Compaction simulator design

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]. 

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. 

Hoag, S. W., Nair, R., and Muller, F. X. (2000), Force-transducer-design optimization for the measurement of die-wall stress in a compaction simulator, Pharm. Pharmacol. Commun., 6(7), 293-298. 

Compaction simulators (Fig. 20) were designed to mimic the compression cycle of any prescribed shape by using hydraulic control mechanisms that are driving a set of two punches (upper and lower) in and out of the die. All hydraulic compaction simulators are similar in design and construction. A compaction simulator consists of several main units the load frame (column supports and crossheads with punches), the hydraulic unit (pumps and actuators that move the crossheads), and the control unit (electronic console and computer). Usually, a simulator accepts F tooling only, but can be retrofitted to use standard IPX B tooling. Under computer control, the hydraulic actuators maintain load, position, and strain associated with each punch. 

In addition, it was shown that the lower and upper punches may not move synchronously. Moreover, maximum force does not coincide in time with the minimum punch gap. These and other considerations (press deformation, contact time, etc.) make the effort of simulating a production press on a hydraulic compaction simulator rather impractical. That is why, to quote from a paper by Muller and Augsburger, " Although compaction simulator have been designed to mimic the displacement time behavior of any tablet press, they rarely have been used in that fashion. ... 

Asgharnejad, M. Storey, D. Application of a compaction simulator to the design of a high-dose tablet formulation. Part I. Drug Dev. Ind. Pharm. 1996, 22 (9 10), 967-975. 

Carlson, G.T. Christie, H.R. Curtiss, A.C. Hausberger, A.G. Jarvas, R.E. Jaxheimer, B.A. Schelhom, J.J. Sinko, CM. Design, Fabrication and Start-Up of a Laboratory Scale Compaction Simulator. AAPS Meeting, November 1998. 

This chapter will provide an overview of compaction simulator theory, construction, experimental design, and applications for the practicing pharmaceutical scientist. 

A compaction simulator must be able to mimic the full compression cycle of the unit operation. Early attempts at compaction simulation utilized mechanical property testing equipment (e.g., Instron and Lloyd type machines) to compact powders into compacts. Although these machines were well suited to apply appropriate compression loads, they were not designed for the high velocities and accelerations necessary to simulate the double-ended compression cycle of a rotary tablet press (2). 

Mechanically powered compaction simulators are also available to replicate the compression event of tablet presses (3). These machines leverage the design of traditional rotary tablet presses where the punches are forced between a set of roll wheels to enable the compression event. The punch type and roll wheels can be changed to replicate the compression event of different press types. In some models, the fill station, compression station(s), and ejection station arc aligned in series on a linear track, where the punches and die travel along this track from station to station to complete the fUl-comprcss-ejection cycle. 

COMPACTION SIMULATOR ANCILLARY FEATURES Tooling Types and Design... 

Compaction simulators are not designed to mimic the powder feeding event of a unit operation. Jackson and coworkers report that die filling on a rotary press involves complex... 

Compaction simulators are beneficial solid dosage formulation development because of their manufacturing versatility. They can be outfitted with a variety of tooling designs and can simulate a nearly infinite range of realistic compre.ssion profiles through the... 

Chemical vapor deposition (CVD) of carbon from propane is the main reaction in the fabrication of the C/C composites [1,2] and the C-SiC functionally graded material [3,4,5]. The carbon deposition rate from propane is high compared with those from other aliphatic hydrocarbons [4]. Propane is rapidly decomposed in the gas phase and various hydrocarbons are formed independently of the film growth in the CVD reactor. The propane concentration distribution is determined by the gas-phase kinetics. The gas-phase reaction model, in addition to the film growth reaction model, is required for the numerical simulation of the CVD reactor for designing and controlling purposes. Therefore, a compact gas-phase reaction model is preferred. The authors proposed the procedure to reduce an elementary reaction model consisting of hundreds of reactions to a compact model objectively [6]. In this study, the procedure is applied to propane pyrolysis for carbon CVD and a compact gas-phase reaction model is built by the proposed procedure and the kinetic parameters are determined from the experimental results. 

As shown in Fig. 4.1, resin feedstocks have a considerable level of interparticle space that is occupied by air. This level of space and thus the bulk density of the feedstock depend on the temperature, pressure, pellet (or powder) shape, resin type, and the level and shape of the recycle material. For a specific resin feedstock, the bulk density Increases with both temperature and the applied pressure. Understanding the compaction behavior of a resin feedstock is essential for both screw design and numerical simulation of the solids-conveying and melting processes. Screw channels must be able to accommodate the change in the bulk density to mitigate the entrainment of air and the decomposition of resin at the root of the screw. Typically, screw channels are set by using an acceptable compression ratio and compression rate for the resin. These parameters will be discussed in Section 6.1. 

Chapter 2 introduces the essential principles of modeling and simulation and their relation to design from a systems point of view. It classifies systems based on system theory in a most general and compact form. This chapter also introduces the basic principles of nonlinearity and its associated multiplicity and bifurcation phenomena. More on this, the main subject of the book, is contained in Appendix 2 and the subsequent chapters. 

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