418 Manufacturing

What distinguishes material removal process from other manufacturing process

Involves material removal. Starts with large part, then material is removed, then finished part is produced

What is the difference between natural aging and artificial aging in precipitation hardening

Natural aging - done at room temp Artificial aging - done at elevated temps

The stresses and strains in metal forming are of which type, elastic or plastic

Platic

What are some of the general considerations the product designers must keep in mind when designing components out of plastic.

Shrinkage Cooling time Number of pouring points in the mold

What are some of the design recommendations for glass parts

corners should have large Radii NO SHARP POINTS

What are the benefits of increasing the shear plane angle in machining

increasing the shear plane angle the lower the shear force

How does the Knoop hardness test work

used for brittle materials- Pyramidal diamond point is pressed into test material for a certain time. Equation HK = 14.2*(F/D^2)

What is the type of deformation by which a chip is formed in metal machining?

Shear Deformation

Describe the forging process

When a work piece is pressed between two dies so die shape is imparted on work piece

By what failure method do brittle materials such as ceramics fail in bending tests?

Cleavage - Separations occurs rather then slip along crystallographic planes

What are the advantages of welding compared to other types of assembly operations

Creates a permanent Joint Very Economical No additional hardware required

What properties determine the quality of a sand mold for casting?

Strength, permeability, thermal stability, reusability

What is the heat-affected zone (HAZ) in a fusion-weld joint in which filler metal has been added?

The location where the metal has experienced temperatures below the melting point but high enough to cause micro-structural changes in the solid metal.

Why is friction in metal forming different from friction encountered in most mechanical systems such as gear trains, shafts in bearings, and other components involving relative motions between surfaces?

The metal forming environment features high pressure between a hardened tool and a soft work piece, plastic deformation of the softer material and high temperatures.

What are the two basic methods of arc shielding

(1) Shielding gas, such as argon and helium (2) flux, which covers the welding operation and protects the molten pool from the atmosphere.

What is the difference between a live center and a dead center, when these terms are used in the context of work holding in a lathe?

1. A live center rotates in a bearing in the tailstock, so that there is nor relative rotation between the work and the live center; hence no friction between the center and the workpiece. 2. A dead center is fixed to the tail stock, so that it doesn't rotate: instead the workpiece rotates about it.

Identify some of the reasons why machining is commercially and technologically important.

1. Can be used on a variety of work materials 2. Can make a variety of part shapes and geometric features 3. Produces good dimensional accuracy 4. Good surface finishes

What is an important precondition for the success of an adhesive bonding operation

1. Cleanliness of the surface

What are the two main categories of cutting fluid according to function?

1. Coolant type - usually water based 2. Lubricants - usually oil-based

Dry machining is being considered by machine shops because of certain problem inherent in the use of cutting fluids. What are those problems associated with the use of cutting fluids?

1. Cutting fluid disposal 2. contamination 3. filtration

Distortion (warping) is a serious problem in fusion welding, particularly arc welding. What are some of the techniques that can be used to reduce the incidence and extent of distortion?

1. Fixture 2. heat sinks 3. Welding Speed

Identify the selective surface-hardening methods.

1. Flame hardening 2. Electro Beam 3. laser 4. high frequency resistance heating 5. induction hardening

What are some of the design guidelines for weldments that are fabricated by arc welding?

1. Good fit-up of parts 2. need enough room for the welding gun 3. design should allow flat welding to be performed

What are some of the advantages of cold working relative to warm and hot working?

1. Greater accuracy( better tolerances) 2. Better surface finish 3. Higher strength and hardness due to strain hardening 4. No heating of work is required. (saves money)

What are the reasons why fusion welding operations are inherently dangerous?

1. High heat(burns), 2. fumes, 3. dangerous gases (explosions), 4. high voltage, 5.arc flash(blindness)

Distinguish between generating and forming when machining part geometries.

1. In generating the geometry of the work part is determined by the feed trajectory of the cutting tool. The path followed by the tool during its feed motion is imparted to the work surface in order to create shape 2. In forming the shape of the part is created by the geometry of the cutting tool. In effect, the cutting edge of the tool has the reverse of the shape to be produced on the part surface. Examples include drilling, form turning, and broaching.

What are some of the disadvantages and limitations of brazing

1. Joints aren't as strong as welded joints 2. Can't be used in high temperature situations. 3. Appearance Filler metal may be a different color then the materials being joined.

What are the factors that affect weldability

1. Melting point 2. thermal conductivity 3. Reactivity 4. surface condition

What are the four categories of engineering materials used in manufacturing? Provide a brief description.

