One day Otto, the manufacturing engineer, did a good deed and guided a lost marketeer back from the hard concrete floors of manufacturing to the plush carpets of marketing. Suddenly, he saw a puff of smoke and a tall green genie appeared. In a booming voice it said, "I am the genie of marketing and I will grant you one wish because of your kind deed."
Although Otto was inherently distrustful of anyone from marketing, he was enough of an engineer to believe the genie. He also was a great fan of basketball. Being a bit shorter than average, he thought it might be useful to be a little taller. He was, however, quite wary of asking to be tall. Just that morning he had ordered a tall cup of coffee at Starbucks, only to discover that this was their smallest size. Certainly, words seem to mean different things to marketing people.
Because he earned his wish on company time, he decided to ask for something that would benefit the company. "I wish engineering would complete the design before releasing it to manufacturing."
"Be careful what you wish for," warned the genie.
"Don't be silly," said Otto. "I'm an engineer and I know what I'm doing." The following day, Otto waited for the next design. "It isn't quite ready," said Sam, the design engineer. "We still have a few issues. Just a few more days." Otto waited and waited, but he never saw another product emerge from engineering.
We all know it's expensive to finish engineering a product on the factory floor. A change that would require a mere click of a mouse several months earlier now demands changing work instructions, obsoleting parts, altering testing protocols, etc. Because it's so costly and wasteful, many observers have concluded that it would be desirable to have no engineering changes take place after a product reaches manufacturing.
We must be very careful regarding such a conclusion. In reality, the factory floor is a very stressful environment for a product. Cruel and ruthless assemblers point out obvious omissions by the design engineer. Weaknesses that would be forgiven by kindhearted engineering technicians are crudely mocked by the assemblers. "Take your sorry product back to the development lab," they say.
However, as tough an environment as manufacturing is, it's a great place to learn the weaknesses of a design. By pushing a product into manufacturing, we can learn a lot very fast. Eight hours in the factory may teach us as much as eight weeks of continuous testing back in the engineering lab.
We don't need to prevent engineering changes from occurring on the factory floor, we simply need to make intelligent tradeoffs. Development delays cost money, and so does rework. We need to know the profit we lose for each month of delay as well as the magnitude of excess rework costs. As a rough rule of thumb, a change made after manufacturing release will cost 10 times more than if it were made just prior to manufacturing release.
Using this information we can make a rational tradeoff. For example, let's say a product's cost of delay was $500,000 per month. With an early production release we could save a month of cycle time and easily pay for $50,000 of extra rework cost. Of course, we couldn't pay for $1 million of extra rework. Like most tough decisions in product development, it's a question of economics, not philosophy.