Die Compaction Process Research Articles

The elastic recovery, ejection work, strength and dissolution of instant coffee tablet containing croscarmellose sodium disintegrant

Croscarmellose sodium disintegrant agent, commonly used in the pharmaceutical tablet formulation was employed in the instant coffee tablet formulation. Various compositions of croscarmellose sodium were added to the instant coffee tablet formulation; 20% w/w, 40% w/w, 60% w/w and 80% w/w respectively. These mixtures were then compacted through the uniaxial die compaction process forming 1 g tablets having 13 mm diameters each at various compaction pressures of 37.7 MPa, 75.4 MPa, 113.0 MPa and 150.7 MPa. The ejection work done when ejecting the tablet from the die was calculated to represent the frictional resistance to tablet motion during ejection. The tablet elastic recovery was measured as a quantitative measure of the tablet physical dimensional stability. Meanwhile, the mechanical strength, as well as the tablet dissolution, were also measured. The results showed that the croscarmellose composition and the compaction pressure affected all the studied tabletting properties. Generally, croscarmellose sodium increased the tablet elastic recovery and lowered the tablet ejection work, tensile strength and dissolution time in experimental conditions employed in this work. However, the extent of the croscarmellose sodium influence was clearly dependent upon the compaction pressures used for instant coffee tablet formation.

Compaction behaviour of mannitol-cocoa powder mixtures and their resulting tablet strength and disintegration characteristics

Cocoa powder is an important ingredient in the confectionery industry and, mannitol is an alternative sugar alcohol. In this work, mannitol powder was mixed with cocoa powder and compacted into tablet form via the uniaxial die compaction process. The frictional, compaction, tablet mechanical and disintegration properties were studied due to their importance in characterizing the behaviour of the tablets during processing and its final product characteristics at varying mannitol contents. The composition of mannitol in the mannitol-cocoa tablet varied at 95% w/w, 50% w/w and 5% w/w, while pure 100% w/w mannitol and cocoa tablets were set as controls. The compaction pressures used in making the tablets varied at 37.67 MPa, 75.34 MPa, 113.01 MPa, 150.68 MPa and 188.35 MPa. The compaction behaviour of the powder during the compaction process was evaluated using the plastic work and the maximum ejection stress values. The tablet strength was determined using the tensile strength method and tablet disintegration study was also conducted. The results showed that the increase in the compaction pressures increased the plastic work, maximum ejection pressure, tablet strength and also its disintegration time. The tablet formed having 95% w/w mannitol composition exhibited the highest plastic work value of 10.32±0.01 J, highest maximum ejection pressure value of 4.4±0.06 MPa, highest tensile strength value of 1.06±0.04 MPa and shortest disintegration time of 171±51 s amongst the three different mannitol compositions studied. Meanwhile, the effects of mannitol composition in the tablet on these observed responses were also dependent upon the compaction pressures used during tablet formation. In conclusion, the addition of mannitol improved the tablet strength and shorten the disintegration time in the experimental range employed in this study.

The Effects of Sintering Schedule on Alloy Powder ASC 100.29 Compacts Formed at Elevated Temperature

This paper presents the outcomes of an experimental investigations on the effect of sintering schedule i.e. holding time and temperature to the final properties of alloy powder ASC 100.29 formed through uniaxial die compaction process at elevated temperature. A lab-scale powder compaction rig with uniaxial compression and installation of heater was designed and fabricated in order to produce green compact from powder mass at elevated temperature. Alloy powder ASC 100.29 (99.7 wt%) and lubricant, zinc stearate (0.3 wt%) were mixed mechanically for 30 min at a rotation of 30 rpm. The powder mass was compacted at 150°C via simultaneous upward and downward uniaxial compression load of 425 MPa. Defect-free green compacts were generated from the compaction and were subsequently sintered at 1000°C using a custom argon gas fired furnace at three different sintering rates, i.e., 5, 10 and 15°C/min for three holding times, i.e., 30, 60 and 90 min, respectively. The final products were characterized through their physical, electrical and mechanical properties and their microstructures evaluated. The results revealed that the sample sintered for a longer period of time, i.e. 90 minutes at the slowest sintering rate, i.e. 5°C/min obtained the better final characteristics.

