Friday, April 6, 2012

SPC - Process Flow Diagram/Pareto Charts

So that little SPC Book goes into 7-tools to use, the next page goes into Process Flow Diagrams and Pareto charts.

Process Flow Diagram

The first tool appears to be the Process Flow Diagram[tm], where one is supposed to draw out the inputs and outputs of each process step. I suppose in the "Lean" world, this is the equivalent of value-stream mapping.

The text of the booklet calls it a

Pictoral display of the movement through a process. It simply shows the various process stages in sequential order.

Normally, I see this on a Powerpoint slide somewhere. And frankly, I've rarely seen it used in practice. More often, if we show this to consultants to get them up to speed.

Pareto Chart

The pareto chart is essentially a pie chart in bar-format. The key difference is that pie charts are for the USA Today readership while pareto charts are for real engineers -- this is to say that if you're putting pie charts in Powerpoint and you're an engineer, you're doing it wrong.

Pareto charts are super useful because they help figure out your most pressing issue. For example, say you're create a table of your fermentation failures:

So you have counted the number of observed failures alongside a weight of how devastating the failure is. Well, in JMP, you can simply create a pareto chart:

and out pops a pareto chart.

What this pareto chart shows you is the most important things to focus your efforts on. If you solve the top 2 items on this pareto chart, you will have solved 80% of your problems - on a weighted scale.

The pareto is a great tool for metering out extremely limited resources and has been proven extremely effective in commercial cell culture/fermentation applications.

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