This blog post started as a parenthetical comment about cycle time in my last blog post from this morning. But the parenthetical grew out of control and I thought it would only confuse things in that post.
So, hopefully, it's more clear here as a standalone post. In the last post, I explained that “cycle time” meant:
“Cycle time” is a term that means how long it takes to do a repetitive job each time.
Unfortunately “cycle time” is also used to mean how long it takes to get through an entire process from start to finish. This is confusing, I know. As an Industrial Engineer, I'll take lumps on behalf of my profession for this poorly chosen terminology (are we to blame?). Some prefer to call this second form of cycle time (end-to-end elapsed time) by an alternative phrase “throughput time” or many in healthcare would call this “turnaround time.”
But the “cycle time” I mean here is the time between a single person (or machine) starting the first piece of work and that person (or machine) starting the second piece of work. Some would call this “operation time” or some other term.
If a doctor, for example, sees six patients per hour, the doctor's cycle time is 10 minutes per patient. If it takes the patient 60 minutes from arrival to departure, then the “turnaround time” is 60 minutes (see why we don't want to also call that”cycle
time?”)
I wish we didn't have this confusing terminology, where “cycle time” means two things. I'm always havin to ask for clarification about “which” cycle time a person means (although “throughput time” is normally MUCH longer than “cycle time” for an individual operation in a process).
How do address that in your workplace?
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My first experience with cycle time was when working at a multistage stamping press and marking a section of the metal strip and following it through the successive stages of the deep draw. The time from flat metal strip to finished piece was cycle time. The number of pieces per minute was the "piece rate". But then others will stand at the end of a process and take the time between two successive pieces and call that cycle time.
APICS Dictionary defines Cycle Time as: 1) In industrial engineering, the time between completion of two discrete units of production. For example, the cycle time of motors assembled at a rate of 120 per hour would be 30 seconds. 2) In materials management, it refers to the length of time from when material enters a production facility until it exits. Syn: throughput time.
Oh well…
Larry — even though I don't encourage blaming, I'll blame APICS then, not industrial engineers :-)
A related cadence is Takt time – the rhythm of the process as a whole: http://en.wikipedia.org/wiki/Takt_time
My experience is that we have had to make sure perspective is clear when we talk about "time". When we are discussing takt time we typically use the phrase "rate of demand" or just "demand" indicating customer perspective at the end of the line.
When we are talking from the product or service point of view we usually say cycle time (start to end of a single "cycle" usually one processing step). It does get confusing if the perspective is not clear.
I believe in Shook's "Learning to See" he uses "lead time" to describe "turnaround time". That term (lead) works for me because I think – "How much time do we need to leave in the schedule to get the material (i.e. patient) through the whole process (appointment)."
I prefer using "throughput time" for internal factory elapsed time from start to finish, where I use "lead time" for how long it takes to get something from a supplier (or to a customer) including transportation time.
We could do a whole other blog post on how people misuse "takt" to mean production rate instead of demand rate.
Maybe "production rate" and "demand rate" are the best terms to use? Except for hospitals, we need a different term than "production"!!
Although I usually blame APICs for eveything bad (just kidding I don't think we should blame either – although I do get frustrated with my inability to help some APICs certicatees see beyond MRP and square roots of lead times, etc.) I usually use the APICs definition listed above as my definition of cycle time and then I compare that to TAKT and try to get cycle time to just below TAKT time. I usually call the time from beginning work on a piece or patient to finishing that piece or patient throughput time or process time.
an excellent way to differentiate cycle time and throughput time/turnaround time! Thanks