An old, very esoteric, post got a four word comment today that sent my mind thinking. And because the topic is esoteric, this post is as well – my apologies.
The post, Is the MRP Algorithm Fatally Flawed, gets a lot of search hits because of the title. The post discusses an obscure PhD dissertation that asserts that the underlying logic of MRP systems share defining characteristics with a debunked model for computational intelligence. The researcher makes a compelling case.
The comment, from Indonesia, said “please send for example”
Assuming I did not misinterpret the comment, I believe the writer was asking for examples of what does not work.
Here is what got me thinking.
In order to refute Dr. Johnston’s thesis, we have to find a non-trivial case where an unaltered application or the MRP algorithm works as intended. Just one. Then we would have to carefully understand that instance to determine if it was truly a case where MRP is working as intended, or something else.
Ironically, the working examples I have seen have gotten there by combining work centers into value streams with pull and systematically turning off the inventory netting and detailed scheduling functions of their MRP. In other words, they are migrating the system toward something that directly connects supplying and consuming processes with each other. These systems are far more able to respond to the small fluctuations that trip up the MRP logic. Those examples, however, confirm, rather than refute, what Dr. Johnston is saying.
Considering that the vast majority of factories are still trying to make the MRP algorithm work, does anyone have an example of where discrete manufacturing order scheduling of each operation actually gives a workable production plan that can be followed without hot lists and other forms of outside-the-system intervention? Just curious now.