Inventory 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 …
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.
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.
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.
The 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.
The customer takt (or takt time) is one of the fundamentals for determining the speed of a production system. It represents the available time divided by the average demand of the customer during that time. Effectively this is the average time between the order of one item. Whenever you design a new production system or change an existing system, one of the early data inputs you need is the customer takt. While the customer takt can be simply calculated by dividing the demand by the time available for production, there are many more details needed to understand it fully.
The speed of your production system is a key aspect of your manufacturing system, and controlling it is important for the success of your organization. Unfortunately, there are many different and confusing ways to measure the manufacturing speed. Even a simple question on how to call a speed is often confused, with many practitioners using the same term for different measurements, or different terms for the same measurements. This post aims to give an overview of what is out there, and what it is good for.
One of the most significant fundamental relations in lean manufacturing is the relation between the inventory, the throughput, and the lead time. The inventory and the throughput are usually easy to measure. The lead time, however, is more difficult. You would need to take the time when a part enters the system and then take the time again when a part leaves the system. Luckily, the lead time can easily and accurately be calculated using Little’s Law, one of the most fundamental laws in lean manufacturing (and also many other places).