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

04/20/23 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!

04/20/23 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 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

04/20/23 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) orMTBF (Mean Time Between Failures)

04/20/23 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 problemobtain repair parts / toolsrepair the failed componentsreturn the unit to operating conditions

MTTR (Mean Time To Repair)

04/20/23 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

04/20/23 IENG 471 Facilities Planning 8

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

04/20/23 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 timesPreventative maintenanceManufacturing policies…

Therefore, both total machines estimates might not really be feasible … it assumes that everything is best case scenario!

04/20/23 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!

04/20/23 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!

04/20/23 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 = 1.037 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?