PSL - Process Capability Improvement Using Six Sigma

Your Gateway to Business Excellence
Determine and
Improve Process Capability

Basic Operation
1)Performance measures
Distance launched
Percentage of “baskets” made
Variance in distance
2) Independent variable
Ball type: perforated or smooth
Number of rubber bands: 1, 2, 3
Launch angle: 0, 15, 30, 45, 60, 75, 90 degrees
Pull-back angle 0-120 degrees
Setting up the X Pult
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Determine the capability of the current process
and the measurement system
• Define Defect, Opportunity, Unit and Metrics
• Develop Data Collection Plan
• Collect the Data
• Determine Process Capability
Why Measure?

• The normal distribution is the most recognized distribution in statistics.
• Many sources of data tend to follow the Normal Distribution or bell shaped curve.
• 99.73% of the area of the normal distribution is contained between -3 sigma and +3
sigma from the mean.
The Normal Distribution

 1


ƒ(x)

 2


 1


 2


 3
 
 3

99.73%
95.46%
68.26%

Data Collection Plan
Performance
Measure /
Metrics
Operational
Definition
Data Source
and Location
Sample
Size
Who will
collect the
data
When will
the data be
collected
How will the data be
collected
Launch
Distance
Measure distance
from fulcrum of X
Pult (table edge) to
the ball landing
point
Catapult
process/Table
5 shots
per
launcher
QC
Operator
Each
catapult
launch
Measurement tape
How will the data be used? How will the data be displayed?
Examples:
 Identifying Baseline / Sigma Level / Cpk
Identification of largest contributors
Identifying sigma level and variation
Root cause analysis
Examples:
 Trend Chart
 Pareto diagram
 Control chart
 Scatter diagram
 Histogram
Developed
earlier 2 3 4 5 6 7
Operational Definition is a precise description of how to obtain the value of the characteristic measured.

Recommended Reading and Resources
• Books DVDs Websites
www.isixsigma.com
www.moresteam.com
Six Sigma DVD

Session Format
• Exercise : Catapult – X Bar R Chart
• Control Charts
• Types of Variation
• Process Capability
• Exercise : Catapult – Root Cause Analysis
• Group Activities
• Homework

Control Charts
• Control Charts indicate when a process is
“out of control”
• Control charts are visual and prompts/flags
non when a process is out of control
• SPC Charts incorporate upper and lower
Control Limits

Continuous Control Charts
• Charts show both Mean and Variability
• Chart Types
– I-MR : Individuals – Moving Range
– Xbar-R : Subgroup Mean and Range
– Xbar-S : Subgroup Mean and Standard
Deviation
• Charts primarily differentiated by Subgroup
Size

Common Cause Variation
• Some examples of common cause variation
are:
– Machinery
Vibration of machines
Temperature fluctuations
Variability in material hardness
Web tension
Viscosity change
– Office
Experience of individual workers
Workers out sick
Internet server response time

Process Capability Index – Cpk
The formula :
Calculate both values and report the smaller number.

1.00
1.67
1.33
• 100% inspect, measure, sort
• Improvement and Action Plan required
• Use control charts to monitor
• Improvement plan required
• First piece checks
• Audits
CPK
Capability Improvement Action Plan

Session Format
• Root Cause Analysis
• Improvement Action Plan
• Exercise : Catapult - Implement Improvement Plan
(X bar R chart and Process Capability Analysis)
• Homework
• Project Closeout Checkpoints
• Project guidelines
• Assessment Criteria

Group Activity : Brainstorm
Create a cause and effect diagram for the factors
that affect the throwing distance of the catapult.
Why couldn’t you hit the 2 meters target
accurately ?
Example :
Pull back distance
Rubber elasticity
Measurement error
Time allocated = 15 minutes

Group Activity - Homework
1) Brainstorm and generate a cause and effect
diagram for your project.
2) Generate a capability improvement plan and
implement the solution for the identified Key
Process Input / Output Variables
3) Generate a revised control chart
4) Calculate the new process capability index

Tools and Templates
1. X Pult tally checklist
2. Frequency plot template
3. X bar R chart (Excel file and A3 sized hardcopy)
4. Process capability calculator (Excel file)
5. Data collection plan
6. Cause and effect diagram
7. Improvement action plan

Lets review your homework
Group Activity - Homework

Appendix : Calculations for X bar-R Charts
1. Determine an appropriate subgroup size and sampling plan.
2. Sample: (Take a set of readings at each specified interval of time).
3. Calculate the average and range for each subgroup.
4. Plot the data. (Both the averages and the ranges).
5. After '20' or more sets of measurements, calculate control limits for
the range chart.
6. If the range chart is not in control, take appropriate action.
7. If the range chart is in control, calculate control limits for the Xbar
chart.
8. If the X bar chart is not in control, take appropriate action.

Appendix : Out of Control Conditions
Any Point Outside Control Limit
Caused by an unstable process - a one of error
- could be a broken drill, low air pressure, poor
vacuum
-3
-2
-1
0
1
2
3
X X
-4
-3
-2
-1
0
1
2
3
4
X
X
-3
-2
-1
0
1
2
3
X
X
A run of 7 points above or below mean
Caused by an unstable process - a one of error
- could be a broken drill, low air pressure, poor
vacuum
A run of 7 points going up or coming down
Trend cut indicate tool wear or machine
maintenance required
Any non random pattern
Could indicate different processes on different
machines or operator or shift

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PSL - Process Capability Improvement Using Six Sigma

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