Review of “Optimizing Factory Performance” by James P. Ignizio

2022-01-23 / Ahn Louise

Introduction

“Optimizing Factory Performance” is a book which seeks to guide the reader to make sustainable improvements to factory performance based on science and the experience of the author, who has worked both as a manager in the industry, consultant and as an academic.

Content

This section lists my key takeaways from the book. There are no quick-fixes but a lot of sound advice.

The Three Dimensions of Manufacturing

Ignizio sees manufacturing as having three dimensions:

The physical features of the building
The physical components within the factory, e.g. workstations, machines, personnel and equipment
The protocols or practices by which the factory is operated.

Here he believes that the last dimension is to a large degree neglected when looking at options for performance improvements. In my experience, I have not found that to be the case, but that could simply be, because my own focus has been more on protocols and principles than on the physical features.

The importance of History and of Taking a Holistic View

One can feel Ignizio’s passion for history when reading the book. He believes that we need to know the history of manufacturing to be successful with our own improvements. Otherwise we will fail to see the connections and understand the big picture.

Ignizio on several occasions mentions how taking a holistic perspective is necessary to make sustainable improvements. He repeatedly highlights that focusing on one or two practices from the Toyota Production System will not suffice to reach the same level of performance as Toyota.

The Three Enemies of Factory Performance

Ignizio states that there are three primary enemies of factory performance:

Complexity
Variability
Lackluster leadership

As should be obvious from the purpose of this site, I fully agree that complexity and variability are key issues to manage. And it is difficult to disagree that leadership is important to performance in most professional situations.

The Three Fundamental Equations of Manufacturing

Three equations are presented which Ignizio labels the “three fundamental equations of manufacturing”:

Little’s law, stating that on average or in steady state
[Work-In-Process] = [Cycle Time]x[Throughput]
An equation which expresses cycle time in terms of arrival + process variability, utilisation and effective process time.
An equation which expresses how variability is propagated through a process flow.

Ignizio believes that every manager in production should know these equations, and I tend to agree. At least, I think that Little’s law should be known to everyone, and the underlying consequences of the other two equations should also be understood, even if I would not expect any manager to be able to recite the equations.

Performance metrics

Measuring performance is difficult – there are numerous metrics which must be balanced against each other. One important point highlighted by Ignizio is the fact that many of the metrics which are generally used should be adjusted for load or utilisation when evaluated. It is for instance very easy to have excellent cycle times, if your capacity is excessive.

For me, one of the most interesting parts of the book is the presentation of a number of performance metrics which I cannot remember to have seen previously:

Waddington Effect Plot: Shows down time, both scheduled and unscheduled, plotted against time. This can highlight clustering of unscheduled down time, especially the Waddington Effect (as labelled by Ignizio) which is the effect that most unscheduled downtime follows closely to the scheduled preventive maintenance.
M-ratio or maintenance ratio which is defined by:
M-ratio = [scheduled downtime]/[unscheduled downtime]
For a typical factory the M-ratio should be 9 or higher according to Ignizio.
Availability Profile Plot: Shows availability (of a machine or workstation) over time
Cycle time Constribution Factor. This formula gives an indication of how large the total process time is compared to cycle time of the single process. This means that if the CTCF is very low, this process is typically high priority in terms of resource allocation:

$CTCF_{ps} = \frac{\sum_{ps = 1}^p PT_{ps}}{CT_{ps}}$

Degree of Re-entrancy (DoR):
DoR = [number of operations] / [number of workstations]
where the number of operations should not include transit-only operations. The degree of re-entrancy is an indication of the number of loops in the workflows, and these create complexity. The ideal factory has a DoR value of 1 according to Ignizio.

Style

Overall I agree with most of Ignizio’s key messages, and the book is certainly worth reading for its content, but I find his style a bit tiresome. Several time he comes through as a being rather grumpy.

Ignizio preaches science (while acknowledging that some parts of optimisation is more of an art), but I find there are many statements without reference or valid proof. Where formulas are given, I have no doubt that these are valid, and that it is only a matter of insufficient citation. Other statements seem more based on his lifelong experience and probably hold a lot of truth, but in my opinion it would be fitting to more clearly separate facts from opinions.

Conclusion

“Optimizing Factory Performance” is definitely worth a read. I personally prefer “Factory Physics” by Hopp & Spearman which covers much of the same material but with more mathematical detail. Others may find Ignizio easier to read, and to me Ignizio is a good add-on and introduces some interesting performance measures.

Rating: 4 out of 5