First problem with MRP systems – the integrity of the data. If there are any errors in the inventory data, the bill of materials (commonly referred to as ‘BOM’) data, or the master production schedule, then the output data will also be incorrect (“GIGO”: Garbage In, Garbage Out). Data integrity is also affected by inaccurate cycle count adjustments, mistakes in receiving input and shipping output, scrap not reported, waste, damage, box count errors, supplier container count errors, production reporting errors, and system issues.
Many of these types of errors can be minimized by implementing using bar code scanning. Most vendors in this type of system recommend at least 99% data integrity for the system to give useful results. Second problem – systems is the requirement that the user specify how long it will take for a factory to make a product from its component parts (assuming they are all available).
Additionally, the system design also assumes that this “lead time” in manufacturing will be the same each time the item is made, without regard to quantity being made, or other items being made simultaneously in the factory.