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ME 350 – Lecture 4 – Chapter 22. Chapter 22 - MACHINING OPERATIONS AND MACHINE TOOLS: Turning and Related Operations Drilling and Related Operations Milling Machining Centers and Mill-turn Centers Gear cutting Broaching. Turning.

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me 350 lecture 4 chapter 22
ME 350 – Lecture 4 – Chapter 22

Chapter 22 - MACHINING OPERATIONS AND MACHINE TOOLS:

  • Turning and Related Operations
  • Drilling and Related Operations
  • Milling
  • Machining Centers and Mill-turn Centers
  • Gear cutting
  • Broaching
turning
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
    • Gear Teach Machining
slide3

Facing

Chamfering

Cutoff

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

slide4

Threading

Contour Turning

Form Turning

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

turret lathe
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
multiple spindle bar machines
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

power requirement
Power Requirement

the specificenergy:

Cutting power per unit volume removal rate

Converted to

Approximation:

U ~Hardness H

specific energy u for cutting
Specific Energy (U) For Cutting

Approximate specific-energy requirements

in class exercise cutting force estimation
In-class exercise – Cutting force estimation
  • A 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
boring
Boring
  • Difference between boring and turning:
    • Boring is performed on the diameter of an existing hole
    • Turning is performed on the outsidediameter of an existing cylinder
  • Boring machines
    • Horizontal or vertical - refers to the orientation of the machine spindle’s: axisofrotation
slide13

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
slide14

Reaming

Tapping

  • Enlarges hole,
  • Provides betterdiametertolerance
  • Improves surface finish

Used to provide internal screw threads on an existing hole. Tool called a tap

operations related to drilling
Operations related to drilling

Center Drilling: necessary for creating a relatively large hole

Countersinking:

Screw holes

Spot facing:

NOT a milling tool

Counterboring:

Hiding bolt heads

drilling rate and time
Drilling Rate and Time
  • D=drill diameter; (length)
  • N = spindle speed; (rev/min)
  • f = feed; (length/rev)
  • d = depth of cut (length)
milling
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) peripheral milling (b) face or end milling

slide19

Slab Milling

Slotting

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

slide20

Face Milling

End Milling

Profile Milling

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

knee and column milling machines
Knee-And-Column Milling Machines
  • (a) Horizontal and (b) vertical knee-and-column milling machines
milling rate and time
Milling Rate and Time

MRR=W×d×v

W: width of cut; d: depth of cut

v: feed rate (need conversion from # of teeth and spindle speed)

v

Milling time= (L+2Lc)/v

W

Lc: extra length for cutter to engage

machining centers
Machining Centers

Highly automated machine tool can perform multiple machining operations under CNC control in one setup with minimal human attention

    • Typical operations are: millinganddrilling
    • Three, four, or five axes
  • Other features:
    • Automatic tool‑changing
    • Pallet shuttles
    • Automatic workpart positioning
mill turn centers
Mill-Turn Centers

Highly automated machine tool that can perform the operations: turning, milling, anddrilling

machining gear teeth
Machining Gear Teeth
  • Form milling - use of a form milling cutter
  • Gear hobbing - also milling but using a special cutter called a hob
  • Gear shaping - two forms
    • Single point tool to gradually shape each gear tooth spacing
    • Cutter has general shape of the gear but with cutting teeth on one side
  • Gear broaching - for internal and external gears
form milling of gear teeth
Form Milling of Gear Teeth
  • The form milling cutter has teeth with the shape of the spaces between teeth on the gear
  • Gear blank is indexed between each pass to establish correct size of the gear tooth
gear hobbing
Gear Hobbing
  • Hob has a slight helix and its rotation must be coordinated with much slower rotation of the gear blank
  • Performed on special milling machines (called hobbing machines) that accomplish the relative speed and feed motions between cutter and gear blank
gear shaping
Gear Shaping
  • To start the process, cutter is gradually fed into gear blank
  • Then, cutter and blank are slowly rotated after each stroke to maintain tooth spacing
  • Performed on special machines called gear shapers
slide30

Broaching

  • Moves a multiple tooth cutting tool linearly relative to work in direction of tool axis

Broaching Video

1

2

3

4

5

6

Which shape(s) could be made without broaching?

drilling a square hole
Drilling a square hole?
  • Square hole cutting video
  • Vikaattachment
  • Also possible with hexagonal holes