Booklet for Machining Process
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Transcript of Booklet for Machining Process
Machining
2.810 Fall 2009
T. Gutowski
go to website below
http://electron.mit.edu/~gsteele/mirrors/www.nmis.org/EducationTraining/machineshop/mill/intro.html
Tools to cut and scrape goback at least 150,000 yrs
Stone work in Cuzco
Readings
Kalpakjian Ch 21-27
“Simplified Time Estimation Booklet
for Basic Machining Operations”
Design for Machining handout
Outline
1. Basics
2. Machine Configurations
3. Production Configurations
4. Processing Planning
5. Environment
Basics: Machining Process Single point machining
Turning, boring, trepanning, planing
Multiple point machining
Drilling, milling, reaming, sawing, broaching, grinding
Tool Stationary: turning, boring…
Tool moves: sawing, milling, drilling, broaching
Work Piece moves: milling, boring…
Both move: milling, 5 axis milling
Machining processes
Horizontal Slab milling Face milling End milling
Cutter Arbor
Arbor
Spindle
Spindle
End mill
Shank
Turning
Milling
* Source: Kalpakjian, “Manufacturing Engineering and Technology”
*
* Grinding
Grindingwheel
DGrains
Workpiecev
V
Horizontal-spindle surface grinderMachine Tools
Column
Base
Head
Table
Saddle
Knee
*
Spindlespeed
selector
Feed change
gearbox
Compound rest and slides (swivels) Apron
Bed
Lead screw
Feed rod
Headstock
Spindle
Cross slideWays
Carriage
Center
Tailstock quill
Tailstock
Basic Lathe
Vertical-Spindle Mill
*
* Source: Kalpakjian, “Manufacturing Engineering and Technology”
*
Basic Mechanics Issues
Power, Forces
Heat, Tool materials, Rate limits
Temperature
Surface finish
See Video on Plastic Deformation
Basic Machining Mechanism
Shear takes place ina narrow zone nearthe tool tip at angle ,the tool has rake angle , the resulting shears is From geometry,
= cot( ) + tan ( - )
becomes large for small , and small or negative
Basic Machining Mechanism
Basic Machining Mechanism
Approximation
us ~ H (Hardness)
t0
tc
Shear plane Shear angle
Tool
V
Chip
Workpiece
+-
Rakeangle
)42(6
1 u
4 2 d u
u 80%) to(65 u u
u energy specific
vol
work
work dt
d(work) Power VF
p
p
friction workplasticS
S
H
Specific energy, uS
For comparison see Table 26.2 for grinding
Hence we have the approximation;
Power ≈ us X MRR
MRR is the Material Removal Rate or d(Vol)/dt
Since Power isP = F * V
and MRR can be written as,d(Vol)/dt = A * V
Where A is the cross-sectional area of the undeformed chip, we can get an estimate for the cutting force as,
F ≈ us A
Note that this approximation is the cutting force in the cutting direction.
Basic Machining Mechanism
Cutting Force Directions in Milling
Fp
Fcn
Fc
Fcn
Fp
Fc
Fcn
Fc
Fp
Fcn
Fp
Fc
Fc ~ H Ac
(Tangential Cutting Force ~
Chip Cross-section Hardness)
Feed per Tooth and MRR
f = feed per tooth (m)w = width of cut (m)
v (m/s)
= rotational rate (rpm)
Consider the workpiece moving into the cutter at rate “v”. In travel time t’ the feed is v t’. The time for one rotation is t’ = The travel for one tooth is
1/4 Hence the feed per tooth is f = v/4 . In general, a cutter may have “N”
teeth, so the feed per tooth is
f = v / NThe material removal rate (MRR) is,
MRR = v w d
where “d” is the depth of the tool into the workpiece.
