case_1

First Case Study

Calculation of Various Reliability Measures using Historical Data

Purpose: To calculate Mean Time Between failures (MTBF), Mean Time To Repair (MTTR), Failure Rate, and

other Reliability, Maintainability, and Availability measures using the reliability data.

Benefits: Reliability data serves several important purposes:

1) To provide failure history, repair history, and other reference data for use in production;

2) To detect current reliability and maintainability problems and assist in their solutions;

3) To provide managers with quantitative information on equipment performance;

4) To assist in reliability improvement programs.

The MTBF/MTTR Model: The main reliability measures are simple to calculate. For instance:

MTBF = (Operating Time)/(Number of Failures)

MTTR = (Unplanned Downtime)/(Number of Failures)

Percent Availability (A) = (Operating Time)/(Operating Time +Unplanned Downtime)

Speed Ratio (S) = (Designed Machine Cycle Time)/(Actual Machine Cycle Time)

Yield (Y) = (Good Products)/(Good Products + Defective Products)

Overall Equipment Effectiveness (OEE) = A.S.Y

Note: There are different ways to define reliability measures, hence you are encouraged to use the definition

that is adopted by your corporation. If you have not been exposed to these definitions, discuss it briefly within

yourselves and choose the most appropriate ones.

Facts about the case: A company was inquiring about a Grinder that was needed for production. There are two

operations Op1 and Op2 and there were 4 machines involved in those operations. Two types of Grinders are

used for two operations. Two identical machines perform the finish grinding on one face while two other

identical machines grind the adjacent faces. We received the following data that were manually collected on

performance of the grinder over a week.

Calculation of Reliability Measures: Calculate different reliability measures and offer your critics regarding

the performance of the machine.

A Summary of the Reported Downtimes:

-----------------------------------------------------------------------------------------------------------

Date Start Resp. Diag. Total Oper. Description

time time time time

----------------------------------------------------------------------------------------------------------- 08/01 00:00 8 7 15 101 startup

08/01 00:00 8 7 15 102 startup

08/01 00:00 8 7 15 201 startup

08/01 00:00 8 7 15 202 startup

08/01 01:20 10 5 15 201 coolant system filter leaking

08/01 04:45 4 1 5 101 clamp arm got stuck picking part

08/01 06:22 0 8 8 101 work didn't chuck up

08/01 07:40 4 1 5 101 clamp arm stuck

08/01 11:30 5 5 10 201 coolant system leaking



08/02 12:17 15 1 16 101 gantry loader reset

08/02 15:40 21 1 22 101 gantry loader reset

08/02 06:56 9 1 10 101 clamp arm stuck when picking parts

08/02 07:15 20 33 53 101 headstock is not advanced auto.


08/02 09:29 10 34 44 101 work chunk being repaired

08/03 11:30 0 12 12 101 gaging, post process


08/03 14:43 0 6 6 102 reset controls

08/03 15:18 0 2 2 101 gaging

08/03 15:22 0 4 4 101 gaging

08/03 05:50 0 20 20 102 problem with loader

08/03 07:37 45 140 185 101 locating dowel for clamp shaft bush.

08/03 00:40 20 1 21 201 overhead conveyor down

08/04 01:55 60 245 305 102 change wheel

08/04 07:37 5 1 6 101 part not chucking up automatically

08/04 08:30 0 69 69 102 mach. was down from wheel change


08/04 09:25 24 113 137 201 wheel head had L/S fault

08/04 12:10 68 5 73 202 coolant filter had a hole in it


08/04 13:40 3 1 4 101 loader/unloader reset

08/04 14:48 0 4 4 101 gaging

08/04 14:57 6 1 7 102 loader/unloader reset

08/04 11:00 0 10 10 202 bad parts

08/04 14:53 0 4 4 101 gaging

08/04 16:11 0 5 5 101 gaging

08/05 09:17 0 4 4 101 gaging

08/05 10:47 2 1 3 101 loader reset

08/05 12:14 12 1 13 102 loader reset

08/05 04:17 0 18 18 101 no stock due to unloader problem

08/05 06:15 0 15 15 102 loader problems

08/05 07:05 4 20 24 101 loader problems

08/05 08:05 10 12 22 102 loader problems

08/05 09:40 20 1 21 201 elevator between 150 and 160 down

08/05 16:09 1 50 51 101 clamp/unclamp air chuck not work.

