Virtual Design And Fabrication Of A Continuous Extrusion Setup With Process Analysis

Virtual Design And Fabrication Of A Continuous Extrusion Setup With Process Analysis

aDepartment of Mechanical Engineering, Indian Institute of Technology, B.H.U. Varanasi (INDIA)

bDepartment of Mechanical Engineering, Indian Institute of Technology, B.H.U. Varanasi (INDIA)

cDepartment of Mechanical Engineering, Indian Institute of Technology, B.H.U. Varanasi (INDIA)

The production of complicated metallic profiles with high degree of dimensional accuracy and control with very thin walls has been the major problem encountered with conventional extrusion process. In this paper a design and fabrication of a continuous extrusion process for extruding complicated endless profiles has been presented virtually using computer aided design and manufacturing concepts. The iterative process of CAD has been used to arrive at the final design of various components and has been fabricated virtually by Auto CAD 2002. The setup has been evaluated using plastic deformation concept to calculate the total power and pressure required for aluminum coil of ¼ inch diameter. The analysis of the design therefore includes hot extrusion die design analysis and the continuous extrusion process analysis using Upper Bound Method and Finite Element Method.

Key words: Continuous Extrusion, FEM, Upper Bound Method

1. The basic principle of continuous extrusion process involves a wire/rod which is inserted in the groove of wheel is drawn by friction against the wheel and the groove closed by a close fitting shoe as shown in Fig.

   1.a and 1.b. The material is prevented to continue its

   passage around the wheel by means of an abutment. As a result, high temperatures and pressures are developed in the material, which becomes plastic and subsequently emerges from the machine through an extrusion die. The product can take a variety of forms including tubes, solids and complex profiles. A critical part of the process is the extrusion shoe, which houses the extrusion die, the separate tooling segments and the abutment. Since the material generates frictional heat and modification heat, temperatures up to 500 degree Celsius or more can be achieved, without using heater for the copper wire. The material is in the high plastic flow state due to the modification to the shear direction at the abutment and the high temperature

   .thus near net shapes of irregular sections become possible. in addition ,since the extruded material is completely recrystallized, it is in a tempered state, since the form of supplied material is a wire rod ,it possible to extrude continuously , without having to stop the machine in order to join pieces of material together . This is advantageous because large coils of products can be formed.

   The continuous extrusion forming process use frictional force between a circular driving wheel and material, as shown in Fig. 1, can produce significantly long continuous products of a variety of sectional shapes which are hard in the classical forming processes owing to their methodological limitation [1]. Because of its superiority and impact on the current forming technology are evident, demand from industry has been growing rapidly. Basic experimental and analytical studies have been underway continuously since the late 1980s. However, theoretical and numerical studies are still insufficient to analyze accurately the complicated process characteristics. Furthermore, study on the effects of major process parameters such as wheel velocity, relative die opening width, and flash gap size is essential for the optimal design of Continuous

   Figure.1a. Details of Continuous Extrusion process

   Figure.1.b. Metal flow from abutment passage to die entry

2. which it can be applied. Die strength, metal flow and internal defects of copper irregular sectional extrusion was examined. Manninen et al. (2006) [9] explain the mechanics of flash formation during steady state continuous extrusion. They developed an analytical model for estimating the flash shape and the amount of scrap produced. Katajarinne et al. (2006) [10] carried out realistic 3D finite element simulations to study the formation of flash in continuous extrusion of copper under different frictional condition. Kim et al. (1998)

   [11] investigated the effects of several significant process parameters on the process characteristics in the CONFORM process, such as material flow, defect occurrence, temperature and effective strain distributions using DEFORM commercial FEM Code.

