Die Land Length Research Articles

Influence of Die Land Length on the Maximum Extrusion Force and Dry Ice Pellets Density in Ram Extrusion Process.

The management of waste materials, particularly non-biodegradable substances such as plastics and composites, is an increasingly pressing issue. Energy efficiency in industrial processes is crucial throughout their life cycle, including the handling of materials such as carbon dioxide (CO2), which has a significant environmental impact. This study focuses on the conversion of solid CO2 into pellets using ram extrusion, a widely used technique. The length of the die land (DL) in this process plays a critical role in determining the maximum extrusion force and the density of dry ice pellets. However, the influence of DL length on the characteristics of dry ice snow, known as compressed carbon dioxide (CCD), remains understudied. To address this research gap, the authors conducted experimental trials using a customized ram extrusion setup, varying the DL length while keeping the other parameters constant. The results demonstrate a substantial correlation between DL length and both the maximum extrusion force and dry ice pellets density. Increasing the DL length leads to a decreased extrusion force and optimized pellet density. These findings provide valuable insights for optimizing the ram extrusion process of dry ice pellets and improving waste management, energy efficiency, and product quality in industries utilizing this technique.

Effects of die land length and geometry on curvature and effective strain of profiles produced by a novel sideways extrusion process

Abstract In the present investigation, effects of length and geometry of die land/bearing on curved profiles/sections produced by a novel process, differential velocity sideways extrusion (DVSE), were studied through physical experiments using plasticine as a model material and finite element modelling. Profile curvature decreases as die land length increases due to its negative influence on exit velocity gradient, and a straight profile is extruded when the ratio of die land length to die orifice diameter exceeds a critical value l 0 which increases as extrusion ratio λ increases and extrusion velocity ratio v 2 / v 1 decreases. Generally, effective strain level of the extrudate slightly increases as the die land length increases. Larger die land length increases the frictional areas between extrudate surface layers and die land (and mandrel for tube extrusion), generating zone of shear along the profile edge and thus increases surface layer effective strain. As a result, the strain homogeneity over the cross-section or wall thickness (for tube extrusion) is decreased. Compared with a sharp die land/container transition corner, a chamfered or radiused die land transition corner leads to an increased curvature due to the decreased effective land length, while it decreases overall effective strain level in the cross-section and strain homogeneity as a result of lower effective strain rate across the deforming region. A sharp die land transition corner is recommended for achieving a relatively large and homogenous effective strain in the cross-section.

Effect of die pockets on the extruded products in Multi-hole Extrusion Process: A finite element simulation study.

Multi-hole extrusion process uses a die with more than one orifice through which the billet material is allowed to flow under compressive load. This process is suitable for obtaining many extruded parts of different shapes and sizes (automobile parts and components for medical devices) from a same billet material. The extrusion load, quality of the extruded parts depend on many process parameters like extrusion ratio, billet length, location of orifices or holes on the die, die land length, die design, lubrication and extrusion speed. During design of a multi-hole die, each hole shape and the profile of the hole are mainly considered. In that context, the die pockets play a major role in the extrusion process. The pockets of different geometry and shape are provided at the entry side of the die, through which the work material flows and subsequently pass through the die land region. The properly designed die pockets help in reducing extrusion load and produces parts with less variation in length. In the present finite element study, 2-hole, 3-hole and 4-hole dies have been used to extrude a billet material of 20 mm length and 20 mm diameter at a extrusion speed of 1 mm/min. This low extrusion speed does not put any strain rate effect in the extrusion process. The FE package DEFORM 3D has been used for this study. The diameter of each hole is 3 mm and the pockets of diameter 6 mm and depths of 3, 4, 5, 6, 7 and 8 mm are used. The billet material of lead alloy is used for understanding the process in both simulation and experiments. The detailed study on the extruded product lengths, mean stress on the product and the effective strain are studied. From the study it is observed that optimum pocket geometry for a particular die provides least variation in the product length, mean stress (compressive) and an in-depth focus on the deformation behavior (effective strain study). The study will help in selecting an optimum die design for obtaining high productivity with better quality products.

Finite Element Analysis and Experimental Study on Forward, Backward and Forward-backward Multi-hole Extrusion Process

The present work investigates the multi-hole extrusion process. Forward, backward and forward-backward multi-hole extrusions have been carried out to determine the extrusion load and variation of extruded product lengths. The process parameters like extrusion speed and die land lengths are considered. The extrusion load depends on the extrusion speed. The friction conditions and the ironing effect also affect the extrusion load. The variations of extruded product lengths depend on the die land length. The 5-hole die and 9-hole dies exhibits different material flow behavior and due to which the load and product lengths vary. The finite element analysis also shows a good agreement in results of experiments.

