h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Why should a customer wait weeks if he can have one off someone's else's shelf?

The product chain does not stop at the factory gate. If a customer thinks he has a problem then he has a problem. It's perceived quality that matters, JIT at the factory may deprive the field people with the means to replace parts and possibly lead to canibalising. Nothing's perfect in the real world and allowance must be made for many factors including transportation.

The factory may build to order and then raid the spares build to correct for short falls. Man hours lost anywhere in the chain may become higher cost than the JIT savings.

You did of course say that it's not always appropriate, but in some cases it became fashionable and used as an excuse to cut inventories shifting costs from one part of the business to another. Thankfully where customers are concerned there are more interested parties than just manufacturing.

Of course this topic needs to be reviewed against Just-In-Case Manufacturing, and Just-Because Manufacturing.

In the instance of Just-In-Time, one must first ask which Time stream the customer is in and is it the same, or close approximation to the one the Manufacturing system is in.

If they are not, then there will be a miss-match of understanding of when the item was promised for and when it, or parts of it, will be delivered to a customer. (which doesn't mean it will be the customer who placed an order).

Of course, all of this will change when Time Travel is sorted out and the Sales Department can go ahead in time to find out who will order what, and provide this information, over a large quantity of beer, to Forecasting, who will of couse have been visited in the future by their suppliers so that they know what they should have supplied before being asked.

However, none of this will actually happen as it will break the basic laws of Marketing, Sales and Manufacturing.

Marketing decide what they would like to sell to justify there enormous expense accounts. Sales sell what they can get their hands on to meet their targets and justify their large expense accounts. Manufacturing will produce what they can cobble together with the parts they have been supplied to keep the production line going and justify their small salaries.

This is a unversal law and can never be broken.

Just-In-Time just means it is done with less planning and delivers product Just In Time not to get the order cancelled.