Root cause analysis to find cause for porosity.pdf

Slide as referance which shows how to present a Root cause analysis and corrective action

1. Root cause analysis to find cause for porosity(defect) in
Composite tubes(part) and measures taken to eliminate
the defect and improve the detectability
BY SITANSHU PANDYA
BASED ON THE WORK DONE AT HIGH STRAIN DYNAMICS

2. Problem Statement
The porosity (defect) was identified on the finished part while going
through Quality Management System.
The entire batch of 2000 pieces were defective resulted in loss of
$40000 in revenue
The defect resulted in unfulfillment of the critical customer
requirements –mechanical strength and surface finish.
Process capability = 1.0
Process stability = 1.0

3. Process Flow Diagram for Roll Wrapping
process
Tool Prep
Material
Cutting
Rolling Tapping Curing
Pulling
Tape
unwrapping
Sanding Cutting
Quality
inspection
Packaging
This was the initial process flow diagram

4. Run chart at final QMS during problem detection
1.019
1.02
1.021
1.022
1.023
1.024
1.025
1.026
1.027
1.00 4.00 7.00
10.00 13.00 16.00 19.00 22.00 25.00 28.00 31.00 34.00 37.00 40.00 43.00 46.00 49.00 52.00 55.00 58.00 61.00 64.00 67.00 70.00 73.00 76.00 79.00 82.00 85.00 88.00 91.00 94.00 97.00
100.00 103.00 106.00 109.00 112.00 115.00 118.00 121.00 124.00 127.00 130.00 133.00 136.00 139.00 142.00 145.00 148.00 151.00 154.00 157.00 160.00 163.00 166.00 169.00 172.00 175.00 178.00 181.00 184.00 187.00 190.00 193.00 196.00 199.00
Dimensions
part number
Run Chart dated 10/02/20
Dimension Mean Lower control limit Upper control limit

5. Root Cause Analysis
Porosity due to
tapping
process
Cause EffectOperatorTapping MachineTape Wrapping
MaterialsEnvironment
Man MachineMethod
Mother Nature
Co-related the defect
to the process using
documentation from
production trials
Direction of wrap
Number of wraps of tape
Glass fiber Prepreg
•Wrong resin content
•Uneven resin
impregnation
Shrink Wrapping tape
•Tape width
•%shrinkage of the tape
Wrong tape start location
Wrong input parameters
Lack of efficient operating skills
Tapping pressure
•Lack of Braking pressure
•Tape deformation
Pitch of the tape
•Programming error
•Wrong pitch value
Tape alignment
•Alignment motor malfunction
Facility temperature
•HAVC malfunction
Facility humidity
•HAVC malfunction
Scanning Laser Micrometer
Measurement
Incorrect sampling rate
Incorrect measuring recipe
Incorrect Feedback
•Braking force
•Tape pitch

6. COPQ analysis
Type of Cost Description Cost
Internal Failure Troubleshooting Work hours spend
finding the cause and troubleshooting
$400
Additional required inventory for
raw material
Ordered extramaterial to complete the order $3000
Labor cost Paid additional overtimelabor cost to completethe order$1200
Thecost of scrapping defective
tubes
Thecost of shipping tubes to recycling facility $150
Appraisal cost Test and Inspection system
addition
Additional hours dedicatedfor testing and inspection + man
hours
$450 + $ 600 = $1050
Prevention cost Implements control systems to
monitor process parameters
during and end of each process
Cost of hardware and hours of control engineer setting up
the system
$1600
External Factor costUnhappy customer Thedeadline was missed
& got bad reputation
$ Beyond calculation as it was the
first big order
Hiddencost due to loss The possiblerevenue could have been generated by sales of
defective tubes
$ 40000
Total $ 47400

7. Improvement steps
I. Fixing the problem on hand
Identified a bad PID controller causing the uneven tapping tension.
Replaced the PID controller within 2 days.
Performed a production trial run and used Run charts to verify the process correction.
II. Process improvements for better detectability of defects
•System generated Run charts were programed to generate to monitor the control limits of the
processes.
•Machines were programmed to generate alarms if the process parameters were beyond the control
limits.
•Made schedule to monitor control parameters with help of daily reports.

8. Run chart at final QMS after solving the problem
1.02
1.021
1.022
1.023
1.024
1.025
1.026
1.027
1.0 4.0 7.0
10.0 13.0 16.0 19.0 22.0 25.0 28.0 31.0 34.0 37.0 40.0 43.0 46.0 49.0 52.0 55.0 58.0 61.0 64.0 67.0 70.0 73.0 76.0 79.0 82.0 85.0 88.0 91.0 94.0 97.0
100.0 103.0 106.0 109.0 112.0 115.0 118.0 121.0 124.0 127.0 130.0 133.0 136.0 139.0 142.0 145.0 148.0 151.0 154.0 157.0 160.0 163.0 166.0 169.0 172.0 175.0 178.0 181.0 184.0 187.0 190.0 193.0 196.0 199.0
Dimensions
Part number
Run Chart dated 10/06/20
Dimension Mean Lower control limit Upper control limit

9. Process Flow Diagram for Roll Wrapping process
Tool Prep
Material
Cutting
Rolling Tapping Curing
Pulling
Tape
unwrapping
Sanding Cutting
Quality
inspection
Packaging
This was the initial process flow diagram
•System generated Run
charts to monitor
control limits of the
process
•Visual Inspection
•Manual measurement
•Better documentation
*Note: More inspection methods were implemented for other processes mentioned above

10. Summary
Before implementing changes After implementing changes
ProcessCapability Index = 1.0 ProcessCapability Index = 1.67
Process Stability Index = 1.0 Process Stability Index = 1.33
Revenue lost = $47400 Revenue saved = $ 42650
Lessons learned
•In-process and end of process inspections can save ton of money and reputation
•Continues improvement is necessary for keeping the quality of parts up to customer expectation
Implementation of learning
•Schedules were made to continuously check and improve the 6M –Man, Machine, Material, Measurement,
Mother nature, Methods for each process.
•Designed and implemented systems to monitor control limits in-process and end of process
•Defined goals to bring facility to and maintain at the process capability and stability at 2.0

11. Thank you so much for your time
QUESTIONS ?