manufacturing exam 1
(SI units) Machinability ratings are to be determined for a new work material using the cutting speed for a specified tool life as the basis of comparison. For the base material (B1112 steel), test data resulted in Taylor equation parameter values of n = 0.24 and C = 450, where speed is m/min and tool life is min. For the new material, the parameter values were n = 0.28 and C = 490. Cemented carbide tools were used. Compute machinability ratings for the new material using as the tool life criterion (a) 60 min, (b) 10 min, and (c) 1.0 min. (d) What do the results show about the difficulties in machinability measurement?
(a) Base material: v60 = 450/600.24 = 168.4 m/min New material: v60 = 490/600.28 = 155.7 m/min MR = 155.7/168.4 = 0.925 = 92.5% (b) Base material: v10 = 450/100.24 = 259.0 m/min New material: v10 = 490/100.28 = 257.2 m/min MR = 257.2/259.0 = 0.993 = 93.3% (c) Base material: v1 = 450/10.24 = 450 m/min New material: v1 = 490/10.28 = 490 m/min MR = 490/450 = 1.089 = 108.9% (d) Different test conditions often result in different machinability results
identify some of the important advantages of shape-casting processes
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 geometry 3. very large parts are possible 4. casting is applicable to any metal that can be melted 5. some casting processes are suited to mass production
Identify the three sources of contraction in a metal casting after pouring
1. contraction of the molten metal after pouring 2. solidification shrinkage during transformation of state from liquid to solid 3. thermal contraction in the solid state
Name the two basic mold types that distinguish casting processes
1. expendable molds 2. permanent molds
what are some of the disadvantages of casting
1. limitations on mechanical strength properties 2. porosity 3. poor dimensional accuracy and surface finish for some casting processes 4. safety hazards due to handling of hot metals and 5. environmental problems
what are some of the factors that affect the fluidity of a molten metal during pouring into a mold cavity
1. pouring temperature above the melting point 2. metal alloy composition 3. viscosity of the liquid metal 4. heat transfer to the surroundings
the heat required to raise the temperature of a metal to the required level for casting is the sum of what three energy components
1. the heat to raise the temperature to the melting point 2. the heat of fusion to convert it from solid to liquid 3. the heat to raise the molten metal to the desired temperature for pouring
(SI units) Machinability ratings are to be determined for a new steel. For the base material (B1112), test data resulted in Taylor equation parameters n = 0.28 and C = 500. For the new material, the Taylor parameters were n = 0.25 and C = 430. Cutting speed units are m/min, and tool life units are min. The tooling was cemented carbide. (a) Compute machinability ratings for the new material using the following criteria: (a) cutting speed for a 30-min tool life and (b) tool life for a cutting speed of 150 m/min.
: (a) Base material: v30 = 500/30.28 = 192.9 m/min New material: v30 = 430/30.25 = 183.7 m/min MR = 183.7/182.8 = 0.95 = 95%
What is meant by the designation 30 cm ´ 90 cm (12 in ´ 36 in) lathe
A 30 cm ´ 90 cm (12 in ´ 36 in) lathe has a 30 cm (12 in) swing (maximum work diameter that can be accommodated) and a 90 cm (36 in) distance between centers (indicating the maximum work length that can be held between centers).
What is a blind hole
A blind hole does not exit the work; by comparison, a through hole exits the opposite side of the work part
What is the difference between a live center and a dead center, when these terms are used in the context of workholding in a lathe
A center holds the workpiece at the tailstock end of the lathe. A live center is mounted in bearings and rotates with the work, while a dead center does not rotate ‑ the work rotates about it
Name two departments that are typically classified as manufacturing support departments.
A common organizational structure includes the following three manufacturing support departments: (1) manufacturing engineering, (2) production planning and control, and (3) quality control.
What is the difference between a pattern and a core?
A core is a full-scale model of the interior surfaces of the part, inserted into the mold cavity prior to pouring, so that the molten metal will flow and solidify between the mold cavity and the core to form the casting's external and internal surfaces.
What is a cupola?
A cupola is a vertical cylindrical furnace equipped with a tapping spout near its base. Cupolas are used for melting cast irons.
What is the difference between fixed costs and variable costs?
