Troubleshooting Problems Affecting Tooling During Tablet Manufacture

It is important that tablet manufacturers implement production process improvements to meet continuing demandfor oral solid-dosage tablets. To improve processes, manufacturers must understand common problems that affect tooling and how to resolve them quickly. Some of the top problems impacting tablet production and methods in which to solve these issues and improve production are considered in this article.

Getting out of a sticky situation

Sticking, when granule accumulates on the punch-tip face, is the most common problem experienced during production. It can severely affect output and increase costs if not resolved quickly and effectively.

There are many reasons why sticking occurs. It can be caused by various factors related to the physicochemical properties of the formulation, the surface characteristics of the punch face, as well as issues related to the tablet press. Additionally, environmental influences like temperature and humidity prove problematic.

The adhesive forces between the ingredients in the formulation and the tablet tooling material, together with the cohesive forces holding the tablet together, can play a significant part in the sticking problem. If the adhesive forces are higher than the cohesive forces, sticking will occur. Adhesive forces are affected by factors such as the environment in which the tablet is produced, as well as the formulation preparation process. A good example is the effect the environment plays in the production of ibuprofen. The API in ibuprofen has a very low melting point, so if the temperature in which it is being manufactured is high, it can negatively impact the tablet. Simply lowering the temperature of the room in which compression is taking place will reduce the probability of sticking.

Humidity is also influential in increasing the risk of sticking. Moisture can enter the production process if there is excess humidity in the compression chamber or formulation preparation and storage areas. Increased moisture can equal increased sticking. This problem can be exasperated further if the granulation being compressed is wet.Excessive moisture within the tablet can amplify adhesive forces due to the increase in capillary action between the tooling surface and the granule. Capillary bridges form, causing high adhesion areas which leads to sticking.

Cohesive forces can also affect sticking. These include Van der Waals forces, which are the attraction of intermolecular forces between molecules; capillary action caused through high moisture content; and electrostatic forces, when granule is particularly dry and forms static electricity.

Any sticking problem requires thorough investigation before a solution can be found; however, one effective answer that is used with great success is the application of anti-stick tool coatings and treatments.

Advanced anti-stick coatings keep a low adhesion force under any environmental condition. If the adhesion forces in the coating are small to begin with, and the elemental composition of the coating does not attract the formulation, it will remain low because the coating is hydrophobic, or less hydrophilic than other coatings.

The selection of the right coating for the job requires a specialist; a tooling expert can match a specific formulation to the tool coating to prevent sticking and improve production.

Increasing productivity

Another problem when it comes to mass-producing tablets is finding a method to quickly increase production capacity cost-effectively. The best solution for this lies with multi-tip tooling. Although it is not a new technology, multi-tip tooling has only been widely adopted in the pharmaceutical industry during more recent years. It has transformed mass-production, and it is now considered the most productive form of tablet manufacture where it can be applied.

Successful implementation of multi-tip tooling can reduce the requirement to invest in more tablet presses, which is a large capital expenditure. It also decreases the number of tool set-ups required per production batch. Each batch is also completed in a shorter timeframe, therefore decreasing the overall production time.

Although almost any tablet press can use multi-tipped punches, it is important to check some vital points before investment, including the following considerations:

• Does the tablet press work efficiently? Check for wear in the turret area. Replace the cams if there are signs of excessive wear or degradation to prevent damage to the punch heads.
• Is the press compatible with multi-tips? The upper turret must have a keyway in the guide to ensure alignment with the tooling.
• The feeder paddles may need modification to ensure the amount of formulation is correct for die filling. The tablet ejection system must also be able to receive larger production volumes.
• Consider the formulation and particle size to be compressed. If the granulation does not flow quickly enough, it can result in problems. Modifying the feeder mechanism to optimize the press speed or reducing the machine speed to allow time for fill to take place can help.
• Revisit your tablet design. Multi-tips can produce most tablet designs, but production is affected by the press and tool-type capabilities. It is important to use a design developed specifically for a multi-tip configuration and ensure all variables (e.g., shape, size, profile, and embossing) are considered.

Keeping your tools in check

Tool condition can have a huge impact on production and causes many problems if maintenance procedures are not correctly upheld. Tools that are out of action due to avoidable damage or unforeseen replacement will affect output. The application of a structured maintenance process will result in the reduction of many common tablet and tooling problems. By adopting best practices in tool maintenance, tablet manufacturers will ensure that the maximum life from tablet tooling is achieved.

A simple way to ensure maintenance processes are completed is to follow a seven-step standard operating procedure (SOP). The first and most critical step is to clean punches and dies to remove any residue and to avoid product contamination and potential issues such as sticking.

Next, assess the tooling to inspect for signs of damage, wear, or corrosion and to validate the cleaning process. If it is found that damage has taken place, repair it. Light surface wear, corrosion, and damage on tooling can be repaired and polished to a useable condition. Follow this step by measuring the tooling to ensure dimensions have been maintained within an acceptable working tolerance. Then polish the tooling to ensure it is maintained to a smooth finish, helping to maximize tooling life and reduce problems, such as sticking.

The next step is to lubricate to protect, preserve, and aid smooth operation of the tooling. Finally, store and transport punches and dies carefully to minimize damage and deterioration.

Having a coordinated tooling SOP ensures punches and dies are ready for production, with the assurance that they are clean, undamaged, and within specification. Additionally, look to deploy a tooling management system to maintain efficient, well-organized, and in-depth monitoring of tablet production. This system can provide a complete audit trail on tooling usage and keep track of the tooling maintenance, which is critical in obtaining maximum life from punches and dies.

Invest in training

When it comes to effective tablet production, manufacturers should consider the technical expertise and skills gaps found within the workforce, which can impact the bottom line. If the skills of the staff decline, so too does the productivity and quality of the end product.

Flexible, online courses designed to identify and address common problems encountered during modern tablet production are available. Training is an important method in which to bring staff in-line with new pharmaceutical manufacturing advances quickly and ensure staff are proficient in their work and can troubleshoot problems with ease. Investment in learning will ultimately result in in optimized tablet production.

About the author

Alex Bunting is I Holland’s marketing manager, alex.bunting@iholland.co.uk.