   Khawaja et al. (2001) [12] investigated an active gap sensing and control system for improving conform extrusion product quality. The gap is measured using an air gauge system and controlled using a hydraulic actuation system. Khawaja et al. (2004) [13] investigated, and designed a high temperature capacitive gap sensing system and implemented on a copper extrusion machine in a production plant. It was shown that machine set-up time was reduced from 35- 40 minutes to 5 minutes with active gap sensing. It was also shown that there is a linear reduction of waste levels from 20% to 2% when gap size is reduced from 1mm to 0.15mm. Clode et al. (2005) [14] investigated and implemented high temperature capacitive gap sensing system on a copper conform extrusion machine in a production plant. They proved that the sensors can be used for on-line direct gap measurement and control and for the first time, provide a detailed view of extrusion zone gap behavior during a full production cycle. Form the experimental results, three different stages of a conform extrusion cycle, start, slugs feed, and steady state extrusion can be clearly identified. The gap sensor is used to evaluate the relationship between gap size, and waste levels. It is shown that there is a linear reduction of waste levels from 20% to 2% when the gap size is reduced from 1 to 0.15.mm.

   Cho et al. (2000) [1] address a parametric investigation on the occurrence of the surface defect in this process. Here, the wheel velocity, the extrusion ratio, the abutment height, the friction coefficient and the flash gap size are taken as parameters and numerous parametric numerical experiments are carried out in order to analyze their effects on the surface defect occurrence. They used DEFORM-3D for the simulation. Cho. et al .(2001)[15] addresses the three dimensional finite element analysis of the process aimed at the parametric investigation of the curling phenomenon and the understanding of the process characteristics closer to the real process .For this goal, they first made the flow dynamic analysis on

   the phenomenon as well as three dimensional finite element analysis of CONFORM process. Cho et al. (2003) [16] numerically examined the effects of wheel diameter on the surface separation and curling phenomenon as well as after significant process characteristics, through the two-dimensional finite element analysis of CONFORM process for solid section aluminum products.

   Peng- yue et al.(2007)[17] carried out study on CONFORM process for producing concave bus bar under different extrusion wheel angular velocities by three- dimensional finite element technology based on software DEFORM-3D .The distributions of velocity field, stress field, strain field, temperature field and damage field were investigated under different extrusion wheel angular velocities.

   Zhu et al. (2004) [18] investigated a new severe plastic deformation (SPD) technique which combines equal channel angular pressing (ECAP) with conform to process ultrafine grained (UFG) materials in a continuous extrusion manner. In this invention principle used to generate frictional force to push a work piece through an ECAP die is similar to the conform process, while a modified ECAP die design is used so that the work piece can be repetitively processed to produce UFG structures. Wei et al

   .(2009)[19] analyzed the deformation behavior of the pure copper rod in the continuous ECAP process using DEFORM-2D.The effect of die angle and the friction between the die channels and the specimen on the stress strain distributions, strain homogeneity, the feature of shear deformation and the torque was investigated. In the continuous ECAP, shear deformation exists in the die angle ranged from 900 to 1200; however the pattern and extent of shear deformation are different to that in Conform and ECAP.The effective strain is uniform in most parts of the work piece. As increases, the corner gap becomes smaller and the strain distributions are less homogeneous. The extent of shear deformation, homogeneity of stress strain can be improved by the friction on the interface of the die and work piece but the maximum torque value increases. The assumed shear deformation was further divided into three stages, which was well explained by torque-time curves and the effective stress fields. The results indicate that the continuous ECAP process is a promising approach for producing ultra-fine sheet, bar, rod and wire. Langdon et al. (2010) [20] made investigation to critically evaluate the ECAP-Conform process with a special emphasis on the two areas where no information is at present available. First, detailed hardness measurements were undertaken to evaluate the extent of homogeneity within the microstructure after processing by ECAP-Conform

   with separate measurements taken to determine both the homogeneity within the cross-sectional planes of processed rods and the variations in the micro structural homogeneity along the lengths of the processed rods. Secondly, mechanical testing was undertaken to determine the extent of any plastic anisotropy at may be present within the rods after processing by ECAP Conform. The experiments were conducted using a commercial Al-6061 alloy.

   Kumar et al.(1999) [21] developed a feature recognition methodology based on wire frame solid modeler to recognize hollow/solid extrudable components using single and multiple hole die for designing extrusion dies.

3. Figure.2. Set-up of Extrusion

4. To make the process continuous a continuous grooved section pressure container is required. And this is most simply provided by having a rotating grooved wheel. The stationary side shoe which fits around part of the wheel circumference and is of sufficient length for the process. The product may be extruded in either a radial or tangential direction, or indeed in both.