Top view of face millingWith 4 tooth cutter
Side view
Ex) Face milling of Al Alloy
w
d D
vw
N = 4 (number of teeth)D = 2” (cutter diameter)
Let w = 1” (width of cut), d=0.1” (depth of cut)f = 0.007” (feed per tooth), vs = 2500 ft/min (surface speed; depends on cutting tool material; here, we must have a coated tool such as TiN or PCD)
The rotational rate for the spindle is= vs / D = 4775 rpm
Now, we can calculate vw, workpiece velocity,f = vw / N => vw= 134 [in/min]
Material removal rate, MRR = vw*w*d = 13.4 [in3/min] Power requirement, P = us*MRR = 5.36 [hp]Cutting force / tooth, F ~ us*d*f = 111 [lbf]
us from Table 21.2 (20.2 ed 4); Note 1 [hp min/in3] = 3.96*105 [psi]
Ex) Turning a stainless steel bar
f
D=1”
d
Tool
Recommended feed = 0.006” (Table 23.4 (22.4))Recommended surface speed = 1000 ft/min
= 1000 ft/min = 3820 rpm1” 1ft/12”
Material removal rate, MRR = 0.1 0.006 1 3820) = 7.2 [in3/min]
Power requirement, P = us*MRR = 1.9*7.2 = 13.7 [hp]
Cutting force / tooth, F ~ us*d*f = (1.9*3.96*105)*(0.1*0.006)
= 450 [lbf]
us from Table 21.2 (20.2 ed 4); Note 1 [hp min/in3] = 3.96*105 [psi]
Let d = 0.1”
Temperature Rise in Cutting
Adiabatic Temperature Rise: cp T = uS
Note : uS ~ H, HardnessTadiabatic > ½ Tmelt (Al & Steel)
Interface Temperature:
T = 0.4 (H / cp)(v f / )0.33
v = cutting speedf = feed
= thermal diffusivity of workpieceNote v f / = Pe = convection/conduction
Typical temperature distribution in the cutting zone
* Source: Kalpakjian, and Schmidt 5th ed
*
* Reference: N. Cook, “Material Removal Processes”
Cutting tool materials & process conditions
Temperature ( F)
Hard
ness
(H
RA)
HR
C
Feed (in/rev)
Cutt
ing s
peed (
ft/m
in)
m/m
in
Year
Mach
inin
g tim
e (
min
)
* Source: Kalpakjian, “Manufacturing Engineering and Technology”
Cutting Speed (ft/min)
Tool lif
e (
min
)
Limits to MRR in Machining
Spindle Power – for rigid, well supported parts
Cutting Force – may distort part, break delicate tools
Vibration and Chatter – lack of sufficient rigidity in the machine, workpiece and cutting tool may result in self-excited vibration
Heat – heat build-up may produce “welding”, poor surface finish, excessive work hardening; can be reduced with cutting fluid
See Video on Rate Limits In Machining
Typical Material Removal Rate
10-4 10-3 10-2 10-1 1 10 102
EBM1 EDM1,2
Grinding3
Machining
Creep Feed2
Grinding
LASER3
Chem. Milling2
[cm3/sec]
25A, 6um RMS1
Rough milling of Al > 35hp
1m X 1m areaNote: 1cm3/sec = 3.67 in3/min
* References: 1. Advanced Methods of Machining, J.A.McGeough, Chapman and Hall, 1988
2. Manufacturing Engineering and Technology, S. Kalpakjian, Addison-Wesley, 1992
3. Laser Machining, G. Chryssolouris, Springer-Verlag, 1991
High speed Machining and AssemblyHigh Speed Machined aluminum parts are replacing built-up parts made by forming and assembly (riveting) in the aerospace industry. The part below was machined on a 5-axis Makino (A77) at Boeing using a 8-15k rpm spindle speed, and a feed of 240 ipm vs 60 ipm conventional machining. This part replaces a build up of 25 parts. A similar example exists for the F/A-18 bulkhead (Boeing, St. Louis) going from 90 pieces (sheetmetal build-up) to 1 piece. High speed machining is able to cut walls to 0.020” (0.51mm) without distortion. Part can be fixtured using “window frame” type fixture.
MRR = f d * N w
Variation Vs Part Size
Machine tool configurations
Machine tool
number of axes, spindles, serial and parallel configurations
Cutter geometry
Form tool, cutter radius, inserts, tool changers
Software
flexibility, geometrical compensation, “look ahead” dynamics compensation
Column
Base
Head
Table
Saddle
Knee
*
* Source: Kalpakjian, “Manufacturing Engineering and Technology”
* Source: Kalpakjian, “Manufacturing Engineering and Technology”
New developments
Diamond turning And grinding of optical parts
Micro machines
Hexapod Milling Machines
Tool
Linear actuator
Stewart Platform
*
* Source: http://macea.snu.ac.kr/eclipse/background/background.html
Hexapod machining center(Ingersoll, USA)
Schematics
Institut für Werkzeugmaschinen und FertigungHexaglide from Zurich (ETH)
www.iwf.mavt.ethz.ch/
Fast Tool Serverhttp://web.mit.edu/pmc/www/index.html
* Source: Reintjes, “Numerical Control 1991”
NC machine tool developed at MIT mid 1950’s
Machining Part 2
System Configurations
Part Holding / Fixturing
Process Planning
Environment
Simple Classification Scheme for Part Geometry
Primary RotationalPrimary Rotational with secondary Primary Planar
Primary Planar with secondary
Primary Rotational and Planar
Primary Rotational and Planar with secondary
Secondary
Pop quiz; how would you make a gun stock?