A fixed cost remains constant for any level of production output, whereas variable costs are paid for as they are used. The cost of the factory and equipment are fixed costs. Direct labor and materials that are used to produce the product are variable costs.
What is a factory that performs casting operations called?
A foundry
What is a machine tool?
A machine tool can be defined as a power-driven machine that positions and moves a tool relative to the work to accomplish machining or other metal shaping process.
What is a machining center
A machining center is a CNC machine tool capable of performing multiple types of cutting operations involving rotating spindles (e.g., milling, drilling); the machine is typically equipped with automatic tool‑changing, pallet shuttles to speed work part changing, and automatic work part positioning
What is the difference between a machining center and a turning center
A machining center is generally confined to rotating spindle operations (e.g., milling, drilling); while a turning center performs turning type operations, generally with single-point tools
What is a pattern in sand casting?
A pattern is a full-sized model of the part, enlarged to account for shrinkage and machining allowances in the final casting.
What are the differences between primary, secondary, and tertiary industries? Give an example of each category
A primary industry is one that cultivates and exploits natural resources, such as agriculture or mining. A secondary industry takes the outputs of primary industries and converts them to consumer and capital goods. Examples of secondary industries are textiles and electronics. A tertiary industry is in the service sector of the economy. Examples of tertiary industries are banking and education.
What is the difference between a process layout and a product layout in a production facility?
A process layout is one where the machinery in a plant is arranged based on the type of process it performs. To produce a product it must visit the departments in the order of the operations that must be performed. This often includes large travel distances within the plant. A process layout is often used when the product variety is large and the operation sequences of products are dissimilar. A product layout is one where the machinery is arranged based on the general flow of the products that will be produced. Travel distance is reduced because products will generally flow to the next machine in the sequence. A product layout works well when all products tend to follow the same sequence of production operations.
In manufacturing processes, what is the difference between a processing operation and an assembly operation?
A processing operation transforms a work material from one state of completion to a more advanced state that is closer to the final desired product. It changes the geometry, properties, or appearance of the starting material. In general, processing operations are performed on discrete work parts, but certain processing operations are also applicable to assembled items (e.g., painting a spot-welded car body). An assembly operation joins two or more components to create a new entity, called an assembly, subassembly, or some other term that refers to the joining process (e.g., a welded assembly is called a weldment)
What is the distinguishing feature of a radial drill press
A radial drill has a long radial arm along which the drill head can be positioned to allow the drilling of large work parts. The radial arm can also be swiveled about the column to drill parts on either side of the worktable
Explain the difference between roughing and finishing operations in machining
A roughing operation is used to remove large amounts of material rapidly and to produce a part geometry close to the desired shape. A finishing operation follows roughing and is used to achieve the final geometry and surface finish.
There are various types of patterns used in sand casting. What is the difference between a split pattern and a match-plate pattern?
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 threading and tapping?
A threading operation is performed on a turning machine and produces an external thread, while tapping is normally performed on a drilling machine and produces an internal thread
What is a tool-chip thermocouple?
A tool-chip thermocouple is comprised of the tool and chip as the two dissimilar metals forming the thermocouple junction. As the tool-chip interface heats up during
How does a turret lathe differ from an engine lathe
A turret lathe has a tool-holding turret in place of a tailstock; the tools in the turret can be indexed to perform a sequence of different cutting operations on the work without the need to change tools as in operating a conventional engine lathe
Manufacturing processes are usually accomplished as unit operations. Define unit operation.
A unit operation is a single step in the sequence of steps required to transform the starting material into a final product. A unit operation is generally performed on a single piece of equipment that runs independently of other operations in the plant
What are some of the typical applications of steel?
Applications of steel include construction (e.g., bridges, I-beams, and nails), transportation (trucks, rails, and rolling stock for railroads), and consumer products (automobiles and appliances).
What are some of the tool life criteria used in production machining operations?
As identified in the text, tool life criteria used in production include (1) complete failure of the tool, (2) visual observation of flank or crater wear by the machine operator, (3) changes in the sound emitted by the tool, (4) degradation of surface finish, (5) power increase, (6) workpiece count, and (7) length of cutting time for the tool.
What are the three basic categories of material removal processes?
As organized in this text, the three basic categories of material removal processes are (1) conventional machining, (2) abrasive processes, and (3) nontraditional processes.
What is meant by the term availability?
