VELOCITY - DEE JACOB [131]
“And prevent an out-of-stock,” added Jayro. “What made you think of this?”
“A number of things. One of them, truth to tell, was that I was downtown talking to Garth Quincy,” said Murphy. “And I asked Garth about this matter, because Garth of course sees it from the other side. We had just started talking when Amy Cieolara happened by, and she told us the story of her grandfather, who was a candy salesman in Ohio, what they call a ‘route salesman’ who represented a wholesaler, and if it was Tuesday her grandfather would be in Akron, and if it was Wednesday he would be in Canton or someplace else, selling candy to the corner stores and newsstands and so on.
“Well, the rule – set by the wholesaler – was that all sales folks were only supposed to sell by the sealed box, containing twenty chocolate bars, or by the case containing many boxes. But this was in the Depression. These little mom-and-pop stores couldn’t pay for a whole box of Hershey bars or gumdrops or whatever, never mind a whole case. So Amy’s grandpa would open up boxes, and sell to his customers only what their customers had actually bought during the past week. So the candy case was always stocked, Amy’s grandpa always had a sale of some sort from everybody every week, the wholesaler forgot about his ironclad rule, and everybody lived happily ever after – until the big chains came along, when everything changed. Anyway, I mention it because time-interval sales with no minimum quantities – that stuff has been around for a while. But the main reason why I think it especially makes sense for us is that it is similar to DBR.”
“Drum-Buffer-Rope,” said Jayro. “How does that figure in?”
“Ordering by time and with no minimum quantity is closely related to how we are managing Godzilla, and thereby, Oakton. The buffer? The cushion that we acknowledge, and that we use to accumulate a ready supply in front of Godzilla, the constraint? Took me a while to realize this, but that buffer is actually based on time, not physical quantity. How much time does it take for work-in-process to reach Godzilla? The exact quantities are less important than the supreme importance that there is always a reservoir of material ready for Godzilla to process. The reservoir rises and falls, but the time to refill it – and that indeed it is continuously refilled on time – is what matters.”
Jayro considered this. He then turned his computer monitor so that Murphy could see it better, and said, “Look here at what I’ve done.”
Murphy put on his reading glasses, peered closely at the screen, and said, “Why, Jayro, it’s a masterpiece.”
“No, it’s a bar chart.”
“Still, the bold use of color, the greens, yellows and reds – you should be in Paris painting the Eiffel Tower!”
“True, but instead I’m here putting up with you,” said Jayro. “Now, what I’ve done is taken some historical data showing demand patterns for a particular material – one that’s given us problems.”
“And these tall bars?” asked Murphy. “These are spikes in demand?”
“Yes, and some of them are huge, as you can see,” said Jayro. “So I’m trying to figure out if there is any regular or meaningful pattern in the timing, but so far the demand seems random and unpredictable, and a few times a year it outstrips our ability to restock given the lead times of the supplier.”
“That’s using min-max, correct?”
“Correct. If I overlay the order and fill dates – here they are in Gators orange and Tar Heels blue – you can see that the order dates at any rate are also random.”
“Yes, interesting,” said Murphy. “You know, I was joking about your artistic ability, Jayro, but this may indeed turn out to be some of your best work.”
“How’s that?”
“Well, here are the really important questions, I think, relevant to what I said to time triggers for