Design, optimization, and manufacturing of a multiple‐thickness profile extrusion die with a cross flow

AbstractThis article presents a procedure to achieve a uniform outlet flow of molten polymer for a complex die profile with various thicknesses in die outlet cross section. According to a specific optimization methodology, the die was optimized based on varying die land length. The scope of this article includes: 3D flow simulation, optimization of the die velocity outputs based on the results of simulation process, and comparison of numerical predictions with the experimental data. Finally a significant result obtained by this work indicates higher ratio of the land length to the height of the zone with cross flow rather than the zones that are directly fed by the extruder. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers.

Pressure and Microstructural Change with Web to Flange Ratio and Die Land Length in Cold Extrusion of I-Shaped Lead Alloy

Plastic deformation process resulting in ultra fine grained materials which are rapidly grasping applications due to their superior mechanical properties remain an area of continued research interest. Generally, the influence of die land length and web to flange ratio in grain refinement subsequent to plastic deformation process have not being adequately exploited especially in complex die opening geometries. In the present study, the effect of these parameters on extrusion pressure and morphological change in I-shaped die opening geometry is investigated and reported. A forward extrusion rig is designed and manufactured for the purpose of experimental investigation. The upper bound analysis shows that increasing die land length leads to increasing relative extrusion pressure. Optimum web to flange ratio of 0.45 is numerically simulated and recommended to extrude I-shaped lead alloy with minimum load requirement. The experimental results reveal that increasing area ratio leads to quasi-sinusoidal pattern in surface hardness of I-shaped section irrespective of strain rate value. Increasing web to flange ratio, therefore, leads to increasing anisotropy of the I-shaped lead alloy. The extruded sections were examined with optical metallurgical microscope, and it is observed that increasing strain rate results in profound refinement of grain and inclusions in lead alloy even at room temperature.

Upper bound analysis of extrusion from square billets through circular and square/rectangular dies

Upper bound elemental technique (UBET) for prediction of extrusion pressure in three-dimensional forward extrusion process is presented. Using square/rectangular billets, the study of the effect of die land length has been extended for the evaluations of extrusion pressures to extrude sections such as circular, square and rectangular shaped sections with power of deformation due to ironing effect at the die land taken into account. The extrusion pressure contributions due to the die land evaluated theoretically for these shaped sections considered are found to increase with die land lengths for any given percentage reduction and also increase with increasing percentage die reductions at any given die land length. The effect of die land lengths on the extrusion pressures increases with increasing complexity of die openings geometry with rectangular section giving the highest extrusion pressure followed by circular with square section die opening, giving the least extrusion pressure for any given die reduction at any given die land lengths. The proper choice of die land length is imperative if excessive pressure buildup at the emergent section is to be avoided so as to maintain good quality and metallurgical structure of the extrudates.

Effects of extrusion variables on temperature distribution in axisymmetric extrusion process

A numerical method was developed to simulate the non-steady-state temperature distributions during forward extrusion process. The velocity, strain rates, and strain fields within the deformation zones during extrusion were obtained, using upper bound method of analysis to obtain internal heat generations coupled to the necessary heat transfer conduction equations. The computer program written in C++ language essentially simulates the extrusion process and takes into account extrusion variables such as material properties, friction conditions, extrusion velocity, extrusion ratio, die preheat temperature, billet height, percentage reduction in area, and die land length. The effects of billet height and percentage reduction in area on the temperature distributions within the dead metal zone give good agreements with experimental results. It is found that the higher the billet's heights and higher the percentages reduction in areas, the higher the temperature rises during the extrusion process. The die land zone shows increasing temperature rise with increasing friction coefficient, while increasing friction coefficient has no effect on the dead zone temperature. Also, increasing speed of deformation shows an increasing dead zone temperature rise than a more gradual die land temperature rise. It can be stated that the extrusion temperature increases proportionally to the increase of the container temperature.

