Kanban Sizing Formula

P

processanalyzer

#1
I have been working on Kanban sizing and found this helpful formula. I thought I would share it with the Networking Forum.
The formula:
Where,

Y: number of cards
D: demand per unit of time
T: lead time
C: container capacity
X: buffer, or safety factor
For example, suppose that hourly demand was 200 units, lead time was 12 hours, and the container capacity was 144 units. Assume that there was variation in lead time or demand, then we can set the safety factor to 15%:

Y = ((200*12)*(1+.15)) / 144= 20 Kanban Cards

How many hours worth of demand will 20 cards represent?

(20 cards * 144 units) = 2880 units
2880 / 200 units per hour = 14.4 hours worth of material

As you can see, this simple yet effective visual approach that encourages flow, reduces the need for forecasting — and all forecasting is almost always wrong no matter which model you choose — and the Kanban reinforces coordination and cooperation within a system.

I found this from Shumla (Blog). It is much easier than the formula I had been using from John Constanza JIT.

Hope this is helpful to someone else! Forward to me from network affiliate Rosemary.:magic:
 
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W

wmarhel

#2
As you can see, this simple yet effective visual approach that encourages flow, reduces the need for forecasting — and all forecasting is almost always wrong no matter which model you choose — and the Kanban reinforces coordination and cooperation within a system.

I found this from Shumla (Blog). It is much easier than the formula I had been using from John Constanza JIT.
Hi processanalsyzer;

Here's something to think about. The use of kanban doesn't encourage flow, it used because their is an absence of flow within a process. The typically order is:

FLOW ---> FIFO Flow ---> Kanban ---> Batch

You use kanban because there is a disconnect between processes, possibly through distance or capacity constraints. Forecasting and kanban are very different animals. Forecasting has its place just as kanban does. Forecasting is a planning technique that even Toyota uses. Whereas forecasting is for planning, kanban is for execution within a process/factory/supplychain.

John Constanza of JCIT (John Costanza Institute of Technology) is the creator of DFT (Demand Flow Technology). He applied mathematical models to production processes in order to take out some issues that occur people. It is a solid method, but I think the absence of people involvement when compared to Toyota, is also one the weaknesses within the system. One of the spreadsheets I've posted here on the cove is based on the DFT methodology. I've seen factories using DFT that worked very well.

What the DFT crowd refers to as an In-Process Kanban (IPK), the lean crowd might refer to it as a supermarket or even just a small FIFO area between two stations in order to account for imbalances.

Wayne
 
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