Availability is a reliability term which is simply the proportion uptime of the equipment
Define batch production and describe why it is often used for medium-quantity production.
Batch production is where groups, lots, or batches of materials or parts are processed together through the manufacturing operations. All units in the batch are processed at a given station before the group proceeds to the next station. In a medium or low quantity production situation, the same machines are used to produce many types of products. Whenever a machine switches from one product to another, a changeover occurs. The changeover requires the machine setup to be torn down and set up for the new product. Batch production allows the changeover time to be distributed across a larger number of parts and hence reduce the average operation time per part.
How does a boring operation differ from a turning operation?
Boring produces an internal cylindrical shape from an existing hole, while turning produces an external cylindrical shape
Why are ceramic cutting tools generally designed with negative rake angles?
Ceramics possess low shear and tensile strength but good compressive strength. During cutting, this combination of properties is best exploited by giving the tool a negative rake angle to load the tool in compression.
What is a chaplet?
Chaplets are metal supports of various designs used to hold the core in place in the sand mold.
What are the common metals used in die casting?
Common die-casting metals include zinc, tin, aluminum, brass, and magnesium
What is the difference between consumer goods and a capital goods? Give some examples in each category
Consumer goods are products purchased directly by consumers, such as cars, personal computers, TVs, tires, and tennis rackets. Capital goods are those purchased by companies to produce goods and/or provide services. Examples of capital goods include aircraft, computers, communication equipment, medical apparatus, trucks and buses, railroad locomotives, machine tools, and construction equipment
Why do costs tend to increase when better surface finish is required on a machined part?
Costs tend to increase when better surface finish is required because additional operations such as grinding, lapping, or similar finishing processes must be included in the manufacturing sequence.
What are the parameters of a machining operation that are included within the scope of cutting conditions?
Cutting conditions include speed, feed, depth of cut, and whether or not a cutting fluid is used.
Which cutting speed is always lower for a given machining operation, cutting speed for minimum cost or cutting speed for maximum production rate? Why?
Cutting speed for minimum cost is always lower because of the fourth term in the unit cost equation, which deals with the actual cost of the cutting edge. This term tends to push the U-shaped function toward a lower value in the case of cutting speed for minimum cost.
Generating refers to creating part geometry using the feed trajectory of the cutting tool; examples include straight turning, taper turning, and profile milling. Forming involves creating part geometry using the shape of the cutting tool; common examples include form turning and drilling.
Distinguish between generating and forming when machining part geometries
In analyzing the costs in a casting operation, there is a basic difference in the way mold fabrication is treated between expendable mold processes and permanent mold processes. What is the difference?
Expendable molds are produced sequentially with the other steps because each casting requires its own mold. The mold cost is a component in the total cost to produce each casting. With permanent mold processes, the mold is an expensive piece of specialized tooling that is used for many castings; its cost is apportioned over the total quantity of parts made throughout the life of the mold.
What is flash in die casting?
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.
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 is the difference between special purpose and general purpose production equipment?
General-purpose equipment is more flexible and adaptable to a variety of jobs. It is commercially available for any manufacturing company to invest in. Special-purpose equipment is usually designed to produce a specific part or product in very large quantities. Another reason may be because the process is unique and commercial equipment is not available. Some companies with unique processing requirements develop their own special purpose equipment.
Which die-casting machines usually have a higher production rate, cold-chamber or hot-chamber, and why?
Hot-chamber machines are faster because cold-chamber die casting machines require molten metal to be ladled into the chamber each cycle 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 in ingredients between steel cutting grades and nonsteel-cutting grades of cemented carbides?
In general, non-steel cutting grades contain only WC and Co. Steel cutting grades contain TiC and/or TaC in addition to WC-Co.
How are product variety and production quantity related when comparing typical factories?
In general, production quantity is inversely related to product variety. A factory that produces a large variety of products will produce a smaller quantity of each. A company that produces a single product will produce a large quantity
What is investment casting?
In investment casting, a pattern made of wax is coated with a refractory material to make the mold, after which the wax is melted away prior to pouring the molten metal. The term investment comes from one of the less familiar definitions of the word invest, which means "to cover completely," this referring to the coating of the refractory material around the wax pattern.
What distinguishes material removal processes from other manufacturing processes?
