10/25/2015 ieng 471 facilities planning 1 ieng 471 - lecture 04 - 2 schedule design: the sequel
TRANSCRIPT
04/20/23 IENG 471 Facilities Planning 1
IENG 471 - Lecture 04 - 2
Schedule Design:
The Sequel
04/20/23 IENG 471 Facilities Planning 2
Assignments
Assignment (Due Today): HW: (HW 1.5)
5 Criteria for the Strangeglove Facility5 Quantitative Measures for the Criteria
One measure for each Criterion
Next Assignment: HW: (HW 3) See Assignment Link
required input for each of the workstationsequipment necessary for each machinesteady state cycle time for each machineideal machine assignment for each machinecompute the idle time unit cost at each workstationtotal 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:
where:S is the standard time to perform the operation, per unitQ 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 timeH 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)
EHR
SQF
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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) orMTBF (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 problemobtain repair parts / toolsrepair the failed componentsreturn the unit to operating conditions
MTTR (Mean Time To Repair)
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% Availability = MTTF
MTTF + MTTR
Availability
Availability is a function of Reliability and Maintainability:
It is the percentage of time that you can count on using it for production
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Since the number of real machines is an integer
The lower bound on the number of machines required is 4 – the sum of the equipment fractions, rounded up …
Theoretical Qty for Job Shop
The upper bound on the number of machines required is 6 – the sum of the ceiling values for each operation…
Theoretical Qty for Mass Prod
But …
Equipment Fractions - continued
Op. No.Equip.
Fraction
Integer
Ceiling
0109 1.1 2
0206 2.3 3
0274 0.6 1
Total Req’d
4 6
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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 timesPreventative maintenanceManufacturing policies…
Therefore, both total machines estimates might not really be feasible … it assumes that everything is 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
F = 4.083 Machines (Job Shop) F = 5 Machines (Mass Prod.)
What is the machine fraction if, instead:A Manufacturing Engineer suggests using a four unit mold instead of a single unit mold? F = 1.037 Machines (Job Shop) F = 2 Machines (Mass Prod.)
An Industrial Engineer suggests running three shifts, eliminating daily warm-up time?
F = 1.202 Machines (Job Shop) F = 4 Machines (Mass Prod.)
An improved facility design reduces the time to get spare parts to 2 min, and the re-warm time to 1 min?
F = 3.963 Machines (Job Shop) F = 4 Machines (Mass Prod.)
What if we did all three suggestions?
F = 0.292 Machines (Job Shop) F = 1 Machine (Mass Prod.)
What are the reasons we might do some but not other suggestions?