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ME 350 – Lecture 5 – Chapter 22

ME 350 – Lecture 5 – Chapter 22. Chapter 22 - MACHINING OPERATIONS AND MACHINE TOOLS: Turning and Related Operations Drilling and Related Operations Milling Machining Centers and Turning Centers Broaching. Turning.

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ME 350 – Lecture 5 – Chapter 22

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  1. ME 350 – Lecture 5 – Chapter 22 Chapter 22 - MACHINING OPERATIONS AND MACHINE TOOLS: • Turning and Related Operations • Drilling and Related Operations • Milling • Machining Centers and Turning Centers • Broaching

  2. Turning Single point cutting tool removes material from a rotating workpiece to generate a cylinder • Performed on a machine tool called a: • Variations of turning performed on a lathe: • Facing • Contour turning • Chamfering • Cutoff • Threading

  3. Cutting edge cuts an angle on the corner of the cylinder, forming a "chamfer" Tool is fed radially into rotating work at some location to cut off end of part Tool is fed radially

  4. Tool follows a contour that is other than straight Tool has the desired geometry, and is fed directly into workpiece Pointed form tool is fed at a large feed rate, thus creating threads

  5. Engine Lathe

  6. Holding Workpiece in a Lathe

  7. Turret Lathe Tailstock replaced by “turret” that holds up to six tools • Tools rapidly brought into action by indexing the turret • Applications: high production work that requires a sequence of cuts on the part

  8. Multiple Spindle Bar Machines • More than one spindle, so multiple parts machined simultaneously by multiple tools. Example: After each machining cycle, spindles (including collets and workbars) are indexed (rotated) to next position

  9. Power Requirement The specificenergy: Cutting power per unit volume removal rate Energy converted to: Approximation: U ~hardness H

  10. Specific Energy (U) For Cutting Approximate specific-energy requirements 1 hp = ft∙lbs/s = in∙lbf/min

  11. In-class exercise – Cutting force estimation • 6 inch long, • 1.5 inch diameter • 304 stainless steel rod Parameters: • cutting speed v=1860 in./min, • f=0.03 in/rev., d= 0.02in., • U= 1.47 hp.min/in3, • Find: the cutting force MRR = Power: Cutting force:

  12. Boring • Difference between boring and turning: • Boring is performed on the diameter of an existing hole • Turning is performed on the diameter of an existing cylinder • Boring machines • Horizontal or vertical - refers to the orientation of the machine spindle’s:

  13. Drilling • Creates a round hole in a workpart • Compare to boring which can only enlarge an existing hole • Cutting tool called a drill or drill bit • Machine tool: drill press

  14. Enlarges hole, • Provides better • Improves Used to provide internal screw threads on an existing hole. Tool called a

  15. Operations related to drilling Center Drilling: necessary for creating a relatively large hole Countersinking: Spot facing: a milling tool Counterboring: Hiding bolt heads

  16. Drilling Rate and Time • D=drill diameter; (length) • N = spindle speed; (rev/min) • f = feed; (length/rev) • d = depth of cut (length)

  17. Milling Machining operation in which work is fed past a rotating tool with multiple cutting edges • Axis of tool rotation is perpendicular to feed • Two forms: (a) (b)

  18. Basic form of peripheral milling in which the cutter width extends beyond the workpiece on both sides Width of cutter is less than workpiece width, creating a slot in the work

  19. Cutter overhangs work on both sides Cutter diameter is less than work width, so a slot is cut into part Form of end milling in which the outside periphery of a flat part is cut

  20. Knee-And-Column Milling Machines • (a) Horizontal and (b) vertical knee-and-column milling machines

  21. Milling Rate and Time W: width of cut; d: depth of cut v: feed rate (need conversion from # of teeth and spindle speed) v W Lc: extra length for cutter to engage

  22. Machining Centers Highly automated machine tool can perform multiple machining operations under CNC control in one setup with minimal human attention • Typical operations are: • Three, four, or five axes • Other features: • Automatic tool‑changing • Pallet shuttles • Automatic workpart positioning

  23. CNC Machining Center

  24. Mill-Turn Centers Highly automated machine tool that can perform the operations:

  25. Moves a multiple tooth cutting tool linearly relative to work in direction of tool axis Which shape could be made without broaching?

  26. Quotes: • To be able to look back upon one's past life with satisfaction is to live twice. -Marcus Valerius Martial • He who will not reason is a bigot; he who cannot is a fool; and he who dares not, is a slave - Sir William Drummond • It is better to be a lion for a day than a sheep all your life. – Elizabeth Kenny • Dance like no one is watching, Love like you'll never be hurt,Sing like no one is listening, Live like it's heaven on earth. – William Purkey

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