In the lock case, there are several pins and stoppers. Also, the face plate and the lock body belong to the lock case.
In the machine, pins and stoppers are all loaded by the bowl feeder station by station onto the preloading
device (fixture) and on one station, manual loading the face plate and the lock body on the preloading device. 
When the preloading device is equipped with all the required parts, the machine will check the existence of each part. 
If nothing is missing, the following station will rivet or assemble all the parts together into a “Lock Case”. 
And then, unload the lock case to the slide.