4- 1 6/13/2014 Process Engineering Basics of Process Planning for computer implementation IE550 -- Manufacturing Systems Fall 2008 Dr. R. A. Wysk.

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Process EngineeringBasics of Process Planning

for computer implementation

IE550 -- Manufacturing Systems

Fall 2008

Dr. R. A. Wysk

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Chapter 6 -- Process Engineering

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The Engineering Process

Stock Material Processes Finished part

Design specifications

Process planningProcesscapability

Inspection

Need to understand the process capabilities.

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PROCESS CAPABILITIES

Process: certain way an operation is carried out, e.g. turning, drilling, milling.

Tool: physical object which is used to carrying out a process, e.g. twist drill, spade drill, gun drill.

Machine tool: machine on which process is carried out, e.g. lathe, drill press, milling machine, machining center.

Process capability: The geometry and tolerance a manufacturing processcan produce, and its limitations, . i.e. shape and size, dimensional and geometric tolerances, material removal rate, relative cost, other cutting constraints.

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LEVELS OF PROCESS CAPABILITIES

Universal level:

Handbook and textbook level data. Aggregate characterization of what can be expected. General measures of the process capability such as shape and size. What the process can accomplish in an average shop on a typical machine tool.

Shop level:

Specific to a particular manufacturing system. What is the best attainable capability in one specific shop, e.g. the turning capability of the student machine shop is far worse than that in the shop of a precision spindle manufacturer.

Machine level:

Specific to a machine. Machines in the same shop has very different capability. A table top lathe can machine a small part, yet a large slant bed lathe may be able to handle a 20"x 10' part.

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PROCESS KNOWLEDGE COLLECTIONFew scientific data available or published.

Most process knowledge are gained during actual manufacturing practice.

Practical manufacturing knowledge is still an art instead of a science.

Certain information can be found in the textbooks, handbooks, machining data handbook, etc.

Tolerance capability may be obtained from control charts, inspection reports, and on-line sensor data.

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EXPERIENCE-BASED PLANNING

Relay on one's experience. Most frequently this is the way industry operates.

Problems:

a. Experience requires a significant period of time to accumulate.

b. Experience represents only approximate, not exact knowledge.

c. Experience is not directly applicable to new processes or new systems.

Need to automate.

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MACHINIST HANDBOOKSUniversal or shop level knowledge.

e.g. Surface-finish chart - limiting extremes of process

8 in - use grinding, polishing, lapping

Usually not with milling, however, finish milling may achieve the specification.

The information is general. It does not mean every machine or shop can achieve that accuracy.

Turning limit (6.3 - 0.4 m or 250 - 16 inch)

Diamond turning at Lawrence Livermore Lab

(12.5 nm or 0.47 inch)

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SURFACE FINISH CHART

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Dimensional accuracies for Process Planning

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HOLE MAKING KNOWLEDGEFollowing data is taken from a manufacturer's process planner's handbook.

I. Dia < 0.5"

A. True position > 0.010"

1. Tolerance > 0.010"

Drill the hole.

2. Tolerance < 0.010"

Drill and ream the hole.

B. True position < 0.010”

1. Tolerance < 0.010"

Drill, then finish bore the hole.

2. Tolerance < 0.002"

Drill, semi-finish bore, then finish bore the hole.

II. 0.05" < dia < 1.00"

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DECISION TABLESTo computerize the decision making, one simple way is to use decision tables.If the conditions set in an entry are satisfied, the actions in the entry areexecuted. The stub contains the condition or action statements. Entries markwhich conditions or actions are applicable. Each entry contain one rule.

Conditions

Actions

Stub Entries

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EXAMPLE DECISION TABLE

Dia < 0.5

0.5 < Dia < 1.0

T.P < 0.010

T.P < 0.010

Tol > 0.010

0.002 < Tol < 0.010

Tol < 0.002

Drill

Ream

Semi-finish bore

Finish bore

X X X X

XXXX X

X

X

X

X

X

X

XX X XX

XX X

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DECISION TREES

Node

Branch

To computerize the decision making, one simple way is to use decision trees.

Decision tree is a graph with a single root and branches emanating from theroot. Each branch has a condition statement associate with it. Actions are written at the terminal. Probabilities may be assigned to the branches. In this case, the tree represents probabilistic state transitions.

Root

terminal

The node may be "AND" nodesor "OR" nodes.

