Hi,

Again a new question for my thesis. I hope you all are offended by me flooding this forum.

Mr. Oliver Wight talks in his book (the executive's guide to successful MRP II, about "closed loop MRP". It isn't quite clear what he means with this term.

Is it the theoretical term for the successor of MRP -> MRP II?

I hope you can help me answering this question.

Regards,
Luuk
Leiden, the Netherlands

Hello Luuk,

the term closed loop describes an automatic control system in which (negative) feedback is used to create a self adjusting well regulated and predictable system in control theory. Feedback means that part of the output of the system (in MRP this is the generated production-/purchase-order quantity) is compared with the input (here the sum of requirements generated throu sales/production,..) the difference is the used to generate new output. The theoretical underpinning is quite complex especially for non linear system which I believe an MRP-System is. In any case here some points to consider:

1- How well does the system react to changed input (sudden increase in customer demand,...)

2- Under certain circumstances casn the feedback become positive for example when the frequency of the MRP runs are not chosen properly. This causes oscillations for example high pitched whisling n amplifiers when microphone is too close to the speaker. In MRP this can manifest itself in wildly varying stock levels.

3- MRP is a special case in that it is not usual in practice to cancel generated orders if requirements suddenly drop. An issued PO usually runs its course causing extra stock in case of drop in demand.

Caveat: These are only my considered opinions and ideas as a Baan-Programmer who happes to have studied electronics. I have not read the works of Mr. Wright so I'm not sure if and how what I've just said in any way represents his thoughts. :)

Now that's a caveat for you !!

I would treat OW's book with care. Although I haven't read it, I have been involved in an ERP implementation which was guided by his theories and the differences in opinion between the experienced ERP consultants and the 'OW consultants' were never fully resolved. I got the impression that his theories are more acceptable to executives than to ERP specialists.

I would agree with previous posting.

Having spent some 20+ years in manufacturing in various functions , including 10 years in Production / Material Control ( currently rebranded Logistics), I was fortunate to hear and meet George Plossl and Oliver Wight. The principles and practices they expounded were right for their time, and many still are today but commerce and industry have moved on and with the "benefits" available from computing and various means of communication balanced against the demand for more customer focussed and leaner organisations result in different methodologies and techniques being employed.

I am assuming that the original source of Wight has not been updated !

Hi !

Thank you for your information.
This is interesting information.

I was wondering, ERP is an extension of MRP II and MRP II is an extension of MRP. MRP is the extension of inventory control.

Peoplesoft was founded with HR software and has made the ERP package at a later stage. Same for BAAN which started with financial modules and created the ERP package to at a later stage.

So, one company's ERP suite cannot always be traced back to the inventory control, the definition of MRP II and ERP is difficult to start with.

I like to read and learn by your comments. Do You have an opinion about these issues?

Regards,
Luuk Jurriens
Leiden, the Netherlands