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​Tooling Designs – Different Mixes Need Different Punches

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14 September 2016 No comments

It has always been difficult to market a tablet in the industry today. Aside from time and capital, research and development is also important; that said, one of the most difficult phases is the actual production of the tablet. Plenty of issues arise during production, including tablet quality to downtime of tablet equipment, which can result to delay in shipping of the product. There are steps that one can take to eliminate as well as minimize the issues before manufacturing actually begins.

The right tooling and tablet design can make and break any tablet manufacturing process. With that said how would one be able to distinguish the right equipment and is it possible to resolve the problems before manufacturing starts? Having an excellent communication with one’s team members and concerned departments as well as having an in-depth knowledge of one’s product can actually help.

Before handling the tablet design for manufacturing to start, the R&D department has an intimate knowledge of the formulation’s entire make-up from the physical structure to chemical specifications. From the start where the formulation is being granulated, preparation for compression up to the final product, there should be communication between team members. The tablet compression team should be involved with the entire process, as they often are responsible for the success of the tablet’s compression as well as launching in the market.

Key factors that also affect the success of the tablet manufacturing process are the powder’s characteristics, tablet design as well as the ambient relative humidity. Experts can analyze these factors and help prevent or avoid issues that are quite common in the tablet manufacturing industry such as sticking or picking. Aside from consulting with the whole team, it is also essential that one consult an experienced tooling vendor.

As the formulation and the compression tooling work together to generate the product, it is integral that one communicate with one’s tooling vendor as they have an in-depth knowledge of the equipment that would complement the powder formulation that the company manufactures. Example is that of powders that have abrasive properties, and as such materials that have resistant properties should be used instead of standard material types.

Common Processing Routes

There are three different ways to prepare different powder formulations for compression. Below is a brief of the different ways that formulations are compressed. Determining which way to go is based on the properties of the tablet to meet the requirements of the medicine.

Direct compression – this is used when the ingredients are able to be blended and a tablet compressed meets the dissolution and uniformity requirements. Direct compression is affordable and less costly as it easily blends all the excipients, lubricants and fillers together. One should take care to ensure that proper blending is observed to ensure uniformity of the dosage before compression.

Granulation is the process whereby all particles are collected to form granules. The particles are either compacted or formed by adding a binding agent.

Dry granulation – dry granulation is used when the formulation is sensitive to heat or moisture and not amenable for direct compression blending. To form the particles, machines such as a chilsonator or a roller compactor are used. By being compacted this way, the tablet increases its density and granules are then formed from the small particles. The pellets are then milledto the right particle size for distribution and then put through the compression process on a tablet press.

Wet granulation –wet granulation is used when the API’s physical properties precludes the use of dry granulation. Here, the APIs and excipients are blended together; adding liquid via the spraying method results to the particles sticking together. To enhance granule growth, binders may also be added to the mixture. The granules will then be left to dry out after which it will undergo milling and blending to obtain the right formulation.

Even if the process of wet granulation is expensive and time consuming, it is important as this meets the specification of specific drugs. The process can cause downtime when there is a retention of latent moisture in the finished powder. Common issues observed include laminating, capping, picking and sticking which manufacturers should resolve before processing starts.

These problems often results from compression tooling equipment especially if the root cause is undetermined and any problems during the developmental stage is addressed. There are wide ranges of tablet design and tooling options available today for tablet manufacturers and as such, one should consider how their granulation method as well as powder preparation can influence and shape tablet designs and tooling equipment.

The tooling equipment should be engineered and developed based on the product that is to be compressed; however, many put emphasis on using standard tablet configuration, even if the formulation is different and unique. Ideally, the compression tools and tablet designs are configured for individual products and formulations. To reduce cost, many companies are now using direct compression blends, which can cause a problem if not addressed at the start.

Consider a formulation that is easy to compress whether one uses a deep or shallow cup tool. This is not always the same case as some formulations may be difficult to compress when using a compound cup but can be compressed easily when using a standard cup.

Another is when one is using the dry granulation method. As the powders are compressed, excess fines or dust may recirculate around the die table, which can affect the next tablet to be compressed. This is when the dust attaches itself to the next tablet causing variability to the tablet’s properties. Aside from compacting, the dust may also migrate to other areas of the tooling equipment, which can cause problems in the tableting process. The dust material can cause premature tip wear, tip binding, heat generation, die bore wear and even discoloration of the tablet. Capping and laminating problems may also occur.

The shifted particles can cause contamination of the machine’s component(s) and may compromise the lubricity of the lower punch barrel and head. This can result to the premature wear of the press components and cause tool binding and downtime. Even if the tablet press works normally, the particles can make cleaning harder resulting to extra time in preparing the equipment.

Although excess dust can be addressed before the actual production starts, one can also use a formulation should it become necessary to do so to reduce its effects to the compression process. This is the reason why it is important to involve the development team throughout the process. If the formulation design causes problems, they may also modify the tablet to ensure compatibility with the tooling design.

The team may also suggest changes to the compression equipment such as narrowing the tip width than normal. Although a small change, a narrow tip in fact is an excellent option to consider especially for dry blends as it can reduce problems brought about by the fine dust particles during the dry granulation process. As the dust can stick to the die wall, a narrower tip with a deeper relief can help remove the dust from the die to prevent any buildup.

The buildup of the dust particles in the die bore as well as the repeated motion can cause friction, which would then lead to heat and can be a problem for heat sensitive formulations. The deeper tip would not only remove the excess particles but also lower the friction. This is because the narrow tip width reduces the contact between the tip and the die bore.

Tablet manufacturers should be aware that plenty of tooling options are available and can provide them with longer lasting dies and punches. Oftentimes, the tooling equipment is often an afterthought; however, talking with one’s team can ensure that the right tooling equipment is used and result to bigger savings for the company. Knowing the formulation characteristics, tablet manufacturers are able to consult with their tooling vendor on the right design and material to be used for their tooling equipment.

Standard steel tools are used for its overall balance and ability to absorb shock; however, these steels may not be suitable for some punches and dies. Example would be when there is a high chrome and carbon content. The D3 steel shows great resistance but has poor load and compression level. As such, this can be used for die but is a poor option for punches.

Steels with high chromium content can be an excellent option for products that are sticky or can cause corrosion. Steels that have high Rockwell hardness are also ideal especially when abrasion is the main concern. There are different tooling options that one can utilize to prevent the lower tips to bend when one is manufacturing small tablets. The punches can also be designed with an extended head flat to increase the dwell time for products that are hard to compress.

These are just of the solutions that are available for tablet manufacturers. Tooling designs can be designed depending on the specification of the formulation properties. Even at the start of the design stage, pre-picking along with cup modification and configuration can prevent problems such as picking, capping, lamination and sticking. Some formulation that has high compression force may also benefit from having a narrower cup depth or additional tablet land.

Simply changing the finish on the punch face can make a great difference on how a specific formulation runs in the press. The tips can be coated with chrome to improve resistance and other coatings can solve other problems as well. That said, adding coatings should not be used often to solve problems; it is important to choose the right steel type and tooling configuration to provide a longer-term benefit. Some coatings are expensive and may cause problems as well later on.

As powder cannot be compressed effectively, choosing the right delivery, clear communication and talking with one’s tooling vendor throughout the developmental process is the best way to ensure a successful tablet production. This would make sure that once the granulation reaches the compression process, the proper tooling is available.

Preparation is important as it brings cost savings to the company. Not only will the company be able to manufacture tablets efficiently, there would be less premature wear for tooling equipment. Some reputable tooling vendors also collaborate with other research organizations to provide insights on powder properties to find the best solution in the future.