A manufacturing execution system (MES) is the software that tracks every order through every machine of a factory. It tells workers what to make next, counts the good and rejected pieces, and keeps the record that traces each batch back. It is also called shop-floor software.
The MES sits below the ERP. The ERP sends it work orders: make this many of this product by this date. The MES splits each order into jobs, sends each job to a machine, and counts what comes out. It gets its counts from SCADA and from the machines, and it sends the finished output back up to the ERP.
Consider a plant near Hosur that makes brake discs for two-wheelers. The ERP sends a work order for 500 discs. The MES shows the operator on the lathe which design to make, and which material lot to use. At the end of the shift, the lathe has made 488 good discs and 12 rejected ones. The MES records both numbers, the lot of steel, the machine and the shift. Three months later, a customer reports a cracked disc. The MES record shows which lot of steel it came from, and which other discs were made from that lot. This is traceability.
The MES exchanges data with many other systems. It receives product designs from product lifecycle management (PLM), inspection results from machine vision and measuring machines, and batch codes from inkjet coding printers. It sends quality records to the quality management system, which regulators audit.
An MES differs from the two systems on either side of it. The ERP knows what the customer ordered and how much stock there is, but not what is happening on a machine now. SCADA shows the state of a machine now, but it does not know which customer order that machine is serving. The MES connects the two: it knows that this machine, at this hour, is making these 500 discs for that order. Plants buy it to cut late orders, to cut scrap, and to give customers the batch records that they demand. The users are the production planner, the shift supervisor and the quality team.
Two special forms exist. Print MIS is built for printing and packaging plants. A connected worker platform guides each worker through the steps of a job on a screen.
Smaller factories often buy an MES together with machine monitoring and edge computing, from the same maker.