Punch Shape Research Articles

Prediction of effects of punch shapes on tableting failure by using a multi-functional single-punch tablet press

We previously determined “Tableting properties” by using a multi-functional single-punch tablet press (GTP-1). We proposed plotting “Compactability” on the x-axis against “Manufacturability” on the y-axis to allow visual evaluation of “Tableting properties”. Various types of tableting failure occur in commercial drug production and are influenced by the amount of lubricant used and the shape of the punch. We used the GTP-1 to measure “Tableting properties” with different amounts of lubricant and compared the results with those of tableting on a commercial rotary tableting machine. Tablets compressed with a small amount of lubricant showed bad “Manufacturability”, leading to sticking of powder on punches. We also tested various punch shapes. The GTP-1 correctly predicted the actual tableting results for all punch shapes. With punches that were more likely to cause tableting failure, our system predicted the effects of lubricant quantity in the tablet formulation and the occurrence of sticking in the rotary tableting machine.

2D CFD description of the kinematic effects of movable inlet and outlet die wall transport motion and punch shape geometry on the dynamics of viscous flow during ECAE through Segal 2θ-dies for a range of channel angles

Minimization of the dead zone (DZA) in the process of material forming is a materials science problem. Geometric and kinematic approaches to the minimization of the DZA during Equal Channel Angular Extrusion (ECAE) have been proposed, developed, analyzed, and documented. The present article is focused on a 2D Computational Fluid Dynamics (CFD) description of the kinematic effects of punch shape geometry and inlet (IDW) and outlet (ODW) die wall motion on the DZA during ECAE of Viscous Incompressible Continuum (VIC) through a Segal 2θ-die for a range of channel angles 60° ≤ 2θ ≤ 135°. Due attention has been given to the independent alternating transport motions of the IDW and ODW. Punch shape geometry and the kinematic modes of IDW and ODW motions for DZA minimization have been determined with a numerical solution of the boundary value problem for the Navier-Stokes equations in curl transfer form for VIC. Experimental verification was accomplished with an introduction of initial circular gridlines-based physical simulation techniques. For the first time, experimental verification of CFD-derived results was made through an additional superposition of empirically-derived digital photos with deformed elliptical gridlines in the channel intersection deformation zones and correspondent 2D numerical plots with CFD-derived flow lines and full flow velocities. An empirical DZA localization was experimentally determined as the location of minimally-deformed near circular markers. The computational DZA localization was numerically determined as a flow-lines-free zone (the first hypothesis) or as a zone with near-zero values of full flow velocities (the second hypothesis). The relative DZA was estimated as a ratio of the measured DZA with respect to the area of the deformation zone in the channel intersection region. A good agreement was obtained between DZA values obtained with the first hypothesis and experimental results.

THE JKR-ADHESIVE NORMAL CONTACT PROBLEM OF AXISYMMETRIC RIGID PUNCHES WITH A FLAT ANNULAR SHAPE OR CONCAVE PROFILES

The JKR-adhesive frictionless normal contact problem is solved for the flat annular and the conical or spherical concave rigid punch indenting an elastic half space. The adhesive solution can be derived analytically from the non-adhesive one, the latter one being calculated by the boundary element method. It is found that the annular flat punch will always start to detach at the outer boundary. The pull-off forces for both concave punch shapes almost do not depend on the pull-off boundary regime and can be significantly larger than the pull-off force for the cylindrical flat punch.

The Influence of the Punch Shape and the Cutting Method on the Limit Strain in the Hole Expansion Test

The article presents a comparison of the hole-flange factors for four steel sheets which have different strength parameters. Three types of punches were applied in the research: cylindrical, spherical and conical. The holes in the samples were made with the use of the following cutting technologies: laser cutting, electrodischarge method using wire and punching. The coefficient of the hole expansion shows that the shape of the used tools has a great impact on the final diameter of the hole. The greatest enlargement of the diameter was obtained for the conical punch, a smaller enlargement for the spherical one and the smallest enlargement for the cylindrical punch. The results of the hole expansion tests using the conical punch diverge from the general rule saying that the greater the plastic deformation of the sheet metal during tensile tests, the more you can enlarge the hole before cracking appears.

