Punches instrumented

Precompression using a Frogerais 0A single-punch instrumented press (Ets. Ed. Frogerais), equipped with flat punches 11,28mm in diameter (surface area, 1 cm2). The speed ofthe machine was adjusted to one tablet s... 

The most often measured force is the upper punch force. For the eccentric machine it is the force which controls densification for rotary tableting machines upper and lower punch forces have ideally the same values. Schmidt et al. [67] measured force with a single punch of a rotary tableting machine. Ejection force is visible as a small lower punch signal which occurs shortly after the end of one compaction cycle. It is measured by lower punch instrumentation but needs more resolution. A review of force measurement is given by Bauer-Brandl [68]. 

Measurement of the punch and die forces plus the relative displacement of the punches can provide raw data which, when suitably processed and interpreted, facilitate the evaluation of many tableting parameters. Many of the workers first involved in instrumenting tablet presses concentrated on deriving relationships between the applied force (FA) and the porosity (E) of the consolidating mass. 

FIGURE 19 A frequent system failure can be caused by punching of the electrode in the vial closure septum due to inaccurate outlining of the autosampler X/Y/Z robotic arms of the most frequently used QC performance Beckman MDQ CE system. Note that the opening of the vials with the PACE 5000 instruments was larger compared to the MDQ system, while the capillary/ electrode interface of both systems is identical. 

All functions of the instrument are controlled by an electronic programming unit equipped with a 42-channel punch tape. 

The use of compaction simulators was first reported in 1976. Since then, a variety of simulators have been developed. Hydraulic simulators, as well as mechanical simulators, are available to characterize raw materials, drug substances, and formulations, as well as to predict material behavior on scale-up. The appeal of simulators is due to the fact that they purport to provide the same compaction profile as experienced on a tablet press while using only gram or even milligram quantities of powders. Compaction simulators can achieve high speeds, as would be experienced on a production tablet press, and can be instrumented to measure a variety of parameters, including upper and lower punch force, upper and lower punch displacement, ejection force, radial die wall force, take-off force, etc. Summaries on the uses of simulators and tablet press instrumentation can be found in (19,20). 

Production machines are usually instrumented for force measurement in order to control tablet weight. However, the entire force-time profile and punch displacement are not usually measured in production, so it is difficult... 

In general, one should be aware that tablet press instrumentation involves the use of strain gauges or piezoelectric transducers to provide a voltage signal proportional to the force applied for the compaction operation. Let us say we can measure forces, such as those applied to the granulation by the punches, that applied to the die wall, that required for tablet ejection, etc. With tlie use of other transducers we can also measure distance. With the measurement of force and distance, we can calculate work, energy, etc. 

If you punch a few holes along the tube, you alter the frequencies of the standing waves that can form in the tube, with the result that different pitches are produced. This is the underlying principle in such musical instruments as flutes and saxophones. 

ISO 200722 specifies a rapid plastimeter procedure using an instrument with one platen either 7.3, 10 or 14 mm diameter and the other platen of larger diameter than the first (i.e. disc type method). The size of the first platen is chosen such that the measured plasticity is between 20 and 85. The test piece is cut with a punch which will give a constant volume of 0.40 0.04 cm, the thickness being approximately 3 mm and the diameter approximately 13 mm. The test piece is pre-compressed to a thickness of 1 0.01 mm within 2 sec and heated for 15 sec. The test load of 100N is then applied for 15 sec when the test piece thickness is measured. The usual temperature of test is 100°C and the result is expressed as the thickness of the test piece at the end of the test in units of 0.01 mm and called the rapid plasticity number. The Wallace rapid plastimeter, and presumably other commercial instruments, conform to this specification but it would be sensible to check with the manufacturers. A technically identical method is given in BS 903 Part A5923. 

The grade determines whether the mica can be used in high technology elecironic instruments, e.g.. computer-aided tomography (CATl scan, or in low technology devices, e.g.. a toaster. Many types of insulators, as well as the base for electronic circuits, are formed from the high quality sheets of mica by a punch pressing operation. 

