Feeders Reality and Misconceptions

Tablet press feeders are critical part of tablet press. The article focuses to remove common  misconceptions

Feeders are classified into two types

1. Force Feeders
2. Gravity Feeders

Gravity feeders are used in older machines these feeders supply granules to dies using gravity as driving force

Force feeders / Power assisted feeders are commonly used in most recent High speed rotary machines the need of force feeders aroused when the speed of tablet presses considerably increased and regular supply of blend in die is required . these feeders have paddles to redirect granules form chute to feed frame .

High spot – Tablet press turret are not uniform at all places at some places it is high and low at some places the highest point should be determined using dial gauge fix the dial gauge using compactor on turret at zero setting now rotate the turret mark the point of highest reading on dial gauge and feeders should always be installed on high spot.

Installation of Tablet press Feeders and crucial checkpoints –

• Level the feeders base it should be above the die table .
• The feeders should be installed on high spot and should not touch die table .
• The distance between feeders and die table should be 0.003″ may vary in case of sticky granules .verify the gap using Filler gauge .
• Take an empty run and verify metal to metal contact it must not occur .

• The gaskets inside the force feeders should never be washed using IPA(Iso propyl alcohol) as it will make them brittle and more prone to damage
• Regular checks should be performed on gaskets and feeder paddles as they are prone to damage due to abrasive nature of granules .
• The Feed frame /Feeder paddles are wear parts and tends to damage with time due to abrasive nature of granules they should be Checked for damage and replaced frequently .
• The speed of feeders should be minimum during run as high speed can induce air in blend and lead to capping .

Different shapes of feeders are available and sometimes it is necessary to use different shapes example bar type feeders tends to break pellets in case of Mups compression so round paddles are used .

Sometimes , Damaged surface of paddles release metals which mixes in blend and appears as spots in tablets .