Tablet tooling upper

Figures 15 and 16 provide a summary of the compression cycles for rotary and single-punch tablet presses. The formation of the tablet compact in these two types of presses mainly differs in the compaction mechanism itself, as well as the much greater speeds achieved with rotary type presses. The single punch basically uses a hammering type of motion (i.e., the upper punch moves down while the lower punch remains stationary), while rotary presses make use of an accordion-type compression (i.e., both punches move toward each other). The former find their primary use as an R D tool, whereas the latter, having higher outputs, are used in most production operations.

All operations take place simultaneously in different stations. Sixteen stations were commonly used in earlier machines with outputs between 500 and 1000 TPM and tablet diameters up to 15 mm. Presses with outputs orders of magnitude greater than the above are now widely available. The dies are filled as they pass beneath a stationary feed frame, which may be fitted with paddles to aid material transfer. The die cavities are completely filled and excess ejected prior to compression. Compression involves the movement of both punches between compression rolls, in contrast to single station operations where only the upper punch effects compression. Ejection occurs as both punches are moved away from the die on cam tracks until the tablet is completely clear of the die, at which point it hits the edge of the feed frame and is knocked off the press. Tooling pressure may be exerted hydraulically, rather than through the use of mechanical camming actions, as is the case with machines produced by Courtoy. 

A standard IPT Type B tooling was used with a f " round flat tool tip. Tablets were made one at a time, and the compression force as well as the upper punch displacement and lower punch displacement were recorded. Tablet weight, thickness, and breaking hardness were measured for each tablet. 

The basic unit of any tablet press is tooling consisting of two punches and a die, called a station. The upper and lower punches come together in the die that contains the tablet formulation. Principally, two different types of machines are used, the eccentric and the rotary press. The eccentric press produces about 50-130 tablets per minute. The rotary press has a multiplicity of stations arranged on a rotating table with the dies. A few or many thousands of tablets can be produced per minute. There are numerous models of presses, manufactured by a number of companies, ranging in size, speed, and capacity. 

The compression zone is located on the back side of the equipment and employs a maximum load force limited by the type of tooling being used. It is of paramount importance to note that, if a load force is applied over the indicated limit, the press unit will not function properly, resulting in premature wear or possible damage to the tooling. The compression set comprises the hopper and feeder system, the die table, the upper and lower compression rollers, the upper and lower turrets, the excess-material scraper, the tablet stripper, the recirculation channel, and the aspiration system. 

Regarding the importance of compression tooling to the performance of the tablet press and the quality of the tablets, it is of paramount importance that punches and dies are handled with care. The first criterion is the identification of the tooling that is, punches and dies should be identified according to the standard and be designated by upper punch without key, upper punch with key, lower punch with key, lower punch without key, or die, the reference of the standard (e.g., TSM, EU, JN, ISO), and the punch or die diameter. Punches and dies should also have a marking that includes at least the manufacturer s identification, the number of the punch in the series, and/or the identification number. Upon... 

Precompression and Main Compression Rollers. After die fill and scrape-off, the punches rotate to the precompression station where an initial force is applied to the compact. The tablet is frequently partially formed during the precompression stage. Subsequently, the upper and lower punches move together under the main compression rollers where the final tablet is formed. The main compression roller is usually larger than the precompression roller. However, latest advances suggest that similar sizes for precompression and main compression rollers with the ability to apply similar loads may result in optimal tablet formation. The compression rollers are made of premium tool steels and are surface hardened. 

Fig. 1 General terminology of tooling (sets of upper and lower punches and dies) for rotary tablet presses.

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