Stresses State and Mechanical Behaviors of the Green Body During Die Compaction and Ejection Process

Finite element simulations for metal powder compaction of a clutch plate were performed to examine the stresses during compaction, unloading, and ejection. To describe the mechanical behavior of compacted green body, a modified density-dependent Drucker–Prager Cap model was utilized to predict the stress and density distribution of the compacted clutch plate during loading and ejection stages. The results indicate that maximum tensile principal stress was a main driving force for the tensile crack initiation during ejection stage, and shear stress may be another driving force in both compaction and ejection stages for shear crack initiation. There were peak value of the stresses during ejection stage, and the stresses are in compressive state only during compaction stage. Therefore, the tensile crack initiation is not possible during compaction except shear crack. Hoop stress in the clutch plate is of less contribution to the crack initiation during compaction, unloading and ejection. Study of criteria of the crack initiation and fracture is necessary in order to obtain uniform density and crack-free components in the manufacturing of metal powder compaction.

Investigation of Floating and Single-Action Dies in Producing Dense Compacts with High Aspect Ratio

In this study, the commercially pure aluminum powder was compacted by single-action and floating dies at room temperature. The effect of compaction method on densification was studied using density distribution, microhardness measurements and scanning electron microscope (SEM) along the compaction axis of processed samples. The density measurements of compacted samples through the floating die process shows more uniform density distribution in comparison with single-action process, which is in good agreement with microhardness and SEM results. Results also show that the densification requires lower compaction load in floating die process than is needed in single-action compaction process, which is due to the improvement of the frictional condition by making change in relative movement in the frictional surfaces of floating die process. Therefore, it makes floating die more beneficial in producing dense compacts with high aspect ratio (ratio of height to diameter) which is not possible in single-action die compaction process.

Particulate Scale Multiparticle Finite Element Method Modeling on the 2D Compaction and Release of Copper Powder

Herein, two‐dimensional (2D) single‐action die compaction process of copper (Cu) powder was simulated by the multiparticle finite element method (MPFEM) at particulate scale. The initial packing structure, generated by the discrete element method (DEM), was used as an input for the FEM model, where the mesh division of each particle was discretized. The evolution of macro‐ and microscopic properties, such as relative density, stress distribution, particle deformation, void filling behavior, and force transmission, during compaction and pressure release processes have been systematically studied. The results revealed that the force is mainly concentrated on largely deformed regions of the particles during compaction and formed a contact force network, which hindered the densification process. In the compact, the shorter side of the large void edges rendered higher stress than the longer side. On the other hand, the stress distribution of small void edges remained uniform. After pressure release, large residual stress was observed at the contact area of the adjacent particles and the maximum stress was observed at the particles’ edges. Moreover, the residual stress did not proceed to the interior of the particles. Meanwhile, the stress of large void edges has been completely released but exhibited a nonuniform distribution. The smaller fraction of void filling resulted in a larger reduction of the released stress after pressure removal. Also, the particles closer to the upper die exhibited higher average equivalent von Mises stress inside the particles during compaction and pressure release processes.

Investigation on Compaction Densification Behaviors of Multicomponent Mixed Metal Powders to Manufacture Silver-Based Filler Metal Sheets

The powder compaction combines sintering process method was used to fabricate silver-based filler metal thin sheet; the densification behaviors of two mixed metal powder (Ag50Cu50 and Ag60Cu30Sn10) were modeled and investigated. The Drucker–Prager Cap model combines with compaction equations was employed to analyze the mixed metal powder compaction behavior. Firstly, various powder compaction experiments were conducted to determine the powder material parameters, and the friction coefficients were determined experimentally by die compaction. Furthermore, the linear Heckel and nonlinear Gerdemann–Jablonski compaction equations were used to analyze the powder compaction mechanisms. It was observed that lubricant affects the powder deformation and rearrangement densification mechanisms during the powder die compaction process. Finally, finite element modeling results were compared with the validation experiments data to validate the determined constitutive model. The result shows that the established models can accurately describe the mixed powders densification behaviors, which could be used in simulation of tool designing and process parameters optimizing.

Effect of Sintering Temperature and Holding Time to the Final Characteristics of Fecral Powder Compacts Formed at Elevated Temperature Through Die Compaction Method

This paper presents an experimental study on the effect of sintering temperature and holding time to the final characteristics of FeCrAl powder compacts formed at 200°C through uniaxial die compaction process. The powder mass was prepared by mechanically mixing iron powder ASC 100.29 with chromium (22 wt%) and aluminum (11 wt%) for 30 min at room temperature. The powder mass was formed at 200°C by applying an axial load of 425 MPa. The as-pressed compacts termed as green products were then cooled to room temperature and subsequently sintered in argon gas fired furnace at a rate of 5°C/min for three different holding times, i.e., 30, 60, and 90 min at three different sintering temperatures, i.e., 800, 900, and 1000°C. The sintered samples were characterized for their density, bending strength, and microstructure. The results revealed that the sample sintered at 800°C for 30 min got higher relative density but lower bending strength. Sample sintered at 1000°C for 30 min achieved the higher bending strength and better microstructure.