08/06 11:01 0 10 10 101 gaging

08/06 11:30 0 3 3 102 gaging

Second Case Study

Practice of Performing FMEA on a Product

This case study will be an open ended project in which you are asked to get into groups of 3 to 4 participants

and select one of the following components, subsystem, or system that your group is familiar with. Then

conduct a brainstorming session aimed at performing all aspects of FMEA on the selected part. Your team can

pick any of the following products for the purpose of conducting Design FMEA.

a) A coffee maker

b) A toaster

c) A cell phone

d) A headphone

e) A bicycle

Your product can be a cheap one with very simple and unsophisticated design or a fancy one with lots of

features, but your grade depends on the complexity of the design. If you prefer you can contact me with a

proposal as to the product of your choice, and upon my approval, you may proceed with FMEA of your own

product.

You are expected to provide me with:

1) A detailed FMEA analysis, covering as much of the steps as practically possible.

2) Some photos of the product showing major components

3) A list of all the pertinent components.

4) Summary of your recommendations.

The group is responsible for performing a detailed FMEA analysis for the part and presenting their findings

along with a description of the recommended actions to the class. The format of the report and the presentation

is as follows: 1) Each team will submit their findings in one report. The report should be typed or printed in a FMEA form.

2) A leader in each team will have 10 minutes to present the case and respond to the critics.

In what follows, few examples of FMEA is depicted.

Failure Mode and Effect Analysis

Page: 1

Date: 8 Nov 2014

Project: Simple Flashlight Example

Function/System: Flashlight

Phase/Mode: Normal Operation Reference Drawing:FL164578-1

Assembly Name: Flashlight Assembly RD: 1

Ref

DesName & Function FMI Failure Mode Local Effect Next Higher Effect

Sev

.End Effect

Detection Method

Compensating

Provisions

Remarks

Failure Cause RD Item Causing

1 Flashlight

- No Data

FAAA constant flashlight output 1 constant flashlight output Comp / Prov:

None

Det. Method:

None

Remarks:

None

Stuck closed 1A2 Switch

FAAB flashlight output dim 3 flashlight output dim Comp / Prov:

None

Det. Method:

None

Remarks:

None

dim light 1A1 Bulb

poor contact 1A3 Contact

low power 1A4 Battery

FAAC flashlight sometimes will

not turn on

3 flashlight sometimes will

not turn on

Comp / Prov:

None

Det. Method:

None

Remarks:

None

intermittent 1A2 Switch

intermittent 1A3 Contact

FAAD no flashlight output 2 no flashlight output Comp / Prov:

None

Det. Method:

None

Remarks:

None

no light 1A1 Bulb

Stuck open 1A2 Switch

no contact 1A3 Contact

no power 1A4 Battery

Page: 2

Date: 8 Nov 2014

Project: Simple Flashlight Example

Function/System: Flashlight

Phase/Mode: Normal Operation Reference Drawing:FL164578-1

Assembly Name: Flashlight Assembly RD: 1

Ref

DesName & Function FMI Failure Mode Local Effect Next Higher Effect

Sev

.End Effect

Detection Method

Compensating

Provisions

Remarks

Failure Cause RD Item Causing

1A1 Bulb

- Provides the light

source for the flashlight

FAAA dim light flashlight output dim 3 flashlight output dim Comp / Prov:

None

Det. Method:

None

Remarks:

None

FAAB no light no flashlight output 2 no flashlight output Comp / Prov:

None

Det. Method:

None

Remarks:

None

1A2 Switch

- Turns flashlight on or

off

FAAA intermittent flashlight sometimes will

not turn on


not turn on

Comp / Prov:

None

Det. Method:

None

Remarks:

None

FAAB Stuck closed constant flashlight output 1 constant flashlight output Comp / Prov:

None

Det. Method:

None

Remarks:

None

FAAC Stuck open no flashlight output 2 no flashlight output Comp / Prov:

None

Det. Method:

None

Remarks:

None

1A3 Contact

- No Data

FAAA intermittent flashlight sometimes will

not turn on


not turn on

Comp / Prov:

None

Det. Method:

None

Remarks:

None

FAAB no contact no flashlight output 2 no flashlight output Comp / Prov:

None

Det. Method:

None

Remarks:

None

FAAC poor contact flashlight output dim 3 flashlight output dim Comp / Prov:

None

Det. Method:

None

Remarks:

None

1A4 Battery

- Provides the power

source for the flashlight

FAAA low power flashlight output dim 3 flashlight output dim Comp / Prov:

None

Det. Method:

None

Remarks:

None

FAAB no power no flashlight output 2 no flashlight output Comp / Prov:

None

Det. Method:

None

Remarks:

None

Third Case Study: Application of Life Cycle Cost

Purpose: To calculate the life cycle cost (LCC) for two different proposals, and to show the impact of Mean

Time Between Failures (MTBF) and Mean Time To Repair (MTTR) on the overall cost of a piece of

equipment.

