Natoli's Tuesday Tech Tips: Side Scores – Design and Function

An increasingly popular solution to meeting tablet splitting dosage uniformity has been the application of side scores. Side scores can be described as bisects along the sideband of the tablet and may be used with or without bisect(s) on the tablet face. Scrutiny has become tighter by regulators on tablet dosage uniformity after splitting. A typical splitting study must demonstrate the tablet splits with a variation that does not exceed 1% in weight. Splitting requirements are detailed in USP <705>. Side scores can be a useful solution.

Side scores are commonly selected when either more space is needed on the tablet face for debossing than a bisect on the face could provide - or applying a?bisect on the tablet face is insufficient to make an even split. Before selecting a side score design, it is important to understand some of its drawbacks:

·???????? Tooling with side scores is more expensive and tends to have longer lead times since they require additional manufacturing steps.

·???????? Alignment between a hobbed bisect on the punch face and side scores can be challenging to manufacture. Tooling vendors may vary in their ability to provide consistent quality tools.

·???????? If tablet take-off occurs with contact occurring between the take-off bar and the side-score’s blend radius, there can be an increased risk of tablet chipping as the force is applied over a smaller area.

·???????? Tablet splitting during ejection may occur depending on the press speed, side score depth, and tablet tensile strength. Particular care must be taken to optimize the design for robust manufacturing.

·???????? Side-score punches can be more sensitive to improper alignment during installation (tips are more easily damaged).

Side scores are defined by their width, depth, angle, corner radius, and blend radius. Of these dimensions, it is the depth that is critical.

·???????? Side score depth is the most important trait as it directly correlates to ease of splitting and splitting accuracy. The deeper the side score, the more functional it is since it reduces the cross-sectional area of the tablet where splitting occurs (vertical plane across the tablet width). Depth is determined by first selecting the desired reduction in cross-sectional area (typically between 10% and 50%).? The reduction is best estimated based on tablet tensile strength and tablet thickness.

·???????? The side score corner radius (at the bottom of the side score) plays a minor role in splitting effectiveness. Smaller corner radii are beneficial but can be more difficult for the tooling manufacturer to produce with an optimal value of 0.15mm (0.006”).

·???????? Side score blend radius (blending the side score to the outside perimeter of the tablet) has a minor effect on the?tablet cross-sectional area (commonly known as the die hole surface area). Larger blend radii can be helpful during tablet ejection as they spread out the force in contact with the take-off bar.? Smaller blend radii increase the effective (measurable) side score depth.? Since side score blend radii can be stress risers on die bores, they should be at least 0.5mm (0.020”).

·???????? Side score angle is most commonly 90°, though smaller angles are sometimes specified even though it does not affect split-ability. The 90° side score angle is easier to manufacture and is therefore recommended.

·???????? Side score width is best determined as a result of angle and depth.

As manufacturing has become more precise and automated, the ability of tooling vendors to provide high-quality side scores on tooling has improved. For more information on side score design or to get a quote, please reach out to us at Natoli Engineering.

Todd Martin, Sr. Technical Service Engineer: 10/22/2024