Upper bound analysis for extrusion at various die land lengths and shaped profiles

The effects of die land lengths, a rarely investigated die extrusion parameter on the die-shaped profiles, on the extrusion pressures are investigated and presented. The analyses of the extrusion pressures by the upper bound method have been extended for the evaluations of the extrusion pressures to complex extruded sections such as square, rectangular, I,- and T-shaped sections with power of deformation due to ironing effect at the die land taken into account. The extrusion pressure contributions due to the die land evaluated theoretically for shaped sections considered are found to increase with die land lengths for any given percentage reduction and also increase with increasing percentage die reductions at any given die land length. The effect of die land lengths on the extrusion pressure increases with increasing complexity of die openings geometry with I-shaped section giving the highest extrusion pressure followed by T-shaped section, rectangular, circular-shaped die openings with square section die opening, giving the least extrusion pressure for any given die reduction at any given die land lengths.

Upper bound analysis of die land length in cold extrusion

Upper bound analysis of the effect of die land length on the cold extrusion of selected geometries is reported. The upper bound determination of extrusion pressure was extended to include the power due to ironing effect for shaped sections (rectangular, square and circular) resulting from boundary friction forces on the surface of the die land. The present investigation reveals that the contribution of die land length to the extrusion pressure increases with increasing complexity of die opening geometry with the rectangular section giving the highest extrusion pressure and the square section giving the least, for certain die reduction in area at a particular die land length. For a percentage reduction in area, the normalized extrusion pressure contribution, ΔPo/Y, increases with increasing die land length. Also, for a particular die land length, the normalized extrusion pressure increases with increasing percentage reduction in area.

Effects of die land on the cold extrusion of lead alloy

In the present investigation, the effects of die land, an uncommonly investigated die extrusion parameter, on the extrusion pressures are experimentally and theoretically evaluated. The analyses of the extrusion pressure determination by the upper bound method have been extended to include the power due to the ironing effect, resulting from frictional forces within the die land region. The extrusion pressure contributions due to the die land evaluated theoretically and practically are found to increase with die land length for any given percentage reduction and also increase with increasing percentage die reductions at any given die land length. There is a good agreement between theory and experiment on the extrusion pressures evaluated. For the purpose of designing for suitable extrusion die to extrude lead material, it is recommended that the die land length should be chosen equal to or greater than 0.6 of the billet diameter for small work pieces and with die exit clearance angle less than 10°, so as to extrude lead products with negligible bend or curvature.

Profile Die Design Based on Flow Balancing

Abstract This paper presents a methodology for the design of profile dies based on the Cross Flow Minimization Method. The flow balancing is described for cases where the flows are balanced by varying the die land length combined with the flow separation. Three different approaches were utilized in the die analysis. First, the flow in two proposed profile dies was calculated by substituting the flow domain by a set of simple geometries. The second approach applied the Cross-Sectional Calculation method, while the last method is a fully 3D FEM non-isothermal calculation. The results are verified by comparison with experimental data. It is shown that each of the calculation procedures may be the choice of preference depending on the geometrical complexity.

Die design and dough expansion in low moisture extrusion-cooking process

An experimental study was developed to investigate the role of die design (die diameter and die land length) on extrudate expansion, through the Sectional Expansion Index and Longitudinal Expansion Index. The extrusion-cooking experiments were made on a corotating twin-screw extruder, at constant specific mechanical energy and moisture content. Detailed consideration is given to die geometry and the driving force of expansion. A four-constant empirical model is proposed to describe the expansion indices. The anisotropy of the expansion phenomena is also discussed.

Analysis and Design of Industrial Hot Extrusion Process through Square Dies for Manufacturing Complicated Al Alloy Profiles

In the analysis and design of hot square die extrusion processes, non-steady state analysis together with temperature analysis is recommended. In the present work, non-steady state analysis are carried out for hot square die extrusion of some typical industrial profiles by using the rigid-viscoplastic arbitrary Lagrangian-Eulerian(ALE) finite element method. Since flow guide and die lands play important roles in controlling the metal flow in the industrial practice, the related analyses are carried out and the effects of die land and flow guide are discussed. In order to estimate the variation of die land length, a scheme has been developed. The scheme is applied to extrusion of L-section without any axis of symmetry. The calculated configuration of die land is compared with the industrial design. As an effective tool for prediction of die wear, a wear map in introduced and demonstrated through the examples.