See video
Machining Systems Classification
Ref J T. Black
Job shop
Flow Shop
L
M
D GL M
A A
L M G G
L D
Receiving
Shipping
Flexible Manufacturing System
Transfer line
* Source: Kalpakjian, “Manufacturing Engineering and Technology”
VM
Machining Cell
S
L
L
HM
VM
G
Final inspection
Finished part cart
Raw materialcart
Worker position
Worker path
Part movement
Decoupler(Kanban square)
OUT
Part Fixturing for Prismatic Parts
Job Shop Vise Jaws / T-slot
Bolt clamps / T-slot
Direct bolt to plate / T-slot
Production Special work holding jaws and clamps
Soft jaws, custom jaws, stops, mechanical clamps, hydraulic clamps, pneumatic clamps, magnetic chuck
Multiple parts fixtures and indexing heads Tombstones, trunnion, indexing heads
Job shop fixturing
Vise Faceplate on lathe
T-slot & clamps on mill
Production
8-station Visehttp://www.te-co.com/toolex/html/10a.html
Quad-Vertical combination Chuckhttp://www.royalworkholding.com/RM3.html
Indexing Trunnionhttp://www.royalworkholding.com
Modular Fixtureshttp://www.royalworkholding.com/RM3.html
Hydraulic Pallet Fixturehttp://www.royalworkholding.com
Collet Index Fixturehttp://www.cuttingtoolmall.com/catalog/standard.cfm?FamilyID=225205
SMED
Single-Minute-Exchange-Die Shigeo Shingo, “A Study of the Toyota
Production Systems”
Stage1: Separating Internal and External Setup
Stage2: Converting Internal to External Setup
Stage3: Streamlining all aspects of the setup operation
Standardized Fixtures
Process planningHow would you machine this part?
Assumption:1. We begin with a stock size of 2.5” X 2.25” X 12”2. This will be manufactured in a job shop for very low quantity
We will use:- A bandsaw to roughly cut the stock to size- A manual vertical mill to create the planar features and the holes- A belt sander to sand the radii ( assuming the tolerance is not
very high)
Machine Operation
Horizontal band saw Saw stock to ~4.125”
Manual vertical mill
Mill two ends to length 4”
Mill width to 2”
Mill out 2”X1.5”X4”
Drill hole 1” diameter
Bore 1” radius
Belt sender Sand 0.5 radii
* Source: http://www.jettools.com/Catalog/Metalworking/CatalogPages/HVBS56M.html
*
Machine Operation
Horizontal band saw Saw stock to ~4.125”
Manual vertical mill
Mill two ends to length 4”Mill width to 2”
Mill out 2”X1.5”X4”
Drill hole 1” diameter
Bore 1” radius
Belt sender Sand 0.5 radii
*
* Source: http://www.hemsaw.com/Videolinkpages/x-vVideopg.htm
Machine Operation
Horizontal band saw Saw stock to ~4.125”
Manual vertical mill
Mill two ends to length 4”
Mill width to 2”Mill out 2”X1.5”X4”
Drill hole 1” diameter
Bore 1” radius
Belt sender Sand 0.5 radii
* Source: http://www.hemsaw.com/Videolinkpages/x-vVideopg.htm
*
Machine Operation
Horizontal band saw Saw stock to ~4.125”
Manual vertical mill
Mill two ends to length 4”
Mill width to 2”
Mill out 2”X1.5”X4”Drill hole 1” diameter
Bore 1” radius
Belt sender Sand 0.5 radii
* Source: http://www.hemsaw.com/Videolinkpages/x-vVideopg.htm
*
Machine Operation
Horizontal band saw Saw stock to ~4.125”
Manual vertical mill
Mill two ends to length 4”
Mill width to 2”
Mill out 2”X1.5”X4”
Drill hole 1” diameterBore 1” radius
Belt sender Sand 0.5 radii
* Source: http://www.hemsaw.com/Videolinkpages/x-vVideopg.htm
*
Machine Operation
Horizontal band saw Saw stock to ~4.125”
Manual vertical mill
Mill two ends to length 4”
Mill width to 2”
Mill out 2”X1.5”X4”
Drill hole 1” diameter
Bore 1” radiusBelt sender Sand 0.5 radii