There are three types of lubricants employed in solid dosage form manufacture. The first class of lubricant is the glidant. The flow properties of a powder can be enhanced by the inclusion of a glidant. These are added to overcome powder cohesiveness. The two other classes of lubricant are antiadherent excipients, which reduce the friction between the tablet punch faces and tablet punches, and die wall lubricant excipients, which reduce the friction between the tablet surface and the die wall during and after compaction to enable easy ejection of the tablet. The level of a lubricant required in a tablet is formulation dependent and can be optimized using an instrumented tableting machine. 

Tableting machine simulators [41-48] have been developed in order to mimic tablet production systems with a very small amount of powder. Similar to eccentric tableting machines, tableting machine simulators use one pair of punches. Working only with a single pair of punches reduces the consumption of tableting materials and facilitates instrumentation for displacement measurement.

The first instrumentation of a tableting machine for measurement of upper punch force was performed by Brake [60], Thus it was for the first time possible to visualize the compression process with regard to force development which results from the material stresses during tablet formation. Only shortly after that, similar measurements were published by another research group [61,62],... 

The sensitivity of force measurement is dependent on the distance between the force transducer and where the force occurs. Thus for force measurement, instrumentation of the punches is more advantageous than instrumentation of the machine frame. However, since punch and die sets have to be exchanged between different runs of the machines, instrumentation of the punch holder, the machine frame, or the roller pin is most widely spread. 

Die Wall Force Measurement During compression of the powder the forces are evolving not only at the punches but also at the die wall [63-65], Therefore die wall force measurement complements upper and lower force measurement. Since the compression process occurs axially, these radially evolving forces are smaller than the forces at the punches. Measurement of die wall force allows, for example, for indication on die wall friction, tablet capping, and lamination. Instrumentation for... 

The first measurement of upper punch displacement was performed in the mid-1950s by Higuchi and co-workers [62, 71] with the aid of inductive displacement transducers. By the same instrumentation the movement of the lower punch can be visualized. Inductive transducers are mounted parallel to the punch and thus give information on punch position. Alternatively touchless measurement of displacement is possible. It is important that the transducers be positioned most closely to the punch in order to minimize the influence of machine deformation. 

Except for the early commercial automated instruments, which used punched tape or drum controllers, all automated synthesizers are microprocessor controlled. The microprocessor controls the driver, which in turn, operates the valves, motors, heaters and sensors. 

The instrument was operated by a punched paper tape (a 42-channel mylar-backed tape). The punched holes specified a particular operation, such as the delivery of a solvent or a reagent into a metered vessel, transfer of that liquid to the reaction vessel, mixing, filtration, etc. The operator could program their own cycles, since an instrument to punch the tape was also provided. In 1984, Beckman introduced the System 990 Synthesizer, which was similar to the Model 990, except it was controlled by a nnicroprocessor. 

Instrumented tablet presses with computer interfaces allow the pharmaceutical scientist to study the mechanism of compaction and the relationship of the mechanism to tablet-compaction properties and formulations. In addition, automated systems are useful to develop compression profiles for reference purposes, to control weight of tablets during development and production, and to monitor punch wear. This automation reduces the burden on personnel faced with the requirements of quality control. Merck Sharp and Dohme s major production facility in the United Kingdom is fully computerized to manufacture a high-volume tablet product as well as multiple-tablet products. " ... 

Production machines are usually instrumented for force measurement to control tablet weight. However, the entire force-time profile and punch displacement are not usually measured in production so it is difficult to make a direct comparison to data that may have been produced using a simulator. One option would be to take a sample of material from production and run it on the simulator and compare the tablet properties to previous small-scale batches. 

Fig. 5 Cross section of an ICP torch and load coil depicting an ignition sequence. (A) Argon gas is swirled through the torch (B) RF power is applied to the load coil (C) a spark produces some free electrons in the argon (D) the free electrons are accelerated by the RF fields, causing further ionization and forming a plasma (E) the sample aerosol-carrying nebulizer flow punches a hole in the plasma. (Courtesy of Perkin-Elmer Instruments.)...

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