Over the years, some MES systems have evolved from Control Systems by adding relational databases and historical archives. These have been moderately successful, however the transactional challenges of:
- Locking Data for Closed Accounting Periods,
- Rolling Back Transactions,
- Editing Historical Data, and
- Structuring the Data for Easy Ad-hoc Analysis
have usually been poorly supported. If the information cannot be easily analyzed, corrected and manipulated, it is not very useful.
Similarly, there have been MES systems that evolved from Business Systems by adding OPC drivers and PLC connectors. These have also been moderately successful, however the real time challenges of:
- Reacting Immediately to Events,
- Easy-to-Use Shop Floor Displays, and
- The Ability to Alert and Continue Operating
have usually been poorly supported. Losing a few seconds on every batch can mean the difference between a plant continuing to operate or shutting its doors.
I can remember many conversations with a plant's new accountant, who couldn't understand why we consistently had 3-5% yield losses that were not accounted for. In his mind, there should be metering and equations that explain the process accurately every time. In the real world, there are numerous variations in raw ingredients, metering errors and other disturbances that make it impossible to be accurate all the time (if ever).
The key point of this anecdote is that an MES system must deal with the realities of complex manufacturing processes, as well as communicating to the new accountant in a way that satisfies his needs. This isn't easy and is the key strength of successful MES systems (and MES Engineers).
How well does your MES system communicate with your Business System and Control System? Does it do both well? If you are transitioning from a Manufacturing Information System to a Manufacturing Execution System, these communication channels will give you the most grief.
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