Tip top tableting

Maintain tooling to maximise tablet production, advises Andy Dumelow

As the most common method to deliver medication, pharmaceutical tablets continue to be in demand. They are efficient, easy to administer, cost-effective to manufacture, have high stability and are easily transported and stored.  With an agieng population and increased interest from developing countries, the requirement for solid dose form is escalating. This in turn increases the competition to manufacture mass-produced tablets at speed.

To meet deliverables, manufacturers need to look carefully at the tooling used and ensure tablet punches and dies are kept in optimum condition to produce large quantities of quality tablets quickly. 

The throwaway culture

Tablet compression tools are often viewed as disposable items. Why maintain them when you can replace old for new? This, however, is a costly mistake and will directly affect production. 
Correctly maintaining punches and dies and ensuring they are in good working condition not only reduces tablet press downtime, but also minimises compression problems. Looking after tooling will enhance efficiency, increase tablet quality and reduce tooling and operating costs. The cost of replacement tooling and potential lost productivity will increase overall expenses and make a substantial difference to a business’ bottom line. Regular maintenance also increases the lifespan of the tooling therefore retaining the value and productivity of each set of punches and dies - another cost-saving.

Poor Maintenance = poor quality 

Badly maintained tooling can cause a number of tableting problems, but perhaps the most common and significant is sticking. When in an optimum condition the surfaces of a tablet punch face are usually polished to a high reflective finish. The exception to this are textured finishes that are designed to alleviate specific sticking issues. This mirror finish can decline over time due to the continuous compaction of granules. This deterioration can lead to tableting defects such as sticking, which occurs from the adhesion of the granule to the worn uneven finish. This degradation in the tool’s surface can be identified quickly if regular maintenance procedures are in place.  Rectifying the problem can be achieved by simple processes including cleaning granule from the surface, to polishing the tooling.  

Another cause of sticking can be from wear caused by abrasive formulations. This can make tooling less effective and lead to poor tablet production. If a standard maintenance procedure is put in place, this problem would be identified immediately on inspection and corrected to improve production.

Steps to better tooling

There are tried and tested processes that all tablet manufactures should implement as a standard operating procedure to ensure productivity per punch can be maximised more effectively to meet with high-capacity manufacturing requirements.

A programme of professionally planned and consistent maintenance procedures should be used at all times to ensure punches and dies are ready for production, with the assurance that they are clean, un-damaged and within specification.

The recommended seven step approach is detailed below.

Clean. This is the most critical step of the maintenance process. Punch and die cleaning is crucial for the removal of residue and to avoid product contamination. It also minimises potential production issues such as sticking and picking caused by old product adhering to the surface of the punch tip. 
This step can be used to highlight damage to punch tip edges and damage that may occur in the form of nicks and bruises causing burrs and occasionally chipping. Approximately 80% of damage to punches and dies is usually caused accidentally when handling the punches through the production and tool care processes. If this procedure is not carried out effectively it will have a negative impact on the subsequent steps in the maintenance process.

Assess. Punches and dies should be visually inspected under magnification for signs of obvious damage like wear or corrosion and to establish if maintenance is required.
It is important to remember that identifying damage off the tablet press is more efficient than running tablet production with faulty tooling.

Repair. Light surface wear, corrosion and damage on tooling can be repaired and polished to a useable condition. Damaged tips can result in poor quality tablets and inferior embossing definition. Minor damage and corrosion can be repaired using a motorised chuck with double ended polishing motors used in conjunction with abrasive polishing accessories.
Importantly, any repair to uncoated punches and dies should only be carried out when necessary and by trained maintenance technicians to ensure tooling does not exceed tolerance limits. 

Measure. Measuring is essential after repair to ensure that the critical working length of the punch has been maintained. Any change to this and the tablet thickness, weight and dosage can be affected. 
Measuring should be carried out at regular intervals even if repair has not been necessary, to check for natural wear due to the compaction process. 

Polish. Automated polishing is crucial to ensure punches have an even and uniform finish and are in an optimum condition. By following this step, costly tablet press downtime caused through poorly maintained tool surfaces will be reduced. Controlled, light polishing on a frequent basis will ensure the tools are maintained to a smooth finish, helping to maximise tooling life. 

Lubricate. Lubrication is important to protect, preserve and aid smooth operation of continuous press tooling operations. A non-toxic, FDA compliant oil or grease is recommended for this step. Consider using a product that offers machine component protection and lubrication performance with a wide temperature range, to ensure it can be used in all equipment.
Store. Tooling storage and transportation should be specifically designed and developed with high security and safety handling considerations a priority. This will reduce the possibility of damage and deterioration. 

Keep track of tooling

A tooling maintenance process is extremely important for efficient tablet production, however the addition of a computer-based tool monitoring system will ensure all steps have been taken and tooling inventory is managed effectively. Crucially, manufacturers should have a complete audit trail covering tooling usage and maintenance that a tool management system can fulfil.This is not only good practice, but an important regulatory requirement in the majority of pharmaceutical environments.

A management system will record where tooling is, prioritise maintenance activity by creating an ‘action’ list and help to assess and monitor the life of the tools. Without this information either unnecessary tooling replacements are made, reducing productivity, or punches are used when they should be in maintenance or replaced.  This then leads to problems with the quality of the end tablet when it is found that the tooling being used does not meet the highly demanding process of tablet manufacture.  

Adopting a simple structured tooling maintenance process is essential to obtain the maximum life from punches and dies. Together with an in-depth computer-based monitoring system, tablet manufacturers will ensure the maximum life from tablet tooling which will result in increased production, tablet quality and direct cost savings.

Andy Dumelow is with iHolland

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