Calculate number of people in processes, considering cycle time/takt time = quantity of people

qualprod

Trusted Information Resource
#1
Hai everybody

Could someone explain the basis to calculate number of people in processes, considering cycle time/takt time = quantity of people?
It doesn't fit in my mind how is calculated.

On the other hand, how can be possible to dimension number of people, without including person efficiency?
Is a very important issue.

Please feed me back, thanks
 
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N

ncwalker

#2
TAKT time is the longest a process can take to make the contracted amount. You get TAKT by dividing the time you run (like if you run two 8 hr shifts a day with no breaks, the time is 16 hrs) by the number of parts you are required to make in this time. No part of your process can be LONGER than this, or you will not make enough parts.

Lets say you have a TAKT of 5 minutes. And you have a manual paint process. What this means is, to paint your part, the operator must be able to get it done in 5 minutes. If you can add another operator (another parallel process) then each operator can take 10 minutes, the combined output must be 5.
 

qualprod

Trusted Information Resource
#3
Thanks , but the question remains, what are the root basis to determine "crew to takt" how Many people needed for any process
Since, when cycle time is obtained, in none place was determined number of people, simply ct was obtained, but in The formula cycle time/takt time= crew , have a doubt reg arding, what is based on, who created such formula.
Thanks
 

Bev D

Heretical Statistician
Staff member
Super Moderator
#4
This formula holds for individual operations. Ncwalker’s example is this formula. A process that takes 10 minutes (cycle time) and a takt time of 5 minutes requires 10/5=2 people to meet takt time.

No person created the formula. It is basic “engineering”.
 
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qualprod

Trusted Information Resource
#5
This formula holds for individual operations. Ncwalker’s example is this formula. A process that takes 10 minutes (cycle time) and a takt time of 5 minutes requires 10/5=2 people to meet takt time.

No person created the formula. It is basic “engineering”.
Thanks, I can understand, your explanation as well the ncwalker viewpoint, but in lean, I have seen the next in lean manufacturing.
Cycle time/ takt time = quantity of people needed to work in any process.
E.g. seconds/seconds per piece= # of people?, Could someone clarify this?
Thanks
 
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Bev D

Heretical Statistician
Staff member
Super Moderator
#6
I am confused on what your question is. you can convert minutes to seconds by dividing by 60.
 

qualprod

Trusted Information Resource
#7
I searched on the net, And found this.
For crew to takt= cycle Time/takt Time, the reason= seconds-person/seconds, simple algebra seconds are eliminated, then have persons , But is a manual process, I wonder how to manage this issue when the time resulted of a process is a mix, person operating a machine.
What will be the results in the equation ?
Or the job is completely done by a machine?
Thanks
 

Bev D

Heretical Statistician
Staff member
Super Moderator
#8
OK, so your question was how the units cancel out to eliminate time and leave people. the effect of units is almost always a 'manual' thing as most math software doesn't take this into account. some specialized scheduling software will take units into account and requires you to enter the units for each variable.

you handle machine heavy operations in the same way. the key is understanding how many parts are made by the machines (in the same units of time as the takt time) that can be run by a single person. it will also tell you how many machines you need
 
N

ncwalker

#9
First - just because you found a formula on the internet, it does not mean that it works.

First some definitions:
Machine Cycle Time : The time the machine cycles to perform the operation.
Total Cycle Time: The Machine Cycle Time PLUS the time to unload/load another part. Operator dependent.

Let's say I have a machine that has a total cycle time of 8 minutes, but a machine cycle time of 6 minutes. So on average, once the machine is done, it takes an operator 2 minutes to: acknowledge the machine has stopped, open the doors, swap out a finished part for a fresh blank, close the doors, and hit the GO button.

This means that running one machine, an operator would be busy for 2 minutes, and standing around for 6 minutes. What this means is I could add three more machines to the cell, WITHOUT adding an operator. They would be very busy running four machines.

Now TAKT time is the time required to make a part. If my TAKT time is 8 minutes, I am fine with one operator and one machine. But my customer wants to order 4 times as many parts. Well, I need 3 more machines. And my CELL TAKT time drops to 2 minutes, but my MACHINE TAKT time stays the same.

Case A and Case B in my example have different TAKT times, different cell cycle times, but the same number of operators.

You cannot determine number of operators from JUST TAKT and cycle times. It's simply not enough information.
 

Bev D

Heretical Statistician
Staff member
Super Moderator
#10
The issue is that cycle time is for the part not the person or the machine. As you pointed out it also includes load an unload time and any other prep or inspection or data entry etc that is associated with actual part time.

There’s nothing wrong with the formula per se, it’s how you assign the correct values to the variables.
 
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