How long does it usually take kidney stone fragments to pass after lithotripsy?

Depends. Stones fragments may never completely pass on their own. Better chance of passing if an easily fragmented stone. Better chance if located within the upper portion of the kidney or within the ureter. Less chance if located in the lower portion of the kidney.
Stones. It depends on their size and how many there are. Small stones or their fragments should pass within a few days. Sometimes more than one lithotripsy is required if there is a lot of stone material in the kidney.