* Source: http://www.hemsaw.com/Videolinkpages/x-vVideopg.htm
*
Machine Operation
Horizontal band saw Saw stock to ~4.125”
Manual vertical mill
Mill two ends to length 4”
Mill width to 2”
Mill out 2”X1.5”X4”
Drill hole 1” diameter
Bore 1” radius
Belt sender Sand 0.5 radii
* Source: http://www.jettools.com/jet-index.html (WMH Tool Group)
*
Process plan
Machine Operation
Horizontal band saw Saw stock to ~4.125”
Manual vertical mill
Mill two ends to length 4”
Mill width to 2”
Mill out 2”X1.5”X4”
Drill hole 1” diameter
Bore 1” radius
Belt sender Sand 0.5 radii
Time estimation (minutes)Machine Operation (V = Volume, A
= Area, P = Perimeter)Fixture Tool
ChangeRun (R=Rough, F=Finish)
Deburr/Inspect/
Measure
Horizontal band saw
Saw stock to ~4.125”
A = 5.6525 in2, P = 9 in0.23 - 2.02 0.30D, 0.05I
Manual vertical mill
Mill two ends to length 4”
V = 0.703 in3
A = 11.25 in2, P = 19in
0.20
0.202
0.13R
0.75F
0.63D, 0.05I,
0.13M
Mill width to 2”
V = 2.5 in3
A = 10 in2, P = 13in
0.20 -0.46R
0.67F
0.43D, 0.05I,
0.13M
Mill out 2”X1.5”X4”
V = 12 in3
A = 14 in2, P = 15in
- -2.19R
0.93F
0.50D, 0.05I
0.13M, 0.13M
Drill hole 1” diameter
-Center drill
-Pilot drill ½”
-Pilot drill 63/64”
-Ream
0.20
2
2
2
2
0.03
0.05
0.04
0.01
0.21D, 0.05I
0.17M
Bore 1” radius
V = 0.79 in3
A = 1.57 in2, P = 7.28in
0.20 20.96R
0.01F
0.24D, 0.05I
0.06M
Belt sender
Sand 0.5 radii
V = 0.05 in3
A = 0.79 in2, P = 3.14in
0.08 -0.20R
0.21F
0.10D, 0.05I
0.06M, 0.06M
Summary Times (minutes)
Fixture Tool Change Run (R=Rough, F=Finish) Deburr/Inspect/Measure
1.31 12 6.08 2.58 3.63
Total Time 25.6 minutes
Environmental issues
Waste material
Energy
Machine, material (embodied energy), temperature controlled environment
Lubricants and hydraulic fluids
Cutting Fluids
Dry machining
The average power plant in the United States is 33% efficient.
A Machine Tool Vs A SUV
50% of the energy from the grid comes from coal
electricity from the US grid comes with
667 kg of CO2/MWh
2.75 kg of SO2/MWh
1.35 kg of NOx/MWh
12.3 g Hg/GWh
etc……..
Data from US Energy Information Administration, DOE 2002 & Klee & Graedel
annual SUV equivalents
the fine print
Assumptions:
Annual emissions resulting from the operation of a typical production machine tool
(22 kW spindle, cutting 57% of the time, 2 shifts, auxiliary equipment, electricity from US grid)
as measured in annual SUV equivalents (12,000 miles annually, 20.7 mpg)
CO2 – 61 SUV’s
SO2 – 248 SUV’s
NOx – 34 SUV’s
Production machining energy Vs production rate
Ref. Toyota
Electricity Breakdown
Constant start-up operations (idle)
Run-time operations (positioning, loading, etc)
Material removal operations (in cut)
Electricity Requirements
Constant start-up operations (idle)
Run-time operations (positioning, loading, etc)
Material removal operations (in cut)
Machine Use Scenario
Arbitrary Number of work hours
Machine uptime
Machine hours (idle, positioning, or in cut)
Percentage of machine hours spent idle
Machine hours spent idle
Active machine hours per 1000 work hours
Machining Scenario
Percentage of machine hours spent positioning
Machine hours spent positioning
Percentage of machine hours spent in cut
Machine hours spent in cut
Electricity Use per 1000 work hours
Constant start-up operations (idle)
Run-time operations (positioning, loading, etc)
Material removal operations (in cut)
Total electricity use per 1000 work hours
Electricity Used per Material Removed
Material Machined