1. Metals - usually an alloy, composed of two or more elements, at least one being metallic. 2. Ceramics - a compound containing metallic or semi metallic and a nonmetallic element 3. Polymers - is a compound formed of repeating structural units called mers, whose atoms share electrons to form large molecules. 4. Composites - is a material consisting of two or more phases that are processed separately and then bonded together to achieve properties superior to those of its constituents.

What are the three basic categories of inspection and testing techniques used for weldments? Name some typical inspections and/or tests in each category.

1. NDT - Non destructive testing (x-ray, ultrasound, 2. DT - destructive testing (strength) 3. Visual inspection ( look for cracks, undercut, inclusions, penetration, warping)

Identify some of the advantages of adhesive bonding compared to alternative joining methods.

1. No heat 2. Can join different material 3. simply part(no holes)

What is the difference between a notching operation and a seminotching operation?

1. Notching involves cutting out a portion of metal from the side of the sheet or strip. 2. Seminotching removes a portion of metal from the interior of the sheet.

What are some of the limitations of adhesive bonding

1. Requires extremely clean surfaces 2. long curing time 3. not good in prying conditions.

Why is friction undesirable in metal forming operations

1. Restricts metal flow 2. It increases forces that are needed 3. Increases tool wear

Explain the difference between roughing and finishing operations in machining.

1. Roughing cuts are used to remove large amounts of material from the starting material from the starting work part as rapidly as possible. Produces a shape close to the desired form, but leaves some material on the piece for a subsequent finishing operation. 2. Finishing cuts are used to complete the part and achieve the final dimensions, tolerances and surface finish

What are the two basic categories of cutting tools in machining. Give at least one example of machining operations that used each tooling type

1. Single Point Tools - Lathe 2. Multi-point Tools - Drilling and face milling

Under what circumstances might brazing or soldering be preferred over welding?

1. Some metals have poor weldability 2. joining different materials 3. When parts can't withstand the heat of welding.

Identify four types of permanent joint processes

1. Welding 2. Brazing 3. Soldering 4. Adhesive bonding

Identify the three major categories of sheet metal working operations

1. cutting 2. Bending 3. Drawing

Identify the two forces that can be measured in orthogonal cutting

1. cutting force 2. thrust force

Identify some of the general principles and guidelines for design for assembly.

1. design the product with as few parts as possible 2. Reduce the number of threaded fasteners 3. Use Standardized fasteners 4. Design parts to be symmetrical 5. Avoid parts that tangle

What are some of the advantages of warm working relative to cold working

1. less force required 2. More intricate shapes can be made 3. No need for annealing

List the advantages often attributed to soldering as an industrial joining process

1. uses less energy then brazing and welding 2. many ways to heat the material 3. good electrical and thermal conductivity

What is the approximate temperature at which glass is melted

1500-1600 degree Celsius

What is a hemming operation in sheet metalworking

180 degree bend at the end to reduce the sharpness of the edge

In factory welding operations, a welder often works with a fitter. What is a fitter? What is the difference between a welder and a fitter? Why would someone have the two separate positions?

A fitter arranges the parts before the weld happens. Welders are skilled labor while fitters are unskilled A fitter can maximize the amount of time the welder is able to weld

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 turret press in sheet metalworking

A press with a variety of punches and dies

Define resistance welding.

A process that applies pressure and current to weld ( spot welding )

What is the difference between a thermoplastic and a thermosetting polymer

A thermoplastic can be heated and cooled multiple times while a thermosetting plastic becomes cured and can't be recycled

How does nitriding work?

A treatment in which nitrogen is diffused into the surfaces of special alloy steels to produce a thin hard casing without quenching.

What is a shear pin

A type of mechanical fastener that is pressed into a hole of a part. Made of softer metals to allow a failure under sudden load to save the rest of the assembly. Acts as a fuse

What is martensite?

A unique phase consisting of an iron-carbon solution whose composition is the same as the austenite from which it was derived.

Identify some of the common compounds that form the thin coatings on the surface of coated carbide inserts

Al2O3 TiN TiC

Define tool life as the term applies to machining

Amount of time a tool can cut and provide the needed quality

What are overhead costs in manufacturing

Are the expenses of operating the company other then material, labor, and equipment. 1. Factory overhead 2. Corporate overhead

What is the effect of carbon content on the machinability of steel?

As the carbon content increases the strength and hardness of the steel increases, reducing the machinability of the steel

Why is cleanliness of the joint surfaces so important in brazing?

