Takt Time vs Manual Cycle Time: The method to calculate the Quantity of Operators.

This article was written based on my experience as consultant.

After many Kaizen event I have found there is 2 misunderstandings about how calculate the Number of Operators that are needed to run a production line or manufacturing cell.

When you implement standardized work a Takt Time base on customer demand must first be established for the area in question, for example 30 seconds TT, this is equal to set a rate of 120 UPH (Units per Hour).

Therefore; the next question is how many workers are needed in the manufacturing area, at this rate?

The answer depends on the total work content in the area and relation to demand ( TT).

It's also known as graph of “Takt Time vs Manual Cycle Time”, in many industries.

The more work content, the greater the number of workers that will be required; the less overall work content, the fewer workers that are needed.

Misunderstanding 1: 

I have found there is a misunderstanding of Overall Work Content, many people take the Cycle Time complete (Machine + Manual) and that is not ok, they must use the “Manual” Overall Work Content (Total Manual Cycle Time)

Please see this example.

The calculation shows that is possible to run this Manufacturing Cell with just 3 operators. 

Misunderstanding 2:  

There is other misunderstanding this is about the representation of TT, many people don’t understand this concept how interpret and calculate the Quantity of operators when they have operators working in parallel.

For example; when there are operations that are not possible to be separated, the activity must be done from the start to the end by one operator at time; and if the cycle time is greater than Takt Time; then you need use more than one operator to cover the rate needed, this means to have two or more operators working in parallel, for this case the Takt Time must be different.

You should never use the average of those operators as the Manual Work Content, you need represent as it is and make the calculations using other Takt Times equivalent.

Please see this example.

The calculation shows that is possible to run this Manufacturing Cell with just 5 operators; please note that here there is two Takt Times, but don't get confuse at the end the Cell will run at 30 Seconds of Takt Time; equivalent to 120 UPH. The operators 1 and 2 must works at 3 process in sequence  (Press, Trim and Spring).

I hope this be useful for you in your next Kaizen event.

Therbligs Motion Analysis, the next Step after Standard Work.

I teach the Therbligs Motion Analysis (TMA) to my customers, just after done the first improvement (Standard Work) on the process or manufacturing line or cell, the reason is very simple, after the first improvement you may think everything is ok, but is not true, due there is more waste, this type of waste are the human micro motions and usually are very difficult to identify since the beginning of Standard Work analysis.

The TMA , will help you to identify the next improvement steps , that may end on implementation of Hanedashi – Auto eject or a full Chaku- ChaKu Line (load–load).

Shigeo Shingo explains in one of his books; the real meaning of work is: “ a person exerts strength on a weighty task”

Thus, rather than assuming that a man in motion is working, we must be sure to ask whether he is really exerting his strength on some task that will produce value added.

Frank B. Gilbreth studied human motion and discovered basic elements of motion, which he called Therbligs. All human movement, he discovered, are composed of a mere 18 Therbligs.

Basic steps for TMA.

1.    Be sure to familiarize yourself with the 18 basic Therbligs Symbols before using this form.

2.    Fill in the basic product and process related information.

3.    Make small sketch of the area you are study for reminder or take pictures.

4.    Observe the motion overall several times to obtain familiarity, draw the Ohno’s circle and stay there.

5.    Write down the left-hand, right-hand, and eye-related motions one by one.

6.    Include a brief word or two of explanation if required in the provided column.

7.    Write down the work elements every few symbols for clarification.

8.    Write down your improvements ideas for each small motion.

Please see the next video, its about machine improvement and automation, please note that event with the Nut Feeder , the operator is doing other motions that not add value, he is using his left hand as bin – Hold “H” , the right hand is used to release load “RL”  and this operation has a Unavoidable delay “UD” is obvious that more work needs to be done.

Please see the next video ;  on this case the operator just needs to load the part and the machine has the Nut Feeder and Auto eject.

If you want to make a Chaku- Chaku line you need to think about this; how the NVA activities can be detected and eliminated? The first step is performing a TMA.

Hope this information helps you in your next project.

Standard Work and the PDCA cycle.

I love teach Standard Work to young Engineers, their expectations are always what type of software I going to show, and they look very confused when I say “ dear Team to day I’ll teach all of you to walk, see, draw and ask why? 5 times, and then Standard Work “...."Genchi Genbutsu".

I recommend to perform the training on Genba rather than, meeting rooms or classroom.

The process to improve a production line using Standard Work is directly related with the PDCA cycle is not just “Before and After”.

The team should PLAN (Draw the current situation Standard Work, ask 5 times why? For all the None Value Add Activities –NVA- that they being capable to see at that moment and creates the Kaizen News Paper – Improvement Plan); and then go ahead with the DO (The first try, or as I call it Try-Storming, physical changes transform the line to U shape cell maybe etc.); following by the CHECK  (this is the second draw or review; for sure the Team will be able to see clear new or more NVA than before, new challenges are going to be added to Kaizen News Paper – Improvement Plan) the Team must now go for the ADJUST ( could be just one or more it is up to the goal achievement in terms of productivity , Takt Time , Operators Numbers, Quality etc.).

On these examples you can see how the changes on production floor are follows.

Obviously many specific improvements on process must being done; this is not easy; the implementation time is up to the Team member’s skills and if tool room that makes possible supports them the process changes. Plus the others formats and tools.

See some improvements that are needed to reach the goal, please take it as examples.

I hope this help you in your next project.