Compaction behaviour and mechanical strength of lactose-sodium starch glycolate and lactose-croscarmellose sodium binary tablets

The focus of this study is to elucidate the effects of adding super disintegrants (SSG and Acdisol) to a filler (lactose) in terms of the compaction behaviour and mechanical strength of the formed binary tablets. The tablets were formed in a uniaxial die compaction process with compaction pressures ranging from 37.7MPa to 150.7 MPa. Consequently, the findings indicated that the increasing of the compaction pressure and the percentage mass composition of the super disintegrants would led to the increased in the strength of the tablets as well as their plastic energies, where this was more apparent for the case of the binary lactose/Acdisol tablets. In addition, as the compaction pressure increased, the maximum ejection pressure required to eject the tablet from the die cavity also increased. In contrast, a decreased in the maximum ejection pressure was observed as the composition of both super disintegrants increased in the lactose-super disintegrant binary tablets. In conclusion, the addition of super disintegrant; SSG with lactose and Acdisol with lactose; would enhanced the mechanical strength of lactose based tablets especially for the case of acdisol-lactose binary tablets in the experimental conditions adopted in this current work.

Sensitivity of elastic parameters during the numerical simulation of pharmaceutical die compaction process with Drucker-Prager/Cap model

Numerical simulation of the die compaction process with Drucker-Prager/Cap (DPC) model is increasingly used to understand the powder behavior during compression. The use of DPC model to numerically simulate the powder compression requires the characterization of a number of parameters like the DPC model parameters, the elastic parameters and the friction coefficient.The methods used to characterize the required parameters are well detailed in the literature. Nevertheless, the values determined for a given parameter of a product varies from a study to another. The effects of the variations of some plastic parameters were already studied in the literature, but the influence of elastic parameters has not been assessed. Then, to investigate such an influence, in this article, we have used already published values for the elastic parameters of microcrystalline cellulose. Moreover, realistic deviations of the values of Young's modulus and Poisson's ratio, based on the differences observed in the literature were introduced in the numerical simulation performed with the Drucker-Prager/Cap (DPC) model and their effects on the results were analyzed.The results show that the variation of the Young's modulus E has no influence on the distribution of the relative density, the axial and radial stresses and on the final tablet thickness. On the other hand, variations of the Poisson's ratio lead to a change of the results of the compaction. The residual radial stresses are low when high Poisson's ratio values are used in the simulation. In particular the residual die wall pressure decreases and tends towards zero when the Poisson's ratio increases. In the case of simultaneous variations of the Young's modulus and the Poisson's ratio, the effects on the numerical results are principally due the change of the Poisson's ratio. Nevertheless, the elastic recovery is more important when the values of the two parameters are low.This work clearly highlights a link between the Poisson's ratio and the residual die wall pressure. Since a correlation was established between the die wall pressure and the occurrence of some defects like capping, it is important to well characterize the Poisson's ratio for a good prediction of capping phenomena when using FEM modeling.

MPFEM simulation of compaction densification behavior of Fe-Al composite powders with different size ratios

In this paper, 2D single-action die compaction process of Fe-Al composite powders with different size ratios was simulated via the multi-particle finite element method (MPFEM) from particulate scale. Different initial packing structures generated by discrete element method (DEM) were imported into FEM model (where each particle was discretized for mesh division) for compaction. The compaction process was reproduced and the densification dynamics and mechanisms were analyzed and identified based on the evolution of macro and micro properties of the compact. The results indicate that, when the Al contents in the composite powder and the compaction pressure are fixed, higher relative densities can be obtained at smaller Fe/Al size ratios. During compaction, large stresses are mainly concentrated within those contacted Fe particles (near the surface region), forming the contact force network which impedes the compaction densification. Upon unloading, the contact force network is broken, and most internal stresses are released while only small amount of residual stresses are remained within Fe particles, which is susceptible to cracking or even failure during further processing. The smaller the Fe/Al size ratio is, the more complete is the release of the residual stress. During compaction, large voids (or pores) formed in the initial packing are filled by particle rearrangement (especially the rearrangement of small Fe particles) and plastic deformation of Al particles. However, there are still some small enclosed pores left in the final compact, which will lead to non-uniform deformation of adjacent particles and stress concentration during the subsequent sintering process.