Wpływ kształtu stempla na siłę nacisku przy wyciskaniu na zimno wyprasek w kształcie naczyń cylindrycznych z miedzi

Wpływ kształtu stempla na siłę nacisku przy wyciskaniu na zimno wyprasek w kształcie naczyń cylindrycznych z miedzi

Finite element analysis of thermomechanical behaviour of powders during tabletting

In the current paper, a systematic finite element (FE) analysis of the thermo-mechanical behaviour of pharmaceutical powders during die compaction is performed using the FE solver ABAQUS. The transformation of irreversible compression work to heat during compaction is considered, so is the energy dissipated by the particle–particle friction, and die-wall friction. Die compaction with various shaped punches to produce flat-face (FF), shallow convex (SC) and standard convex (STC) tablets at different compression speeds are then analysed. Evolutions of density and temperature distributions during compaction are examined. The effect of die wall friction on thermo-mechanical behaviours is also explored. It is shown that the punch shape, the compression speed and die-wall friction significantly affect the thermo-mechanical behaviour. The maximum temperature and temperature distribution of the compressed powder changes dramatically when different shaped punches are used. The maximum temperature of the tablet upon ejection can be reduced by decreasing the die-wall friction or the compression speed.

Indentation of Metal Foam Core Sandwich Beams: Experimental and Theoretical Investigations

Indentation behavior of metal foam core sandwich beams is investigated experimentally and theoretically. The deformation mechanisms of indentation are explored. The interaction of plastic bending and stretching in the local deformation regions of the top face sheet is considered. An analytical model is developed to predict large deflections of indentation of the sandwich beams transversely loaded at any location of the span. The analytical predictions are in good agreement with experiment results. Effects of the punch shape, the face sheet thickness and loading location on the indentation are discussed. It is shown that the loading location drives various deformation mechanisms of indentation for a given sandwich beam. The membrane force plays an important role in the large deflection of indentation of sandwich beams when the loading point exceeds the face sheet thickness.

Influence of punch shape on geometrical profile and quality of hole piercing-flanging under high pressure

Hole hydro-piercing-flanging is a new hybrid technology by using high internal pressure as the support medium instead of rigid die. By this process, holes can be punched and flanged successively on hydroformed tubular parts without secondary positioning and fabrication. However, punch shape as an important factor has not been concerned enough so far. In this study, the influence of punch shape on geometrical profile and quality of holes was investigated both by experiments and simulations with three different shapes of transition zone between the piercing punch and the flanging punch. Results show that the geometrical size of roll-over depth, straight-wall height, and thickness varied with punch shapes. Considering the quality of the hole’s edge, ellipsoidal punch is the best one with the largest smooth zone and the least damage, but the conical punch gives the worst results. Finally, the mechanism of hydro-piercing-flanging process affected by the punch shape was clarified by the stress and strain distribution during plastic deformation by finite element analysis.

Contact problems of the sliding of a punch with a periodic relief on a viscoelastic half-plane

A method is proposed for the analytical solution of problems of the sliding of a punch with a periodic relief on a viscoelastic half-plane under conditions when they are in complete contact as well as problems on the loading of a viscoelastic half-plane with a piecewise-constant pressure that moves at a constant velocity on its surface. The problems are considered in a quasistatic formulation. The method is based on the expansion of the sought functions in trigonometric Fourier series and finding the relation between the displacements of the boundary and the contact pressures. Examples of different shapes of punches are considered and the dependencies of the contact characteristics and the mechaical component of the friction force on the sliding velocity, the viscosity parameters of the base and the geometric characteristics of the surface are studied.

高強度熱延鋼板の円錐穴広げ性に及ぼすパンチ形状および板厚の影響

高強度熱延鋼板の円錐穴広げ性に及ぼすパンチ形状および板厚の影響

가변 단면을 가지는 비대칭 얇은 관 부품의 액압성형 연구

Abstract Hydroforming of a non-axisymmetric thin-walled tubular component with variable cross sections was analyzed. In order to solve the sealing problem which occurred due to the thin and non-axisymmetric shape, the use of a lead patch on the punch, which had been successful in hydroforming of thin tubes, was evaluated. A lead patch was attached to the punch to solve the sealing problem, which was caused by the stress gradient in the non-axisymmetric shape. FEM and experiments were also performed to analyze these sealing problems associated with the punch shape and non-axisymmetric shape. Finally, the lead patch was attached at tube surface where intensive local strain concentration would occur to enhance the hydroformability. These methods were successfully used to fabricate non-axisymmetric thin-walled tubular component with variable cross sections that had previously failed during traditional hydroforming. Key Words : Hydroforming, Thin-wall Tube, Non-axisymmetric Shape, Variable Cross Sections, Sealing Problem, Lead Patch