Benefits: The LCC Technique helps utilize manufacturing machinery characteristics in life cycle cost

comparisons. The "Guideline" showed that an additional initial cost could save greater amount of cost at the

operation and support stages of that machinery. In light of that issue, LCC goals are to:

1) Consider the big picture: "Pay me now or pay me later",

2) Highlight the impacts of R&M on support cost,

3) Low purchase price does not always imply best deal,

4) More expenditure does not always imply more reliability,

5) Helps consider the competing suppliers on an equal basis.

The LCC Model: LCC Cost = Acquisition Cost + Ownership Cost

where:

Acquisition Costs = Purchase Price + Installation Cost + Training/ Documentation Cost + Transportation Cost

and

Ownership Costs = Operations Costs + Maintenance Costs + Future Cost of Money

Each of these Costs may consist\ of more basic costs. For instance:

Purchase Price = Cost of Design + Cost of Build + Acceptance Testing + Initial Spares;

Operations Costs = Machine Operators + Inventory Management + Consumable/ Expendable;

Maintenance Costs = Preventive Maintenance + Predictive M. + Corrective (Unscheduled M.).

Each of those Costs may consist of more detailed costs. For instance:

Consumable Costs = Tooling Cost + Lubricant Cost + Coolant Cost + Machine Electricity Cost

Preventive/Predictive Maintenance Costs =

Maintenance Labor Cost + Materials Cost + Logistics Support Cost

Corrective Maintenance =

Maintenance Labor Cost + Cost of Failed items/Spare + Logistics Support Cost

+ Lost Productivity Cost

Facts About The Case: A company was in the process of ordering a Grinder, described in the previous case

study. The division had two sources, hereon named Source #1 and Source #2. A study was initiated to

determine which source was offering a better option for purchase .

The following requirements were imposed by the process and had to be considered in our analysis:

Production machinery life 10 years

Production quantity required 1,400,000 parts/year

Machinery operating hours per month 532 hours

Estimated maintenance cost per hour 34 $/hr

Inventory carrying cost (in percent per year) 17%

Cost of crisis downtime per hour 200 $/hr

Floor and foundation cost per square foot $100 $/SqFt

Electricity cost per KWHr 0.0301 $/KWHr

Shipping cost per pound 0.32 $/Lbs

Initial dollar year of study 1995

Annual Inflation ratio 2%

Annual Interest rate of money 8%

A detailed analysis of the first supplier's proposal revealed that the equipment had the following parameters:

Machine yield (95%); Mean Time Between Failures (MTBF of 40 hrs); Mean Time To Repair (MTTR

of 0.49 hrs); non-spared items requiring major rework (0.10%); Mean Time to Re-tool (0.50 hrs);

machine production capability (14 parts/hr); machine weight (100,000 lbs); and footprint of each

machine (832 SqFt).

The acquisition costs associated with the first machine are:

Machine acquisition cost per machine ($931,000); warranty cost ($30,000); warranty period (2 years);

installation cost per machine ($15,000); machine development cost ($35,000); and initial spares cost

($30,000).

Additional support requirements are:

Hardware ($1,000); software upgrade ($1,000); training hours (40 hrs at a training cost of $500 per

hour).

Additional information on the maintenance requirements for the equipment supplied by the first supplier are:

5 hours of preventive maintenance per month; 5 hours of predictive maintenance per month; $30,000

spares is needed to be stocked at plant; and major rework turn around is estimated at 0.1666 months.

Finally the consumable requirements for the first supplier's equipment are:

Tool set cost ($16,520 with a tool life of 15,235 parts/tool); lubricant cost ($1,000 per year); coolant

cost ($500 per year); electricity consumption (35 KW/hr); and $1000 misc consumable.

Similar analysis of the second supplier's proposal showed the following specification:

Machine yield (90%); MTBF of 100 hrs; MTTR of 0.59 hrs; non-spared items requiring major rework

(0.10%); Mean Time to Re-tool (0.50 hrs); machine production capability (12.2 parts/hr); machine

weight (100,000 lbs); and footprint of each machine (832 SqFt).

The acquisition costs associated with the second machine are:

Machine acquisition cost per machine ($710,000); warranty cost ($20,000); warranty period (2 years);

installation cost per machine ($10,000); machine development cost ($20,000); and initial spares cost

($40,000).

Additional support requirements are:

Hardware ($1,000); software upgrade ($1,000); training hours (40 hrs at a training cost of $600 per

hour).

Additional information on the maintenance requirements for the equipment supplied by the second supplier are:

5 hours of preventive maintenance per month; 5 hours of predictive maintenance per month; $40,000

spares is needed to be stocked at plant; and major rework turn around is estimated at 1 months.

