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Questions and Answers
Which nose radius and feed parameters best describe the roughing process?
What is a primary purpose of using cutting fluids in machining?
Which factor can help eliminate vibrations in machining processes?
What defines a turret lathe compared to a basic lathe?
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In turning, what is the effect of spindle rotation on the cutting process?
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What is a disadvantage of the turning process in machining?
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Which of the following is NOT a benefit of using cutting fluids?
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What role does the shape of the cutting tool play in turning?
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What is the primary purpose of a drilling operation?
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What does the term 'blind hole' refer to in drilling?
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Which factor is NOT considered to influence the cost of drilling?
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What is the function of the flutes on a drill bit?
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Which of the following statements about reaming is correct?
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What type of drilling machine provides the most adjustability?
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What is the primary limitation of conventional drilling at depths greater than four times the drill bit diameter?
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Which operation is used to create a stepped hole for hiding a bolt or screw head?
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What type of hole is created through the process of tapping?
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Which is NOT a characteristic of an upright drill press?
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What is a major advantage of using CNC for machining?
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Which of the following is considered a disadvantage of machining?
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What factor can limit the cutting speed and overall productivity in machining?
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Which of the following statements about cutting tools in machining is true?
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What can be a consequence of using low-quality cutting tool materials?
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Which of the following represents a factor affecting the machined surface finish?
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Why can machining be more time-consuming than other manufacturing methods?
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What is a common drawback associated with achieving high dimensional accuracy in machining?
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What is the primary difference between casting and forging processes?
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Which of the following processes is classified as material addition?
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What does the term 'net shape' refer to in manufacturing?
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What is the main purpose of machining in shaping processes?
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Which factor does NOT affect the material removal rate during machining?
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What does the term 'near net shape' indicate?
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Which of the following best describes machining as a subtractive manufacturing process?
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In the context of shaping processes, which of the following is a characteristic of bulk deformation?
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What is an essential requirement for a material to be processed through conventional machining?
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Which process uses heat to join separate material parts into a final shape?
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What is the primary goal of manufacturing from an economical perspective?
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Which factor affects the cost of manufacturing when increasing the complexity of a part?
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What determines the achievable resolution and surface finish in manufacturing?
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How does production volume relate to manufacturing complexity?
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Which of the following materials is typically heavier and more cost-effective for car wheels?
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What is the role of manufacturing support systems?
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What would likely be the consequence of using standard part shapes and sizes in manufacturing?
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What is likely to happen to costs as production quantity increases?
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What aspect of manufacturing is affected by material limits?
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Which of the following statements regarding flexibility in manufacturing is correct?
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Which manufacturing process is typically used for creating the general shape of car wheel parts?
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What does the term 'near net process' refer to in manufacturing?
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Which feature is essential for assessing quality in manufactured parts?
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What impacts the accuracy and consistency of a manufacturing process?
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Study Notes
Manufacturing
- Manufacturing: the transformation of raw materials into products of greater value by one or more processing and/or assembly operations
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Manufacturing System: a coordinated network of people, equipment, facilities, procedures, and information that transforms inputs into outputs.
- Macro View: Manages materials and processes (facilities, people, equipment, procedures)
- Micro View: Individual equipment and operators that perform processing and/or assembly operations on a starting raw material (specific machines, mill, lathe, operators, workpiece, cutting tools)
- Manufacturing Support Systems: Increase productivity but do not make the final product (people and procedures used to manage production operations)
Manufacturing Considerations
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Costs:
- Setup costs (equipment and tooling)
- Running costs (energy and labor)
- Waste/pollution (environmental costs)
- Cost decreases with increasing quantity
- Cost increases with increasing complexity and variety
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Production Rate:
- Parts per unit of time
- Speed of production
- Labor: Number of people required to operate the manufacturing system
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Geometric Complexity:
- Part shape
- Part size
- Number of features
- Geometric transitions
- Holes/cores and non planar surfaces
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Accuracy:
- Achievable resolution, feature size, surface finish
- How accurate and consistent the process is (variation)
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Quantity/Production Volume:
- Product quantity to be made
- Low (1-100): custom
- Medium (100-10,000): jets, exotic cars
- High (10,000+): bottles, cars, phones, laptops
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Material Limits:
- Physical limitations
- Use standard materials (exotic high strength materials are expensive and difficult to process)
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Quality:
- Achievable resolution, feature size, surface finish
- How accurate and consistent the process is (variation)
- Material or part quality (net vs near net process)
- Tolerance: allowable variation in dimensions or size (cost increases with increasing precision)
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Flexibility:
- Scalability to different physical sizes of parts
- Compatibility with different part geometry
- Scalability to different production quantities
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Limitations:
- What processes can/can't be used
- What materials can/can't be worked with
- What shapes can/can't be made
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Manufacturing Plant Capability:
- Manufacturing plant capability
- Number of components
- Use standard part shapes and sizes to reduce cost
- Minimize part complexity
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Product Variety:
- Different product types or models produced in the plant
- Soft: Slight changes, many common parts
- Hard: Great changes, few common parts
- Cannot manufacture many parts if all parts are different across different products due to cost
Shaping Processes
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Solidification Process: Starting material is melted and solidified.
- Casting (metals and ceramics): Molten material is poured into a mold.
- Moulding (plastics): Material is pressed into a die.
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Deformation Process (Bulk): Starting material is shaped by forces exceeding the yield strength of the material.
