From this PDF, it is clear that they mean 'to position the next piece while the machine is still working on the previous piece'.
www.go-fluid.com/includes/it/varie/attrezzi_ sistemi.pdf?PHPSESSID=a3dba462bac96fd71825199b4ee4e3ac -
"Qualora necessario, due unità laterali di parcheggio consentono all’operatore di predisporre un nuovo pezzo da collaudare in tempo mascherato, ossia mentre la macchina di misura sta ancora eseguendo il collaudo su un altro pezzo."

This bilingual PDF calls it "shadow time":
www.breton-ct.it/common/tools_php/include/ fileDownload.php?td=catalogo&id=118&numero=1

However, I can't find other reliable instances of the phrase used this way. You could just work it into your sentence to indicate that the piece is staged for the robot while the machine continues with another task; when the robot is ready the piece will be waiting.

Hope that helps a little,

Amy

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Note added at 6 hrs 52 mins (2005-07-28 19:18:41 GMT)
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It looks like my cut and paste introduced extraneous spaces - if you remove them the links should work.