1 Before you begin: Turn on the sound on your computer. There is audio to accompany this presentation. MET 33800 Manufacturing Processes Chapter 24 Milling Chapter 24 - 1 Materials Processing Chapters 15-17 Chapters 30-33 Chapters 20-27 Chapters 11-13 Chapter 24 - 2 Milling Milling is a complex process: Surface generated by progressive chip removal. Workpiece fed into a rotating cutting tool. Typically uses a multiple tooth cutter = interrupted cutting. High material removal rate. Chapter 24 - 3
Transcript
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Before you begin: Turn on the sound on your computer. There is audio to accompany this presentation.
MET 33800 Manufacturing Processes
Chapter 24
Milling
Chapter 24 - 1
Materials Processing
Chapters 15-17
Chapters 30-33
Chapters 20-27
Chapters 11-13
Chapter 24 - 2
MillingMilling is a complex process:
Surface generated by progressive chip removal.
Workpiece fed into a rotating cutting tool.
Typically uses a multiple tooth cutter = interrupted cutting.
High material removal rate.
Chapter 24 - 3
2
Basic Milling Operations
Peripheral or slab milling Face and end milling
Chapter 24 - 4
Peripheral (Slab) Milling
Surface generated by teeth located on periphery of cutter.
Surface is parallel with axis of rotation of cutter.
Flat and contour surfaces produced.
Slab milling usually on horizontal spindle machines.
Chapter 24 - 5
Face (End) Milling
Chapter 24 - 6
3
Face (End) Milling Most of the cutting done by teeth located on periphery
of cutter with face (end) providing some finishing action.
Surface is at right angle to axis of rotation of cutter.
Both horizontal and vertical-spindle machines.
Chapter 24 - 7
* Ns = Spindle Speed (rpm)
D = Cutter diameter (inch)
V = cutting speed (fpm)
12 V
N = S D
Milling Cutting Parameters
*applicable to both face and peripheral milling types Chapter 24 - 8
*fm = Feedrate (ipm)
ft = feed/tooth (ipr)
n = number of teeth
Milling Cutting Parameters
m t sf = f N n
*applicable to both face and peripheral milling types Chapter 24 - 9
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Cutting Parameters Slab Milling
Chapter 24 - 10
Tm = cutting time (min)
t = depth of cut
D = cutter diameter
LA = approach length
Am
m
A
L + LT =
f
L = t (D - t)
Cutting Parameters Slab Milling
Chapter 24 - 11
*W = cut width (inch)
t = depth of cut (inch)
fm = feedrate (ipm)
mMRR = W f t
Cutting Parameters Slab MillingMRR = Material Removal Rate (in3/min)
*note that W is cut width, not cutter width Chapter 24 - 12
5
Example Problem Process: Slab Milling
Cutter: 3.0 dia x 4.0 wide, HSS, 6 teeth
Material: 3.0 wide x 10 length, 6064-T6 Aluminum Alloy
Operation: remove 0.250” (1) pass
Determine the Machining Parameters
Chapter 24 - 13
Example Problem
Chapter 24 - 14
Chapter 24 - 15
Example Problem
6
Chapter 24 - 16
Example Problem
Chapter 24 - 17
Example Problem
Example Problem
Chapter 24 - 18
7
Chapter 24 - 19
Example Problem
Chapter 24 - 20
Example Problem
Cutting Parameters Face Milling
Chapter 24 - 21
8
Tm = cutting time (min)
L = length of cut
LA = approach length
LO = over travel length
fm = feedrate (ipm)
A Om
m
L + L + LT =
f
Cutting Parameters Face Milling
Chapter 24 - 22
LA = approach distance
LO = over travel distance
*W = cut width
D = cutter diameter
A O
A O
DL L W (D W) for W
2D D
L L for W2 2
Cutting Parameters Face Milling
*note that W is cut width, not cutter width Chapter 24 - 23
mMRR W t f
Cutting Parameters Face Milling
*W = cut width (inch)
t = depth of cut (inch)
fm = feedrate (ipm)
MRR = Material Removal Rate (in3/min)
*note that W is cut width, not cutter width
Chapter 24 - 24
9
Example Problem #2 Process: Face Milling
Cutter: 6.0 inch dia, 6 carbide inserts
Material: 3.0 inch wide x 10 inch length, 6064-T6 Aluminum Alloy
Operation: remove 0.250” (1) pass
Determine the Machining Parameters
Chapter 24 - 25
Example Problem #2
Chapter 24 - 26
Chapter 24 - 27
Example Problem #2
10
Chapter 24 - 28
Example Problem #2
Chapter 24 - 29
Example Problem #2
Example Problem
Chapter 24 - 30
11
Chapter 24 - 31
Example Problem #2
Chapter 24 - 32
Example Problem #2
Cutting Parameters End Milling
Chapter 24 - 33
12
Cutting Parameters End Milling
m
s m
hpd =
hp x f x DOI
Maximum Material Removal
hps = specific horsepower
hpm = machine horsepower
d = depth of cut (DOC)
DOI = depth of immersionChapter 24 - 34
UP and DOWN Milling
Chapter 24 - 35
Conventional (Up) Milling Cutter rotates against direction of work feed.
