Seven Tablet Press Inspection Points to Increase Quality
Inspecting tooling and press components for wear or defects could be the most important step in improving tablet quality. There are certain tablet press inspection points that are easy to overlook yet can cause significant tablet quality issues and limit tool life. Spend a little time checking the following items for wear or defects to quickly increase tablet quality and reduce tooling cost.
The most critical punch dimension when using a rotary press as it is responsible for
consistency in tablet weight, hardness, and thickness. This should be measured directly and shouldn’t exceed a variation of .002 inches across a set of upper or lower tools. Working length should be thoroughly inspected on in-process tooling and spot checked on new tools when they are received.
Die Bore Wear
This inspection point is often overlooked during in-process tool inspection because, until recently, a lack of effective and affordable technology prevented wear measurement. New machines such as a Tooling Condition Monitor allow tooling wear to be measured and tracked. Die bore wear can cause capping, laminating, and excessive tablet flashing.
Punch Tip and Cup Wear
Punch cups should be checked for a condition called “J-hook.” J-hook is characterized by the edge of the punch tip curling inward toward the punch face. This type of wear can cause picking during tablet production. Punch tips should also be inspected for excessive clearance as they correspond to die bore wear. Just as with die bore wear, this can be measured using a Tooling Condition Monitor or by using an optical comparator. A traditional micrometer cannot properly check tip wear.
A part of the tablet press, punch retainers can play an important role in tablet quality. Check the tips for excessive wear. If they are worn out, they should be replaced, as wear can cause variances in tablet weight.
Another inspection point on the tablet press, pressure rolls should be checked for “run-out,” also known as concentricity. It is recommended that run out be measured on the pressure roller as it can cause inconsistencies in tablet hardness and weight. Concentricity can be checked by using a dial indicator affixed to a metal pole and magnetic base. The measurement is taken and averaged to determine if pressure roll wear is within the tolerance range.
Cam Wear and Depth of Fill
Cams should be inspected for wear either visually on the machine, or more thoroughly after removal. Cams also should be inspected and selected for proper depth of fill. Improper depth of fill can lead to excessive product loss and weight variance in tablets.
This inspection point should be checked with a straight edge. The edge should just meet the punch tip to ensure there is adequate clearance during tablet takeoff. Setting ejection cams to a proper height will reduce tablet chipping. 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 given tolerances, and in good condition.
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