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Work Process Analysis and Improvement of 4-170 Piezoelectric Accelerometer

at CEC Vibration Products in Covina, CA

By: Joey Uken, Gilbert Sun, Dariusz(Darek) Tyrawa, Clint Stark, Isaac Hwang

See Appendix R for Project teams resumes

Project Completed for Cal Poly Pomona Work Analysis Class IME 224

IME 224 Professor: Luiz Armendariz

See Appendix R for Luiz Armendariz resume

February 25, 2015

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Statement of Disclaimer

This engineering work analysis project is the result of a class assignment that was graded and

accepted in fulfillment of a Cal Poly Pomona IME 224 class. Acceptance does not imply any

technical accuracy or reliability of the material included in this report. Any use of this

information or material is done at the users risk. Neither California State Polytechnic

University, Pomona, nor its faculty are liable for any problems or damages that result from the

use of any material contained in the report.

Acknowledgement

We would like to thank CEC Vibration Products employees Thomas Wong and Jeff Copeland

for allowing us access to the facility and answering any questions we had; both critical to the

success of this project. We would also like to apologize for any inconvenience we may have

created during the course of data collection or question gathering.

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Product Description of 4-170 Piezoelectric Accelerometer

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Performance specifications of 4-170 Piezoelectric Accelerometer

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Abstract:

CEC Vibration Products in Covina, CA has been working on the 4-170 piezoelectric

accelerometer design for at least the last 20 years. Features of this piezoelectric accelerometer

includes self generated (no external power), balanced differential output, and operates in high

temperatures up to +500 degreees Farenheit. Applications for Piezoelectric Accelerometer

include gas turbine engine monitoring, ground testing, APU testing and compressor/gear box

monitoring.

The main objective for this project was to analyze the entire work process of the 4-170

piezoelectric accelerometer and provide suggestions to improve the process. However since

CECVP cant really change their work stations of welding and nonesuch we focused primarily

on the shim stack assembly where CECVP could actually change the work stations in order to

improve the work process.

Numbered below is a brief summary of some of the items that we accomplished in order to

provide a meaningful work process analysis.

1. Created a work process flow chart

2. Created a floor plan of the current setup of the work stations for this work process

3. Created work instructions for the process that show the flow of product and people

4. Video taped the process and used protime and excel to analyze the data collected

5. Analyzed non-value added and value added parts of the operation in order to reduce the

cycle time of the entire work process.

6. Classified every work element as Internal or External so that we could use SMED to

reduce setup time to improve the run time of the various operations in the process

7. Determined the Labor Productivity Index.

8. Made Pareto Chart in order to determine number of inspections needed after various steps

9. Safety standards practiced by CECVP is ISO 9000 and AS 9100.

This simple representation is helpful in

understanding how a piezoelectric

accelerometer works

In this picture the piezoelectric accelerometer is

actively vibrating.

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Brief Summary of Work Instructions:

Materials needed for work process

Floor plan of the work stations for our work process

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Work Station (A) (Work elements 1 -3)

During this station we cut 3 shims out of the shim sheet, two of which are connected with two wires.

Spot Welding Station (B) (Work elements 4 -6)

This is our spot-weld station here we will weld stainless steel wire right on the edge of the shims.

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Work Station (A) (Work elements 7 -13)

1) We are coming back to our work station where we place one of the connected shims with welded wire on 10 pico-coulomb stack. Then we place first crystal with positive charge facing down.

2) Then we place the single shim with welded wire over the first crystal making sure wires are not crossing over. Then place the second crystal with positive charge facing upwards.

3) fold the second of the two connected shims over the entire pile.

Chemical Storage Area D (Work elements 14-15): Now we are going to chemical storage area to spray

glue on the two insulators. Now we going back to our work stations.

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Work Station (A) (Work elements 16-24)

1. Place the insulator on central shaft. 2. Transfer the Pile on central shaft. 3. Place the tungsten weight

4. Place the second insulator, , central piece, nut bolt. 5. After this we inspect the assembly and tighten the nuts. 6. Check for any crystal and shim for proper alignment, wire should not touch each other

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Testing Station (C) (Work elements 26)

During this station test the stack to make sure there are no

1. broken crystals 2. missing insulators 3. upside-down flipped crystals

Assembly of Part B and A: Below is the second portion of the work process. During this process we will

be attaching the previously assembled part A inside of part B.

