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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

IENG 471 - Lecture 04 - 2

Schedule Design:

The Sequel

IENG 471 Facilities Planning

assignments
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 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
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
  • 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
  • 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

% 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
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 continued1
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
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 feet1
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
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