Chip thin at beginning of tooth entry and increases in thickness.
Cutter tends to push work and lift work off table.
Direction tends to eliminate problems associated with looseness of feed screw.
Less horsepower required.
Less accuracy and lower surface finish.
Chapter 24 - 36
13
Conventional (Up) Milling
Chapter 24 - 37
Conventional (Up) Milling
Chapter 24 - 38
Climb (Down) Milling Cutter rotation in same direction as feed rate.
Maximum chip thickness at beginning of tooth entry and decreases in thickness.
Cutter tends to pull work into cutter.
Cutter pushes work into work holding device.
Climb milling not possible on machine with looseness in feed screw.
More horsepower required.
Higher accuracy and better surface finish.
Chapter 24 - 39
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Climb and Conventional Milling
Chapter 24 - 40
Milling Cutters1.Shank Mounted Cutters:
a. End mills - peripheral and end teeth. Straight or helical tooth form.
b. Face Mills: Most use insert tooth design.
c. T-slot: teeth on periphery and both sides.
d. Woodruff key seat: standard sizes for key seat
e. Fly: single cutting edge.
Chapter 24 - 41
Shank Mounted Cuttersa. Plain End Mills: HSS, coated, carbide.
Chapter 24 - 42
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a. Insert End Mills: Use indexable carbide inserts.
Shank Mounted Cutters
Chapter 24 - 43
a. Shell End Mills: multiple tooth cutters without a shank.
Shank Mounted Cutters
Chapter 24 - 44
a. Hollow End Mills: tubular cross section. Used on screw machines to size stock.
Shank Mounted Cutters
Chapter 24 - 45
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b. Face Mills: Most use insert tooth design.
Shank Mounted Cutters
Chapter 24 - 46
b. Face Mills: Most use insert tooth design.
Shank Mounted Cutters
Chapter 24 - 47
c. T-slot - teeth on periphery and both sides.
d. Woodruff key seat - standard sizes for key seat.
Shank Mounted Cutters
Chapter 24 - 48
17
e. Fly Cutters - single cutting edge.
Shank Mounted Cutters
Chapter 24 - 49
Milling Cutters2. Arbor Mounted Cutters:
a. Plain - used for slab milling. Straight or helical tooth.
b. Side - similar to plain mill except tooth extends radially.
c. Interlocking slotting - similar to side mill except more than one cutter used.
d. Staggered-tooth - free cutting action for deep slots.
e. Slitting saw - 1/32 to 3/16 wide with dished sides for slotting and cut-off.
f. Angle - conical or V-shaped teeth.
g. Form - teeth ground to special shape.Chapter 24 - 50
Arbor Mounted Cutters
Chapter 24 - 51
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Arbor Mounted Cuttersa. Plain - used for slab milling. Straight or helical tooth.
Chapter 24 - 52
Arbor Mounted Cuttersb. Side - similar to plain mill except tooth extends radially.
Chapter 24 - 53
Arbor Mounted Cuttersc. Interlocking slotting - similar to side mill except more
than one cutter used.
Chapter 24 - 54
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d. Staggered-tooth - free cutting action for deep slots.
Arbor Mounted Cutters
Chapter 24 - 55
e. Slitting saw - 1/32 to 3/16 wide with dished sides for slotting and cut-off.
