TABLETING
The LVS uses laser vision to inspect punches
coating and excessive dust in packaging for uncoated tablets.
PUNCH TIP AND CUP WEAR Punch tips should be inspected for excessive clearance to mitigate the same tablet quality conditions that can be experienced with die cavity wear. Tip wear is generally pronounced at the very edge of the punch tip, making it virtually impossible to measure with traditional inspection equipment. Once the punch tip edge wears the punch cup should be inspected for a wear condition referred to as “J-hook.” Te condition is characterised by the edge of the punch tip curling inward toward the punch face. Tip wear can cause capping during tablet production and lamination as the tablet de-compresses after the compression event. Te optical comparator is one of the best and most
Tool inspection technology
affordable inspection tools to measure punch tip edge wear.
PUNCH RETAINERS Te lower punch retainers can play an important role with tablet quality. Worn retainers should be replaced immediately to mitigate variances in tablet weight. Punch retainers are properly adjusted when the retainers just hold the lower punch in position against its own weight. Worn or improperly adjusted punch retainers can cause excessive tool and cam wear if adjusted too tight and excessive tablet weight deviation if they are worn.
PRESSURE ROLLS
Another inspection point on the tablet press is the pressure rolls and these should be visually inspected for surface pitting, which can transfer to the punch head. Te pressure rolls should be free spinning and checked for “run-out” or concentricity. An out of round pressure roll will cause inconsistencies in tablet hardness and weight. Check by using a dial indicator affixed to a magnetic base. Manually spin the roller while the indicator is slightly pressed on the roller. Te measurement is taken and averaged to determine whether pressure roll wear is within the tolerance range.
FILL CAM SELECTION Proper fill cam selection is imperative to consistent tablet weight and clean operation of a tablet press. A fill cam that does not have a sufficient depth of fill will result is inconsistent tablet weight. Rotary tablet presses operate
42
www.scientistlive.com
on an overfill principle where an approximate 20% overfill is required to achieve consistent tablet weight. Te weight/dosing cam will raise the lower punch to scrape off the excess formulation resulting in consistent tablet weight. If the fill is too deep, excess formulation, due to centrifugal force of the turret rotation may be thrown into the die cavity, again causing inconsistent tablet weight. Te excess formulation will also result in contamination of tooling lubricants.
EJECTION CAMS Ejection cam height should be checked with a straight edge across die table above the die cavity. Te edge should just meet the lower punch tip to ensure there is adequate clearance during tablet take-off. Setting ejection cams to a proper height will reduce tablet chipping and damage to the punch tip and feeder.
Checking the suggested inspection areas
and correcting any wear issues or defects is a step that is well worth its time, as it will improve product quality and reduce tooling cost due to wear and breakage. It’s also important for written inspection procedures to be developed to ensure that best practices are followed. It is crucial for staff to thoroughly check that press parts and tooling are within their respective tolerances and in good condition.
Dale Natoli is president of Natoli.
www.natoli.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60
