Instrumentation of an automatic capsule-filling machine

Area of Science:

• Pharmaceutical Engineering
• Mechanical Engineering
• Materials Science

Background:

• Tablet press instrumentation techniques were adapted for capsule-filling machines.
• Monitoring compression and ejection forces is crucial for optimizing capsule fill quality.

Purpose of the Study:

• To instrument an automatic capsule-filling machine to measure compression and ejection forces.
• To analyze the stages of powder slug formation during capsule filling.

Main Methods:

• Strain gauges were bonded to the compression piston of the dosing unit, forming a Wheatstone bridge.
• The instrumented piston was calibrated, and a mercury contact swivel was used for rotation.
• A solenoid switching system controlled gelatin shell feeding for the instrumented piston.

Main Results:

• Oscilloscope tracings identified two stages: precompression and actual piston compression.
• Maximum slug compression force typically dropped rapidly upon piston retraction, with occasional retention force noted.
• Lubricated batches showed lower ejection forces (< 1 kg).

Conclusions:

• The developed instrumentation system allows for effective monitoring of forces during capsule filling.
• The study provides insights into powder behavior and slug formation.
• This technique requires minimal permanent modification to the capsule-filling machine.