   Figure.3. Diagrammatic arrangement of continuous extruder

   It is possible to predict the grip lengths necessary to ensure that extrusion will occur from knowledge of the geometry, feedstock property, coefficient of friction and the extrusion ratio.

   l2=extrusion grip length l1=primary grip length

   effective, the other two sides canceling each other. Then

   Primary driving force =2 Yµxl1

   This must generate axial yield=YA

   Where, Y=compressive yield strength of feedstock

   X=contact width

   l1=primary grip length

   A=cross sectional area of feedstock =cross sectional area of groove

   Now if groove depth =groove width =w, then-

   A=w2

   And if, X=w/4 then,

   l1=2w/µ

   Extrusion grip length: – there is increase in contact stress between the feedstock and container wall from the point at which yielding occurs up the point at which shearing of the feedstock can occur. The contact stress for this discontinuity between skidding and shearing is given by:

   Pc=k/ µ

   Figurwe.5. variation of pressure along extrusion grip length

   l2=al+as

   Figure.4. detail showing grip length

   The coining of the feedstock into the groove compresses the material setting up yield stress in the outer fibers containing the sided of the container. The primary grip length friction force must set up axial yield in the metal, and only two sides of the groove are

   Then,

   PeA=2w [al /4+as]

   Where;

   al=length over which sliding can occur as=length over which shearing can occur w=depth and width of groove

   k=shear strength of feedstock

   µ=coefficient of friction Pe=extrusion pressure Pc=contact pressure

   A=cross sectional area of groove (w2)

   In the extrusion of metals with low shear strength,

   al << as Then, l2= as

   The extrusion grip, l2=[ Pew/2k]= [Pe/Y]

   Now the total power requirements for extrusion of feed rod have the following components

   2. Pc=2 µ (0/3) Lopt R0 V0 watts

      Where, Lopt=optimum die length R0=radius of feedstock V0=peripheral velocity of wheel

      0=yield shear stress of feedstock material

   3. PB= µ (/3) L1P1Vend2 watts L1=bearing length of feedstock P1=perimeter of product

      Vend2=velocity of product

      =flow stress of the feedstock material

   4. Pb=Y µxl1* V0 watts

   5. Shear power=shear force*deformation velocity

      =wl2K*(peripheral velocity of wheel)

   6. When the feed stock strikes the abutment, the feedstock finds only the way into the container surface after reflecting from the abutment .there are feedstock attains the plastic stage and turns into the grooved surface of container .so, the expression for consumed is

   Pturning= /3* µ* L1* P1* V0*Cos Where, =angle between horizontal container surface and feedstock while turning

   So, the total power required for extrusion of feedstock is given by

   Pe= (PD) + (Pc) + (PB) + (Pb) + (Pf) + Pturning

   Total average pressure required for extrusion of feed stock

   0

   = [(total power)/ R 2V (peripheral)]

   Also the total torque can be estimated in the fallowing way

   Total power (P)=[(2 N T)/60} Or, T= [(P*60)/2 N]

   Design of slot (Wheel groove) :- the trapezoidal groove is cut on the periphery of the wheel. Feedstock when passed through this groove very high frictional force is developed .this frictional force play vital in raising the temperature .so, the design of slot should be as such to attain the extrusion temperature .so; the design of slot should be as such to provide thigh friction to feedstock while making entry into the groove.

5. T= (Pf*tc)/ (Vs*Cp)

   Where,

   t c =constant time of feed stock with the

   groove

   = density of feed stock material Cp=specific heat of feedstock material Vs =volume of feedstock material

   Design of gearing system: – To rotate the wheel at optimum rpm the worm gearing arrangement is designed.

   Torque in shaft is given by T= Where T is Torque and N is rpm of the shaft

Vol. 1 Issue 8, October – 2012

1. Cho, J.R., Kim, Y.H., Kim, K.S., Jeong,

   H.S. and Yoon, S.S. (2000), A study of the application of upper bound method to the CONFORM process, Journal of Materials Processing Technology 97,153-157.

2. Tonogi, Tatsuya., Okazato,Kazuhiko and Tsukada,Saburou (2002), Precise Extrusion Technology by Conform Process for Irregular Sectional Copper, Hitachi Cable Review 21, 77-82.

