Seven Steps to Solving Tabletting and Tooling Problems---Step 5: Polish

We have talked previously about the importance to maintaining a logical, planned, and professional approach to tooling maintenance and storage to ensure tablet tooling failures are avoided. Step 1: Clean of the recommend PharmaCare seven-step process is the most critical part of the program. Punch and die cleaning is essential for the removal of residue to avoid product contamination and potential production issues, such as sticking and picking, caused by old product adhering to the surface of the punch tip.

A good cleaning regime goes hand in hand with a good polishing regime, which forms Step 5 of the process and is arguably the next most critical step. It is cleaning and polishing that deliver most noticeable benefit into production, reducing tablet press down time and helping to increase productivity.

Step 5: POLISH

Automated polishing is an integral part of this seven-step process and will maximize trouble-free tablet production by helping to keep tooling in optimum condition. By following this process and correct maintenance, costly tablet press downtime and compression problems associated with capping, tablet weight and thickness variation can also be reduced.

With today’s modern tooling often being supplied with coatings, automated polishing is essential to ensure punches are evenly polished to a consistent finish so these coatings are not removed prematurely. Automated polishing ensures optimum and consistent tooling condition for maximum productivity, reduced sticking, and saved labor costs in terms of time spent on polishing.

Manual polishing using polishing pastes with a motorized chuck or double ended motor may be considered as remedial action. However, this is an abrasive polishing method and care must be taken not to deform the tip profile and embossing causing a deviation from the tablet specification. Extensive polishing of die bores is not recommended as this can easily alter the size and geometry of the bore leading to ejection problems and incorrect tablet size, weight, and thickness. Only light polishing or cleaning should be undertaken manually. Polishing should result in a mirror finish and smooth tooling surface. Due to the controlled and repeatable process, adoption of an automated polishing regime would always be preferable as all punches are polished to an even finish.

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 85 punches to be polished in one 20-minute cycle, providing efficiency gains. Re-cleaning after polishing is not required provided that a food grade polishing media and paste is used during this operation.

One method of polishing is to use the new I Holland MF80 automated punch and die polishing machine. With a 80-litre media drum and punch holders, giving a maximum of 85 B or 60 D punches per polishing cycle, it is an important part of this critical fifth step in the PharmaCare seven-step process.

Andy Dumelow is PharmaCare manager at I Holland.