casting and vacuum molding?
Answer. Vacuum permanent-mold casting is a form of low-pressure casting in which a vacuum is used to draw molten metal into the cavity. Vacuum molding is sand casting in which the sand mold is held together by vacuum pressure rather than by a chemical binder. 11.7 What are the most common metals used in die casting? Answer. Common die-casting metals include zinc, tin, lead, aluminum, b
A three-plate mold offers which of the following advantages when compared to a two-plate mold (two best answers): (a) automatic separation of parts from runners, (b) gating is usually at the base of the part to reduce weld lines, (c) sprue does not solidify, and (d) stronger molded parts?
Automatic separation of parts from runners Gating is usually at the base of the part to reduce weld lines
Which of the following are advantages of die casting over sand casting (four best answers): (a) better surface finish, (b) closer tolerances, (c) higher melting temperature metals, (d) higher production rates, (e) larger parts can be cast, and (f) mold can be reused?
Better surface finish, Closer tolerances, Higher production rates, mold can be reused
In sand casting, the volumetric size of the pattern is (a) bigger than, (b) same size as, or (c) smaller than the cast part?
Bigger than
1. The difference between the traditional ceramics and the new ceramics (one correct answer)?
Traditional ceramics are based primarily on clay products
Which of the following riser types are completely enclosed within the sand mold and connected to the main cavity by a channel to feed the molten metal (two correct answers): (a) blind riser, (b) open riser, (c) side riser, and (d) top riser
Answer. (a) and (c).
3. Which one of the following casting processes is the most widely used: (a) centrifugal casting, (b) die casting, (c) investment casting, (d) sand casting, or (e) shell casting?
Sand casting
What are some of the factors that affect the fluidity of a molten metal during pouring into a mold cavity?
Answer. The factors include (1) pouring temperature above the melting point, (2) metal alloy composition, (3) viscosity of the liquid metal, and (4) heat transfer to the surroundings.
Casting is a glassworking process used for (a) high production, (b) low production, or (c) medium production?
Answer. (b). Casting is used in glassworking for large components like giant telescope lenses in small lot sizes. It is a slow process for these large products.
In a sand-casting mold, the V/A ratio of the riser should be (a) equal to, (b) greater than, or (c) smaller than the V/A ratio of the casting itself?
Answer. (b).greater
If a glass part with a wall thickness of 5 mm (0.20 in) takes 10 minutes to anneal, how much time would a glass part of similar geometry but with a wall thickness of 7.5 mm (0.30 in) take to anneal (choose the one closest answer): (a) 10 minutes, (b) 15 minutes, (c) 20 minutes, or (c) 30 minutes?
Answer. (c). The rule is that annealing time varies as the square of the wall thickness. That would indicate an annealing time of (0.30/0.20)2 = 2.25 times 10 minutes or 22.5 minutes. 20 minutes is closest.
A thermoforming mold with a convex form is called which one of the following: (a) a die, (b) a negative mold, (c) a positive mold, or (d) a three-plate mold?
Answer. (c).a positive mold
Which one of the following processes or processing steps is not applicable in glassworking: (a) annealing, (b) pressing, (c) quenching, (d) sintering, and (e) spinning?
Answer. (d). Sintering is used to cause bonding of particulate materials such as metal and ceramic powders.
Chvorinov's rule states that total solidification time is proportional to which one of the following quantities: (a) (A/V)n, (b) Hf, (c) Tm, (d) V, (e) V/A, or (f) (V/A)2; where A = surface area of casting, Hf = heat of fusion, Tm = melting temperature, and V = volume of casting?
Answer. (f).(V/A)2
What is a eutectic alloy?
Answer. A eutectic alloy is a particular composition in an alloy system for which the solidus and liquidus temperatures are equal. The temperature is called the eutectic temperature. Hence, solidification occurs at a single temperature, rather than over a temperature range.
There are various types of patterns used in sand casting. What is the difference between a split pattern and a match-plate pattern?
Answer. A split pattern is a pattern that consists of two pieces; a match-plate pattern consists of the two split patterns attached to opposite sides of a plate.
What is the difference between an open mold and a closed mold?
Answer. An open mold is open to the atmosphere at the top; it is an open container in the desired shape which must be flat at the top. A closed mold has a cavity that is entirely enclosed by the mold, with a passageway (called the gating system) leading from the outside to the cavity. Molten metal is poured into this gating system to fill the mold.
What is the relationship known as Chvorinov's rule in casting?
