As advancements in drug-development technology continue, solid oral dosage forms (SODFs) are now produced in an ever-expanding range of shapes, sizes, colours and material compositions. With multiple coating options available to enhance a drug’s appearance, texture and taste, the customisation possibilities seem virtually limitless.
These wide-ranging physical variations exist for several purposes, from achieving specific drug-delivery functions to enhancing marketability and overall consumer appeal. Because of this diversity, the need for clear labelling and marking on SODFs pushes marking machine manufacturers to design adaptable, precise machine features.
Considering the high cost and time involved in drug development, understanding how a tablet’s physical characteristics influence the final product is crucial. A well-informed approach can help pharmaceutical companies save both time and money during the production process.
Tablet Shape and Dimension
Variations in tablet shape directly affect print quality. Tablet designers must evaluate the factors that determine the acceptability of printed logos, such as placement, clarity and completeness. These parameters depend on the tablet’s shape, dimensions and surface lubricity, all of which influence print accuracy.
A key step in establishing a successful tablet printing process is thoughtful design of the tablet’s shape and dimensions. Generally, the more geometric variation a product has, the harder it becomes to feed/handle during printing.
A product’s structure can be described in dimensions, for instance, a sphere has one dimension, a flattened sphere (tablet) has two and an elongated version (caplet) has three. As the number of dimensions increases, the difficulty of orienting and printing the product also rises.
Although almost any shape can be printed successfully, certain shapes perform better in automated printing systems. Round tablets typically yield the best print results, while the likelihood of achieving a clean print decreases for simple caplets, bi-convex caplets and more complex shapes like LCTs.
Tablet Identity
Efficient feeding and precise positioning of an SODF in a printing machine are essential for achieving consistent, high-quality prints.
If the tablet’s dimensions cannot be reduced to a sphere, which can be printed in any direction, manufacturers must clearly identify a “target face” for printing. The ease with which a tablet’s printable side can be distinguished from its other sides determines its identity. A tablet with a well-defined, easily recognisable face is said to have high identity.
A well defined tablet identity ensures correct positioning during marking.Machine designs use geometric features (like curves or edges) to position tablets accurately during printing.
Machined pockets used for positioning tablets are designed to fit expected geometric contours, ensuring that tablets align in one consistent way. This process is most effective when the tablet’s sides differ noticeably from its printable face. Features such as curved crowns or tapered edges increase the likelihood that the machine will orient the tablet correctly.
One of the most common challenges in high-volume tablet production is overexposure of belly bands, the straight sides of compressed tablets. When the ratio of a tablet’s face width to its belly band approaches 1:1, it becomes more difficult to feed the tablet correctly, leading to poor print quality.
To prevent this, designers must balance the belly band’s width with the tablet’s overall thickness and face curvature. Because belly bands are necessary for manufacturing but inherently flat, they have lower identity than the tablet’s curved surfaces. Even when slightly curved, a belly band’s curve is typically limited to one axis, reducing its recognisability.
In geometric terms, identity can be defined as the number of unique alignments a tablet’s shape allows. A surface curved in two axes (like a rounded face) provides higher identity than one curved in only one axis (like a belly band). Thus, for two tablets of equal surface area, the one with a smaller belly band offers better orientation control and print results. The closer the band’s width gets to the tablet face’s width, the harder it becomes to achieve a clean, legible print.
Marking equipment designers must account for this by creating tooling that minimises the risk of tablets standing on their edges, which can result in logos being printed across belly bands, leading to incomplete or unclear prints. Ideally, the difference between a tablet’s width and thickness should be at least 0.100 inches (2.54 mm). A higher width-to-thickness ratio and a smaller belly band generally lead to better tablet positioning and superior print quality.
Print Area
For a tablet logo to be clear and consistent, it’s not enough to just position the tablet accurately, the printed design must also be fully visible and legible. The print area is a crucial factor and should be defined early in the design phase since it directly influences the choice of printing equipment.
Single-lane printing machines are suitable for small-batch production but typically allow logos to cover only about half of a tablet’s face. In contrast, flatbed and drum multilane printers support higher production volumes and larger print areas. These machines offer better precision and include features like vacuum pockets (in drum printers) to hold tablets securely and expose more of their surface for printing.
As tablets increasingly incorporate larger, more detailed logos, including barcodes and functional design elements for identification or dissolution control, manufacturers often transition to flatbed or drum printers. These machines ensure a better grip and more precise alignment, resulting in higher-quality and larger print areas for intricate or brand-differentiating markings.
Summing Up
The physical design of a solid oral dosage form, its shape and dimensions, identity and print area, directly affects print quality and production efficiency. By carefully balancing these factors, pharmaceutical manufacturers can achieve reliable, high-quality markings while minimising rejections and delays.
To discover how advanced printing and inspection technologies can optimise your tablet production, reach out to us at vivek@groverholdings.com or dial +91 98211 11623.