Finite Element Analysis of Reciprocating Screw for Injection Molding Machine

Transcription

1 Nagsen B. Nagrale et al. / International Journal of Engineering and Technology Vol.3 (3), 11, Finite Eleent Analysis of Reciprocating Screw for Injection Molding Machine #1, Nagsen B. Nagrale, Dr.R.N.Baxi #1, M-Tech IV Se,(CAD/CAM) G.H Raisoni College of Engg.Ngp. ru_nbn@rediffail.co, Associate Professor, Mech.Dept.G.H.Raisoni College of Engg. r_baxi@yahoo.co Abstract This paper deals with, the solution of proble occurred for reciprocating screw of Injection olding achine. It identifies and solves the proble by using the odeling and siulation techniques. The proble occurred in the reciprocating screw of achine which was wearing of threads due to affect of teperature of old aterials (flow aterials) i.e. Nylon, low density polypropylene, polystyrene, PVC etc., The ain work was to odel the coponents of achine with diensions, asseble those coponents and then siulate the whole assebly for rotation of the screw. The odeling software used is PRO-E wildfire 4. for odeling the achine coponents like body, ovable platen, fixed platen, barrel, screw, nozzle, etc. The analysis software ANSYS is used to analyze the reciprocating screws. The objectives involved are:- To odel all the coponents using odeling software Pro-E 4. To asseble all the coponents of the achine in the software. To ake the assebly run in Pro-E software. Analysis of screw of achine using Ansys 11. software. To identify the wearing of threads and to provide the possible solutions. This proble is ajor for all industrial injection olding achines which the industries are facing and they need the peranent solution, so if the better solution is achieved then the industries will think for ipleenting it. The industries are having teporary solution but it will affect the life of the screw, because the stresses will be ore in achined screw on lathe achine as copared to noral screw. Also if the screw will fail after soe years of operation, the new screw available in the arket will have the sae proble. Also the cost associated with new screw and its ounting is uch ore as it is the ain coponent of achine. Key Words - Reciprocating, Wearing, FEM Introduction Injection olding is the ost coonly used anufacturing process for the fabrication of plastic parts. A wide variety of products are anufactured using injection olding achine, such as plastics housings, consuer electronics, and edical devices Including valves & syringes which vary greatly in their size, coplexity and application. The injection olding process requires the use of an injection olding achine, raw plastic aterial, and a ould. The plastic is elted in the injection olding achine and then injected into the old, where it cools and solidifies into the final part. The barrel contains the echanis for heating and injecting the aterial into the ould. This echanis is usually a reciprocating screw. A reciprocating screw advance the aterial forward by either a hydraulic or electric otor. During this process the aterial is elted by heat & pressure. The aterial enters the grooves of the screw. The screw copletes the shot volue & returns to reverse position. The proble occurred in the reciprocating screw is of the wearing of threads due to affect of high elting teperature & pressure of old aterials. Industries are having teporary solution to ake repair of threads on Lathe achine. This reduces weight & strength of screw resulting isalignent in assebly. The screw is the ost crucial part of a achine. The aterial for the screw is EN-41B (SAE 51), other alternate aterials are EN9 (SAE155), EN8 (SAE 14), EN4 (SAE434). ISSN : June - July

