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 capsule quality.

Purpose of the Study:

• To develop and validate an instrumentation system for monitoring compression and ejection forces in an automatic capsule-filling machine.
• To analyze the forces involved in powder compression and slug formation during capsule filling.

Main Methods:

• Strain gauges were bonded to the compression piston of the dosing unit, forming a Wheatstone bridge circuit.
• An amplifier-recording system measured bridge unbalance voltage to monitor events.
• The instrumented piston was calibrated using a physical testing machine.

Main Results:

• The system successfully monitored compression and ejection events, identifying "precompression" and actual compression stages.
• Maximum slug compression force generally dropped rapidly upon piston retraction, with occasional retention forces noted.
• Lubricated batches showed ejection forces below 1 kg.

Conclusions:

• The developed instrumentation system provides a viable method for analyzing forces during capsule filling.
• Understanding compression and ejection dynamics is essential for optimizing capsule manufacturing processes.
• The system requires minimal permanent modification to the capsule-filling machine.