Manufacturing Exam 2
What is stretch forming
forming of sheet metal of simultaneously stretching and bending to achieve shape
Why are specific energy values so much higher in grinding than in traditional machining processes such as milling
1. Smaller particles have higher specific energy 2. Extremely negative rake angles 3. Not all grains are working to cut, some are just creating friction
24.3 What are the principal abrasive materials used in grinding wheels
1. aluminum oxide 2. silicon carbide 3. cubic boron nitride 4. diamond
24.1 Why are abrasive processes technologically and commercially important
1. applications on all types of materials 2. very fine finishes 3. Close tolerances
Identify the three basic types of sheet metalworking
1. cutting 2. bending 3. drawing
What are 2 basic categories of structural frames used in stamping presses
1. gap frame 2. straight-sided frame
What are the three mechanisms of grinding wheel waer
1. grain fracture 2. attritious wear 3. bond failure
What are the functions of grinding fluid
1. reducing friction 2. removing heat 3. removing chips 4. reduce temperature
24.4 Name some important bonding materials used in grinding wheels
1. vitrified bond clay/ceramics 2. silicate 3. rubber 4. resinoid 5. shellac 6. metallic
What are some possible defects in drawn sheet metal parts
1. wrinkling 2. tearing 3. earing 4. surface scratches
21.6 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).
5.2 What is the difference between a bilateral tolerance and a unilateral tolerance?
A bilateral tolerance allows variation in both positive and negative directions from the nominal dimension, whereas a unilateral tolerance allows the variation from the nominal dimension to be either positive or negative, but not both.
21.10 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.
21.8 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.
What abrasive material would one select for grinding a cemented carbide cutting tool
A diamond wheel
20.8 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.
21.17 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.
21.18 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.
20.7 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.
21.4 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.
5.1 What is a tolerance?
A tolerance is defined as the total amount by which a specified dimension is permitted to vary.
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
21.9 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.
How does abrasive belt grinding differ from conventional surface grinding operation
Abrasive particles are on a belt which is moved around a pulley system to accomplish grinding
5.3 What is accuracy in measurement?
Accuracy is the degree to which the measured value agrees with the true value of the quantity of interest. It is a measurement that is absent of systematic errors.
5.5 What is meant by the term graduated measuring device?
Answer. A graduated measuring device has markings (called graduations) on a linear or angular scale to measure an object's feature of interest (e.g., length).
5.14 What causes the various types of changes that occur in the altered layer just beneath the surface?
Answer. Energy input to the surface resulting from the manufacturing process used to generate the surface. The energy forms can be any of several types, including mechanical, thermal, chemical, and electrical.
5.4 What is precision in measurement?
Answer. Precision in measurement is the degree to which random errors are minimized.
5.9 How is surface texture distinguished from surface integrity?
Answer. Surface texture refers only to the surface geometry; surface integrity includes not only surface but the subsurface layer beneath the surface and the changes in it.
5.6 What are some of the reasons why surfaces are important?
Answer. The reasons why surfaces are important include aesthetics, safety, friction and wear, effect of surface on mechanical and physical properties, mating of components in assembly, and as electrical contacts.
22.15 Name the seven elements of tool geometry for a single-point cutting tool
Answer. 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.
22.7 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.
20.1 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.
21.5 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.
How can high temperatures be harmful in grinding
Can create surface burns and cracks, as well softens metal that have been heat treated for high hardness
22.16 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.
5.15 What are the methods for assessing surface roughness?
Common methods for assessing surface roughness are (1) comparison of the specimen surface with standard test blocks having known surface roughness values, (2) stylus type electronic instruments which measure average roughness, and (3) optical techniques (e.g., light reflectance, lasers).
What is bend allowance intended to compensate
Compensates for stretching of sheet metal that occurs in a bending operation
23.4 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.
20.6 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.
23.10 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.
What is centerless grinding
Cylindrical work parts are fed between two rotating wheels, can be high speed and low speed
What is springback in sheet metal bending
Elastic recovery of the sheet metal after bending
How does creep feed grinding differ from conventional
For creep feed, depths are thousand times lower as well as feed rate
21.2 Distinguish between generating and forming when machining part geometries.
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.
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
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.
21.11 What is the distinguishing feature of a radial drill press?
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.
21.12 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.
21.15 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.
What is a wheel structure
Indicates the relative spacing of the abrasive grains. Open structure means grains are spaced far apart. Dense structure means grains are spaced close together
What is Wheel Grade
Is ability to retain the grains in the wheel. Depends on the bond strength and material. A hard wheel will retain grains better than a soft wheel
23.1 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.