Answer. Chvorinov's rule is summarized: TTS = Cm(V/A)2, where TTS = total solidification time, Cm = mold constant, V = volume of casting, and A = surface area of casting.
What is the continuity law as it applies to the flow of molten metal in casting?
Answer. The continuity law, or continuity equation, indicates that the volumetric flow rate is constant throughout the liquid flow.
What is the difference between a pattern and a core in sand molding?
Answer. The pattern determines the external shape of the cast part, while a core determines its internal geometry if the casting includes a cavity.
Name the two basic mold types that distinguish casting processes.
Answer. The two mold types are (1) expendable molds and (2) permanent molds.
What properties determine the quality of a sand mold for sand casting?
Answer. The usual properties are (1) strength - ability to maintain shape in the face of the flowing metal, (2) permeability - ability of the mold to allow hot air and gases to escape from the cavity, (3) thermal stability - ability to resist cracking and buckling when in contact with the molten metal, (4) collapsibility - ability of the mold to give way during shrinkage of the solidified casting, and (5) reusability - can the sand be reused to make other molds?
Why should turbulent flow of molten metal into the mold be avoided?
Answer. Turbulence causes the following problems: (1) it accelerates formation of oxides in the solidified metal, and (2) it causes mold erosion or gradual wearing away of the mold due to impact of molten metal.
Cupolas are furnaces used to melt which of the following metals (one best answer): (a) aluminum, (b) cast iron, (c) steel, or (d) zinc?
Cast iron
Besides helping to preserve the environment, the use of recycled glass as an ingredient of the starting material in glassmaking serves what other useful purpose (one answer): (a) adds coloring variations to the glass for aesthetic value, (b) makes the glass easier to melt, (c) makes the glass stronger, or (d) reduces odors in the plant?
Makes the glass easier to melt
3. A misrun is which one of the following defects in casting: (a) globules of metal becoming entrapped in the casting, (b) metal is not properly poured into the downsprue, (c) metal solidifies before filling the cavity, (d) microporosity, and (e) "pipe" formation?
Metal solidifies before filling the cavity
For which one of the following reasons is a green mold named: (a) green is the color of the mold, (b) moisture is contained in the mold, (c) mold is cured, or (d) mold is dry?
Moisture is contained in the mold,
The charge in glassworking is which one of the following: (a) the duration of the melting cycle, (b) the electric energy required to melt the glass, (c) the name given to the melting furnace, or (d) the starting materials in melting?
Starting materials in melting
How does solidification of alloys differ from solidification of pure metals?
Answer. Pure metals solidify at a single temperature equal to the melting point. Most alloys (exceptions are eutectic alloys) start to solidify at the liquidus and complete solidification occurs at the solidus, where the liquidus is a higher temperature than the solidus.
What is meant by the term superheat?
Answer. Superheat is the temperature difference above the melting point at which the molten metal is poured. The term also refers to the amount of heat that is removed from the molten metal between pouring and solidification.
What is the Antioch process?
Answer. The Antioch process refers to the making of the mold. The mold is 50% sand and 50% plaster heated in an autoclave and then dried. This mold has greater permeability than a plaster mold.
Identify the three sources of contraction in a metal casting after pouring.
Answer. The three contractions occur due to (1) contraction of the molten metal after pouring, (2) solidification shrinkage during transformation of state from liquid to solid, and (3) thermal contraction in the solid state.
Which one of the following casting metals is most important commercially: (a) aluminum and its alloys, (b) bronze, (c) cast iron, (d) cast steel, or (e) zinc alloys?
Cast iron
In rotational molding, centrifugal force is used to force the polymer melt against the surfaces of the mold cavity where solidification occurs: (a) true or (b) false?
It is the force of gravity in the doubly rotating mold that forces the polymer against the mold surfaces.
3. Investment casting is also known by which one of the following names: (a) fast-payback molding, (b) full-mold process, (c) lost-foam process, (d) lost-pattern process, or (e) lost-wax process?
Lost-wax process?
Identify some of the important advantages of shape-casting processes.
Answer. Advantages include (1) complex part geometries are possible; (2) some casting operations are net shape processes, meaning that no further manufacturing operations are needed to accomplish the final part shape; (3) very large parts are possible; (4) they are applicable to any metal that can be melted; and (5) some casting processes are suited to mass production.
Which of the following processes are associated with the production of plastic sheet and film (three correct answers): (a) blown-film extrusion process, (b) calendering, (c) chill-roll extrusion, (d) doctor blade method, (e) spinning, (f) thermoforming, and (g) transfer molding?