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EXAMPLE DECISION TREE

Dia < 0.5

0.5 < Dia < 1.0

T.P < 0.010

T.P < 0.010

Tol > 0.010

Tol < 0.010

0.002 < Tol < 0.010

Tol < 0.002

Drill

Drill, then ream

Drill, then finish bore

Drill, semifinish bore,then finish bore

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PROCESS-CAPABILITY ANALYSIS

; ; twist drilling (code 1); 111: hole( ( if (shape ! 111 = ) ( length ! 12.0 diameter ! * <= ) ( diameter! 0.0625 >= ) ( diameter! 2.000 <= ) ( tlp ! diameter ! 0.5 ** 0.007 * >= ) ( tln ! diameter ! 0.5 ** 0.007 * 0.003 + >= ) ( straightness ! length ! diameter ! / 3. ** 0.0005 * 0.002 + >= ) ( roundness ! 0.004 >= ) ( parallelism ! length ! diameter ! / 3. ** 0.001 * 0.003 + >= ) ( true ! 0.008 >= ) ( sf ! 100 >= ) )

PROCESS BOUNDARY Data

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PROCESSES, TOOLS, AND MACHINES

•

Process Sub-Process Cutters

Milling

Plain Shell end Hollow end Ball end

End milling

Peripheral milling Plain Slittting Saw Form Inserted-tooth Staggered-tooth Angle T-slot cutter Woodruff keyseat cutter Form milling cutter

Face milling Plain Inserted-tooth

Drilling

Twist drill Spade drill Deep-hole drill Gun drill Trepanning cutter Center drill Combination drill Countersink Counterbore

ReamingShell reamer Expansion reamer Adjustable reamer Taper reamer

Boring Adjustable boring bar Simple boring bar

BroachingForm tool

Machines

Vertical milling machine Horizontal milling machine Column-and-knee Bed type Planer type Special type Machining center

Column & upright Gang drilling machine Radial drilling machine Multispindle drilling machine Bench type Deepth hole drilling machine

Drill press Lathe

Lathe Boring machine Jig bore

Turning

Turning Facing Parting Knurling Boring Drilling Reaming

Plain Inserted

Knurling tool

Boring bars Drills Reamers

Speed lathe Engine lathe Toolroom lathe Special lathe Turret lathe Screw machine

Broaching press Vertical Pull-down Vertical Pull-up Surface broaching machine Horizontal broaching machine Surface broaching machine Rotary broaching machine

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PROCESSES, TOOLS, AND MACHINES

Shaping Form tool

Planing

Inserted tool

SawingHacksaw Bandsaw Circular saw

Process Sub-Process Cutters Machines

Grinding

Cylindrical grinding Centerless grinding Internal grinding External grinding Surface grinding

Reciprocating saw Band saw Circular saw

Shaper Horizontal & Vertical

Double housing planer Open-side planer Edge planer Pit Planer

Grinding wheels Points

External cylindrical grinder Internal cylindrical grinder Surface grinder Creep feed grinder Tool grinder Disk grinder

Honing Honing stone Honing machine

Lapping Lap Lapping machine

Tapping Tap Drill press Milling machine Machining center

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CUTTING EDGE AND FEED

Drill

cutting edge

Boring Reaming

Turning

Peripheral Milling

minor feed

Face Milling

feed range

Ball End Milling

Broaching Sawing

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VOLUME PRODUCING CAPABILITIESProcess Sub-Process Cutters

Milling

Plain Shell end Hollow end Ball end

End milling

Peripheral milling Plain Slittting Saw Form Inserted-tooth Staggered-tooth Angle T-slot cutter Woodruff keyseat cutter

Face milling Plain Inserted-tooth

Drilling

Twist drill Spade drill Deep-hole drill Gun drill Trepanning cutter Center drill Combination drill Countersink Counterbore

Reaming

Shell reamer Expansion reamer Adjustable reamer Taper reamer

BoringAdjustable boring bar Simple boring bar

Broaching Form tool

Volume Capabilities

flat bottom volume

round hole round hole deep round hole deep round hole large round hole shallow round hole multiple diameter round hole countersink hole counterbore hole

thin wall of round hole thin wall of round hole thin wall of round hole thin wall of round holethin wall of round hole thin wall of round hole

Turning

Turning Facing Parting Knurling Boring Drilling Reaming

Plain Inserted

Knurling tool

Boring bars Drills Reamers

? disk disk ? thin wall of round hole round hole thin wall of round hole

flat bottom volume slot step polyhedral through hole formed through volume

flat bottom volume slot formed volume T-slot Internal groove

pocket, slot, flat

sculptured surface, flat

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VOLUME PRODUCING CAPABILITIES

Shaping Form tool

Planing

Inserted tool

SawingHacksaw Bandsaw Circular saw

Process Sub-Process Cutters Volume Capabilities

Grinding

Cylindrical grinding Centerless grinding Internal grinding External grinding Surface grinding

?

flat bottom volume, slot

flat bottom volume

Grinding wheels Points

? internal wall of round hole flat bottom volume

Honing Honing stone ?