In material removal processes, material is cut away from the work part so that the remaining material has the desired part geometry
What is the difference between peripheral milling and face milling?
In peripheral milling, the axis of the tool is parallel to the surface being machined, and the operation is performed by cutting edges on the outside periphery of the cutter. In face milling, the axis of the cutter is perpendicular to the surface being milled, and machining is performed by cutting edges on both the end and outside periphery of the cutter
What is the difference between true centrifugal casting and semicentrifugal casting?
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 that centrifugal force is used to distribute the molten metal to the exterior of the mold so that the density of the final metal is greater at the outer sections
Describe the difference between up milling and down milling
In up milling, the cutter speed direction is opposite the feed direction; in down milling, the direction of cutter rotation is the same as the feed direction
Define machinability.
Machinability can be defined as the relative ease with which a material can be machined using an appropriate cutting tool under appropriate cutting conditions.
Why can diamond cutting tools not be used to machine steel and other ferrous metals?
Machining steel and other ferrous metals with SPD tools is not practical because of the chemical affinity that exists between these metals and carbon, because diamond is carbon.
Name the various ways in which a work part can be held in a lathe
Methods of holding the work in a lathe include: (1) between centers, (2) chuck, (3) collet, and (4) face plate
What is the difference between net shape processes and near net shape processes?
Net shape processes are manufacturing processes that transform nearly all of the starting material into product and require no subsequent machining to achieve final part geometry. Near net shape processes are ones that require minimum machining to produce the final shape
Why is the orthogonal cutting model useful in the analysis of metal machining?
Orthogonal cutting is useful in the analysis of metal machining because it simplifies the rather complex three-dimensional machining situation to two dimensions. In addition, the tooling in the orthogonal model has only two parameters (rake angle and relief angle), which is a simpler geometry than a single-point tool.
What is an orthogonal cutting operation?
Orthogonal cutting uses a wedge-shaped tool in which the cutting edge is perpendicular to the direction of speed motion as the tool is forced into the work material.
What are overhead costs in a manufacturing company?
Overhead costs consist of all of the expenses of operating the company other than material, direct labor, and equipment
What is pocket milling
Pocket milling uses an end milling cutter to machine a shallow cavity (a "pocket") into a flat work part
What are the principal alloying ingredients in high-speed steel?
Principal alloying ingredients in HSS are (1) either tungsten or a combination of tungsten and molybdenum, (2) chromium, (3) vanadium, and (4) carbon. Some grades of HSS also contain cobalt.
Describe profile milling
Profile milling generally involves the milling of the outside periphery of a flat part
21.1 What are the geometric differences between rotational parts and prismatic parts in machining?
Rotational parts are cylindrical or disk‑shaped and are machined on a turning machine (e.g., a lathe); prismatic parts are block‑shaped or flat and are generally produced on a milling machine, shaper, or planer.
What is a shell molding?
Shell molding is a casting process in which the mold is a thin shell, typically 9 mm (3/8 in) made of sand held together by a thermosetting resin binder. The surface of the shell-mold cavity is smoother than a conventional green-sand mold, and this smoothness permits easier flow of molten metal during pouring and better surface finish on the final casting.
What is the difference between soft product variety and hard product variety, as these terms are defined in the text?
Soft product variety is when there are only small differences among products, such as the differences among car models made on the same production line. In an assembled product, soft variety is characterized by a high proportion of common parts among the models. Hard product variety is when the products differ substantially, and there are few common parts, if any. The difference between a car and a truck exemplifies hard variety
What is the specific energy in metal machining?
Specific energy is the amount of energy required to remove a unit volume of the work material.
What is the definition of steel?
Steel can be defined as an iron-carbon alloy containing 0.02% to 2.11% carbon. Its composition often includes other alloying elements as well, such as manganese, chromium, nickel, and molybdenum, to enhance the properties of the metal.
Name some of the steps that can be taken to reduce or eliminate vibrations in machining.
Steps to reduce vibration in machining include (1) increase stiffness or damping in the setup; (2) operate at speeds away from the natural frequency of the machine tool system; (3) reduce forces in machining by changing feed or depth, and (4) change the cutter design to reduce forces (e.g., reduce rake angle)
what is meant by the term superheat
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?
The Antioch process refers to the making of a mold that is 50% sand and 50% plaster, heated in an autoclave and then dried. This mold has greater permeability than a plaster mold.