Effects of sintering time and temperature to the characteristics of FeCrAl powder compacts formed at elevated temperature

This paper presents the outcomes of an experimental investigation on the effect of sintering schedule, i.e., holding time and temperature to the final properties of FeCrAl powder compacts prepared through uniaxial die compaction process at above room temperature. The feedstock was prepared by mechanically mixing iron powder ASC 100.29 with chromium (22 wt%) and aluminium (11 wt%) for 30 min at room temperature. A cylindrical shape die was filled with the powder mass and heated for one hour for uniform heating of the die assembly together with the powder mass. Once the temperature reached to the setup temperature, i.e., 150°C, the powder mass was formed by applying an axial pressure of 425 MPa simultaneously from upward and downward directions. The as-pressed green compacts were then cooled to room temperature and subsequently sintered in argon gas fired furnace at a rate of 5°C/min for three different holding times, i.e., 30, 60, and 90 min at three different sintering temperatures, i.e., 800, 900, and 1000°C. The sintered samples were characterized for their density, electrical resistivity, bending strength, and microstructure. The results revealed that the sample sintered at 1000°C for 90 min achieved the better characteristics.

Effects of forming temperature and sintering rate to the final properties of FeCuAl powder compacts formed through uniaxial die compaction process

This paper presents the outcomes of an experimental investigation on the effects of forming temperature and sintering schedule to the final characteristics of FeCuAl powder mass formed at different temperature and sintered at different schedule. A lab-scale uni-axial die compaction rig was designed and fabricated which enabled the compaction of powder mass at room temperature as well as elevated temperature. Iron (Fe) powder ASC 100.29 was mechanically mixed with other elemental powders, namely copper (Cu), and aluminum (Al) for 60 minutes and compacted at three different temperature, i.e., 30°C, 150°C, and 200°C by applying 425 MPa of simultaneous downward and upward axial loading to generate green compacts. The as-pressed samples were inspected visually and the defect-free green compacts were subsequently sintered in an argon gas fired furnace at 800°C for 60 min at three different heating/cooling rates, i.e., 5, 10, and 15°C/min, respectively. The sintered samples were then characterised for their physical, electrical, and mechanical properties. The microstructures of the sintered samples were also analysed. The results revealed that a forming temperature of 150°C and a sintering rate of 10°C/min could produce a product with better characteristics.

Compaction properties of dry granulated powders based on Drucker–Prager Cap model

Dry granulation by roll compaction is a process of size enlargement used to produce granules with a good flowability for further die compaction process. To gain in the understanding of how granulated powders behave during die compaction and why they exhibit different behaviors different from those showed by the feed powder, the main material parameters proposed in Drucker-Prager Cap (DPC) model, were determined for MCC101 powder and two granule sizes obtained from roll-compacted ribbons. For that, the standard procedure calibration of DPC was used.Results showed that all the material properties are density-dependent and the properties of feed powder are higher than those of granulated powder. Moreover, the yield hardening function showed a decrease with the increase of the granule size, which highlighted that the granules of MCC 101 exhibit a softer work hardening than feed powders. Overall, the granules have smaller yield surface than the feed powder. Particularly, it was found, for both granule sizes and the MCC 101 powder, an overlapping of shear failure line at high relative density. Nevertheless, at low density, the cohesion was affected by the roll compaction of MCC 101, but no variation was observed for the internal friction angle. The obtained results are in agreement with the literature, where the granules were prepared from mini-tablets rather than from roll-compaction. However, some discrepancies were highlighted.

Sintering of FeCuAl powder compacts formed through die compaction process at elevated temperature

This paper presents the outcomes of an experimental investigation regarding the sintering characteristics of FeCuAl powder compacts formed through uniaxial die compaction process at elevated temperature. A lab-scale uniaxial die compaction rig was designed and fabricated in order to shape powder mass at elevated temperature. Iron powder ASC 100.29 (92 wt%) was blended mechanically together with other elemental powders, i.e., copper (7.5 wt%), and aluminum (0.5 wt%) at a rotation of 30 rpm for 30 min. The prepared feedstock was shaped at 200°C through simultaneous upward and downward axial loadings of 325 MPa and the product generated through this process is known as green compacts. The defect-free green compacts were subsequently sintered in argon gas fired furnace at constant temperature, i.e., 800°C at three different sintering rates, i.e., 5, 10 and 15°C/min for three different holding times, i.e., 30, 60 and 90 min, respectively. The final products were then characterized for their physical, electrical, and mechanical properties and their microstructures were evaluated. The results revealed that the sample sintered for a shorter period of time, i.e., 30 min at a moderate heating/cooling rate, i.e., 10°C/min obtained the better final characteristics, i.e., higher relative density, lower volumetric expansion, lower electrical resistivity, higher strength and more uniform microstructure.