Because if the surface isn't clean the filler material will stick to the debris instead of the actual material

Why should turbulent flow of molten metal into the mold be avoided

Can cause erosion of the sand Sand can get into the mold affecting the quality of the mold Can lead to the formation of oxides

Identify some of the important advantages of shape-casting processes.

Can make complex shapes Suitable for mass production Can be done on any metal that can be melted.

Why is a six-spindle bar machine more productive then a single-spindle bar machine.

Can produce 6 parts at a time.

What is the chip load in a milling operation

Chip thickness per tooth

Why is it difficult to deliver cutting fluid to the point of a conventional twist drill during a drilling operation

Chips flows up and can bring the fluid up with it

identify the mechanisms by which cutting tools wear during machining

Diffusion, abrasion, fracture, plastic deformation, adhesion, chemical reactions

Define drawing in the context of sheet metalworking.

Drawing is a sheet-metal-forming operation used to make cup-shaped. Box-shaped, or other complex-curved and concave parts. It is performed by placing a piece of sheet metal over a die cavity and then pushing the metal into the opening with a punch.

Which of the following welding processes produce the highest power density, resistance welding or electron beam welding?

Electron Beam Welding

State Hooke's law

Equation 3.3 ( s=Ee )

What is explosive forming in sheet metalworking?

Explosive forming involves the use of an explosive charge to form sheet metal into a die cavity.

Describe the extrusion process.

Extrusion is a compression process in which the work material is forced to flow through a die opening to produce a part with a cross-sectional shape that is the same as the shape of the die opening. Like toothpaste flowing out of the tube.

Broaching is performed using a rotating multi-tooth cutting tool, true or false?

False

In form milling of gear teeth, each gear tooth is milled individually by a form-milling cutter whose cutting edges have the shape of the gear tooth, true or false.

False

Of the two parameters that have the greatest influence on the ideal surface roughness Ri in a turning operation, which one has the greatest influence

Feed Rate

Why is a spade drill preferable to a twist drill for a large diameter holes such as 100mm (4.0 in)?

First of all so much metal is required in the drill bit and the amount of mass in the spade bit is much less than that of the twist bit.

In which category is a broaching operation classified, generating or forming

Forming

What is friction stir welding (FSW), a

Friction Stir Welding - a solid-state welding process in which a rotating tool is rotated along the joint line between the two work-pieces, generating friction heat and mechanically stirring the metal to form the weld seam.

What are the two types of structural frame used in stamping presses?

Gap frame and the straight sided Frame press.

In which category is taper turning classified, generating or forming

Generating

Identify three desirable properties of a cutting-tool material

Hardness- resistance to wear Toughness- doesn't fracture Heat resistance - doesn't become ductile @high temps

Electron-beam welding has a significant disadvantage in high-production applications. What is that disadvantage?

Has to be done in a vacuum and involves radiation(x-ray). EXPENSIVE

When a solid metallic element is heated to its melting temperature, it requires a certain amount of heat to transform tho the liquid phase

Heat of Fusion

For what kinds of cutting tools is high-speed steel especially suitedd

High detailed tools (tools with complex geometry)

How is a product variety and production quantity related

High variety => low production quantity

Is the hardness of cemented carbides higher or lower than the hardness of high-speed steel?

Higher

What are the three functions of the clamping unit during the injection molding cycle?

Hold the two parts together To keep the mold closed To open and close the mold

What is the difference between internal broaching and external broaching?

Internal broaching is accomplished on the internal surface of a hole in the part while external broaching is accomplished on the external surface of the workpiece. Both have a purpose of creating a certain cross-sectional shape.

What does the term soaking mean?

Is a process that is used to hold the metal at a certain temperature for a required time.

Why can diamond cutting tools not be used to machine steel and other ferrous metals?

It can not be used because of the chemical affinity that exists between ferrous metals and carbon(diamond is a carbon)

What is the distinguishing feature of a radial drill press?

It is a large drill press designed to cut holes in large parts; it has a radial arm along which the drilling head can be moved and clamped

What is a flux, used in arc shielding

It is a material that is used to help protect the weld from impurities, and prevents oxidations.

Gear hobbing is basically which of the following types of machining operations: grinding, milling, or shaping.

It is a milling operation but is much more complex.

Is the elastic modulus of cemented carbides higher or lower than the hardness of high-speed steel?

Lower

Define machinability.

Machinability can be defined as the relative ease with which a material can be machined

Define manufacturing. What are the categories of manufacturing?

Manufacturing- is the making of articles on a large scale using machinery; industrial production 1. Technological : Creation of Parts 2. Economical : Taking already made parts and creating something more useful.