Describe in words what the Merchant equation tells us.
The Merchant equation states that the shear plane angle increases when rake angle is increased and friction angle is decreased.
what does heat of fusion mean in casting
The amount of heat required to solidify the metal from the liquid state
What is the chemical formula of the ceramic material used in almost all ceramic cutting tools?
The chemical formula is Al2O3 for aluminum oxide.
Identify some of the common compounds that form the thin coatings on the surface of coated carbide inserts.
The common coatings are: TiN, TiC, and Al2O3.
What is the expanded-polystyrene casting process?
The expanded-polystyrene casting process uses a mold of sand packed around a polystyrene foam pattern that vaporizes when the molten metal is poured into the mold. The foam pattern includes the sprue, risers, and gating system, and it may also contain internal cores (if needed), thus eliminating the need for a separate core in the mold.
What are the factors on which the selection of feed in a machining operation should be based?
The factors are (1) type of tooling (e.g., a cemented carbide tool should be used at a lower feed than a high-speed steel tool), (2) whether the operation is roughing or finishing (e.g., higher feeds are used in roughing operations), (3) cutting forces limitations that would require lower feeds, and (4) surface roughness requirements.
What are the basic factors that affect surface finish in machining?
The factors that affect surface finish are (1) geometric factors such as type of operation, feed, and tool shape (nose radius in particular); (2) work material factors such as built-up edge effects, and tearing of the work surface when machining ductile materials, which are affected by cutting speed; and (3) vibration and machine tool factors such as setup and work part rigidity, and backlash in the feed mechanism
Name the four categories of cutting fluid according to chemistry.
The four categories of cutting fluids according to chemistry are (1) cutting oils, (2) emulsified oils, (3) chemical fluids, and (4) semi-chemical fluids.
What are the four categories of engineering materials used in manufacturing?
The four categories of engineering materials are (1) metals, (2) ceramics, (3) polymers, and (4) composite materials, which consist of non-homogeneous mixtures of the other three types.
One of the three general types of processing operations is shaping operations, which are used to create or alter the geometry of the work part. What are the four categories of shaping operations?
The four categories of shaping operations are (1) solidification processes, in which the starting material is a heated liquid or semifluid that cools and solidifies to form the part geometry; (2) particulate processing, in which the starting material is a powder, and the powders are formed and heated into the desired geometry; (3) deformation processes, in which the starting material is a ductile solid (commonly metal) that is deformed to shape the part; and (4) material removal processes, in which the starting material is a solid (ductile or brittle), from which material is removed so that the resulting part has the desired geometry
Identify the four forces that act on the chip in orthogonal cutting but cannot be measured directly in an operation.
The four forces that act on the chip are (1) friction force at the tool-chip interface, (2) normal force to friction, (3) shear force at the shear plane, and (4) normal force to shear.
Name and briefly describe the four types of chips that occur in metal cutting.
The four types are (1) discontinuous, in which the chip is formed into separate segments; (2) continuous, in which the chip does not segment and is formed from a ductile metal; (3) continuous with built-up edge, which is the same as (2) except that friction at the tool-chip interface causes adhesion of a small portion of work material to the tool rake face, and (4) serrated, which are semi-continuous in the sense that they possess a saw-tooth appearance that is produced by a cyclical chip formation of alternating high shear strain followed by low shear strain.
Identify the four types of permanent joining processes used in assembly
The four types are welding, brazing, soldering, and adhesive bonding
The unit cost in a machining operation is the sum of four cost terms. The first three terms are: (1) cost of time the tool is actually cutting the work, (2) part load/unload cost, and (3) cost of the time to change the tool. What is the fourth term?
The fourth term is the cost of the tool itself (purchasing the tool and grinding it, if applicable).
What are the parameters that have the greatest influence in determining the ideal surface roughness Ri in a turning operation?
The ideal surface roughness is determined by the following geometric parameters of the machining operation: (1) tool nose radius and (2) feed. In some cases, the end cutting edge and end cutting edge angle of the single-point tool affects the feed mark pattern on the work surface.
Identify the mechanisms by which cutting tools wear during machining
The important tool wear mechanisms are (1) abrasion, (2) adhesion, (3) diffusion, (4) chemical reactions, and (5) plastic deformation of the cutting edge.
