MES for a Hot Dip Galvanizing Line- III

The Relationship Between ERP and Manufacturing Execution Software(MES)

Introduction
In my previous article I had described the set-up of Manufacturing Execution Software, or MES as a number of Local Server Units, or LSU's acting alone, each networked to its own clients.Based on observations over the last few months,I had concluded that such software yielded powerful analytical results on their own.

I now turn to what further needs to be done and tested.

One of the main objectives of the MES software was, that it should submit production data, or a subset of this data to the ERP Server so that :

• The complete factory production data can be interlinked.
  
• The complete factory production function can be interlinked with all the other enterprise functions.
  
• The submission should be automated as far as possible to reduce input time, errors and cost.
  

A suggested configuration is shown in Figure 1 below:

Figure 1

Only 3 LSU's are shown linked to the ERP in the figure: in actual fact there could be a dozen or more.

The work of the Java application below the ERP is the following:

• Connect, in turn, to each LSU.
  
• Extract the data, or the required subset of the data from each relevant table in each
  database attached to each LSU, convert into a text-file of the type understood by the ERP database and submit it to the ERP database.
  
• Some additional tables may exist in the ERP: eg. the inventory between production units.These tables are also to be updated.
  
• The updation of the data will typically be done once a day.
  
• The entire process will be automated.
  

Validation of inputs.

I have already mentioned that identification of input batch, or coil numbers is a major problem. A coil may have wrong, or no labels.Of 90 billets making up a batch number, only 87 may be found.The list of problems is endless.

The nature and extent of the problem varies across organizations( reflecting managerial competence) and within shops in an organization( there are genuine difficulties in crowd wed and ill laid-out shops).Nobody has ever estimated the percentage of correct labeling within a steel plant.I have been in plants operating at 100% correctness, and in plants where achieving 95% accuracy would be considered an accomplishment.

To circumvent this issue, the best way is to design a "loosely coupled" ERP database, that uses the batch id number for its records, but does not break when the inserted id is blank, or invalid. When this happens, certain specific queries will return "no information available", but major reports to management will remain unaffected.The blank or invalid numbers can be put in a separate table, to be mapped against the correct id at some future date, if it can be found.The number of invalid ids generated by a department can be reported to management as an indicator of departmental efficiency.

In myconcluding article I will answer some questions relating to the demo set-up of the MES software that is currently in operation.