"Morning! my name is Sara and I'm living with my loving husband Chris and our 3 children: Theodore, Leila, and John. In my home, I feel like I'm running some kind of a plant in my kitchen. Every day, my husband and my children order their breakfast, lunch, and dinner for the next day."
Time Buffers
A time buffer is assigned to a task that has a time of execution and a due date. The time buffer is supposed to provide enough time to execute the action and have enough protection time in order not to be late in very high chances, and yet not wasting valuable time.
Let's go back to Sara. Sara needs to make meals for the whole family 3 times a day. Each time a family member asks for something to eat, Sera estimates the required time buffer for that meal. In the next table, you can see some of the orders for tomorrow:
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Now, the important question is when should Sara start cooking each meal?
Release time
By definition, the buffer is the appropriate time to dedicate to the action. Starting the action less than a buffer before the due date can cause tardiness (lateness) and will be a waste of the protection time. On the other hand, starting the action more than a buffer before the due date will cause inflation of the action (meaning it will take more time than needed just because there is time) and even worst, could cause a cold meal!
So, the best time for the release is a time buffer before the due date. In Sara Case:
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OK. Now we know when to start each action. What we miss still is an urgency index.
Order Urgency
The easiest and fastest visual index for most people is color. Like a traffic light that gives a red warning for "STOP", a yellow warning for "PREPARE" and a green approval for "GO", in the most intuitive way, Onebeat uses color indexes in a similar way:
Every order, in every given time, has its defining color: There are three colors, exactly like in a traffic light: Red, Yellow, and Green. Two additional colors are used when the situation deviates from the desired. The first, as if the traffic light has suffered from an electrical power interruption: The color to be used when an order is already late will be Black. Additional color is set to indicate orders that were released prior to their recommended release date: These Work Orders will be colored in Cyan.
Black WOs - Most urgent - already late.
Red WOs - Very urgent - about to be late soon.
Yellow WOs - We're OK.
Green WOs - We have time, don't worry.
Cyan WOs - We are moving too fast. This WO shouldn't be processed yet.
The second prioritization mechanism within the same color is done by Buffer Penetration or BP. The BP value also determines the buffer color to be used.
Buffer Penetration
The BP is an urgency index. The term Buffer Penetration represents its meaning - penetration to the buffer - or in other words, what portion of the buffer has already been spent.
The formula to calculate BP is the following:
The deeper the penetration into the buffer is, the more urgent the order is.
The extremities are the easiest to understand: 0% BP represents that this is the exact time that the order should be released to production. 100% BP represents that now is the due date. Negative BP represents that now is too early to release the order. More than 100% BP represents tardiness.
Where:
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So, now is May 19th 2007 at 12:30. Let's calculate the order's BP.
For Example: MEAL_002 BP = (2-(14:00-12:30))/2 = 0.5/2 = 25%
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Everything is clear now. MEAL_001 is very very late and most urgent. MEAL_005 is getting close to the due date, we should expedite it. MEAL_004 is yellow, nice stable state. MEAL_002 is still green, we can relax but go on and execute it. MEAL_003 we shouldn't start yet. We need to wait to reach positive BP.
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