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Work Station (A) (Work elements 27 -31)

1) Take the two wires and start positioning them inside the two pins of the connector. 2) Slowly keep pulling the wires, while placing the stack in the connector. 3) Make sure that the wires dont touch each other. 4) Cut off the extra wire.

Brazing/Welding Station (J) (Work elements 32-34):We now walk to braze welding station because after

cutting off extra wires it is required to apply brazing on top of the pins.

Water Welding Station (E) (Work elements 35-38):Then we walk to water welding

Dremel Station (F) (Work elements 39-41):After water welding we go to the Dremel station. This is

important to remove hard edges.

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EB Welding Station (T) (Work elements 42-44)

Now we using E.B welding machine to weld the bottom of the assembled part.

Testing Station (C) (Work elements 45-46)

Inspection of the assembly part.

Arc Welding Station (G) (Work elements 46-49):At the Arc welding station we are tacking the nut

EB Welding Station (T) (Work elements 50-52): At the E.B welding station we are welding the top part of

the assembly

Testing Station (C) (Work elements 53): We now do final inspection of the assembled parts.

Etching Station X (Work elements 54-56):Walk to the Etching station for engraving information.

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Precedence Chart for entire work process:

Data: See Appendix D for Raw Data in the form of a work process chart

Calculations: **See appendix G for general formulas of all calculations shown.

1. Labor Productivity Index (LPI) = P(new)/P(baseline) = (1/60)/(1/30) = .5 or 50%

2. Work Process Chart has the total cycle times

3. Percent Cycle Efficiency of the entire work process (%PCE)

%PCE = VA / (VA+NVA) = 1159/(1159+4068) = .221= 22.1%

4. Baseline for the shim stack is 1 every 60 seconds if there are 5 stations each with a max

of 30 seconds and the cycle time of the shim/stack is 207 then the balance delay = ((Max

station time * Stations) - cycle time) / (Max station time * Stations) = ((30*5)-

207)/(30*5) = .38 or 38%

Input Data not in work process chart

1. Rough annual demand of 1000 units per year

2. material cost per part is $396

3. labor cost is $12.80 per hour

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Protime Calculations: Batch Internal/External Seconds

1. Cycle Time (Tc)=715.38 mins,

2. Standard Time (Tstd)=822.68mins

3. labor cost/unit=$175.51

Protime Calculations:Batch Value Added /Non Value Added Seconds

1. Cycle Time (Tc)=753.43 mins,

2. Standard Time (Tstd)=866.44mins

3. labor cost/unit=$184.84

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Shim Stack Assembly Line Balancing Calculations:

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Analysis: **See Appendix G for general concepts of work process analysis

Using External(EXT)/Internal(INT) classification:

Classify every work element as internal or external so that

SMED can be used to reduce setup time which in turn will

improve the run time of various operation in the work

process.

Using Value Added (VA) and Non-Value Added (NVA)

classification:

Classify every work element as NVA or VA. Then try to

reduce the Non Valued Added parts of the work process

in order to reduce the cycle time of the entire work

process.

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Recommendations:

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Recommendations continued:

Tools to use for improvement:

1) Cause and Effect Diagram- Use this in order to determine the cause of various problems

with the process.

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2) Takt Time Chart- Use this in order to determine the takt time needed in order to

achieve a particular demand.

3) Production Rate Chart- Use this in order to determine the production rate needed

in order to achieve a particular demand.

4) Defects Diagram- Use this after the cause and effect diagram is made.

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5) Pareto Chart- Use pareto excel file to create a pareto chart in order to determine the

number of inspections needed after various work elements.