Material Removal Rate 20.0 cm3/sec 4.7 cm
3/sec 5.0 cm
3/sec 1.2 cm
3/sec 5.0 cm
3/sec 1.2 cm
3/sec 1.5 cm
3/sec 0.35 cm
3/sec
Material removed per 1000 work hours 40824000 cm3
9593640 cm3
4212000 cm3
1010880 cm3
4212000 cm3
1010880 cm3
510300 cm3
119070 cm3
Electricity used/Material removed 14.2 kJ/cm3
60 kJ/cm3
2.3 kJ/cm3
10 kJ/cm3
4.7 kJ/cm3
20 kJ/cm3
4.9 kJ/cm3
21 kJ/cm3
kWh
35%
315 hours
351 hours
40%
Aluminum Steel
13.2%
20.2%
65.8%
1.2
100
Aluminum Steel Aluminum SteelAluminum Steel
kWh
160996 kWh 5553 kWh 700 kWh2744 kWh
6237 kWh 702 kWh
600kWh 3033 kWh
673 kWh
1033
kWh
5471 kWh 1818 kWh 0 kWh
1038 kWh149288
30%
567 hours 234 hours 94.5 hours234 hours
70% 40%
70%
243 hours 351 hours 221 hours
60%30% 60%
585 hours
810 hours 585 hours 315 hours585 hours
90 hours 315 hours
900 hours
10% 35% 65%
900 hours900 hours 900 hours
1000 hours
90% 90% 90%90%
1000 hours 1000 hours1000 hours
22 kW 6.0 kW5.8 kW
3.4 kW
2.1 kW
0.7 kW
0 kW3.1 kW
kW
1.8
166 kW
6.8 kW kW
11.3%
0% (manual)
48.1% 69.4%
24.9%3.5%
31.6%
Manual Milling Machine (1985)Production Machining Center (2000)
85.2% 27.0%
Automated Milling Machine (1998) Automated Milling Machine (1988)
eye chart for energy values
Electricity Breakdown
Constant start-up operations (idle)
Run-time operations (positioning, loading, etc)
Material removal operations (in cut)
Electricity Requirements
Constant start-up operations (idle)
Run-time operations (positioning, loading, etc)
Material removal operations (in cut)
Machine Use Scenario
Arbitrary Number of work hours
Machine uptime
Machine hours (idle, positioning, or in cut)
Percentage of machine hours spent idle
Machine hours spent idle
Active machine hours per 1000 work hours
Machining Scenario
Percentage of machine hours spent positioning
Machine hours spent positioning
Percentage of machine hours spent in cut
Machine hours spent in cut
Electricity Use per 1000 work hours
Constant start-up operations (idle)
Run-time operations (positioning, loading, etc)
Material removal operations (in cut)
Total electricity use per 1000 work hours
Electricity Used per Material Removed
Material Machined
Material Removal Rate 20.0 cm3/sec 4.7 cm
3/sec 1.5 cm
3/sec 0.35 cm
3/sec
Material removed per 1000 work hours 40824000 cm3
9593640 cm3
510300 cm3
119070 cm3
Electricity used/Material removed 14.2 kJ/cm3
60 kJ/cm3
4.9 kJ/cm3
21 kJ/cm3
Aluminum Steel
100
Aluminum Steel
kWh
160996 kWh 700 kWh
6237 kWh
600kWh kWh
5471 kWh 0 kWh
149288
30%
567 hours 94.5 hours
70%
70%
243 hours 221 hours
30%
585 hours
810 hours 315 hours
90 hours
900 hours
10% 65%
900 hours
1000 hours
90% 90%
1000 hours
22 kW 2.1 kW
0.7 kW
0 kW
166 kW
6.8 kW
11.3%
0% (manual)
69.4%
3.5%
31.6%
Manual Milling Machine (1985)Production Machining Center (2000)
85.2%
Results are in terms of primary energy
Ref Smil
Sample calculation
1 kg part made from 2 kg of aluminum stock 2024
production machining 14.2 kJ/cm3
1000 g /2.7 g/cm3 = 370 cm3
(14.2 X 370 = 5.25 MJ) X 3 = 15.8 MJ
material production
(284.5 MJ/kg X 2 kg = 569 MJ)+15.8 = 585 MJ/ kg of part
Power plant efficiency
C. Smith 2001
emissions for the power station
585 MJ of primary energy (195 MJ of electricity / efficiency = .33), or .06 MWh. This gives:
33.35 kg of CO2
140 g of SO2
0.6 g of Hg
all for a 1 kg part
Home works
See webpage
Re-do “face milling of Al alloy” example with uncoated tools
estimate % of spindle power (7hp) used for “tool break video”