2 Nagsen B. Nagrale et al. / International Journal of Engineering and Technology Vol.3 (3), 11, Wearing of screw threads Fig. 1.1 wearing of threads of reciprocating screw Objectives The proble occurred in the reciprocating screw of injection olding achine, was wearing of threads. The objective of the project was to find out the cause of wearing and provide the solution. The industries have teporary solution of aking threads on Lathe achine, but this will affect the strength of the screw. Other than this it will be difficult to align the screw with the otor. The objectives involved are:- a. To odel reciprocating screw using odeling Software Pro-E 4. b. Analysis of reciprocating screw using Ansys 11. software c. To identify the wearing of threads and provide the possible solution. Reason for selecting proble: a) Probles can arise using different aterials with sae screw without knowing its teperature affect on screw. When the deand is ore wrong aterial can affect the threads of screw and a ajor loss to the screw can occur. b) Melt teperature control is critical to control the elt due to low quality grains causes overheating of screw. c) The olding achine has specified for its working capacity, an excessive assigned work load causes high teperature & high pressure resulting wear and bending of screw. d) Faulty heater cause uneven teperature distribution of olding flow over the screw causing tiger arks on the surface. e) Materials left inside the achine gets stick to the surface of screw. The aterials if not reoved before starting of achine, which affect the life of screw. f) Soe grains contain lot of oisture in their cheical properties which stick to reciprocating screw causing corrosion to the screw. g) The aterial used for the injection olding process ust be clean and free fro ipurities such as etal, water and volatiles. Metal containation to the polyer, plastic gets chocked which causes blocking of barrel. h) The pressure flow control board has a transistor failure that causes over current flow. The teperature inside the barrel increases which affect daage of screw. Modeling of reciprocating screw using Pro-E Wildfire 4.: Pro-E Wildfire 4. has been developed by raetric Technology Corporation (PTC) of U.S.A. This is CAD/CAM/CAE software but we are using this for only 3-D part odeling (CAD). This CAD includes. 1. Sketcher. rt Modeling (part design) ISSN : June - July 11 19

3 Nagsen B. Nagrale et al. / International Journal of Engineering and Technology Vol.3 (3), 11, Advanced rt Design 4. Surface Design 5. Assebly Design Fig 1. Coplete Working Assebly using Pro-E Fig D odel of screw using Pro-E Need of Finite Eleent Method: There are nuber of needs of finite eleent ethod. But we are considering soe basic needs. i) To reduce the aount of prototype testing. ii) To siulate design that is not suitable for prototype Testing. iii) The botto line iv) Cost saving. v) Tie saving. Finite Eleent Analysis of screw using ANSYS 11. (workbench): Reciprocating screw. Model Analysis of Screw is done using following steps:- a. Click on new siulation file. b. Give nae as EN41B (Flex. PVC). c. Iport geoetry (screw. part) fro folder of Pro-E files. d. Meshing the odel using the option generate esh. e. Select new analysis, Select static structural. f. Apply boundary conditions. g. Select the area for fixed support. ISSN : June - July

4 Nagsen B. Nagrale et al. / International Journal of Engineering and Technology Vol.3 (3), 11, h. Find the total deforation for each ode by selecting solve option. i. Find von- ises stress selecting von-ises option. j. Find directional heat flux by selecting the option. k. Find total heat flux by selecting the option. l. Generate report preview.. Save the file. n. In discretization the no. of nodes fored are 199 and no of eleents are 599 Fig 1.4 Meshed odel of screw Fig 1.5 Modal Analysis of screw Fig 1.6 Structural Analysis of screw Fig 1.7 Structural Analysis of screw (Teperatures) Fig 1.8 Structural Analysis of screw (Total heat flux) Fig 1.9 Alternating stress paraeters of screw ISSN : June - July

5 Nagsen B. Nagrale et al. / International Journal of Engineering and Technology Vol.3 (3), 11, Screw aterial EN41B (SAE 51) Property Nylon Low density polyethylene Polypropylene Flexible PVC Polystyrene Tep. C Thera flux e Directional Heat Flux 9145 :1.353e Von-ises stress 6.794e e e e e+6 :1.7433e e e e e+9 Total deforation e e e e e-4 Table 1.1 Results of screw aterial EN41B ISSN : June - July

6 Nagsen B. Nagrale et al. / International Journal of Engineering and Technology Vol.3 (3), 11, Screw aterial EN9 (SAE 155) Property Nylon Low density Polypropylene Flexible Polystyrene polyethylene PVC Tep. C 6. C 8. C 6. C 19. C 6. C 4. C 6. C 17. C 6. C 3. C Thera flux Directional Heat flux e :1.353e Von-ises stress 6.794e e e+6 :1.63e e+6 :1.5358e e e e e+9 Total deforation e e e e e-4 Table 1.Results of screw aterial EN9 For reciprocating screw of injection olding achine, Steady state Theral analysis & Static structural analysis perfored on screw using finite eleent analysis applying tep. At various points & and fixed support. The reciprocating screw aterial is EN41B, EN9, EN8 & EN 4.The flowing ould aterial is Nylon, Low density roly-poly prop, Flexible PVC & Polystyrene. The results obtained are plotted on charts. Results plot one shaft aterial four ould aterials. RESULTS FOR SHAFT MATERIAL (EN-41B) ISSN : June - July

