IENG 471 - Lecture 04 - 2

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IENG 471 - Lecture 04 - 2. Schedule Design: The Sequel. Assignments. Assignment (Due Today - Now): HW: (HW 2) Product BOM Product Operation Process Chart Product Precedence Diagram Next Assignment: HW: (HW 3) See Assignment Link required input for each of the workstations

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### IENG 471 - Lecture 04 - 2

Schedule Design:

The Sequel

IENG 471 Facilities Planning

Assignments
• Assignment (Due Today - Now):
• HW: (HW 2)
• Product BOM
• Product Operation Process Chart
• Product Precedence Diagram
• Next Assignment:
• HW: (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

IENG 471 Facilities Planning

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!

IENG 471 Facilities Planning

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 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)

IENG 471 Facilities Planning

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)

IENG 471 Facilities Planning

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)

IENG 471 Facilities Planning

% 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

IENG 471 Facilities Planning

Equipment Fractions - continued
• Since the number of machines is an integer
• 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 …

IENG 471 Facilities Planning

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!

IENG 471 Facilities Planning

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!

IENG 471 Facilities Planning

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!

IENG 471 Facilities Planning

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?

IENG 471 Facilities Planning