Lapping Lap most surfaces

Tapping Tap threaded wall of hole

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PROCESS TOLERANCE RANGEProcess Sub-Process Cutters

Milling

Plain Shell end Hollow end Ball end

End milling

Peripheral milling

Plain Slittting Saw Form Inserted-tooth Staggered-tooth Angle T-slot cutter Woodruff keyseat cutter Form milling cutter

Face milling Plain Inserted-tooth

Drilling

Twist drill Spade drill Trepanning cutter Center drill Combination drill Countersink Counterbore Deep-hole drill Gun drill

Reaming

Shell reamer Expansion reamer Adjustable reamer Taper reamer

BoringAdjustable boring bar Simple boring bar

Broaching Form tool

Turning

Turning Facing Parting Knurling Boring Drilling Reaming

Plain InsertedKnurling toolBoring bars Drills Reamers

Tolerances, surface finish, etc. capabilities

roughting finishing tol 0.002 0.001 flatness 0.001 0.001 angularity 0.001 0.001 parallelism 0.001 0.001 surface finish 50 30

roughting finishing tol 0.002 0.001 flatness 0.001 0.001 surface finish 50 30

roughting finishing tol 0.004 0.004 parallelism 0.0015 0.0015 surface finish 60 50

length/dia = 3 usual =8 maximum mtl < Rc 30 usual < Rc 50 maximum Dia Tolerance 0 - 1/8 +0.003 -0.001 1/8-1/4 +0.004 -0.001 1/4-1/2 +0.006 -0.001 1/2- 1 +0.008 -0.002 1 - 2 +0.010 -0.003 2 - 4 +0.012 -0.004

usuall best True position 0.008 0.0004 roundness 0.004 surface finish 100

Dia Tolerance < 5/8 0.0015 >5/8 0.002

surface finish > 100 straightness 0.005 in 6 inch

Dia Tolerance 0 - 1/2 0.0005 to 0.001 1/2- 1 0.001 1 - 2 0.002 2 - 4 0.003

roughting finishing roundness 0.0005 0.0005 true position 0.01 0.01 surface finish 125 50

length/dia 5 to 8

Dia Tolerance roughing finishing 0 - 3/4 0.001 0.0002 3/4- 1 0.0015 0.0002 1 - 2 0.002 0.0004 2 - 4 0.003 0.0008 4 - 6 0.004 0.001 6 - 12 0.005 0.002

straightness 0.0002 roundness 0.0003 true position 0.0001 surface finish 8

diameter tolerance to 1.0 0.001 1 - 2 0.002 2 - 4 0.003

surface finish 250 to 16

tolerance 0.001 surface finish 125 to 32

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PROCESS TOLERANCE RANGE

Shaping Form tool

Planing Inserted tool

Sawing Hacksaw Bandsaw Circular saw

Process Sub-Process Cutters

Grinding

Internal grinding Cylindrical grinding Centerless grinding External grinding Surface grinding

Honing Honing stone

Lapping Lap

Tapping Tap

Tolerances, surface finish, etc. capabilities

length tol squareness surface finish cutting rate material 0.01 0.2 200 - 300 3-6 sq in/min to Rc45 0.01 0.2 200 - 300 4-30 sq in/min to Rc45 0.008 0.2 125 7-36 sq in/min to Rc45

roughting finishing location tol 0.005 0.001 flatness 0.001 0.0005 surface finish 60 32 (cast iron) surface finish 125 32 (steel)

Dia Tolerance roughing finishing 0 - 1 0.00015 0.00005 1 - 2 0.0002 0.00005 2 - 4 0.0003 0.0001 4 - 8 0.0005 0.00013 8 - 16 0.0008 0.0002

