Of course automatic reporting of machine-states and part counter values by the manufacturing devices was great progress but the customer now needed to see this data in context with work-orders, operations and part numbers to be able to create meaningful reports. Because this information is written on a document called ‘work-order traveler’ (A) accompanying the workpiece and not known by the machine ways had to be found to join these things together.
Contextualize work-order related information with machine states and output
FIG 1: Part of a work order traveler with barcode containing work order number and operation (click to enlarge)
One possible option would have been to ‘inform’ the machine about the work order it currently performs and then read it just like machine states and part counter values. For PLC, CNC and PC controlled machines this can be done by transmission of these numbers to the controller via OPC or CNCnetPDM and storing them as variables that can be read afterwards.
For CNC and PC controlled machines it is also possible to insert these values as variables into the NC program and read them when the program is executed.
There are pros and cons for both techniques. In case the values are stored at the controller as variables major benefits would be that no additional hardware like barcode readers or PC’s is needed at the shop floor and no additional tasks have to be performed by the machine operators. However, someone has to perform this task when the work order starts and clear out the variables as soon as the work order ends. If this doesn’t happen states and part counts are either assigned to the wrong (previous or next) work order or the work order continues to run even it is already finished.
In case the NC program variant is used it would also be advantageous that neither additional hardware at the shop floor nor actions performed by the employees are required. However, it has to be taken into account that NC programs typically are part-, not work-order-specific. This would require one NC program for every work order even if its content stays the same. In addition, the fact that most operators leave the machine switched on with the last NC program loaded at the controller even when the work order is finished is more an argument against using this method.
To finally accomplish this task another route was taken. The customer’s program for operational data acquisition (ODA) that runs on PC’s at the shop floor could be used. Whenever a work order is started the operator selects the machine in the ODA program and scans the barcodes which contain work order number, operation and part number from the work order traveler. To finish or interrupt the work order the employee again selects the machine and chooses the appropriate action. The ODA program stores the data in a SQL database at the data acquisition server.
For contextualization of machine with operational data CNCnetPDM as well as the customer’s Data Service program have the ability to, whenever data is queried from the machines, automatically lookup the current work order, operation and part number for a machine in the ODA program’s database and add it to the data received from the device. This turned out to be the most effective and less error prone method.
Addition of work-order, part-number and operation to machine data
Enabled contextualization of work-order related data with machine data
Eliminated the need for external devices for operational data acquisition at the machines
Reduced implementation costs by utilizing the customers solution for operational data acquisition