Finally the consumable requirements for the second supplier's equipment are:

Tool set cost ($7,090 with a tool life of 5,454 parts/tool); lubricant cost ($1,000 per year); coolant cost

($500 per year); electricity consumption (25 KW/hr); and $1000 misc consumable.

Selection Process: Select the better proposal. Your decision should be based on an overall cost

analysis of the two proposals, and should show the difference in the overall cost of the two

proposals over the life of the equipment.

Hint: As you perhaps know, the only costs that may affect your decisions are the ones that are different. Hence,

for sake of time, you are encouraged to focus on the differences in cost between competing suppliers and ignore

those components that are identical.

Fourth Case Study: Application of Life Testing

Life Testing of Valves for two Suppliers

Date: May 11, 2015

We performed a life test on 40 vlaves that were provided to us from a local company. 20 of these valves were manufactured

by the company, here called Supplier A, and the other 20 were provided by the competition, here called Supplier B.

You are asked to perform a detailed analysis of the data and provide a comprehensive report.

Valve number refers to the location of the valve on the test equipment. There were four rows (A, B, C, D) of testing,

each equiped with five columns (1-5) of air nozzles, on either side (Right and Left).

Current Cycle Count: 50,000,000

Valve

Number

Count

when

Turned On

Count when

Turned Off

Under Test

Cumulative

Cycles of

Operation

Test

Complete

Total Cycles

to Failure

Valve

ManufacturerApparent Failure Mode

A1L 0 28,263,000 28,263,000 Supplier A Failure to shift, excessive leakage

A1R 0 10,614,677 10,614,677 Supplier B Excessive leakage

A2L 0 10,614,677 10,614,677 Supplier B Excessive leakage

A2R 0 18,568,000 18,568,000 Supplier A Excessive leakage

A3L 0 9,235,045 9,235,045 Supplier B Failure to shift


A4L 0 2,224,025 2,224,025 Supplier B Failure to shift


A5L 0 5,314,000 5,314,000 Supplier A Excessive leakage

A5R 0 2,224,025 2,224,025 Supplier B Failure to shift

B1L 7,583,315 42,416,685 Supplier A

B1R 9,430,000 10,614,677 1,184,677 Supplier B Excessive leakage, leakage out body of valve

B2L 10,614,677 34,719,000 24,104,323 Supplier A Leakage out body of valve

B2R 9,235,045 19,796,000 10,560,955 Supplier B Failure to shift

B3L 10,614,677 13,604,591 2,989,914 Supplier A Excessive leakage

B3R 2,774,000 9,430,000 6,656,000 Supplier B Failure to shift

B4L 2,774,000 13,181,000 10,407,000 Supplier B Leakage out body of valve, failure to shift

B4R 2,774,000 2,774,000 0 Supplier A Failure to shift

B5L 10,614,677 13,935,400 3,320,723 Supplier B Failure to shift

B5R 13,604,000 37,328,000 23,724,000 Supplier A Excessive leakage

C1L 13,635,250 17,640,000 4,004,750 Supplier B Failure to shift

C1R 13,935,400 16,603,000 2,667,600 Supplier A Excessive leakage

C2L 16,674,000 20,301,000 3,627,000 Supplier A Excessive leakage

C2R 18,568,000 30,761,000 12,193,000 Supplier B Failure to shift, excessive leakage

C3L 18,568,000 20,301,000 1,733,000 Supplier A Excessive leakage

C3R 19,796,000 23,181,000 3,385,000 Supplier B Failure to shift

C4L 20,378,000 20,378,000 0 Supplier A Excessive leakage at startup

C4R 20,378,000 22,729,000 2,351,000 Supplier B Excessive leakage

C5L 20,378,000 29,622,000 Supplier A

C5R 23,460,000 24,890,000 1,430,000 Supplier B Excessive leakage

D1L 23,460,000 40,830,000 17,370,000 Supplier B Excessive leakage

D1R 25,317,000 45,291,000 19,974,000 Supplier A Excessive leakage

D2L 25,738,000 40,128,000 14,390,000 Supplier B Failure to shift

D2R 25,317,000 25,707,000 390,000 Supplier A Excessive leakage

D3L 30,826,000 19,174,000 Supplier A

D3R 29,087,000 37,918,000 8,831,000 Supplier B Leakage out of valve body

D4L 34,719,000 49,201,000 14,482,000 Supplier B Excessive leakage

D4R 34,719,000 34,719,000 0 Supplier A Excessive leakage before startup

D5L 34,719,000 15,281,000 Supplier B

D5R 37,413,000 46,534,000 9,121,000 Supplier A Excessive leakage

Documents

case_1