Wright Williams & Kelly
Factory Explorer® v2.2 Technical Alert #5
Summary: At batch tools with units-based batch sizes, setting the minimum batch size equal to the maximum batch size can, in certain situations, cause Factory Explorer® to halt with an internal error during the simulation. In particular, if the maximum batch size is equal to the maximum product lot size, Factory Explorer® will not flag this input model error during model validation. This error is corrected in Factory Explorer® v2.3 beta 4.
Details: In Factory Explorer®, batch tools may specify minimum and maximum batch sizes in terms of units or lots. If specified in terms of units, Factory Explorer® checks the minimum and maximum batch sizes at model load time to ensure that it will always be possible to sequentially select lots from the input queue for processing. The following check is enforced:
then sequential lot selection cannot be guaranteed, and Factory Explorer® flags the situation as a model validation error. This rule is enforced so that when Factory Explorer® sees there are enough units waiting in queue to satisfy the minimum batch size, it will always be possible to sequentially select lots waiting in queue (according to the dispatch rule in force at the tool) and form a batch that meets both the minimum and maximum batch size requirements.
Factory Explorer® v2.2, however, does not exercise this validation check if the maximum batch size equals the maximum product lot size. It is possible, therefore, to create a model where the simulation may not be able create a batch that meets minimum and maximum batch size requirements, even though it thinks it should be able to. In this case, Factory Explorer® will halt with the internal error:
Assertion Failed: *r_batchsize >= minbatch, File: C:\FX\TGROUP.C, Line: 3242.
Workaround: Check the model to see if any batch tools with units-based batch sizes have the same minimum and maximum batch size (the maximum batch size is probably equal to the product lot size, otherwise Factory Explorer® would have already flagged the error). For these tools, lower the minimum batch size so that the maximum batch size exceeds the minimum batch size by at least the product lot size minus one.
© 1995-2003 Wright Williams & Kelly, Inc.