7 Nagsen B. Nagrale et al. / International Journal of Engineering and Technology Vol.3 (3), 11, THERMAL FLUX (W/M) THERMAL FLUX (W/M) VONMISES STRESS() VONMISES STRESS() FOR SCREW MATERIAL EN-41B SUITABLE MOULD MATERIAL IS NYLON-66 & POLYPROPYLENE. RESULTS FOR SHAFT MATERIAL (EN-9) 1 THERMAL FLUX (W/M) NYLON LDP POLY. FLEXI. POLYS THERMAL FLUX (W/M) VONMISES STRESS() NYLON LDP POLY.P FLIXI.PVC POLYST VONMISES STRESS() FOR SCREW MATERIAL EN-9 SUITABLE MOULD MATERIAL IS NYLON-66, POLYPROPYLENE & POLYSTYRENE. RESULTS FOR SHAFT MATERIAL (EN-8) 3 1 THERMAL FLUX (W/M) NYLON LDP POLY. FLEXI. POLY THERMAL FLUX (W/M) 1 VONMISES STRESS() VONMISES STRESS() FOR SCREW MATERIAL EN-8 SUITABLE MOULD MATERIAL IS NYLON-66 & POLYSTYRENE. RESULTS FOR SHAFT MATERIAL (EN-4) ISSN : June - July

8 Nagsen B. Nagrale et al. / International Journal of Engineering and Technology Vol.3 (3), 11, THERMAL FLUX (W/M) VONMISES STRESS() THERMAL FLUX (W/M) VONMISES STRESS() FOR SCREW MATERIAL EN-4 SUITABLE MOULD MATERIAL IS NYLON-66 & POLYPROPYLENE. Finite Eleent Method to find the von-ises stress in the RECIPROCATING SCREW: F F F = Force on screw = AEαΔT Nuber of threads = x1xx1 6 x1.7x1-6 x (8-6) = 438 N = 3895 = x 1 3 KN. ν = Poisson s ratio =.9 t = Thickness of eleent, 1 Cross sectional Area = bx t =x1= Von-Mises Stresses in Each Eleent= Von-Mises stress in eleent is given as: Where I = I I 1 3I = + 1 x y = 5.73 x 1 14 M x y τ xy = = -.98 x 1 8 M Where = = I ( ) 3(.98 1 ) = M I 1 3I = + 1 x y = M I x y τ xy = = = M = ( ) ( 1 ) =.71 1 M 8 = ISSN : June - July

9 Nagsen B. Nagrale et al. / International Journal of Engineering and Technology Vol.3 (3), 11, Fig 1.1 Results validation (Equivalent stress-en9 Nylon) References [1] Akinci, I.D Yilaz and M. Canakci, 5. Failure of a rotary tiller spur gear. J. Eng. Failure Anal., 1:4-44 [] A Guide to Injection Molding Of Plastics By Prabodh C. Bolur [3] Nanaware, G K. and M.J. ble, 3 Failure of rear axle shafts of 575 DT tractor. J. Eng Failure Anal., 1: [4] Rahan, M.M., A.K. Arffin, N. Jaaludin, S. Abdullah and M.M. Noor, 8. Finite eleent based fatigue life prediction of a new free piston engine ounting. J. Applied Sci., 8: [5] Machine Design By R. S. Khuri, J.K. Gupta [6] Manual of Injection Molding Machine By Klockner Windsor India Ltd. [7] The Finite Eleent Method By Zeinkiewiczs O.C, Taylor R.L. [8] Introduction to Finite Eleents in Engineering Prentice By Chandrapatla T.R. ISSN : June - July