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Items provided to CECVP in soft copy folder:

1. A Cause and Effect diagram 2. Information about predetermined motion time systems, Therblgs, MOST, General formulas,

SMED, and lean production 3. A diagram displaying visualy where the defects are most likely to appear on the part 4. A pareto chart that just needs information put into it to display a histogram of problems 5. Explanations on how to use the preto chart 6. A picture and layout of an efficient work station

Appendix D: Raw Data

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Appendix G: General formulas and concepts used to make Calculations and Analysis

1) Labor Productivity Index (LPI) Labor Productivity=P P=Output/Input

Labor Productivity Index=LPI

LPI=Pnew/Pbaseline

Ex1) LPI=1.5= increase in productivity of 5O%

Ex2) LPI=.5=Decrease in productivity of 5O%

2) Cycle Time (Tc) Tc=Tn/Pw or Tn=Tc*Pw

Tc=Time*Pw/Demand, Tn=normal time, Tc=Actual time

Tc=Cycle Time, Pw=worker pace

Ex1) Find: Tn Given: Worker is working at 11O% for 5 sec

Tc=5 sec,Pw=11O%

Tn=Tc*Pw=5*1.1= >>>Tn=5.5sec

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5) PFDs PFDs

P=personal time

Ex)bathroom breaks

Phone calls

F=fatigue

Ex)rest breaks

Used to reduceFatigue

D=Delays

Ex)interruptions, Equipment Breakdowns

15%PFD time is standard

6) Standard Hours(Hstd) Hstd=Q*Tstd

Hstd=standard hrs = work actually accomplishd (hrs)

Q=quantity ofwork units(pc)

Tstd=standard time=Allowed time per Work unit(hr/pc)

7) Worker efficiency (Ew) Ew=Hstd/Hsh Ew=worker efficiency (normally in%)

Hsh=#of shft hrs (hrs)

Hstd=#of standard hours of work accomplished

during shift (hrs)

8) percent cycle efficiency (PCE) %PCE=%VA=

%PCE=VA/(VA+NVA)

PCE=percentage

cycle efficiency

VA=value added

NVA=Non-val added

Value added(3Fs)means it modifies

1)Fit

2)Form

3)Function

Ex)O=2Omin

Trngl=1OOmin

D=1Omin,=1Omin

O=VA,trngl,D=NVA

%VA=2O/15O=15%

O=VA,

Sqr,trngl,D,=NVA

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9) SYMBOLS O-operation

Procesng matrl

Square=inspection

Chk for quantity

or quality(sqr)

=move-transport

Of material

D=delay-material

Waiting to be Processed

Triangle=storage-material kept in Protected spot

10) One Best Method (OBM) OBM-One Best

Method Princple

1bst method that

Minimizes time and

Effort.

*Main Objective in work

Design is determinea one best method and standardize its use.

*always try to reducelearning Curve of workers

11) Bottleneck (BTLNK)

Bottleneck=slowest operation in the sequence

12) Single Piece Flow (SPF) SPF=single pieceFlow

Sngle pc flow is preferable to batch processing

*2main problems with batch processing

1)set up changeovers between batches

2)work-in-process=Multiple batches Competing for same Equipment.

Ex)queues form in front of equipment resulting in large inventories

13) Work Cell Work cell=a gourp of workstations

*u-shaped work cells are preferred cuz better communication among workers.

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14) Largest Canidate Rule (LCR) Largest Canidate Rule (LCR) = Minimize the

time difference between work elementsor work stations.

Ex)S1=1,S2=.81

S3=.98,S4=59,

S5=.62

the bottlneck=S1.

However according to LCR combine S4 and S5

operations and make that the new bottlneck

15) TAKT Time Takt time=Time availble/demand (hrs/pcs)

Rp=Demand/time availble(pcs/hr)

Rp=hourly production rate

Tc in this is

Tc=Time available*Pw/Demand

16) Balance Delay balance delay=d=(At-Tc)/At

At=A*#of stations

A=allowble time

per station

Tc=total of

all Tc

Tc=cycle time

17) Production Rate (RP) RP= Hstd/Tc

RP=Daily

Production rate

Hstd=Standard Hours

Tc=Cycle Time

18) SUM Tc Tc or Te is

Work content Time

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Safety Standards Currently Used by CECVP