Investigation of processing‐structure‐properties relationships in polyethylene blown films

AbstractMolecular orientation imparted during film fabrication is known to have a major effect on mechanical and thermal properties of both glassy and semicrystalline polymers. A three‐variable Box‐Behnken designed experiment was used to study the effects of die gap, die land length, and blowup ratio (BUR) on key linear low density polyethylene (LLDPE) blown film properties at constant final film thickness. In addition, differences in molecular orientation in the films were studied using optical birefringence and shrinkage methods. Measured key film properties were correlated to processing conditions and to measured molecular orientation. Die land length had no significant effect on film structure and properties. All LLDPE films exhibited about 70 to 80% shrinkage in the machine direction (MD) but expanded in the cross direction (CD). Most films exhibited negative in‐plane birefringence. MD Elmendorf tear was found to be inversely related to drawdown ratio and MD shrinkage, suggesting that MD tear is dependent primarily on amorphous chain extension and hence, amorphous segments orientation for LLDPE blown films. Dart impact strength of the films was shown to be related to MD shrinkage and to the induced surface roughness due to varying die gap. In a separate study, blown films of three high pressure LDPEs were fabricated under nearly identical conditions. No correlation was found between birefringence and shrinkage data on the LDPE blown films.

Die design for rigid PVC—the effect of die land length on extrudate swell

AbstractPVC profile extrusion compounds have a unique morphology. While other polymers gradually decrease in extrusion die swell with increasing length/thickness (L/D) ratio, PVC profile extrusion compounds have a low die swell, quite independent of the die's L/D ratio in the range of 5 to 20. The fact that the die land length can be changed without changing the extrudate swell is an important consideration, which makes die design and balancing dies simpler and easier for PVC profile extrusion compounds. While other polymers substantially increase extrudate swell with increased shear rate, the swell of the PVC profile compounds is not much affected by shear or extrusion rate. This unique behavior allows wider processing latitude in profile extrusion and faster extrusion rates than with other polymers. Another unique factor in the rheology of PVC profile extrusion compounds is that extrusion die swell increases with increasing melt temperature, while other polymers have decreasing die swell with increasing melt temperature. The unusual rheology of PVC profile extrusion compounds is attributed to its unique melt morphology, where the melt flow units are 1 um bundles and molecules that have low surface to surface interaction and entanglement at low processing temperatures but increased melting and increased entanglement at higher processing temperatures. Other polymers, unlike PVC, have melt flow at the molecular level.

Extrudate swell and drawdown effects on extruded profile dimensions and shape

AbstractPlastic profile die design is a complex task because of cross section area and shape changes occurring after die exit. Dimensions of the profile are increased by the extrudate swell phenomenon and decreased by drawdown and shrinkage. An experimental study on the effect of processing conditions on extrudate swell and on the shape of a rectangular profile was done for rigid poly(vinyl chloride), PVC, and high density polyethylene, HDPE, resins. Extrudate swell was found to be a strong decreasing function of residence time in the die and also, for short dies, of entrance geometry. For PVC, equilibrium swell increased with melt temperature. The differences in swelling for the two polymers are explained with the help of creep/recovery data obtained on a stress rheometer. Drawdown, die land length, and melt temperature were shown to have an important effect on the shape of a rectangular profile. Decreasing the die land and increasing the melt temperature had the effect of increasing preferably the thickness while drawdown, by inhibiting the swelling, decreased the thickness.

Formation of die lines during extrusion of AA6063

The die line phenomenon during extrusion of AA 6063 has been investigated and the effects of temperature and strain rate established. The influence of die land length on the surface generated features was also determined. The results indicate that the surface formation mechanism is one of generation and modification; the surface is generated on the leading edge of the die land in the absence of oxygen and interacts thereafter with the remainder of the die land, resulting in material transfer between extrudate and die land, thus increasing the surface roughness. Two mechanisms were identified, both of which involved extrudate die land interaction. The aluminium film on the forward portion of the die land was observed to be more stable and its morphology wasfound to relate directly to the die line features. From these trials, optimum process conditions together with a minimum die land length were identified. Processing at the optimum conditions continued to generate die lines, but these were observed to be finer and less deep, and were termed ‘microdie lines’. The origin of the micro die lines was observed to stem from the structure formed by deformation and the nature of the shear zone.MST/1108

Formation of die lines during extrusion of AA6063

AbstractThe die line phenomenon during extrusion of AA 6063 has been investigated and the effects of temperature and strain rate established. The influence of die land length on the surface generated features was also determined. The results indicate that the surface formation mechanism is one of generation and modification; the surface is generated on the leading edge of the die land in the absence of oxygen and interacts thereafter with the remainder of the die land, resulting in material transfer between extrudate and die land, thus increasing the surface roughness. Two mechanisms were identified, both of which involved extrudate die land interaction. The aluminium film on the forward portion of the die land was observed to be more stable and its morphology wasfound to relate directly to the die line features. From these trials, optimum process conditions together with a minimum die land length were identified. Processing at the optimum conditions continued to generate die lines, but these were observe...