Making high-quality tablets in an efficient manner depends on choosing the right compression tooling, says Dale Natoli. And central to getting that right is excellent communication between the equipment supplier and the manufacturer
Tablet compression tooling, commonly referred to as punches and dies, is probably the most misunderstood element of the tablet manufacturing process. Tooling is responsible for the tablet shape and face configurations, and is also an integral factor for an efficient tablet operation. A good tablet design with proper tooling can help gain market share, consumer confidence and higher profits, whereas a poor shape can cost literally thousands, if not millions, of dollars in lost sales, revenue and additional operating expenses.
Tablets designed for human consumption should be elegant and visually pleasing with the perception of being easily swallowed. In many cases, the specific tablet design is greatly influenced and directed by marketing concerns relating to customer recognition, confidence and loyalty. It is also necessary for the tablet design to be practical, easily compressed, coated and packaged. Consideration and attention to the idiosyncrasies of each product is necessary in order to achieve efficiency and optimum operating performance.
At the conception of a new product, frequent communication is essential. Departments such as marketing, research and development, engineering, production, packaging and the tooling supplier itself should collectively initiate a team spirit through an exchange of ideas and concerns. The tooling supplier usually proves vital to an efficient operation. Yet it is still too often that a tablet makes its way through research and development, testing, and documentation, and then gets to production and can?t be produced at a rate set forth by marketing.
Some of the most common issues created with an improper tool or tablet design are:
- product sticking/picking to the tool face
- tablet capping and/or lamination
- edge erosion and chipping
- broken tablets at ejection, coating and handling
- film coat fill-in and bridging, poor legibility of engraving on tablet
- premature tool failure created by extreme compression forces
- tablet discolouration from high ejection force
- tool binding commonly caused from sticky products or excessive fines in the formulation
This is just a basic list of the common issues encountered by tablet manufacturers on a daily basis. If you make tablets, then you can relate to some, if not all, of these issues. Most can be avoided with timely and frequent communication.
The majority of tooling manufacturers maintain staff that spends countless hours researching these issues and are willing to assist with tablet and tool design. In order for a tool manufacturer to propose a tablet and tool design tailored for optimum efficiency, a detailed interview should be conducted. It is helpful for the tool manufacturer to have knowledge of:
- Product characteristics: compressibility, abrasiveness, pH factor and stickiness
- Delivery method: depending on whether the product is chewed, swallowed, time release or quick dissolve
- Tablet identification: if the tablet is engraved, embossed or printed
- Film coating requirements: using aqueous or solvent solutions, or enteric coating shellacs and methods of application
- Demographics: children, geriatric, gender and/or general population
- Tablet press type: required production rate
- Packaging requirements: bulk, bottles or blister packs
Once the tool manufacturer understands the final product, he or she is then able to propose a proper tablet shape, cup configuration, and steel and hardness requirement. Tablet designs using deep cup punches, for example, will require more pressure to form a tablet compared to standard cups. A deep cup tool is required to compress as well as squeeze the tablet to its proper hardness, thereby requiring a higher compression force. This additional force places the tool in a position conducive to failure.
A deep cup punch design is greatly restricted to available compression force due to its more fragile characteristics. Because a deeper cup has more volume, overall press speed will be slower and more time will be required to exhaust trapped air before final compression can occur. Also, due to product abrasion along the sidewall, a deeper cup is prone to cause rapid tool erosion.
Although a deep cup tablet configuration has many disadvantages, it also has many advantages. For example, a deep cup can produce a tablet that appears smaller and thinner than a standard cup due to a narrower tablet sidewall or band. Deep cups can also assist tumbling in the coating pan for film-coated products and reduce twinning and thin-coated edges, and can eliminate edge erosion and chipping.
Another good piece of advice is not to place engravings at the apex of a tablet, especially if the product is prone to erosion. Such engravings will wear during contact with other tablets and hard surfaces. The edges of the engraving can erode causing those particles to be mixed in the coating pan, adhering to wet tablets being coated creating an undesirable appearance or generating product dust in packaging, which accumulates at the bottom of the bottle.
Also, keep engraving to a minimum. Some manufacturers have a tendency to want excessive engraving on the surface to identify a product name, product number, company name or logo. Excessive engraving can create a weakened tablet surface making it prone to erosion, picking and sticking, as well as weakening the tool design by causing tool chipping and fracturing.
For film-coated tablets, the amount of engraving can dictate the engraving cut depth, angle and width critical to the film coating process. Improper engraving cut configurations for coated tablets will result in bridging and/or fill in of the coating solution, which greatly reduces legibility.
Tooling steel selection is vital to both the tablet quality and operating expense. As tooling wears, tablet quality diminishes. In almost all cases, the wear of a tool is not determined by physical tool size, but overall tablet quality. As a punch wears, the critical edge of the punch becomes distorted and in most cases conforms to the inside of the cup and can cause a sharp burr commonly referred to as a J hook. This condition will cause excessive flashing, capping, lower yields, high ejection forces, increased operating temperatures and accelerated press wear.
Tool steel selection is based on tablet shape, required compression force and product characteristics. The proper steel selection based on the described criteria will prolong tool life, enhance overall tablet quality, and reduce labour and operating expenses. Today, the tool manufacturer has a greater selection of newer generation and exotic steels, many virtually unknown to the tablet manufacturer. Timely and frequent communication with the tool manufacturer regarding product characteristics will assure the proper tool steel selection.
The tool manufacturer does not manufacture tablets, nor does the tablet manufacturer produce tablet compression tools. Both play an integral part in the tablet manufacturing process. Like electricity is to a light bulb, one will not work without the other. The tool and tablet manufacturers are experts in their respective fields. Therefore, the ability to communicate and share knowledge will only enhance product quality and efficiency, and increase market share. Communication will reduce waste, downtime and operating expense.
Regardless of company size or number of products, timely communication will help develop product success. Communication is the key to tablet operation. As you can see, it is beneficial that all departments involved in designing, marketing, researching, producing and packaging tablets communicate concerns with the tool manufacturer. The manufacturer has to satisfy all of these areas, and each one is equally important to the success of a product.
Dale Natoli is vice president of operations and marketing of Natoli Engineering, a Missouri-based punches- and-dies supplier. www.natoli.com.
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