What are the criteria by which machinability is commonly assessed in a production machining operation?
The machinability criteria include (1) tool life, (2) forces and power, (3) surface finish, and (4) ease of chip disposal.
What are some of the operations required in sand casting after the casting is removed from the mold?
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
What is the physical interpretation of the parameter C in the Taylor tool life equation?
The parameter C is the cutting speed corresponding to a one-minute tool life. C is the speed-axis intercept on the log-log plot of the tool life data
What is the physical interpretation of the parameter n in the Taylor tool life equation?
The parameter n is the slope of the log-log plot of the tool life data. It indicates how strongly tool life is affected by cutting speed.
How is the power required in a cutting operation related to the cutting force?
The power required in a cutting operation is equal to the cutting force multiplied by the cutting speed.
Name some of the important mechanical and physical properties that affect the machinability of a work material.
The properties mentioned in the text include hardness, strength, and ductility.
Identify some of the reasons why machining is commercially and technologically important.
The reasons include the following: (1) it is applicable to most materials; (2) it can produce a variety of part geometries; (3) it can achieve closer tolerances than most other processes; and (4) it can create good surface finishes
What is the relationship between the coefficient of friction and the friction angle in the orthogonal cutting model?
The relationship is that the coefficient of friction is the tangent of the friction angle ( mu = tan beta ).
Name the seven elements of tool geometry for a single-point cutting tool.
The seven elements of single-point tool geometry are (1) back rake angle, (2) side rake angle, (3) end relief angle, (4) side relief angle, (5) end cutting edge angle, (6) side cutting edge angle, and (7) nose radius
What does the term size effect mean in metal cutting?
The size effect refers to the fact that the specific energy increases as the cross-sectional area of the chip (to x w in orthogonal cutting or f x d in turning) decreases.
One of the dimensions of manufacturing capability is technological processing capability. Define technological processing capability
The technological processing capability of a plant (or company) is its available set of manufacturing processes. Certain plants perform machining operations, others roll steel billets into sheet stock, and others build automobiles. The underlying feature that distinguishes these plants is the processes they can perform. Technological processing capability includes not only the physical processes, but also the expertise possessed by plant personnel in these processing technologies.
What is meant by the term castability and upon what factors does it depend?
The term castability refers to the ease with which a cast part can be produced. It depends on (1) the part design, (2) the metal used for the casting, and (3) the proper selection of casting process to economically satisfy production requirements.
What is the difference between cemented carbides and cermets used as cutting tools in machining?
The term cermet in cutting tool technology refers to ceramic-and binder combinations other than WC-Co and WC-TiC-TaC-Co, which are known as cemented carbides, although technically, cemented carbides satisfy the general definition of a cermet.
What is a machine tool?
The term developed during the Industrial Revolution, when it referred to powerdriven machines used to operate cutting tools previously operated by hand. Modern machine tools are described by the same basic definition, except that the power is electrical rather than water or steam, and the level of precision and automation is much greater today
Define manufacturing
The text defines manufacturing in two ways: technologically and economically. Technologically, manufacturing is the application of physical and chemical processes to alter the geometry, properties, and/or appearance of a given starting material to make parts or products; manufacturing also includes assembly of multiple parts to make products. Economically, manufacturing is the transformation of materials into items of greater value by means of one or more processing and/or assembly operations. The key point is that manufacturing adds value to the material by changing its shape or properties, or by combining it with other materials.
Name the three most common machining processes.
The three common machining processes are (1) turning, (2) drilling, and (3) milling.
Name the three modes of tool failure in machining.
The three tool failure modes are (1) fracture failure, (2) temperature failure, and (3) gradual wear
Name the two basic categories of casting processes.
The two categories are (1) expendable mold processes, and (2) permanent mold processes.
Name and define the two categories of overhead costs in a manufacturing company
The two categories are (1) factory overhead and (2) corporate overhead. Factory overhead consists of the costs of running the factory excluding materials, direct labor, and equipment. This overhead category includes plant supervision, maintenance, insurance, heat and light, and so forth. Corporate overhead consists of company expenses not related to the factory, such as sales, marketing, accounting, legal, engineering, research and development, office space, utilities, and health benefits
What are the two basic categories of cutting tools in machining? Give an example of machining operations that use each tooling type
The two categories are (1) single-point tools, used in operations such as turning; and (2) multiple-edge cutting tools, used in operations such as milling and drilling.
