The knock-off drum with perforated cage type A 307 B is used when injection-molded or die-cast parts are still firmly attached to the sprue after demolding and must first be knocked off or separated from each other before the actual separation via the holes can take place. It is based on a perforated drum type 307 B.

Depending on the part geometry and the strength of the bond between the good part and the sprue, it is sometimes sufficient for the components to be rolled around in the separating drum, thus breaking the bond. If this is not sufficient, knock-off media such as plastic rods, wooden rods, plastic or steel rollers, etc., are used, which also repeatedly fall onto the parts to be separated. This removal medium lies loosely in the drum cage. This type of separating drum is also used, for example, with thermoset parts when debris or protruding "skin" needs to be removed from the mold parting line. In this case, drum cages made of soft materials such as rubber or silicone are often used to protect the components as much as possible. To remove the debris, additional removal elements such as plastic rods, wooden rods, or brush rollers can be placed in the cage as needed, which then "roll over" the components. and thereby knock off the skins.

Knock-off drums are usually equipped with reversing drive units that are able to regularly change the direction of rotation of the drum cage. This ensures that the knock-off media actually roll over the components and fulfill their purpose.

To prevent the knock-off elements from falling out of the cage, a catch plate is mounted on the end face of the separating drum's outlet. The distance between the drum cage and the catch plate is adjusted so that the components can fall out unhindered.

The hole spacing on this drum is approximately 700 mm. Depending on the specific task, lengths of 500mm, 1000mm or 1200mm are also used.