Wright Williams & Kelly

Factory Explorer® v2.3
Technical Alert #12
Per-Batch Times for Non-Batch Tools


Summary: It is an error for a process step in a Factory Explorer® model to include a per-batch process time, but to specify a non-batch tool group. Normally, Factory Explorer®'s validation routines will catch such an error, but if the step does not specify a batch ID, the condition is not flagged and no validation error is generated. In this case, the number of batches is always calculated as zero (since the step does not use a batch tool), and the per-batch process time is effectively ignored. A validation check for this condition will be added to the next release of Factory Explorer®. To avoid this problem, check to see that steps specifying batch process times also specify a batch ID.

Details: When performing model validation for a process step, Factory Explorer® checks to ensure that the step's attributes are consistent with the definition of the tool group used by the step. For example, it is a validation error to specify a batch ID for the process step that is not defined for the tool group. It is also an error to specify a per-batch process time for the process step, if the step specifies a non-batch tool group (i.e. the tool group does not have any batch ID's defined). However, if a step includes only a per-batch process time, but no batch ID, Factory Explorer®'s validation routines will not catch the error. In the capacity analysis and simulation engine, the number of batches will always be calculated as zero, since the step uses a non-batch tool, and hence the per-batch time entered is never considered as part of the overall process time.

Workaround: Ensure that all steps with per-batch process times also specify a batch ID. As long as this is true, Factory Explorer®'s validation routines will flag the case where a batch step specifies a non-batch tool group. The next release of Factory Explorer® will contain a validation check for the situation where a process step specifies a per-batch time but no batch ID and the step uses a non-batch tool group.

Techalert tafx12-9802


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