What production quantity range is cellular manufacturing most closely associated

Medium Quantity production (100-10,000 units)

A stress-strain relationship that exhibits behavior that is elastic and perfectly plastic is characteristic of what types of materials.

Metal when heated to sufficiently high temperatures (above Recrystallization )

Why are metals better conductors then ceramics and polymers

Metals have electrons in their outer shell that can move freely ( They form a "sea" of electrons rather then orbiting the atom.)

What are some of the general defects encountered in sand casting process? Name and describe at least three

Misruns- castings that solidify before completely filling the mold. Cold shuts - occurs when two portions of the metal flow together but don't fuse together Cold shots - the result from splattering during pouring causes solid gobules of metal be become entrapped in the casting.

What is pearlite

Mixture of ferrite and carbide that forms thin parallel plates

Describe the melting characteristics of a non-crystalline material such as glass.

No definite melting point, it continually transforms from the solid state to the viscous plastic state

What is the difference between processing and assembly operation

Processing- uses energy to alters a work part shape, physical properties, or appearance to add value to the material. Assembly is when two or more separate parts are joined to form a new entity.

In blanking of a circular sheet-metal part, is the clearance applied to the punch diameter or the die diameter

Punch Diameter

What is the purpose of a tapping operation?

Putting threads in a hole

When a punch and die are mounted in a press, is the punch attached to the ram or the bolster plate of the press

Ram

Name the machining operation that is sometimes used after a drilling operation to achieve tighter tolerances on the hole diameter and improve surface finish

Reaming

Why are cutting fluid filter systems becoming more common, and what are their advantages?

Removal of contaminants from the fluid

What are the disadvantages of welding compared to other types of assembly operations?

Requires skilled labor Permanent Lots of heat Dangerous Quality (defect can be hard to detect)

what is hardness and how is it generally tested?

Resistance to permanent indentation tested by the Brinell and Rockwell hardness test

Which casting process is the most important commercially?

Sand Casting

What are some of the operation required in sand casting after the casting after the casting is removed from the mold

Sanding, polishing, removal of sprues, runners, risers and flash

Discuss some of the defects that can occur in plastic injection molding.

Shrinkage due to cooling Short shots - solidification before the mold is completely filled. Flashing - Melted plastic if forced between the two mold plates

What is the fundamental feature that distinguishes fusion welding from solid-state welding?

Solid state Welding - coalescence of the part is achieved by pressure along with heat Fusion welding - coalescence is achieved by melting the two parts surfaces to be joined and in some cases a filler material is added

What are two differences between the ISO standard and the ANSI standard for specifying the threaded fasteners such as screws and bolts

The ISO standard includes the nominal major diameter in mm followed by the pitch in mm. The ANSI standard specifies the major diameter in inches followed by the number of threads per inch.

Define technological processing capability

The available set of manufacturing processes in a plant. Different sets of manufacturing processes produce different products of quality

What is the difference between full annealing and normalizing

The cooling time, full annealing is air cooled while normalizing is cooled faster then it would be done by air cooling

Define volumetric specific heat as a material property

The heat required to raise the temperature of the unit mass of a given substance by a given amount (usually one degree Celsius).

what is the most common reason for heating a metallic work piece before it is subjected to a deformation process

To increase Ductility

What are the factors on which the selection of feed in a machining operation should be based?

Tooling, Roughing or finishing, Constraints on feed in roughing, surface finish requirements in finishing.

What is a weld nugget in resistance welding?

Weld nuggets are formed at the projections of a resistance weld when current is applied. It is the fused zone between the two parts.

Describe the wire drawing process.

Wire drawing is an operation in which the cross section of a wire is reduced by pulling it through a die opening.

What is Shell Molding?

a casting process in which the mold is a thin shell, typically 9mm made of sand held together by a thermosetting resin binder

What is the definition of a cermet

a combination of a ceramic and a metal

What is a spot weld?

a small fused section between the surfaces of two sheets or plates. Usually more then one spot weld is need to join the parts.

What is spinning in sheet metalworking

is a process where a part is gradually shaped over a mandrel/form while it spins

What is work hardening?

is the strengthening of a metal or polymer by plastic deformation. It increases the hardness by hammering, rolling, or drawing. Dislocations decrease the ductility of the material.

What are the two main problems that cutting fluids are designed to address

reduce heat and to act as a lubracant

Define the viscosity of a fluid

the resistance to flow of a fluid material; the thicker the fluid, the greater the viscosity.