Investigating the effect of tablet thickness and punch curvature on density distribution using finite elements method

Finite elements method was used to study the influence of tablet thickness and punch curvature on the density distribution inside convex faced (CF) tablets. The modeling of the process was conducted on 2 pharmaceutical excipients (anhydrous calcium phosphate and microcrystalline cellulose) by using Drucker–Prager Cap model in Abaqus® software. The parameters of the model were obtained from experimental tests.Several punch shapes based on industrial standards were used. A flat-faced (FF) punch and 3 convex faced (CF) punches (8R11, 8R8 and 8R6) with a diameter of 8mm were chosen. Different tablet thicknesses were studied at a constant compression force.The simulation of the compaction of CF tablets with increasing thicknesses showed an important change on the density distribution inside the tablet. For smaller thicknesses, low density zones are located toward the center. The density is not uniform inside CF tablets and the center of the 2 faces appears with low density whereas the distribution inside FF tablets is almost independent of the tablet thickness.These results showed that FF and CF tablets, even obtained at the same compression force, do not have the same density at the center of the compact. As a consequence differences in tensile strength, as measured by diametral compression, are expected. This was confirmed by experimental tests.

Numerical evaluation of the capping tendency of microcrystalline cellulose tablets during a diametrical compression test

Capping is one of the major problems that occur during the tabletting process in the pharmaceutical industry. This study provided an effective method for evaluating the capping tendency during diametrical compression test using the finite element method (FEM). In experiments, tablets of microcrystalline cellulose (MCC) were compacted with a single tabletting machine, and the capping tendency was determined by visual inspection of the tablet after a diametrical compression test. By comparing the effects of double-radius and single-radius concave punch shapes on the capping tendency, it was observed that the capping tendency of double-radius tablets occurred at a lower compaction force compared with single-radius tablets.Using FEM, we investigated the variation in plastic strain within tablets during the diametrical compression test and visualised it using the output variable actively yielding (AC YIELD) of ABAQUS. For both single-radius and double-radius tablets, a capping tendency is indicated if the variation in plastic strain was initiated from the centre of tablets, while capping does not occur if the variation began from the periphery of tablets. The compaction force estimated by the FEM analysis at which the capping tendency was observed was in reasonable agreement with the experimental results.

ECAP process improvement based on the design of rational inclined punch shapes for the acute-angled Segal 2θ-dies: CFD 2-D description of dead zone reduction

Abstract. This article is focused on a 2-D fluid dynamics description of punch shape geometry improvement for Equal Channel Angular Extrusion (ECAE) or Equal Channel Angular Pressing (ECAP) of viscous incompressible continuum through acute-angled Segal 2θ-dies with 2θ < 90°. It has been shown both experimentally with physical simulation and theoretically with computational fluid dynamics that for the best efficiency under the stated conditions, the geometric condition required is for the taper angle 2θ0 of the inclined oblique punch to be equal to the 2θ angle between the inlet and outlet channels of the Segal 2θ-die. Experimentally and theoretically determined rational geometric condition for the ECAP punch shape is especially prominent and significant for ECAP through the acute angled Segal 2θ-dies. With the application of Navier-Stokes equations in curl transfer form it has been shown that for the stated conditions, the introduction of an oblique inclined 2θ0-punch results in dead zone area downsizing and macroscopic rotation reduction during ECAP of a viscous incompressible continuum. The derived results can be significant when applied to the improvement of ECAP processing of both metal and polymer materials through Segal 2θ-dies.