Blown-film extrusion process, Calendering, Chill-roll extrusion
Shell molding is best described by which one of the following: (a) casting operation in which the molten metal has been poured out after a thin shell has been solidified in the mold, (b) casting process in which the mold is a thin shell of sand bonded by a thermosetting resin, (c) sand-casting operation in which the pattern is a shell rather than a solid form, or (d) casting operation used to make artificial sea shells?
Casting process in which the mold is a thin shell of sand bonded by a thermosetting resin,
The parting line in injection molding is which one of the following: (a) the lines formed where polymer melt meets after flowing around a core in the mold, (b) the narrow gate sections where the parts are separated from the runner, (c) where the clamping unit is joined to the injection unit in the molding machine, or (d) where the two mold halves come together?
Where the two mold halves come together
Which of the following qualifies as a precision-casting process (two correct answers): (a) ingot casting, (b) investment casting, (c) plaster-mold casting, (d) sand casting, and (e) shell molding?
Investment casting, Plaster-mold casting
1. One of the major groups of metals
Nonferrous
1. The common alloying elements in low alloy steel are Cr, Mn, Mo, Ni, and V.
True
2. Precision in measurement is the degree to which random errors are minimized.
True
Given that Wm = weight of the molten metal displaced by a core and Wc = weight of the core, the buoyancy force is which one of the following: (a) downward force = Wm + Wc, (b) downward force = Wm - Wc, (c) upward force = Wm + Wc, or (d) upward force = Wm - Wc?
Upward force = Wm - Wc?
4. Use of a parison is associated with which one of the following plastic shaping processes: (a) bi-injection molding, (b) blow molding, (c) compression molding, (d) Answer. (b).pressure thermoforming, or (e) sandwich molding?
blow molding
What is a chill in casting?
Answer. A chill is a heat sink placed to encourage rapid freezing in certain regions of the casting.
What are the most common metals used in die casting?
Answer. Common die-casting metals include zinc, tin, lead, aluminum, brass, and magnesium.
Which casting process is the most important commercially?
Answer. Sand casting is the most important casting process.
1. Name the three basic categories of composite materials (three selections)
Metal matrix composites (MMCs) Polymer matrix composites (PMCs). Ceramic matrix composites (CMCs)
Which one of the following terms refers to the glassy state of a material: (a) crystalline, (b) devitrified, (c) polycrystalline, (d) vitiated, or (e) vitreous?
Vitreous
2. The tensile strength is the maximum load experienced during the tensile test multiplied by the original area
False
1. What are some of the important applications of nickel (three answers)?
As an alloying ingredient in steel To form nickel‑based alloys noted for high‑temperature performance For plating of steel to resist corrosion.
In plaster mold casting, the mold is made of which one of the following materials: (a) Al2O3, (b) CaSO4-H2O, (c) SiC, or (d) SiO2?
CaSO4-H2O
4. Which of the following are sections of a conventional extruder barrel for thermoplastics (three best answers): (a) compression section, (b) die section, (c) feed section, (d) heating section, (e) metering section, and (f) shaping section?
Compression section Feed section, and Metering section
2. Surface roughness is defined as the average value of the vertical deviations from the nominal surface over a specified surface area.
False
1. Some of the important applications of FRPs:
All are correct
1. One of the categories of engineering materials used in manufacturing?
All of the Answers
2. In a compression test, the specimen cross‑sectional area decreases as the test progresses; while in a tensile test, the cross‑sectional area increases.
False
2. Surface texture is an approximate deviations from the nominal surface, including roughness, waviness, lay, and flaws.
False
2. Viscosity can be defined as the ease with which a fluid flows.
False (Resistance)
1. The super alloys divide into three basic groups, according to the base metal used in the alloy. Name the three groups.
Iron‑based alloys Cobalt‑based alloys Nickel‑based alloys
2. Which one of the following materials has the highest hardness:
Alumina ceramic
3. Which of the following metals would typically be used in die casting (three best answers): (a) aluminum, (b) cast iron, (c) steel, (d) tin, (e) tungsten, and (f) zinc?
Aluminum, Tin, and Zinc
A lehr is which of the following: (a) a lion's den, (b) a melting furnace, (c) a sintering furnace, (d) an annealing furnace, or (e) none of the above?
Annealing furnace
In which of the following properties do plastic parts often compare favorably with metals (two best answers): (a) impact resistance, (b) resistance to ultraviolet radiation, (c) stiffness, (d) strength, (e) strength-to-weight ratio, and (f) temperature resistance?
