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IENG 471 - Lecture 04 - 2

IENG 471 - Lecture 04 - 2. Schedule Design: The Sequel. Assignments. Assignment (Due Today): HW: (HW 2) E-mailed as an Excel spreadsheet attachment Next Assignment: HW: (HW 3) See Assignment Link required input for each of the workstations equipment necessary for each machine

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IENG 471 - Lecture 04 - 2

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  1. IENG 471 - Lecture 04 - 2 Schedule Design: The Sequel IENG 471 Facilities Planning

  2. Assignments • Assignment (Due Today): • HW: (HW 2) • E-mailed as an Excel spreadsheet attachment • 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

  3. 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

  4. 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

  5. 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

  6. 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

  7. % 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

  8. Equipment Fractions - continued • 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 … IENG 471 Facilities Planning

  9. 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, both total machines estimates might not really be feasible … it assumes that everything is best case scenario! IENG 471 Facilities Planning

  10. 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

  11. 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

  12. 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 = 1.021 Machines (Job Shop) F = 2 Machines (Mass Prod.) • An Industrial Engineer suggests running three shifts, eliminating daily warm-up time? F = 1.255 Machines (Job Shop) F = 2 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 = 0.305 Machines (Job Shop) F = 1 Machine (Mass Prod.) • What are the reasons we might do some but not other suggestions? IENG 471 Facilities Planning

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