This granulator was used to reduce the particle size of granules and coarse powders in order to achieve a more uniform particle size distribution. This is critical for the compression stage since large particles may result in tablets that do not have uniform weight and might be out of specifications.
It has a sieve made from stainless-steel wire mesh which is securely fitted onto a rotor which rotates to the left and to the right in sequence never finishing a complete circle. The advantage of this is that, in case of hard granules, the resistance is overcome by rotation in the opposite direction. Despite that however, it was found that in some case, the stainless-steel wire mesh could be torn thus possibly releasing small metal particles into the product and this type of granulators were therefore decommissioned many decades ago. They have been replaced with granulators having sieves made from perforated stainless-steel plates which are not prone to tearing.