Category Archives: Math

Posts including calculations and formulas.

The Many Different Flavors of the OEE

OEE flavorsIf imitation is the sincerest form of flattery, the OEE (Overall Equipment Effectiveness or Efficiency) is indeed one of the most appreciated measures in lean. I counted at least eight different variants and adaptions of the basic OEE – although let me tell you that I am not impressed with all of them. Many of them seem to be theoretical academic constructs with little meaning for your shop floor. Also, identical acronyms and similar terms are often used in a completely different way, adding quite a bit to the confusion. On top of that, I think the OEE is used way too much in industry where it does not make sense, and many OEE numbers are heavily fudged. Anyway, let me show you the many different flavors of the OEE. Continue reading The Many Different Flavors of the OEE

Good and Bad Ways to Calculate the OEE

Smiley Frowney PercentThere are different ways to calculate an OEE. I know of at least three different ways. However, some of them are easier and more practical than others.

Maybe you have seen a formula similar to OEE = A x P x Q. I see this formula often, but for me it is a very impractical way to calculate the OEE. Let me show you why by comparing the three different ways to calculate an OEE.  Continue reading Good and Bad Ways to Calculate the OEE

How Product Variants Influence Your Inventory

Array of carsThe sales & marketing department often aims to create more and more product variants to target even the smallest niche in the market. Yet, it is common wisdom that more variants also mean more inventory.

However, the relation is not quite as clear cut. In my last post I wrote about the Relation between Inventory, Customer Takt, and Replenishment Time. The relation is similar for variants, and it all depends on the ratio of the customer takt to the replenishment time.  Continue reading How Product Variants Influence Your Inventory

The Relation between Inventory, Customer Takt, and Replenishment Time

Kid with GlassesInventory is helpful for a fast delivery of goods. If you have it in stock, you can deliver to the customer right away. In that respect, more inventory is better. Yet, at the same time, inventory creates cost, some visible, some more hidden. Hence, one of the goals of lean is to reduce inventory and therefore reduce cost. During my research I stumbled on a very interesting relationship between inventory, customer takt, and replenishment time. Let me elaborate … Continue reading The Relation between Inventory, Customer Takt, and Replenishment Time

Cycle Times for Manual Processes

Alfonsina Morini
Even more on cycle times…

In my last two posts I described how to measure cycle times. However, for manual processes measuring cycle times is quite different, since the humans that are measured usually strongly dislike being measured. Therefore, it is difficult to measure it directly. There is an alternative to calculate it, but this also has lots of pitfalls. Let me explain you a bit about human psychology, and how to measure manual cycle times. Continue reading Cycle Times for Manual Processes

How to Measure Cycle Times – Part 2

Bicycle New Zealand
More on Cycle Times …

This is the second post on how to measure the cycle time of a process. Again, the cycle time is the fastest repeatable time in which you can produce one part. Hence, as part of a series on manufacturing speed measurements I continue with more details on what cycle times really are. This is the second post on how to measure cycle times (post 1 here), with an additional third post focusing on the details of manual cycle times coming up next. Continue reading How to Measure Cycle Times – Part 2

How to Measure Cycle Times – Part 1

Quadracycle 1886
The good old cycle times …

The cycle time of a process is a key to match the supply with the demand in lean manufacturing. Everybody working on a shop floor knows the term. Yet, I still find that people sometimes confuse what exactly it means. The cycle time is the fastest repeatable time in which you can produce one part. Hence, in this post as part of a series on manufacturing speed measurements I would like to dig deeper into what cycle times really are, and how to best measure them. As it turns out, there is actually quite some detail on how to measure cycle times, hence I split this post into two parts (second part How to Measure Cycle Times – Part 2), with an additional third post focusing on the details of manual cycle times. Continue reading How to Measure Cycle Times – Part 1

Pitfalls of Takt Times

UCLA Marching BandThe customer takt (or takt time) is one of the fundamentals for determining the speed of a production system. After my post on How to determine Takt Times,  this second post on takt times gives a bit of history, and then goes into more details about possible pitfalls and problems when calculating the customer takt. I also added an example for easier understanding. Continue reading Pitfalls of Takt Times