Wright Williams & Kelly

Factory Explorer® v2.2
Technical Alert #10
HoldTool and Alternative Steps

Summary: When a HoldTool region includes alternative process steps, it can cause the Factory Explorer® simulation to not properly free the HoldTool when lots leave the HoldTool region. This error is corrected in Factory Explorer® v2.3 beta 7 and forward.

Details: When a HoldTool region includes alternative process steps, Factory Explorer®'s simulation engine is sometimes unable to release the HoldTool when a lot leaves the HoldTool region. The problem occurs when the HoldTool region includes alternative process steps. When a lot reaches an alternative process step, Factory Explorer® creates a duplicate of the lot for each alternative. These duplicates are identical except for an identifying lot tag number. The lot that starts processing first is kept, while the remaining (duplicate) lots are destroyed. If a lot seizes a HoldTool, then enters an alternative process step, and the original lot is not chosen for processing, the duplicate lot is then unable to properly free the HoldTool, because it does not have the same lot tag number as the lot used to seize the HoldTool. To avoid this problem, the simulation HoldTool seize/release code has been changed to use a unique lot number that is assigned sequentially to all lots, and which remains the same even as duplicate lots are created and destroyed at alternative process steps.

Workaround: There is no known workaround at this time, other than ensuring that HoldTool regions do not include alternative process steps.

Techalert fx10-9710


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