MRP is a standard function of most ERP systems, but is usually tuned for the most basic acquisition models on the purchasing side with more care going into the Sales order side and Job planning sides. This model suits the average mass-production company very well, but there are those who do custom batches, producing different products daily or having short and infrequent runs. Contract manufacturing is one such area, others are tool producers and packaging producers. These kinds of manufacturing/production factories have a much more difficult supply-chain planning requirement. If you procure stock that you might only use once (making any excess a loss), or you are buying large quanities of a stock which will tie up cashflow for months (perhaps due to infrequent runs), or if you often run into shortages of long lead-time stock - then you need a much more clever MRP system that will keep supply in line with usage along a tight plan and with early-warning flags when future production is in danger.
Planning for materials can be a very specialized system, but may well be incoporated within other Systems (Such as our Production Planning or Inventory Planning and ERP enhancement Systems). In our MRP system implementations a lot more is customizable than the standard off-the-shelf systems:
Give buyers a clear instruction list on which orders to place, cancel, amend or move. See directly how stock will be consumed (for WIP or Sales-Orders) on any item and how existing orders will replenish it and what the resulting balances will be. While showing all that, display what the proper action is to take, plus what the ideal action is (we might have to order 200 Kg due to the MOQ, but if the supplier is willing to run less or already have stock on-hand, we might ideally only want 62 Kg, as is the case in this example):
(Please Note: The following example images are all from actual live systems, so some sensitive values are obscured here, but in the working systems they appear normal.)
Automate it all once the system tested correctly. Place the order in ERP, mail the supplier or use electronic web API. Save time, save money, and reduce finger errors. There are very few limits to what can be achieved in a bespoke system.