TL;DR
Weight variation on a rotary tablet press is most often a feed system or fill depth problem. Check the feed frame paddles, hopper level, and die fill depth before adjusting.
What you might see
- in-process weight checks failing USP limits
- weight variance increasing over production run
- feed paddle speed fault alarm
- hopper level dropping unevenly
Likely causes
Feed frame paddle wear reducing consistent die filling
Hopper bridging or rat-holing interrupting product flow
Die fill depth cam setting drifting from specified position
Blend segregation in the hopper causing local density variation
Required tools
- Analytical balance (minimum 0.1 mg resolution)
- LOTO kit
- Feeder paddle clearance gauge
- Feed frame removal tools
Safety first
- Pharmaceutical dust from the tablet press can be potent or sensitizing. Wear respiratory PPE per product SOP.
- Lock out the press before reaching into the feed frame area. The turret rotation hazard is severe.
- Do not adjust compression force or fill depth outside the validated design space without a change control.
Procedure
- 1
Stop the press and take a set of 20 tablet weight samples. Calculate the mean and standard deviation.[1]
- 2
Lock out and tag out the press drive and dust extraction.
- 3
Remove the feed frame and inspect the paddle vanes for wear or missing pieces.[1]
- 4
Inspect the inside of the hopper for bridging, product caking at the walls, or rat-holing at the outlet.
- 5
Verify the die fill depth cam setting against the process order specification. Re-set if the cam has moved.
- 6
Check the feed paddle speed setpoint and compare to the validated process parameter.
- 7
Reassemble and take a 20-tablet weight check. If weight variation is still out of spec, increase feeder agitation or consult the formulation team about flow aids.
Sources
Fette Compacting Fette FE 1200i / 3090 Tablet Press general technical documentation, Fette Compacting
Fette FE 1200i / 3090 tablet press general weight variation diagnosis and feed system procedures (general)
More guides for Fette Compacting Fette FE 1200i / 3090
How to diagnose main drive overload on a Fette FE 1200i / 3090 tablet press
Main drive overload usually means a mechanical jam, a broken punch, or a drive fault. Inspect the turret and punch set before attempting a restart.
How to fix punch sticking on a Fette FE 1200i / 3090 tablet press
Punch sticking means material is adhering to the punch face. Inspect punch surface quality, verify lubrication, and check product moisture before adjusting compression force.
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