Schedule & Facilities Design
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Transcript Schedule & Facilities Design
IENG 471 - Lecture 04 - 2
Schedule Design:
The Sequel
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Assignments
Assignment (Due Today - Now):
HW:
(HW 2)
Product BOM
Product Operation Process Chart
Product Precedence Diagram
Next Assignment:
HW:
4/7/2015
(HW 3) See Assignment Link
required input for each of the workstations
equipment necessary for each machine
steady state cycle time for each machine
ideal machine assignment for each machine
compute the idle time
unit cost at each workstation
total cost per good unit
square footage for each workstation and the total space required
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Equipment Requirements
Equipment Fractions are the number of
machines of one type required to produce
the required volume of product(s)
Some machines can be used to perform multiple
operations…
So, if idle time on the machine exists, and there are
multiple products scheduled, then fewer total machines
may be required!
Some machines may not be able to perform the
required operation(s) fast enough to reach the
required volume with only one machine…
So, more copies of the machine may be required!
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Estimating Equipment Fractions
The equipment fraction for each req’d machine is based on all
of the operations the machine will perform
Good thing we got those Operations Process Charts!
To find the number of machines of a type for the facility:
The number of workstations for a shift (F) is:
F
where:
SQ
EHR
S is the standard time to perform the operation, per unit
Q is the quota of output units per shift
E is the efficiency of production on the machine, expressed as a
percentage of the standard operation time
H is the hours available for production on the machine during
the shift (or whatever unit of time matches parameter S)
R is the availability (reliability*) of the machine, expressed as %
of the “up time” that the machine is available to work (%H)
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Reliability
Reliability is a measure of how often a
system fails:
How long (on average) you can run it until it
stops working right
How do you know that it’s not working right?
MTTF (Mean Time To Failure) or
MTBF (Mean Time Between Failures)
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Maintainability
Maintainability (serviceability) is a
measure of how long it takes to return
the system to proper operation:
Sum of the times required to:
diagnose the problem
obtain repair parts / tools
repair the failed components
return the unit to operating conditions
MTTR (Mean Time To Repair)
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Availability
Availability is a function of Reliability
and Maintainability:
It is the percentage of time that you can
count on using it for production
% Availability =
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MTTF
MTTF + MTTR
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Equipment Fractions - continued
Since the number of
machines is an integer
Op. No.
Equip.
Fraction
Integer
Ceiling
0109
1.1
2
0206
2.3
3
0274
0.6
1
Total
Req’d
4
6
The lower bound on the
number of machines
required is 4 – the sum of
the equipment fractions
The upper bound on the
number of machines
required is 6 – the sum of
the ceiling values for each
operation…
But …
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Equipment Fractions - continued
We should adjust the required number of
machines to also account for:
Frequency of changeover (flexibility)
Set-up times
Preventative maintenance
Manufacturing policies…
Therefore, the four machines estimate might
not really be feasible … it assumed that
everything was best case scenario!
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Ex: Injection Mold Rubber Feet
Process for juicer is:
Mold & trim feet – 2% scrap rate
Transport trimmed feet to line – 1% scrap rate
Assemble juicer – 0.5% scrap rate
3 grams of rubber needed per foot
Find the number of feet to be processed at each
workstation!
Find the raw rubber needed for this process!
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Ex: Injection Mold Rubber Feet
Shift is 8 hr, but reduced by two 15 min breaks, and 35 min
machine warm-up (to heat the mold and material).
Production schedule requires 2450 sets of feet daily
MTTF is 38 hours
MTTR comprises 5 min to diagnose, 55 min to obtain spare
parts, 7 min to fix, 18 min to re-warm
Run one shift per day
Obtain one set of four feet per cycle
Cycle time is 40 s (steady state)
Find the equipment fraction for this process!
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Questions
What is the machine fraction if, instead:
A Manufacturing Engineer suggests using a four unit
mold instead of a single unit mold?
An Industrial Engineer suggests running three shifts,
eliminating daily warm-up time?
An improved facility design reduces the time to get
spare parts to 2 min, and the re-warm time to 1 min?
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