Eliminating the overproduction problem using Takt time

Last time we talked about Takt time and I hope you have enjoyed reading it . If you have missed it , you can read it here

??????What's Takt time and why is it important ?????

While we discussed largely on meeting the customer demand on time , Takt time was originally designed to avoid "Over production", which is referred to the biggest waste in the Lean management concept . Remember you can still achieve a 100% on time delivery by always producing more than your customer demand by working faster than your Takt time. This is not exactly what Takt time is for. In fact, the goal is to achieve a continuous flow in the production line by producing the exact quantity required by the customer when its needed ! To understand better , lets look at the type of wastes in Lean

You can see there are seven types of wastes . Let's focus on the Over production right now

Why is Over production so bad ?

Well , while all types of wastes are bad , Over production can cause all kinds of other wastes and hence is called the mother of all wastes. Over production is defined as any product produced in excess amount of the actual requirement of the customer and / or produced before the actual requirement. This will lead to more inventory than needed, and thus disturbs the entire system by breaking the flow of the production system . Also , Over production will make your system less visible to the problems that may occur, because you will always have products to ship. For example , you wouldn't worry about a machine breakdown so much , if your shipment is not going to be delayed right ? Similarly, it takes out the urgency and the need for preventive actions of problems like defects, raw material shortage or an unskilled labour . Here is an illustration that will give you a better idea on this concept

Also ,If you would like to read a brief about the 7 Mudas or wastes in Lean , you can look up here

https://kanbanize.com/lean-management/value-waste/7-wastes-of-lean

How can Takt time avoid Over production ?

Takt time , as we discussed , gives the exact time to perform a task so as to complete it when its due . This avoids early or late completions . The only problem here is that , In the practical world , the system is not always balanced equally because the machines and tasks have different capacities based on the processing times and the capabilities . That's why it takes a continuous effort to balance the system based on the changing requirements of your customer. Balancing the line to Takt 80% is also a good way to start provided any disruptions in achieving that , raises an urgency and calls for immediate action and problem solving .

Balancing the Line of Processes :

Let's look at the example that we discussed last time and see how to balance the work stations in a manufacturing line .

Balancing any process requires constant attention on the capabilities of each and every work stations involved in it

You can see that each of the work stations have got almost different cycle times and only stations 1, 2 , 4 , 5 , 9 and 10 are under the Takt 80% time 46 seconds . This means two things , all other stations are not capable of producing what's needed and the workstations under takt time are capable of over producing ! ( because no workstation matches the exact time of 46 seconds , which is the referred Takt time ) . Although , In practice , every work station is inter connected and the output of the line is going to be the output of the slowest workstation , these stations are usually called as the Bottleneck stations ( in this case , station number 3 ) which we will discuss later as its a different topic . Balancing the line is to make every work stations capable of producing what's needed while making the cycle times as closer to the Takt time.

There are many things that should be considered while balancing a line , we will discuss the core concepts and methods here

1. Re allocation of work : One of the easiest method of balancing the line is to breakdown the works of each stations in to small elements and re allocate the possible tasks from stations which have higher cycle times to those stations having lower cycle times . This can be done by conducting basic time studies of each work stations and developing a Time stack of work elements. Here is an example from the book "How to implement Lean Manufacturing" by Lonnie Wilson

While it seems simpler , re allocating the work elements often requires small to large changes in the layout , additional tools required to perform them , cross training of employees etc , but it could lead to breakthrough results in the output of your production line as it reduces the cycle times of work stations below your takt time . Remember , you should not reduce the cycle times much lower than the Takt time for any given station , as it would result in over producing of WIP ( work in progress inventory ) between stations.

Flexible working hours : Re allocating the work elements may not be possible for every tasks. Some times , some of the tasks can only performed with certain machines . In such cases , adding machines to improve the cycle times may not be a good option as it will always require huge investments . In such cases, the best possible solution is to adopt flexible working hours for slower workstations so as to balance the entire production line . Say for eg: station 3 (57 seconds) may have to work for more than 8 hours so that it can deliver WIP inventory that's needed for further stations . This can be either done by

a) Starting early : Starting the work stations of higher cycle times early will result in producing a good amount of WIP which can be consumed by the next station quickly when the shift starts

b) Switching the lunch time for the employees at slow work stations : This will ensure that the machine runs continuously during all break times and thus consumes the entire WIP from the previous stations

c) Running the machine after the shift hours to consume and produce the WIPs

All of these methods should be carefully adopted by calculating the number of hours that slower workstations should be operated , how much inventory should be kept before and after these workstations and the manpower allocation during the break times so as to keep every workstations balanced and avoid over producing.

That's it for today , Hope you have enjoyed reading !

Also, please feel free to comment or suggest anything that could be worth discussing or writing in the future, Thank You !