Tablet tooling

TABLE 6.20 Tablet Tooling Strength as a Function of Tablet Size and Fill Weight (Adapted from Ref. 38)... 

Extrinsic lubrication is provided via mechanisms that apply a lubricating substance, normally paraffin oil, to the tableting tool surface during processing. One method makes use of an oiled felt washer attached to the lower punch below the tip. This washer wipes the die cavity with each tablet ejection. To avoid having tablets stick to the punch faces, materials such as poly-tetrafiuorethylene or polyurethane have been applied to the faces. Another lubrication method sprays a thin layer of lubricant (either liquid or solid lubricant) onto the tool surfaces after one tablet is ejected and before the granulate of the next tablet enters the die cavity. 

Ensuring a controlled inventory of critical spare parts, e.g., tablet tooling... 

Dissociation of HCl or HBr from drug salts may occur, resulting in the release of the hydrohalide gas.f These gases in turn may interact with excipients or corrode tableting tooling. Such dissociation with gas loss may be induced and/or facilitated by processing, e.g., freeze-drying. 

On the other hand, tablet tooling design opens up for many possibilities for overcoming common tableting problems that cannot be solved by modifying the materials or the compression process, such as lubrication problems which in general are also a function of tooling size and shape. 

Schumann, S. The effects of chromium nitride ion bombardment treatment of tablet tooling on tablet adherence. Drug Dev. Ind. Pharm. 1992, iS (19), 1037-1061. 

Tsiftsoglou, T.B. Mendes, R.W. Effect of boron alloy coating of tableting tools. Pharm. Technol. 1982, 6 (April), 30-32, 36-38. 

Corrosiveness salts of weak bases with strong acids need to be tested whether or not they are corrosive on tableting tools. 

The stamp associated with the extreme hardness values (number 7, Fig. 4.12, left use STAMP.dat with program MULTI) is the next suspect It is identified and inspected on disassembly of the tablet press Due to mechanical wear, the movement of the stamp assembly is such that an above-average amount of granulate drops into cavity number 7, and is thus compressed to the limiting hardness supported by the granulate. The hardness for stamps 4, 8, and 11 tends to be low, and high for 12, but the data is insufficient to come to definite conclusions for these tools. The tablets from these stamps contaminated what would otherwise been a fairly acceptable product. Because... 

Insoluble Lubricants. Lubricants act by interposing an intermediate layer between the tablet constituents and the die wall. The smaller the amount of stress needed to shear the material, the better its lubricant properties will be. Since they are primarily required to act at the tooling/material interface, lubricants should be incorporated in the final mixing step after all granulation and... 

The force of tablet ejection from the die, Fr, is a function of both and the residual die wall force, RD WF, that exists after decompression. As the friction decreases, one will obviously see a corresponding drop in Fr. It is important to remember here that it is desirable for Fr to be as low as possible so that minimal damage is imparted to both the tablet and the tooling. 

All tableting presses employ the same basic principle—they compress the granular or powdered mixture of ingredients in a die between two punches with the die and its associated punches being called a station of tooling. Tablet machines can be divided into two distinct categories ... 

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. 

ITMs provide a valuable service to all phases of tablet manufacture, from research to production and quality control [109 111]. As a research tool, ITMs allow in-depth study of the mechanism of tablet compaction by measuring the forces that develop during formation, ejection, and detachment of tablets. ITMs can also provide clues about how materials bond,... 

Although UV/VIS diffuse reflectance spectroscopy has not been used extensively in the study of pharmaceutical solids, its applications have been sufficiently numerous that the power of the technique is evident. The full reflectance spectra, or the derived colorimetry parameters, can be very useful in the study of solids that are characterized by color detectable by the human eye. It is evident that questions pertaining to the colorants used for identification purposes in tablet formulations can be fully answered through the use of appropriately designed diffuse reflectance spectral experiments. With the advent of newer, computer-controlled instrumentation, the utility of UV/VIS diffuse reflectance as a characterization tool for solids of pharmaceutical interest should continue to be amply demonstrated. 

Raman spectroscopy is emerging as a powerful analytical tool in the pharmaceutical industry, both in PAT and in qualitative and quantitative analyses of pharmaceuticals. Reviews of analyses of pharmaceuticals by Raman spectroscopy have been published.158 159 Applications include identification of raw materials, quantification of APIs in different formulations, polymorphic screening, and support of chemical development process scale-up. Recently published applications of Raman spectroscopy in high-throughput pharmaceutical analyses include determination of APIs in pharmaceutical liquids,160,161 suspensions,162 163 ointments,164 gel and patch formulations,165 and tablets and capsules.166-172... 

A major concern of DEA special agents is the identification of the source of drug evidence. One of the methods they use to meet this requirement is through ballistics examinations of tablets. A ballistics examination, in the sense used here, is a combination of in-depth chemical analysis and tool-mark examination of tablets and capsules for the purpose of identifying the manufacturer of the drug. The technique consists of accurate measurements of size scoring, imprints, or bevels the microscopic examination of the imperfections... 

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