There are many different metrics that measure how long it takes to manufacture one piece. One might say, too many. Part of the problem is that many of these metrics measure the same thing under different names. It can be very confusing.
The largest source of confusion is the inconsistency in how metrics are named and defined. To help sort this out, we can take a cue from software development best practices, where ubiquitous language refers to establishing a shared vocabulary used by everyone within a given problem domain. Let’s establish some ubiquitous language related to takt and cycle metrics.
We will start by naming and defining the two major time domains to which cycle-based metrics apply:
Run time is when the manufacturing process is actually running (parts are being produced). In terms of cycle metrics, ideal cycle time is the preferred benchmark metric. In terms of six big losses, run time includes slow cycles, small stops, and defects.
Planned run time is when the manufacturing process is expected to be running (parts are intended to be produced). In other words, it includes run time (actually running) and downtime (should be running). In terms of cycle metrics, operable takt time is the preferred benchmark metric. In terms of six big losses, planned run time includes slow cycles, small stops, defects, and downtime.
As two different time domains, run time and planned run time each have their own cycle-based benchmark.
|Time Domain||Cycle-Based Benchmark|
|Run Time||Ideal Cycle Time|
|Planned Run Time||Operable Takt Time|
We will define these in greater detail below, but for now:
Ideal cycle time and cycle time are cycle-based metrics that are measured across time that the manufacturing process is actually running. In other words, they use run time as their time base.
Ideal cycle time is the absolute fastest time per part that can be achieved by your manufacturing process on a sustained basis. It is sometimes referred to as nameplate capacity. It represents perfect production.
Ideal cycle time is a very well-defined and important metric due to its integral role in OEE. In fact, the simplest formula for calculating OEE is:
OEE is calculated by multiplying Good Pieces by Ideal Cycle Time and then dividing that by Planned Production Time.
The numerator in this calculation, Good Pieces x Ideal Cycle Time, equates to fully productive time. In other words, it is just another way of saying manufacturing only good pieces as fast as possible (i.e., at ideal cycle time) with no downtime.
Cycle time is a highly overloaded term. It is used in many different ways, by people in many different roles, and in many different contexts. For the sake of ubiquitous language, our definition will lean into the fact that ideal cycle time is a well-established and consistently defined metric (thank you, OEE). In other words, we will define cycle time in a way that pairs it nicely with ideal cycle time.
In other words, cycle times should only be measured while the process is actually running. The sum of all individual cycle times (i.e., total cycle time) should equal run time. Or, putting it another way, cycle time is a “run” phenomenon. It is not affected whatsoever by unplanned stop time or planned stop time.
This definition enables meaningful comparisons to be made between cycle time and ideal cycle time, which is an extremely valuable real-world tool. Cycle time should always be slower than or equal to ideal cycle time. If it is not, ideal cycle time is specified incorrectly (it is too slow, which will hide loss). This happens surprisingly often, usually because a budgeted rate number (described later) from an MES or ERP system is used to specify the ideal cycle time.
Takt time, operable takt time, and effective cycle time are cycle-based metrics that are measured across time that the manufacturing process is expected to be running. In other words, they use planned run time as their time base. Budgeted rate is a similar metric but is sometimes expressed as a rate.
Takt time is the amount of production time you have available to manufacture each part in order to exactly meet customer demand. It is a customer-centric metric.
Takt time is a well-defined metric due to its established role in lean manufacturing, where it is used to promote flow and balance (production moving to the rhythm and beat established by takt time).
Traditionally, takt time is calculated as:
Takt time is traditionally calculated as Available Production Time divided by Customer Demand.
Available production time is defined as time when the manufacturing process is expected to be running (parts should be being produced). In other words, it includes run time (actually running) and budgeted downtime (should be running but is not), and it excludes planned stop time (e.g., changeovers).
For a more detailed discussion of calculating takt time, read our article about the Nuances of Calculating Takt Time.
Operable takt time is the amount of production time required to manufacture each part based on the current, real-world capabilities of your manufacturing process. It is a manufacturing-centric metric.
Operable takt time is a measured value, not a calculated value. It reflects the pace of production you are able to achieve with your current equipment and people.
Operable takt time is often used interchangeably with takt time, which can cause significant confusion. Each has a different role to play:
Effective cycle time is the actual manufacturing time per part as measured across an extended period of time that includes down events (planned run time variant) or down events plus planned stop events (planned production time variant).
There are two common variations of effective cycle time, which use different time domains:
Either variant is fine to use as long as you define it clearly and apply it consistently. We usually recommend using planned run time as the time domain as it enables you to directly compare effective cycle time to operable takt time.
Budgeted rate is the expected rate of production used for scheduling and costing. As such, it includes expected or “budgeted” losses. It is a value that often comes from MES and ERP systems, and the name is likely to differ depending on the specific MES or ERP package.
Budgeted rate is similar in concept to operable takt time or effective cycle time; although, sometimes, as its name suggests, it is expressed as a “rate” (e.g., parts per hour) instead of as a “cycle time” (e.g., seconds per part).
Note that when expressed in the same units of time, rate and cycle time are reciprocals of each other.