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Chapter 22 - MACHINING OPERATIONS AND MACHINE TOOLS

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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 – PowerPoint PPT presentation

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Title: Chapter 22 - MACHINING OPERATIONS AND MACHINE TOOLS


1
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

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
  • Gear Teach Machining

3
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
4
Contour Turning
Threading
Form Turning
Tool has the desired geometry, and is fed
directly into workpiece
  • Tool follows a contour that is other than
    straight

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 specific energy Cutting power per unit
volume removal rate
Converted to
Approximation U Hardness H
10
Specific Energy (U) For Cutting
Approximate specific-energy requirements
11
In-class exercise Cutting force estimation
  • A 6 inch long, 1.5 inch diameter 304 stainless
    steel rod
  • parameters cutting speed v1860 in./min,
  • f0.03 in/rev., d 0.02in.,
  • U 1.47 hp.min/in3,
  • Find the cutting force

12
Boring
  • Difference between boring and turning
  • Boring is performed on the diameter of an
    existing hole
  • Turning is performed on the outside diameter of
    an existing cylinder
  • Boring machines
  • Horizontal or vertical - refers to the
    orientation of the machine spindles axis of
    rotation

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
Reaming
Tapping
  • Enlarges hole,
  • Provides better diameter tolerance
  • Improves surface finish

Used to provide internal screw threads on an
existing hole. Tool called a tap
15
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
16
Drill Press Radial Drill
17
Drilling Rate and Time
Ddrill diameter (length) N spindle speed
(rev/min) f feed (length/rev) d depth of cut
(length)
18
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
19
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
20
Face Milling
End Milling
Profile Milling
Cutter diameter is less than work width, so a
slot is cut into part
  • Cutter overhangs work on both sides

Form of end milling in which the outside
periphery of a flat part is cut
21
Knee-And-Column Milling Machines
  • (a) Horizontal and (b) vertical knee-and-column
    milling machines

22
Milling Rate and Time
  • MRRWdv

W width of cut d depth of cut v feed rate
(need conversion from of teeth and spindle
speed)
v
Milling time (L2Lc)/v
W
Lc extra length for cutter to engage
23
Machining Centers
  • Highly automated machine tool can perform
    multiple machining operations under CNC control
    in one setup with minimal human attention
  • Typical operations are milling and drilling
  • Three, four, or five axes
  • Other features
  • Automatic tool-changing
  • Pallet shuttles
  • Automatic workpart positioning

24
CNC Machining Center
25
Mill-Turn Centers
  • Highly automated machine tool that can perform
    the operations turning, milling, and drilling

26
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

27
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

28
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

29
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

30
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?
31
Drilling a square hole?
  • Square hole cutting video
  • Vika attachment
  • Also possible with hexagonal holes
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