ieng 217 cost estimating for engineers
DESCRIPTION
IENG 217 Cost Estimating for Engineers. Operation Estimating. Tooling. Estimated Operation Cost. Direct Labor. Prime Cost. Direct Material. Operation Cost Elements. Turning Operation. Operation Time. t pr = total process time = machine time + handling time + tool change time - PowerPoint PPT PresentationTRANSCRIPT
IENG 217Cost Estimating for
Engineers
Operation Estimating
Operation Cost Elements
Direct Material
Direct Labor
Tooling
Prime Cost
EstimatedOperation
Cost
Turning Operation
Operation Time tpr = total process time = machine time + handling time + tool change time
= tm + th + tc(tm/T)where
tm = machine time
th = time to load/unload machine
tc = time to change a tool
(tm/t) = no. parts that can be produced before a tool change is required
T = life of a tool
Operation Time
cpr = production cost
= batch cost + machine cost + tool cost
cc
Nc t t
t
Tt c
t
T
where
c
total machine operator rate
c of tool
N batch size
prb
bo m h
mc pt
m
b
pt
b
( ) ( )
&
cost of batch setup
c
costo
Machining Time Function of rate of processing
t tool path length feed speed
L
f N
where
f feed inches tooth revolution
N rpm
m
/
( / / )
Machining Time Function of rate of processing
t tool path length feed speed
L
f N
L
fVD
L D
f V
m
/
12 12
Example 3” diameter piece to be turned to 2.8” diameter,
length of stock to be turned is 10”, f = 0.01”/rev., V = cut speed = 200 fpm, d = depth of cut = .2”.
Find machine processing time
Tool Life V
V
t
T
where
n
V cutting speed
T tool life
V ref cutting speed
t ref tool life
r
rn
r
r
FHIK
constant
.
.
n
r
r T
t
V
V
Tool Life
V
V
t
T
TV
Vt
Tt V
V
C
V
r
rn
n rrn
r rn
n
FHIK
1
1
/
/
n
r
r T
t
V
V
Example
HSS cutter; at 250 sfpm tool lasts 30 min; at 100 sfpm tool lasts 60 min. Find tool life eq.
Operation Time
tpr = total process time
= machine time + handling time + tool change time
= tm + th + tc(tm/T)
cc
Nc t t
t
Tt c
t
Tprb
bo m h
mc pt
m ( ) ( )
Operation Time
tpr = total process time
= machine time + handling time + tool change time
= tm + th + tc(tm/T)
cc
Nc t t
t
Tt c
t
Tprb
bo m h
mc pt
m ( ) ( )
Q: Do we want to minimize processing time or do we want to minimize part cost?
Example Turning operation; L=10 inches, D = 3inches to
2.9 inches, feed = 0.1 inch/rev, load and unload = 2 min, cutter change = 3 min, tool life given by
T = 1.7x105 V-1.7, Co = $35/hr, Cpt = $3 / cutter
Example Turning operation; L=10 inches, D = 3inches to 2.9 inches, feed = 0.1
inch/rev, load and unload = 2 min, cutter change = 3 min, tool life given by T = 1.7x105 V-1.7, Co = $35/hr, Cpt = $3 / cutter
nV
D
VV
V fn V V
tL
V VV
f
mf
12 123 2 9
2
1 273
0 1 1 273 1273
10
127378 5 1
. .
. ( . ) .
.
Example
tL
V VV
t t t t t T
VV
x V
V V
mf
pr m h c m
FHG
IKJ
10
127378 5
78 5 2 378 5
1 7 10
78 5 2 001386
1
11
5 1 7
1 1
.
( / )
..
.
. .
. 715
1
1071
578..
.
Vx
V
Operations Analysis Factual time and cost estimating catalogues Product design Process knowledge Operations sheet preparation Time and cost finding
Time Elements Setup time Cycle time
Setup TimeElement Time (hrs)Punch in, study drawing 0.2Turning Equipment First machining tool 0.8 Additional tool 0.3 Collet 0.2 Fixture 0.2Milling Equipment Vise 0.6 Fixture 1.2 Collet 0.5Drilling Equipment Fixture 0.3 Vise 0.1 First Spindle 0.7 Additional spindles 0.4Total Setup Time 5.5
Cycle Time Elements Element Time (min) Time (min)General Start/stop machine 0.10 Air clean part 0.09 Brush chips 0.12 Inspect w/micrometer 0.30 Total General 0.61Turning Equipment Advance/Index turret 0.08 Cross slide adv/index 0.09 Advance stock 0.23 Place guard / start 0.16 Total Turn Specific 0.56Milling Equipment 1.8Drilling 1.2Total Setup Time 4.17
Product Design
Process knowledge
Workstation Ops. No. DescriptionTurret Lathe 10 Turn and cutoffVertical Mill 20 End Mill SlotHorizontal Mill 30 Slab Mill FlatNC Drill Press 40 Drill and Tap Holes
Operations Sheet
Cost Estimates Design Length 18.750Facing Length 0.015Cutoff Length 0.187Total Length 18.952Units / 12 ft bar stock 7.598Units / 12 ft bar stock 7Bars per Lot (200) 28.571Bars per Lot (200) 29Cost per bar (8.178 lb/ft x 12 ft x $1.5/lb) $147.20Lot Cost (bars/lot x cost per bar) $4,268.92Cost per unit (Lot Cost/Lot Size $21.34Material Yield (200 x fl / total length) 89.8%
Setup & Cycle for Operation 10Setup Elements Punch in, study drawing 0.2 First machining tool 0.8 Additional tool 0.3 Collet 0.2 Fixture 0.2Total Setup, Oper 10 1.7
Handling Start/stop machine 0.10 Advance stock 0.23 Brush chips 0.12 Place guard / start 0.16 Advance/Index turret 0.08 Cross slide adv/index 0.09 Inspect w/micrometer 0.30Total Handling 1.08
Machining Times Dimension Depth Length Safety Stc Length Diameter Velocity feed Min Face 1.45 0.015 0.875 1/32 0.906 1.75 350 0.007 0.17 Rough turn 1.15 0.15 16.5 1/32 16.531 1.75 350 0.015 1.44 Rough turn 1.10 0.15 16.5 1/32 16.531 1.45 350 0.015 1.19 Finish turn 1.735 0.025 16.5 1/32 16.531 1.15 350 0.007 2.03 Turn 1.75 0.0075 0.5 1/32 0.531 1.75 350 0.007 0.1 Cutoff 0.187 0.875 1/32 0.906 1.75 350 0.015 0.08Total Mach. Time 5.01Total Cycle Time 6.09
Entry for Opr 10 to Ops Sht. Setup hr 1.7 Hrs/100 units 10.15