Improving Tablet-Press Tooling Maintenance and Storage

Poor tooling condition can cause many tableting problems, but these problems can be minimized or eliminated 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 steps are summarized as follows:

• Clean: 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., inside 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.

• Assess: 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.

• Repair: Light surface wear, corrosion, and damage on tooling can be repaired and polished to a useable 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.

• Measure: 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 semiautomatic, 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.

• Polish: 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.

• Lubricate: Lubrication is important to protect, preserve, and aid smooth operation of the tooling. A range of oils and greases can be recommended for different applications.

• Store: Tooling storage and transportation should be specifically designed to maximize security and safe handling to minimize damage and deterioration. There are different ways to 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.

For examples of how the seven-step process can be applied to real tooling problems, read the article by Trevor Higgins in the upcoming February 2013 issue of Pharmaceutical Technology.

—Trevor Higgins is a technical expert at I Holland, tel: +44 (0)115 9726153