Identify the two forces that can be measured in orthogonal cutting.
The two forces that can be measured in the orthogonal cutting are (1) cutting force in the direction of cutting speed and (2) thrust force, which is perpendicular to cutting force. Thrust force is the force that causes the cutting edge to penetrate beneath the surface of the work.
Name the two main categories of cutting fluid according to function
The two functional categories of cutting fluids are: (1) coolants and (2) lubricants
What are the two principal aspects of cutting-tool technology?
The two principal aspects of cutting tool technology are (1) tool material and (2) tool geometry.
How does a universal milling machine differ from a conventional knee‑and‑column machine
The universal milling machine has a worktable that can be rotated about a vertical axis to present the part at any specified angle to the cutter spindle
What properties determine the quality of a sand mold for sand casting?
The usual properties are (1) strength - ability to maintain shape in the face of the flowing metal, (2) permeability - ability 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 to give way during shrinkage of the solidified casting, and (5) reusability - can the sand be reused to make other molds?
Identify the three alternative ways of holding and presenting a cutting edge for a singlepoint cutting tool during machining.
There are three principal ways: (1) solid shank, in which the cutting edge is an integral part of the tool shank, an example being high speed steel tooling; (2) brazed inserts, used for some cemented carbides; and (3) mechanically clamped inserts, used for most hard tool materials including cemented carbides, coated carbides, cermets, ceramics, SPD, and CBN.
What are the principal lubricating mechanisms by which cutting fluids work?
There are two lubricating mechanisms that are believed to be effective in metal cutting: (1) boundary lubrication, which involves the formation of a thin fluid film to help
What is the difference between a thermoplastic polymer and a thermosetting polymer?
Thermoplastic polymers can be subjected to multiple heating and cooling cycles without substantially altering the molecular structure of the polymer. Thermosetting polymers chemically transform (cure) into a rigid structure on cooling from a heated plastic condition.
Identify three desirable properties of a cutting-tool material.
Three desirable properties are (1) toughness to resist fracture failure, (2) hot hardness to resist temperature failure, and (3) wear resistance to prolong the life of the tool during gradual wear.
Describe the turning process
Turning is a machining process in which a single-point tool removes material from the surface of a rotating cylindrical workpiece, the tool being fed in a direction parallel to the axis of work rotation
What is vacuum permanent-mold casting?
Vacuum permanent-mold casting is a form of low-pressure casting in which a vacuum is used to draw molten metal into the cavity
What are the two principal locations on a cutting tool where tool wear occurs?
Wear occurs on the top face of the cutting tool as crater wear and on the side or flank of the tool, called flank wear.
what is a eutectic alloy
a particular composition in an alloy system for which the solidus and liquidus temps are equal; aka the eutectic temp. Therefore solidification occurs at a single temp rather than over a temp range
What is the difference between an open mold and a closed mold
an open mold is open to the atmosphere at the top it is an open container in the desired shape which must be flat 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 into the cavity. Molten metal is poured into this gating system to fill the mold.
what is bernoulli's theorem
bernoulli's theorem states that the sum of the energies (head, pressure, kinetic, friction) at any two points in a flowing liquid are equal
How does solidification of alloys differ from solidification of pure metals?
pure metals solidify at a single temperature equal to the melting point. most alloys (not 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
Which casting process is the most important commercially?
sand casting
what is the continuity law as it applies to the flow of molten metal in casting
the law / equation states that the volumetric flow rate remains constant throughout the liquid
what is meant by the term mushy zone during solidification of a metal alloy
the mushy zone is a mixture of solid and liquid metal that occurs while the temperature of the metal is between the liquidus and solidus for the alloy
what is the difference between a pattern and a core in sand molding
the pattern determine the external shape of the cast part while a core determined its internal geometry if the casting includes a cavity
what is the relationship known as chvorinov's rule in casting
total solidification time = mold constant (V_casting/A_caastingsurface)^2
Why should turbulent flow of molten metal into the mold be avoided?
turbulence causes the following problems 1. it accelerates formation of oxides in the solidification metal 2. it causes mold erosion or gradual wearing away of the mold due to impact of the molten metal