Answer. (a) and (e).impact resistancestrength-to-weight ratio
Which of the following processes would be applicable to produce hulls for small boats (three best answers): (a) blow molding, (b) compression molding, (c) injection molding, (d) rotational molding, and (e) vacuum thermoforming?
Answer. (a), (d), and (e).blow moldingrotational moldingvacuum thermoforming
The term encapsulation refers to which one of the following plastics shaping processes: (a) casting, (b) compression molding, (c) extrusion of hollow forms, (d) injection molding in which a metal insert is encased in the molded part, or (e) vacuum thermoforming using a positive mold?
Answer. (a).casting
In foundry work, a runner is which one of the following: (a) channel in the mold leading from the downsprue to the main mold cavity, (b) foundryman who moves the molten metal to the mold, or (c) vertical channel into which molten metal is poured into the mold?
Answer. (a).channel in the mold leading from the downsprue to the main mold cavity,
Sand casting is which of the following types: (a) expendable mold or (b) permanent mold?
Answer. (a).expendable mold
In casting, a flask is which one of the following: (a) beverage bottle for foundrymen, (b) box which holds the cope and drag, (c) container for holding liquid metal, or (d) metal which extrudes between the mold halves?
Answer. (b).box which holds the cope and drag
During solidification of an alloy when a mixture of solid and liquid metals is present, the solid-liquid mixture is referred to as which one of the following: (a) eutectic composition, (b) ingot segregation, (c) liquidus, (d) mushy zone, or (e) solidus?
Answer. (d).mushy zone,
What is a cupola?
Answer. A cupola is a vertical cylindrical furnace equipped with a tapping spout near its base. Cupolas are used for melting cast irons.
What is a factory that performs casting operations usually called?
Answer. A foundry.
What is a chaplet?
Answer. Chaplets are metal supports of various designs used to hold the core in place in the sand mold.
2. Surface texture includes which of the following characteristics of a surface (three correct answers):
Deviations from the nominal surface Feed marks of the tool that produced the surface Surface cracks
Which of the following casting processes are permanent mold operations (three correct answers): (a) centrifugal casting, (b) die casting, (c) expanded polystyrene process, (d) sand casting, (e) shell molding, (f) slush casting, and (g) vacuum molding.
Centrifugal casting, Die casting, Slush casting
4. Which one of the following processes is used to produce glass tubing: (a) Danner process, (b) pressing, (c) rolling, or (d) spinning?
Danner process
Which of the following defects or problems is associated with injection molding (three correct answers): (a) bambooing, (b) die swell, (c) drag flow, (d) flash, (e) melt fracture, (f) short shots, or (g) sink marks?
Flash, Short shot, Sink marks
1. The feature that distinguishes glass from the traditional and new ceramics:
Glass is amorphous
2. Which one of the following manufacturing processes will likely result in the best surface finish:
Grinding
Which of the following casting processes are expendable mold operations (four correct answers): (a) centrifugal casting, (b) die casting, (c) investment casting, (d) low pressure casting, (e) sand casting, (f) shell molding, (g) slush casting, and (h) vacuum molding?
Investment casting, Sand casting, Shell molding, Vacuum molding
3. Turbulence during pouring of the molten metal is undesirable for which of the following reasons (two best answers): (a) it causes discoloration of the mold surfaces, (b) it dissolves the binder used to hold together the sand mold, (c) it increases erosion of the mold surfaces, (d) it increases the formation of metallic oxides that can become entrapped during solidification, (e) it increases the mold filling time, and (f) it increases total solidification time?
It increases erosion of the mold surfaces, It increases the formation of metallic oxides that can become entrapped during solidification
4. The two most common polymer foams are which of the following: (a) polyacetal, (b) polyethylene, (c) polystyrene, (d) polyurethane, and (e) polyvinylchloride?
Polystyrene and Polyurethane
1. The manufacturing industries are considered part of which of the following industry classifications:
Secondary
2. Which one of the following is the correct definition of ultimate tensile strength, as derived from the results of a tensile test on a metal specimen:
The maximum load divided by the original area of the specimen
1. Technological Processing Capability of a plant is:
The plant's available set of manufacturing processes
2. Which one of the following materials has the highest specific heat:
Water
3. A riser in casting is described by which of the following (three correct answers): (b) gating system in which the sprue feeds directly into the cavity, (c) metal that is not part of the casting, (d) source of molten metal to feed the casting and compensate for shrinkage during solidification, and (e) waste metal that is usually recycled?
source of molten metal to feed the casting and compensate for shrinkage during solidification waste metal that is usually recycled metal that is not part of the casting