Dia Tolerance roughing finishing 1 +0.0005-0.0 +0.0001-0.0 2 +0.0008-0.0 +0.0005-0.0 4 +0.0010-0.0 +0.0008-0.0

surface finish 4 roundness 0.0005

roughing finishing tolerance 0.000025 0.000015 flatness 0.000025 0.000012 surface fin 4-6 1-4

tolerance 0.003 roundness 0.003 surface fin 75

roughing finishing tolerance 0.0005 0.0001 parallelism 0.0005 0.0002 roundness 0.0005 0.0001 surface fin 8 2

roughing finishing tolerance 0.001 0.0001 parallelism 0.001 0.0001 surface fin 32 2

center ground

flat

and centerless

Internal

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AUTOMOTIVE PARTS REQUIREMENTS

• Cylinder bore 13 - 25 in honed

• Main bearing bore 63 - 200 in• Crankshaft bearing 3-13 in polished

• Brake drum 63-125 in turned

• Clutch pressure plate 25-100 in turned

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BASIC MACHINING CALCULATIONS

tm = L + L

v f

Machining time

Total amount of time to finish a workpiece.

For drilling, one pass turning, and milling:

L : clearance or overhang distance.

For multipass turning

n p =

Do – Di

2 a p

+

integer round up

For milling

n p = h

a p

+ w D

+

n p : # of passes

h : total height of material to be removed

w : workpiece width : cutter overlapping factor

= effective cutting width / tool dia 1.0

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BASIC MACHINING CALCULATIONS

Machine control parameters are: f, V, ap.

a. Feed and feedrate

f: inch / rev

turning or drilling

milling

rp m

N :# of teech in milling1 in drilling

n : rpm

V f = f nN

V f = f n

V f : inch / min

Vf

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BASIC MACHINING CALCULATIONSCutting speed

D: Diameter

Depth of cut

a p inch

a p =

Do – Di

2

D

V

surface speed

V in sfpm

Di

D0

V = D n12

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BASIC MACHINING CALCULATIONSMetal removal rate

MRR cutting time tool life

MRR in3minin3min

Drilling

Turning

Milling

W

v f

a p

MRR = D 2

4v f

= 3D f V

MRR =

( D2

o – D2

i)4

v f

= 6(Do – Di ) f V

v f

(D2o –D 2

i)4

MRR = a p w v f

=12 a p w n

Df V

D2

4

v f

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BASIC MACHINING CALCULATIONS

tm = L + L

v f

Machining time

Total amount of time to finish a workpiece.

For drilling, one pass turning, and milling:

L : clearance or overhang distance.

For multipass turning

n p =

Do – Di

2 a p

+

integer round up

For milling

n p = h

a p

+ w D

+

n p : # of passes

h : total height of material to be removed

w : workpiece width : cutter overlapping factor

= effective cutting width / tool dia 1.0

L

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CUTTING FORCE AND POWER

Process Sub-Process

Milling

End milling

Peripheral milling

Face milling

Drilling

Reaming

Boring

Shaping

Planing

Broaching

TurningFacing

Turning

Cutting Force F Power (hp)

KF f FapFDt

Fbw z

KF v FafFap

F bwFz FDt

F

KF f FapF

KF f FapF Dt

F

KF apF Dmzc

c (lb)

Fc Vc

33,000 m

Fc Vc

33,000 m

Fc Vc

33,000 m

Ts rpm63,030 m

where:

Vc :: cutting speed fpm m : machine efficiency Ts : Torque

torque

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MATERIAL REMOVAL RATE

Process Sub-Process

Milling

End milling

Peripheral milling

Face milling

Drilling

Boring

Shaping

Broaching

Turning

W: width of the cutter ap : depth of cut f : feed n : number of teeth N : spindle rpm

D : tool diameter

tr : rise per tooth W : Width of the tool V : cutting speed n : number of tooth in contact with part

12 tr W V n

( D2/4) f N

12 V f ap

12 V f ap

Facing

Turning

6 V f ap

L t f NsL : strock length Ns : number of strock per minute

W ap f n N

MRR

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CONSTRAINTS

nmin nw nmax

ntmin nt ntmax

Fc Fc,max

Spindle-speed constraint:workpiecetool

Feed constraint:

Cutting-force constraint:

Pm Pmax

Power constraint:

Ra Ra,max

Surface-finish constraint:

fmin f f max

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MODELSMultiple pass model

t pr th + (t i

mi = 1

n p

+t i

m

t t t)

c pr cb

nb+ cmth + ci

pri = 1

n pi : pass number

Additional constraint:

depth of cut

: number of passes is a function of the depth of cut.

a p

n p

Productivity model: pr

s – c pr

t pr

s: sale price/piece