3. Manninen, T., Katajarinne, T. and Ramsay,P. (2006), Analysis of Flash formation in continuous rotary extrusion of copper, Journal of Materials Processing Technology 177,600-603.

4. Manninen, T., Katajarinne, T. and Ramsay,P. (2006), Numerical simulation of Flash formation in continuous rotary extrusion of copper, Journal of Materials Processing Technology 177,604-607.

5. Kim,Y.H., Cho, J.R., Kim, K.S., Jeong,

   H.S. and Yoon, S.S. (1998), A study on optimal design for CONFORM process, Journal of Materials Processing Technology 80-81,671-675.

6. Lu,J., Saluja,N., Riviere,A.L. and Zhou,Y. (1998), Computer modeling of the continuous forming extrusion process of A6061 alloy, Journal of Materials Processing Technology 79,200-212.

7. Manninen, T., Ramsay,P. , and Korhonen,A.S.(2010), Three-Dimensional Numerical Modeling of Continuous Extrusion, Journal of Materials Processing Technology 177,600-603.

8. Khawaja,Kafeel.and Seneviratne, Lakmal. (2001),Sensing& Control of Conform Extrusion Gap Between Wheel and Tooling Plates, IEEE/ASME International Conference on Advanced Intelligent Mechatronics Proceedings,8-12 July 2001.

9. Khawaja,Kafeel. , Clode, M.P., Althoefer,K.and Seneviratne, Lakmal.

   (2004), Gap Sensing Benefits in Conform Extrusion Machinery, IEEEInternational Conference on Robotics and Automation Proceedings, April 2004.

10. Khawaja,Kafeel. , Clode, M.P. and Seneviratne, Lakmal. (2005), Benefits of Wheel-Tool Gap Sensing in Conform Extrusion Machinery, IEEE/ASME International Conference on Mechatronics V0l . 10 NO. 4, August 2005.

11. Cho,J.R. and Jeong,H.S. (2000),Parmetric investigation on the surface defect occurrence in CONFORM process by the finite element method,Journal of Materials Processing Technology 104,236-243.

12. Cho,J.R. and Jeong,H.S. (2001),Parmetric investigation on the curling phenomenon in CONFORM process by three-dimensional finite element analysis ,Journal of Materials Processing Technology 110,53-60.

13. Cho,J.R. and Jeong,H.S. (2003), CONFORM process :surface separation, curling and process characteristics to the wheel diameter, Journal of Materials Processing Technology 136,217-226.

14. Peng-yue,WU.,Shui-sheng,XIE.,Hua- qing,LI.,Ming,YAN.,Guo-jie,HUANG.and Lei,CHENG.(2007),Effect of extrusion wheel angular velocity on continuous extrusion forming process of copper concave bus bar, Transactions of Nonferrous Metals Society of China 17,280-286.

15. Zhu,T.Y.,Georgy,J.,Valiev,Z. and Lowe.C.(2004), Continuous processing of ultrafine grained Al by ECAP-Conform , Materials Science and Enginnering A 382, 30-34.

16. Wei,w., Zhang,W., Kun,w.,Zhong,Y., cheng,G., and Jing,Hu.(2009),Finite element analysis of deformation behavior in continuous ECAP process, Materials Science and Enginnering A 516, 111-118.

    Vol. 1 Issue 8, October – 2012

17. Langdon,G.T.,Cheng,Xu.,Schroeder,S. and Berbon,B.P.(2010), Principles of ECAP- Conform as a continuous process for achieving grain refinement: Application to an aluminum alloy, Acta MATERIALA 58, 1379-1386.

18. Agrawal, B.K., Conform Extrusion : A New Concept to Produce Endless Profiles, ISTE Summer School Report, IT-BHU, Varanasi, India, 2002, pp. 119-139.

19. Green, D., Conform : A new concept for continuous extrusion forming of metals, Journal of Engineering for Industry, Transaction ASME, Volume 96, 1974 pp. 893.

20. C. Etherington, CONFORMa new concept for the continuous extrusion forming of metals, ASME Trans. of 96B (3) (1974) J. Eng. Ind. 893900.