Tablet manufacturing problems and tablet-tooling failures are generally the result of one or a combination of the following:
- Difficult product/granule
- Inappropriate tablet design
- Incorrect tablet-press setup and operation
- Inadequate tablet-press maintenance
- Poor condition of tablet tooling.
Poor tooling condition, in particular, can cause many problems. These problems can be minimized or eliminated, however, by
adopting a simple, seven-step, tool-care process. The seven-step process is a logical, planned, and professional approach
to tooling maintenance and storage that has been adopted by many companies around the world as a standard operating procedure
The seven-step process
When tooling is removed from the tablet press, it should be thoroughly cleaned and dried to remove any oil or product residue,
especially from difficult-to-reach areas (e.g., in embossing and keyways). Equipment used for this process could include ultrasonic
cleaning and automated washing processes. It is essential, however, that the process does not cause corrosion of the tooling
material, and to that end, a corrosion inhibitor should be used.
Punches and dies should be visually inspected under magnification for signs of damage, wear, or corrosion and to validate
the cleaning process. This assessment will establish if the production process is running well or not. The assessment will
also give clues to problems with the tablet press or tooling itself and indicate if any tooling maintenance is required. Typical
equipment includes high magnification lenses and microscopes.
Light surface wear, corrosion, and damage on tooling can be repaired and polished to a usable condition. Worn tips can result
in poor quality tablets and inferior embossing definition, which can lead to picking and sticking. Equipment such as a motorized
chuck and double-ended polishing motor are used in conjunction with polishing accessories. Repair should be carried out by
well-trained and experienced maintenance technicians to ensure that the tooling is not taken out of tolerance limits. Repair
should not be carried out on coated tooling as this may remove the coating from the punch.
Measuring is essential after repair to ensure that crucial tooling dimensions have been maintained within an acceptable working
tolerance. The equipment for measuring can range from simple hand-held micrometers, vernier callipers, and height gauges to
semi-automatic, computerized, digital gauging systems. Measuring should be carried out at regular intervals, even if repair
has not been necessary, to check for natural wear during the compaction process. The essential measurement is the critical
working length of the punch as this controls tablet thickness, weight, and dosage.
Controlled, light polishing on a frequent basis will ensure that the tools are maintained to a smooth finish, helping to maximize
tooling life and reduce problems such as sticking and capping. Remedial, manual polishing can be conducted using double-ended
polishing motors with nylon polishing wheels and fine abrasive compounds. A more controlled and consistent process is the
automated, drag polishing system, which relies less on the skill and experience of the operator. This also allows for up to
70 punches to be polished in one 20-minute cycle, thus providing efficiency gains. Recleaning after polishing is not required
provided that a food-grade polishing media and paste is used during this operation.
Lubrication is important to protect the tooling and aid smooth operation. A range of oils and greases can be recommended
for different applications.
Tooling storage and transportation should be specifically designed to minimize damage and deterioration. There are different
ways of safely and securely storing tablet tooling; these range from storage cabinets to custom-designed storage containers.
Whichever system is adopted, it is important that the tooling is separated to avoid contact and that the tooling condition
does not deteriorate during storage.
Application of the seven-step process will have a direct impact on the reduction of many common tablet and tooling problems,
thus resulting in a better quality tablet, and can provide direct cost saving for the tablet manufacturer.