Compaction simulator

M Celik, K Marshall. Use of a compaction simulator system in tablet research. Drug Dev Ind Pharm 15 758— 800, 1989. 

When the work is carried out on a compaction simulator, it is possible to subject the formulation to high-speed tableting cycles in order to evaluate strain forces in the compacts. This work can be of utmost importance, since it appears that strain rates can exert strong influences on a variety of tablet properties [64]. The information gathered in this way can be used to aid in the transfer of the manufacturing process among different types of instrumentation, and to aid ir the technology transfer process. 

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). 

Compaction simulators can have utility throughout the life of a drug product. Some of the uses for a simulator in pharmaceutical development and production are listed below ... 

The following paragraphs provide several examples for uses of a compaction simulator during development and scale-up. In these cases, the Presster was used as the compaction simulator. 

Despite the diligent use of predictive studies, compaction simulation, pilot scale work, the state of the art of tablet scale-up still provide opportunities for problems to arise. The issues typically encountered are those that have multiple factors involved, and are difficult to predict and simulate at smaller scale. Of these problems, tablet mixture flow, including weight uniformity and segregation, and sticking and picking of the tablet mixture to the tools and tablet specks, are common occurrences. 

Muller FX, Augsburger LL. The role of the displacement-time waveform in the determination of Heckel behaviour under dynamic conditions in a compaction simulator and a fully instrumented rotary tablet machine. J pharm pharmacol 1994 46 468-475. 

Compaction properties Compaction simulator or instrumented tablet press ... 

Tablet mechanical properties measured on samples prepared on an instrumented tablet press or compaction simulator are an excellent means to characterize excipients under dynamic conditions (8,9). Meaningful data analyses are best achieved if both tablet preparation and tablet property measurements are performed at carefully controlled conditions using standardized procedures. Such testing in the authors ...

Compaction properties of each material were determined with a standardized test performed on a custom-built hydraulic compaction simulator using 8 mm (0.3150 in.) round flat-faced punches. A linear saw-tooth upper punch position profile was selected with a punch velocity of 300 mm/sec for both punch extension and retraction. The lower punch position was at a fixed position within the die during the compaction event. The powder weight loaded into the die for each compression was calculated from the equation below so as to form a cylindrical tablet having a thickness-to-diameter ratio of 0.30 at a theoretical SF of 1.0. These dimensions are typical of commercially elegant tablets. 

Some of these measurements can also be performed on compaction simulators, which are single-stroke presses specifically designed to evaluate individual materials and/or full formulations [ 12]. The simulation of short dwell times and of many different profiles for punch movement in real time are the advantages of this type of measurement. Recent work with a compaction simulator has even included a thermodynamic analysis of compaction [13,14]. 

Minimize the compression force required to achieve target tablet hardness Manufacturability Compaction simulator or tablet press Compression force... 

A small rotary press is most likely used when the initial formulation and process is developed at small scale. However, a large rotary press, used in a production area, may have significant differences in the number of stations, dwell time, and compression speed compared with smaller compression machines. Thus, early formulation design should consider the performance requirements of commercial production. Compaction simulators provide a useful tool able to reproduce the punch speeds of production machines and require only small quantities of powder blends for testing.86 The simulators can play an important role in formulation and process development and can also facilitate the technical transfer from development to commercialization. 

Wang, JJ, Guillot MA, Bateman SD, Morris KR. 2004. Modeling of adhesion in tablet compression. II. Compaction studies using a compaction simulator and an instrumented tablet press. J. Pharm. Sci. 93(2) 407-417. 

Mechanical properties Dynamic mechanical analyzer Texture analyzer Compaction simulator Instron material test system... 

A direct correlation between the results of an eccentric press and a rotary press cannot always be drawn. In addition there are many different tablet presses with different settings and possibilities. These problems can be overcome by using a compaction simulator early in the development stage. An advantage of such a simulator is its versatility, that is, all types of presses can be simulated with small amounts of solid. The problem, however, is that such a simulator is very expensive. 

The first compaction simulators developed were hydraulic [41-45], The hydraulic system is electronically controlled. An example is given in Figure 7. Either compression force cycles or movement of the punches was freely adjustable. This allowed... 

FIGURE 7 Example hydraulically working compaction simulator left, machine view right, detail view into compression chamber. (ESH compaction simulator, Courtesy of Huxley Bertram.)... 

However, hydraulical compaction simulators are still used in research for basic material characterization. They show the advantage of controlling speed exactly and of using low and high punch travel speeds, between 10 and 300 mm/s. Mostly a simple displacement profile is used for characterization (e.g., a saw tooth or a sine wave profile), and the evolving forces at the lower and upper punches are measured. Further the speed of the punches can be controlled separately and both punches move freely and independently from each other. Time intervals in which the punches stand still can be freely set. Thus lots of freedom for material characterization is possible and these compaction simulators are important tools. 

Another advantage of compaction simulators is that only small amounts of material are necessary to produce a tablet. One single tablet can be produced at low as well as at high speed of the punches. This is important in order to evaluate defor-... 

More recently mechanical compaction simulators have been developed. The first was the linear mechanical rotary table ting machine simulator Presster (Figure 8), which was introduced in 1998 [55,56], It can mimic the mechanics of different rotary tableting machines and is called a linear rotary tableting machine replicator. The name Presster was combined from press and tester. 

The newest development for compaction simulation is a mechanical tableting machine simulator which operates with a cam. Thus it is called Stylcam (Figure 9) [59], The cam is positioned on the lower compression wheel and allows the simulation of different tableting machines and their dwell times due to different acceleration of the punches. It was introduced in 2005. 

Using mechanical compaction simulators allows us to simulate the tableting process of rotary tableting machines to a greater extent than when using hydraulical compaction simulators. Thus they will be mainly used in formulation development and scale-up. 

However, for mechanical compaction simulators the movement of the punches is mechanically determined and, compared to hydraulic compaction simulators, not freely programmable. Thus, for basic material characterization and early formulation development, hydraulical compaction simulators can be advantageous. 

Celik, M., Ong, J. T., Chowhan, Z. T., and Samuel, G. J. (1996), Compaction simulator studies of a new drug substance Effect of particle size and shape, and its binary mixtures with microcrystalline cellulose, Pharm. Dev. Technol., 1,119-126. 

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