IENG 217
Cost Estimating for Engineers
Estimating
Operational Methods



Cost estimating relationships
Time estimating relationships
Performance time data
Cost Estimating Relationships

Parameters
Ca = -23.3 + 20(length)
bar stock length ( 5 inches ) used in CER ( $76.70 )
is often called a parameter – it is not
CER is actually a parametric equation
Cost Estimating Relationship
( I x V x Cur / 1000 ) x 12 in./ ft.
C pc 
S x 60 min / hr. x M
where
C pc  power cost per foot
I  welding current, amperes
V  welding voltage
Cur  utility power cost, dollars per KWhr
S  travel speed of arc welding process,in. per minute
M  machine efficiency, percentage
Cost Estimating Relationship

Typical arc welder draws 200 amps for
a 20 volt arc welding process. If we
have a 10 in/min welding travel speed
and a 95% machine efficiency, estimate
the cost per foot of a weld if the utility
costs are $0.08 per KWhr.
Cost Estimating Relationship

WWII military aircraft constructed of
aluminum (regression; 10 contractors)
F  0.001244 A1.160 S1.371 Q1D.281
where
F  flight test operations cost,(1970 base year )
A=weight without engines, fuel, pounds
S=maximum airspeed, nautical miles / sec
QD  number of flight test airframes
Performance Time Data
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
Time Study
Work Sampling
Performance Time Data Alg.
1.
2.
3.
4.
5.
6.
7.
8.
Collected several measurements from ops.
Classify elements into common group
Regress element time against one or more
independent causal variables
Determine if TER is constant or variable
If TER is constant, determine value
If TER is variable, convert to time table or eq.
Collect all constant variable elements for operation
If accuracy is acceptable, use information for
estimating designs
Constant or Variable ?

5 time measurements taken on a manual
handling task
Weight, lb.
1
3
4
5
7
Time, min.
.15
.20
.30
.40
.50
Regression yields
y  0.06  0.0625 x
Constant or Variable ?

Test 1
ymax  ymin
x 100  P1%
ymin

Test 2
yave
x 100  P2 %
yt
yt  total dependent value for x of operation elements
Constant or Variable ?

5 time measurements taken on a manual handling
task (test 1, P1 = 100%)
Weight, lb.
Time, min.
yhat
1
3
4
5
7
.15 .20
.1225
.30
.40
.50
.4975
ymax  ymin .4975  .1225

 3.06  306%
ymin
.1225
Carriage / Support Assembly
Regression
Element
Load Carriage
Machine Carriage
Unload Carriage
Align to support
Spot Weld Assem
Unload / Store
Parameter (xi)
Carriage Length
Carriage Length
Support girth
Support girth
No. Welds
Carriage Length
a
0.20
1.20
0.40
0.15
0.15
0.30
b
0.08
0.20
0.04
0.10
0.12
0.02
Carriage / Support Assembly
Element
Load Carriage
Machine Carriage
Unload Carriage
Align to support
Spot Weld Assem
Unload / Store
xmin
5.00
23.00
7.00
5.30
12.40
6.80
xave
6.20
27.20
7.40
7.20
15.20
7.00
xmax
8.00
29.30
8.20
8.40
18.80
7.20
SUM =
ymin
0.60
5.80
0.68
0.68
1.64
0.44
9.83
yave
0.70
6.64
0.70
0.87
1.97
0.44
11.32
ymax
0.84
7.06
0.73
0.99
2.41
0.44
12.47
Test 2 = .7/11.32 = 6.2%
Carriage / Support Assembly
Element
Load Carriage
Machine Carriage
Unload Carriage
Align to support
Spot Weld Assem
Unload / Store
Test I
Test II
Conclusion
Carriage / Support Assembly
Element
Load Carriage
Machine Carriage
Unload Carriage
Align to support
Spot Weld Assem
Unload / Store
Test I
40.0%
21.7%
7.1%
45.6%
46.9%
1.8%
Test II
6.2%
58.7%
6.2%
7.7%
17.4%
3.9%
Conclusion
Var
Var
Const
Var
Var
Const
Carriage / Support Assembly
Element
Load Carriage
Machine Carriage
Unload Carriage
Align to support
Spot Weld Assem
Unload / Store
Test I
40.0%
21.7%
7.1%
45.6%
46.9%
1.8%
Constant Elements
Unload Carriage
Unload / Store
Total Time
Std Time w/Allow
Test II
6.2%
58.7%
6.2%
7.7%
17.4%
3.9%
Conclusion
Var
Var
Const
Var
Var
Const
Time
0.70
0.44
1.14
1.31