트리밍펀치 형상과 전단 각에 따른 전단하중 특성에 관한 연구

By investigating the practical use of trim punch configurations for shearing of vehicle panels, the current study first reviews the shearing angle as part of the shearing die design. Based on this review, four different types of trim punch shapes (i.e., horizontal, slope, convex, and concave type) and shearing angles(i.e., 0.76°, 1.53°, 2.29°, 3.05°, 3.81°) were investigated. In order to conduct shearing experiments, four types of trim punch dies were made. The four trim punch dies were tested under various conditions. The experiments used the four trim punch shapes and the five shearing angles. The shearing force varied by shape and decreased from horizontal, slope, convex, to concave for the same shearing angle. The magnitude of shearing force showed differences between the convex and the concave shapes due to the influence of constrained shearing versus free shearing. The test results showed that compared to the horizontal trim punch shearing force, the decrease of the slope, convex, and concave shearing forces were 22.6% to 60.4%. Based on the results, a pad pressure of over 30% is suggested when designing a shearing die.

Frictionless elastic contact of crowned roller: Approximate analytical calculation of compliance and contact area

Formulas for Hertzian frictionless elastic contact are well-known and have been used for a long time. However, they are not directly applicable for a crowned roller, a cylindrical roller with symmetrically rounded corners, deflecting a half-space. For this punch shape, the approximate analytical method of Barber and Billings ( Int J Mech Sci 1990; 32(12): 991–997) was adapted to compute the load–deflection curve and the contact boundary avoiding calculation of pressure distribution. Comparisons were performed with finite element method (FEM) simulations, an adaptive Hertzian quadratic punch surface approximation (AHA) and other published results. Good agreement of analytical load–deflection curves with FEM results was noted but the AHA results deviated significantly from the former two. The FEM contact area resembled a dog-bone shape, the analytical a bow-tie shape and the AHA, by design, an ellipse. Though the AHA contact area was closer to the FEM result numerically, the contact boundary aspect ratio of the analytical model was closer to the FEM. The analytical results simulating conditions from other publications agreed quantitatively for the load–deflection curves and qualitatively for the contact boundary. The non-linear spring characteristic of the crowned roller was quantitatively evaluated for a diverse range of geometry.

410 部分横据込みにおけるパンチ形状による変形挙動への影響

410 部分横据込みにおけるパンチ形状による変形挙動への影響

The Influence of the Punch Shape on the Socket Spanner Extrusion Process

Punch is a key component in Socket-Spanner extrusion and its shape influence the extrusion molding heavily. Using the FEA software DEFORM, the paper simulated the extrusion process of three kinds of upper and lower extrusion punch combinations which have different shape and studied the influences of the punch shape on metal flowing, Z direction punch load and equivalent stress. By contrasting the simulation data, the best punch shape was chosen. Our results could provide theory evidence for optimization design of Socket-Spanner extrusion punch. It was shown that the tapered bottom punch is the most suitable shape for the socket-spanner extrusion than the flat tapered and the flat one.

Effect of Punch Shapes on Micro Backward Extrusion of Brass

This study considered four types of punch, which were flat, conical, spherical and standardized punched, to investigate the effect of the punch shapes on the micro backward extrusion of brass. Brass (JIS C2600) materials were annealed at 500 °C, 600 °C, and 700 °C and resulted in different microstructures with grain sizes of 50 μm, 70 μm and 111 μm, respectively. The annealed brass materials were carefully machined as cylindrical billets with the same dimension of 1.1 mm in diameter and length. The billets were later used in the experiments of the micro backward extrusion to form cups with 1.1 mm diameter and 0.2 mm thickness. The experimental results show that the type of punch affecting load in an increasing order are spherical, standardized, conical and flat punches. The results also show that load increases with the punch speed, and reduces as grain size increases.

Strain gradient effects in periodic flat punch indenting at small scales

Experiments on soft polycrystalline aluminum have yielded evidence that, besides the required punch load, both the size and shape of imprinted features are affected by the scale of the set-up, e.g. substantial details are lost when the characteristic length is on the order of 10μm. The objective of this work is to clarify the role played by strain gradients on this issue, and to shed light on the underlying mechanisms. For this, indentation by a periodic array of flat punch indenters is considered, and a gradient enhanced material model that allows for a numerical investigation of the fundamentals are employed. During a largely non-homogeneous deformation, the material is forced up in between the indenters so that an array of identical imprinted features is formed once the tool is retreated. It is confirmed that the additional hardening owing to plastic strain gradients severely affects both the size and shape of these imprinted features. In particular, this is tied to a large increase in the mean contact pressure underneath the punch, which gives rise to significant elastic spring-back effects during unloading.