Process Capability is the measure of your quality.
You can express it in different ways but what I use
is DPMO (defects per million opportunities) and Sigma
value (short term).
Simply put: Process capability describes how much of your
output is falling outside the specification of the customer.
The higher the DPMO value, the lower the Sigma value of
your process, therefore the more defects and mistakes you make
in a given process.
So the objective is to reduce DPMO, to increase the Sigma
value of your process, therefore you make less mistakes.
Meaning: YOU IMPROVE QUALITY.
I though you would appreciate if I share with you
my advice I have given to one of my student.
He is working in a factory producing electronic
parts. His question was:
“How to Increase Process Capability of the
So if you are working at a manufacturing company,
here are some easy steps you can follow and you will
improve the quality of your process, guaranteed.
Here is the copy of my email:
As promised, I provide you with my advice free of
charge. I put my advice into this email because it
is your preferred way of communication.
Based on your request on how to increase process
capability of the production of electronic
products, you should follow these clear steps:
1. What is your problem? Which electronic part
production has the lowest process capability? You
mention you produce different items, therefore you
need to determine your focus of improvement.
Use Pareto chart to see the biggest contributor to
2. After you decided which electronic product you
want to focus on to improve the process capability
then you have to decide where the most waste is
created. Or with other words at which step do you
make the most off-spec parts. So you have to scope
your focus area as small as possible.
3. You know the product, you know the production
area/step. Now you can start collecting data for
your base line chart. Decide on what to measure?
– % of off-spec parts per day or per hour
– Deviation of a certain actual measurement vs
– Anything that is continuous data showing the
CURRENT process performance in time
4. After collecting 20-30 data points, now you can
plot it on a runchart and also calculate the
current process control limits.
5. If you (and your team) are confident in the way
you collect data (with other words: the variation
in the data caused by the measurement system is
low) then you continue with the next step.
Otherwise improve you measurement system FIRST.
6. Now have a brainstorming session with you
project team – by the way: all that is mentioned
above should be done with a project team with
members knowing the most about the problem.
During this session you should use Ishikawa diagram to
get all the possible causes of the high waste rate
/ high off-spec % / (or whatever metric you have
chosen and measured during previous steps).
7. Decide as a team on the top 3 most important
causes to the problem.
8. Agree on actions to attack those 3 probably
most important causes of the problem.
9. Execute the actions and keep measuring to
detect changes/improvements in the performance of
10. Agree if changes in the process resulted in
acceptable process capability improvement or not.
If not, carry out more actions based on the result
of the brainstorming.
11. Administrate your findings: what you measure,
what changes you made and what specifications
everybody should take into account for both output
(metric you have measured, point 3) and inputs
(action and changes of point 7 and 8).
12. Train people according to the new process and
audit after 3-5 month.
I hope this will help you to improve your process
In case you want to get your most important questions answered