22.14 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
21.7 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 a notching operation and a seminotching operation
Notching remove a piece from the side of the sheet while seminotching removes an interior portion
20.10 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
20.9 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
21.14 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.
What is dressing, in reference to grinding wheels
Procedure to break off old grits and expose new ones
5.16 Name some manufacturing processes that produce very poor surface finishes.
Processes that produce poor surfaces include sand casting, hot rolling, sawing, and thermal cutting (e.g., flame cutting).
5.17 Name some manufacturing processes that produce very good or excellent surface finishes.
Processes that produced very good or excellent surfaces include honing, lapping, polishing, and superfinishing.
21.13 Describe profile milling.
Profile milling generally involves the milling of the outside periphery of a flat part.
What is truing in grinding wheels
Restores wheel to cylindrical shape using diamond pointed tool
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.
5.10 Within the scope of surface texture, how is roughness distinguished from waviness?
Roughness consists of the finely spaced deviations from the nominal surface, while waviness refers to the deviations of larger spacing. Roughness deviations lie within waviness deviations.
What is Guerin Process
Sheet metal forming that uses rubber die that flexes to force sheet metal to take shape of block
5.11 Surface roughness is a measurable aspect of surface texture; what does surface roughness mean?
Surface roughness is defined as the average value of the vertical deviations from the nominal surface over a specified surface length.
5.12 Indicate some of the limitations of using surface roughness as a measure of surface texture.
Surface roughness provides only a single measure of surface texture. Among its limitations are: (1) it varies depending on direction; (2) it does not indicate lay; (3) its value depends on the roughness width cutoff used to measure the average.
5.8 Define surface texture.
Surface texture is the random and repetitive deviations from the nominal surface, including roughness, waviness, lay, and flaws.
20.17 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.
23.7 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).
20.15 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.
5.13 Identify some of the changes and injuries that can occur at or immediately below the surface of a metal.
The changes and injuries include residual stresses, surface hardening or softening, cracks, craters, heat affected zones, inclusions of foreign particles, and intergranular attack of chemicals.
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 are the five basic parameters of a grinding wheel?
The parameters are 1. Abrasive material 2. grit size 3. bonding material 4. whell structure which refers to the relative spacing of grains 5. wheel grade with refers to the bond strength of the wheel
20.16 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.
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.
23.5 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
22.19 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.
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.
20.11 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.
23.9 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).
23.6 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
22.4 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.
23.2 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.
5.7 Define nominal surface.
The nominal surface is the ideal part surface represented on an engineering drawing. It is assumed perfectly smooth, perfectly flat if referring to a planar surface, perfectly round if referring to a round surface, etc.
22.6 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
22.5 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.
23.3 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
20.3 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.
20.14 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 = tanB ).
20.18 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 w in orthogonal cutting or f d in turning) decreases.
22.11 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.
Name the three most common machining processes.
The three common machining processes are (1) turning, (2) drilling, and (3) milling
22.2 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
20.5 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.
20.13 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.
22.1 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.
21.16 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.
22.17 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.
22.20 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
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.
21.3 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 an embossing operation
Used to create indentations in sheet metalworking
Define drawing in the context of sheet metalworking
Used to produce cup shaped or box shaped parts
Describe each of the two types of sheet metal-bending operations: V-bending and edge bending
V-bending uses punch and die with angle, edge bending uses punch forces over a die edge to obtain bend angle
22.3 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.
In sheet metalworking operations, what is the name of the tooling and what is the name of the machine tool used in the operations
a) punch and die b) stamping press
What are the relative advatages and disadvantages of mechanical presses versus hydraulic presses in sheet metalworking
advantage of mech- faster cycle rates. advantage of hyd- longer ram strokes and uniform force
What is the difference between a cutoff operation and a parting operation
cutoff separates each part by shearing one edge of each part in sequence. Parting is cuts out a slug
Name some abrasive operations available to achieve good surface finishes
honing, lapping, superfinshing, buffing, polishing
In blanking of circular sheet metal part, is clearance applied to punch diameter or the die diamter
punch diamter is smaller by twice the die diameter
What is the difference between redrawing and reverse drawing
redrawing - shape change is significant it must be carried out in two steps with annealing. Reverse- two draws on a part in one direction and an opposite directions
What is the difference between roll bending and roll forming
roll bending involves large sheet and plate metal sections into curved forms. roll forming involves feed metal into a series of rotating rolls