Some powders are more difficult to dose than others. One of the many challenges lies in the fact that formulations must not be altered once they were officially approved. They must therefore be processed as they are - the same applies to the target containers. In principle, the product determines the process.
The first focus is on finding a dosing system to suit the powder in question. Most Harro Höfliger machines are equipped with volumetric dosing systems, dealing with small quantities to be filled into small-sized containers, with filling levels up to 100%. Another thing are powders with particle sizes of 10µm and less: Due to the interparticle adhesion force these tiny particles flow very poorly, they agglomerate and stick to the surfaces of the filling machine.
Appropiate dosing system
For this reason, powder properties like the flow behavior are being tested in the laboratory first. Even in small-scale this indicates potential problems for the later full-size machine. If a powder flows poorly, the dosing chamber is insufficiently filled. This might be improved with the help of vibration, ultrasound or vacuum, and once a suitable system is found it can be scaled up to the real production machine.
More than 90% of the projects Harro Höfliger is involved in relate to medicines and medical products. It is essential to perfectly match powder and processes to ensure stability throughout the entire storage and administration period. For example, Biopharmaceuticals containing proteins and peptides are increasingly being used. They often come in the form of lyophilisates or spray-dried powders and require specific ambient conditions like a low relative humidity. If it is too low, though, electrostatic charging makes the dosing process difficult to control. Consequently, such difficult substances require the development of customized machinery.