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TABLETING 59


Granulation flow is


important as there will be the need for increased fill. If flow into the die is not at an optimum level, and the correct speed, then the use of multi tips will be affected and productivity increases will not be as high. Modification of the feeder mechanism may be required to increase formulation flow, allowing for optimum press speed to be maintained. Alternatively, the speed of the press being used may need to be reduced to allow extra time for the fill to take place. Particle size is another


important factor. If there are high percentages of fines, problems typically experienced when using single tip tooling can be multiplied. Te particle size must be within certain limits for the tooling to work effectively; however, with modification to features of the tablet design, such as tip


Example of a 16-tip tool


length and types of undercut, and changes to the working tolerances, multi tips can be accommodated.


New coating tool R


ecently, I Holland launched a further improvement to one


of its most advanced tool coatings – PharmaCote ECxtra. The protection of tablet


punches from problems such as corrosion, wear and formulation sticking to the punch tip face is a renowned issue in tablet manufacturing. One way of combating the problem is with the use of coatings. Traditionally, electro-plated hard chromium is the most popular coating used within the tablet tooling industry but it has serious drawbacks. When hard chromium


is applied to tooling, a certain amount of hydrogen penetrates the substrate, which can decrease the steel’s working load by up to 20%. To counter this effect,


the plated tools undergo a baking process known as de-embrittlement that reduces, but does not totally eliminate, the unwanted characteristic. It is also subject to micro-cracks that can develop during the plating process when the internal stress exceeds the tensile strength of the chromium. PharmaCote ECxtra has


been developed to stop the issues encountered by hard chrome, but still provide a coating that offers excellent tooling protection at a competitive price. It is a chromium-rich coating that is applied via an advanced sputtering technique. This process causes a very smooth and dense coating which helps to create an anti-stick surface.


Multi tips can produce most tablet designs, but this is influenced by the press and tool type capabilities. Users must look at the tablet size to evaluate the number of tips to fit the punch. Shapes such as ovals can be more challenging to arrange while delivering a robust tool and optimising die filling and tablet take-off positions. Te tablet size in relation to the punch type dictates the number of tips per punch. With tablets moving towards the ‘micro’ size, which can be produced quickly using punches with many tips, this design is growing. Any tip size of 4mm and


below is considered a micro tip. Tablet diameters of this size can represent a challenge to the tooling design and it may be necessary to incorporate reinforced punch tips to prevent bending during compression. Tis means fitting restricted fill cams that control and limit the movement of the lower punch to restrict the depth of fill. Tis prevents the punch tip from


dropping too low in the die bore. Recessed dies must also be incorporated to accommodate the reinforced tip, preventing it from meeting the die bore. If your requirement is to


increase production capacity within a short timeframe, multi- tips are considered to be the best solution, and the key driver to increased tablet production. Tey can eliminate the expense and time delay that can be experienced waiting for new capital projects to be approved and implemented. Tey can also drive a reduction in plant running costs without decreasing output and reduce the time needed to get tablets to market. With the combination of


correctly designed tablets and well manufactured multi-tip tooling, using the correct raw material and coatings, the use of multi-tips is the obvious answer to greater productivity, and a reduction in run-time per output of tablets. Tis leads to less maintenance per batch and reduced press set-up time, which in turn reduces costs


Steve Osborn is with I Holland. www.tablettingscience.com www.scientistlive.com


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