- Sheet metal forming or stamping: Flat sheet metal is formed into desired shapes.
- Forging: Material is hammered or pressed into shape.
- Extrusion: Material is pushed through a die to create a desired shape.
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Material Subtraction (Machining): Excess material is cut away from a starting workpiece.
- Turning: Material is cut from a rotating workpiece using a single point cutting tool.
- Drilling: Material is cut from a workpiece using a rotating drill bit.
- Milling: Material is cut from a workpiece using a rotating milling cutter.
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Material Addition Process (3D Printing): Material is added together to form the final part shape.
- Particulate processing: Starting materials are metal or ceramic powders which are pressed and sintered (heated near melting temperature).
- Powder bed fusion process: Laser fuses powder together (additive manufacturing or AM).
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Material Joining Process: Separate bulk material parts are joined to form the final shape
- Adhesive bonding/glueing
- Welding/brazing
- Fastening with bolts
Material Removal/Subtractive Manufacturing
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Conventional Machining: Uses a sharp and hard cutting tool to mechanically cut away material to shape and enhance finish of material or add extra details by forming chip.
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Factors:
- Relative motion and trajectory between tool and workpiece
- Shape of cutting tool
- Strength of cutting tool material
- Cost of cutting tool
- Target Material: Typically for metal, but plastic or ceramic materials may be used depending on machinability.
- Target Stage: Typically performed after other basic near-net shape manufacturing processes such as casting, forging, etc.
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Advantages
- Versatile
- High dimensional accuracy
- Good surface finish (net finish)
- Few defects
- Easily automated (CNC)
- Can have replaceable inserts
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Disadvantages:
- Wasteful of material
- Costly to recycle
- More time consuming than other methods (low-medium rate)
- Can leave machining marks
- Shape limited by tool access
- Material machinability
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Considerations:
- Cutting tools wear out or fail (break) over time due to higher loads
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Factors:
Machined Surface Finish
- Can show visible machining marks
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Factors:
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Geometric tool factors: Nose radius (NR) & feed (f)
- Roughing: (High feed, low speed), uses a sharp nose radius to get near-net shape by removing large amounts of material quickly.
- Finishing: (Low feed, high speed), uses a round nose radius to get net shape (final dimensions, tolerance, and surface finish).
- Eliminate vibrations/chatter: Increase stiffness of setup, reduce feeds and depths to reduce forces, change cutter design to reduce forces, use a cutting fluid.
- Process used:
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Geometric tool factors: Nose radius (NR) & feed (f)
Cutting Fluids
- Machining often requires use of cutting fluids (oil, water):
- To remove heat
- To lubricate the chip-tool interface
- To wash away chips
- To avoid part oxidation
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Contributes to:
- Chip removal
- Reduced stress on cutting tool
- Increased tool life
- Better part accuracy (reduced thermal expansion)
- Less surface damage
Turning
- Uses lathe and single tip tool to create a rotational part (circular cross section).
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Process:
- Material is spinning (primary motion).
- Rotating tool moves horizontally (secondary motion).
- Creates divots into the circular part.
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Factors:
- Relative motion and trajectory between tool and workpiece (cutting speed and feed motion) to achieve various geometries/shapes.
- Shape of cutting tool.
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Types of Lathes:
- Basic lathe: Bed, tool post, chucks, tailstocks.
- Turret lathe: Tailstock replaced by turret that holds several tools, tools rapidly brought into action by indexing the turret, saves changeover time.
- CNC lathe: Advanced programmable “Computer Numerical Control” (CNC) of position, tool change, and tool feeds.
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Advantages:
- Precision and Accuracy
- Versatility
- Flexibility
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Disadvantages:
- Material Waste
- Requires specific machinery
- Knurling: Forming operation to produce patterns in the work surface, no cutting of material, just deformation.
Drilling
- Drilling machine/press uses a drill bit (multiple points) to create a prismatic part (rigid non-rotational cross section).
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Process:
- Material is stationary.
- Rotating tool moves along one axis.
- Creates circular holes into the part.
- Through Hole: Drill exits the opposite side of the work.
- Blind Hole: Drill does not exit the opposite side.
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Factors that influence cost:
- Cutting speed (v)
- Feed rate (fr)
- Depth of cut (d)
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Types:
- Machine Used:
- Upright drill press: Simple manually operated machine with limited adjustability.
- Radial arm drill press: More adjustability (horizontal and vertical), manually operated.
- CNC drill: More adjustability (horizontal and vertical), computer positioning, advanced computer numerical control operated.
- Drill bit used:
- Body of flutes, spiral grooves, used to guide chip removal and deliver cutting fluids.
- Cutting points - number of flutes.
- Reaming: Slightly enlarges a hole, enhances tolerance and surface finish (removes machine marks).
- Tapping: Cuts internal screw threads on an existing hole.
- Counterboring: Creates a stepped hole.
- Countersinking: Used for hiding bolt/screw head.
- Machine Used:
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Advantages:
- High accuracy and repeatability
- Can drill a wide range of hole sizes and depths
- Relatively easy to automate
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Limitations of Conventional Drilling:
- At depths of over 4 times the diameter of the drill bit, chips can accumulate, cutting fluid flow is restricted, interrupted cut drilling (peck drilling).
- Long/deep and narrow holes (small diameter) are difficult/impossible to drill conventionally due to drill bits being fragile and likely to break or wonder/skew.
- Small holes: Difficult to drill conventionally due to smaller drills being fragile.
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