What causes PCB bow and twist？-Assembly Conveyor Setup

Modern assembly equipment will generally use a conveyor system to transport boards through the assembly process. If the conveyor is a side rail system, it's possible the spacing is too tight and it's placing stress on the board causing it to bow. Check to make sure your conveyor system is uniformly parallel along the entire length of the track. The spacing may be perfect at one end but may start to widen or become tighter in other places.
If your system includes a center support, also check to make sure the support's height is consistent across the entire track.

 

To know more:
What causes PCB bow and twist？-Uneven Copper Distribution
What causes PCB bow and twist？-Unbalanced Stack Up
What causes PCB bow and twist？-Pre-Preg Materials Arranged Incorrectly
What causes PCB bow and twist？-Mixed Material Types
What causes PCB bow and twist？-Finished Thickness
What causes PCB bow and twist？-Moisture
What causes PCB bow and twist？-Rapid Heating During Assembly
What causes PCB bow and twist？-Assembly Conveyor Setup