Characteristics of FeCuAl Powder Compacts Formed through Uniaxial Die Compaction Route

This paper presents the development of FeCuAl powder compacts through uniaxial die compaction process. Iron powder ASC 100.29 was mechanically mixed with other elemental powders, i.e., copper (Cu), and aluminum (Al) for 30 minutes at a rotation of 30 rpm. The feedstock was subsequently shaped at three different temperatures, i.e., 30°C, 150°C, and 200°C through simultaneous upward and downward axial loading of 325 MPa. The as-pressed samples termed as green compacts were then sintered in argon gas fired furnace at 800°C for three different holding times, i.e., 30, 60, and 90 min at a rate of 10°C/min. The sintered samples were characterized for their relative density, electrical resistivity, and bending strength. The microstructure of the sintered samples was also evaluated through scanning electron microscopy (SEM). The results revealed that the sample formed at 150°C and sintered for 30 min obtained the best final characteristics, i.e., higher relative density, lower volumetric expansion and electrical resistivity, and higher bending strength. Microstructure evaluation also revealed that the sample formed at 150°C and sintered for 30 min obtained more homogeneous distribution of grains and less interconnected pores compared to the other samples.

Spark plasma sintering and complex shapes: The deformed interfaces approach

Over the last few decades, the SPS technique has proven its benefits in terms of microstructure control, reduction of cycling time and a general stability of the results. However, to overcome the so-called “valley of death” between fundamental research and successful industrialization, the next step is to prove the ability of this technology to perform the total densification of highly complex shape samples. The elaboration of complex shapes with die compaction processes often present densification inhomogeneity because of the thickness differences of the sample. In this paper, we present a method to solve this problem with an approach we called the “deformed interfaces method” that uses sacrificial materials. This method can be generalized to all the pressure assisted sintering techniques and allow a complete densification whatever the shape complexity of the part. This method is tested with different materials (Al, CoNiCrAlY, PMMA, Al2O3, 4Y-ZrO2) and shapes. To prove the effectiveness of this method on very high complex shapes, a 98% dense turbine blade shape has been made.

A sacrificial material approach for spark plasma sintering of complex shapes

An optimized process for the densification of a complex shape part is studied. Production of samples with a complex shape is very difficult in uniaxial die compaction processes because of the thickness differences responsible for densification inhomogeneities. To solve this problem in the case of a particular shape, we propose a solution consisting of homogenization of the shrinkage distances by means of the use of a sacrificial material. This solution was first studied by a finite element approach and then tested experimentally. We obtained a part of complex shape with an overall relative density of 99% and a homogeneous microstructure.

Modelling the mechanical behaviour of metal powder during Die compaction process

In this work, powder compaction process was investigated by using a numerical material model, which involves Mohr-Coulomb theory and an elliptical surface plasticity model. An effective algorithm was developed and implemented in the ANSYS finite element (FEM) code by using the subroutine USERMAT. Some simulations were performed to validate the proposed metal powder material model. The interaction between metal powder and die walls was considered by means of contact elements. In addition to the analysis of metal powder behaviour during compaction, the actions transmitted to die were also investigated, by considering different friction coefficients. This information is particularly useful for a correct die design.

Effect of roll compactor sealing system designs: A finite element analysis

In the pharmaceutical industry, the roll compaction is part of the dry granulation process, densifying fine powders into ribbons that will be later milled to produce granules with good flowability for subsequent die compaction process. Roll compactors are constructed with a sealing system, limiting the loss of powder from the sides. However, the sealing system may result in unwanted non-uniformity of the ribbon's properties. In this work, a 3D Finite Elements Method (FEM) modeling is used to analyze the roll compaction process and the effect of sealing system designs on the compacted ribbon's density distribution. A density dependent Drucker–Prager Cap (DPC) constitutive model for microcrystalline cellulose (Avicel PH-101) was calibrated and implemented in Abaqus/Explicit. Two different FEM models were investigated, one with a fixed side sealing called cheek plates and another where the side sealing is integrated with the bottom roll called rimmed-roll. Both numerical and experimental results clearly show the non-uniform roll pressure and density distribution for the cheek plates assembly, whereas the rimmed-roll shows an overall more uniformly distributed resultant pressure and density distribution. These results demonstrate the capability of FEM modeling to provide insight and help achieving a better understanding of the roll compaction process.