Design & Analysis in Injection Moulding Machine System to Reduce the Torsional Failure of Screw

Design & Analysis in Injection Moulding Machine System to Reduce the Torsional Failure of Screw

Amol J. Asalekar1

Department of Mechanical Engineering Alard College of Engg. & Management, Marunje, Pune

Savitribai Phule pune University, Pune, India

Somashekhar G. Ganiger2

Department of Mechanical Engineering, JSPM's Imperial College of Engg. & Research, Wagholi, Pune

Savitribai Phule pune University, Pune, India

Abstract The Injection moulding process is commonly used manufacturing process for the production of plastic parts. The plastic being melted in injection molding machine and then injected into the mould. The barrel contains reciprocating screw for injecting the material into the mould and the material is also melted into the barrel. This project deals with, the solution of problem occurred for reciprocating screw of Injection molding machine. It identifies and solves the problem by using the modeling and analysis techniques. The problem occurred in the reciprocating screw of machine which is wearing of threads due to effect of temperature of mold materials (flow materials)

1. Nylon, low-density polypropylene, polystyrene, PVC etc., The main work was to model the components of machine with dimensions, and perform static and thermal analysis with parts of injection molding machine parts like reciprocating screw.[2] The analysis of reciprocating screw provides the possible solution to reduce the wear or damage on reciprocating screw, hence avoiding the high cost and time lapse

   Keywords Reciprocating screw, gear box, motor capacity, rigid flange coupling, barrel heaters, Catia V5 and Ansys 14.

   1. INTRODUCTION

      The injection molding process is most commonly used manufacturing process for production of plastic parts. As a raw material plastic is used in this process such as low density polyethylene, nylon, polypropylene, flexible PVC, polystyrene and machine used for the injection process is the injection molding machine. Raw material is melted in the injection molding machine and then forwarded into the mold with the help of reciprocating screw where it cools and solidifies into the final product part. The reciprocating screw is mounted on gear box in the barrel; barrel contains heaters for heating the raw material. In the injection process raw material is melted by heat and pressure. While forwarding material the material enters the grooves of reciprocating screw. The reciprocating screw completes the shot volume and returns to reverse position. Two types failure occurs in the injection process bending failure and torsional failure of threads due to effect of high melting temperature of mold material and pressure created because of that. The objectives involved are:-

      1. To model reciprocating screw using modelling Software CATIA V5R20

      2. Analysis of reciprocating screw using ANSYS 14.5 software

      3. To identify the wearing of threads and provide the possible solution.

      4. To provide thermal solution for the system.

   2. MATERIALS AND METHODES

      This chapter describes the details of injection molding process, design of reciprocating screw with material EN-41B (SAE 52100) , design of coupling such that coupling should become weaker element to avoid the failure of reciprocating screw because of torsional failure causes in injection molding process due to effect of temperature of mold materials (flow materials).Various materials can be used in this process like linear low density polyethylene, Nylon, polystyrene, PVC etc. But, material of product used in this process is linear low density polyethylene (LLDP).

      A .Design Of Reciprocating Screw

      For designing the coupling we need the value of maximum torque, which is occurring in the injection process. That value is possible to calculate using motor power (kW) and existing damaged reciprocating screw design. Motor used for the injection process is of 15 HP i.e. 11.1855kW, Motor RPM = 1440 Gear box used in injection process is 1:15. Because of gear box effective power causing to the reciprocating screw is

      Effective power =

      = 167.7825

      Torque transmitted will be, T=

      1. Modelling Of Reciprocating Screw

         For the further static and thermal analysis of reciprocating screw we have to make model. For making model it requires dimensions of reciprocating screw. It is taken by using digital Vernier Calliper and modelling has been done by using CATIA V5. It is shown as in figure.

         Fig-1 3D Model of reciprocating screw

      2. Analysis of Existing Reciprocating Screw

      Analysis of existing reciprocating screw is done by using software ANSYS R14.5 by providing properties of reciprocating screw material and CATIA model. Then it is feed into the ANSYS R14.5 and static and thermal analysis has been done. We have made analysis by using properties of two different materials. First of all we have made analysis by using material EN24, it could not avoid that much failure of reciprocating screw,

      Fig-3 Coupling Broken

   3. RESULT AND DISCUSSION

A. Analysis results for material EN 24

After analysis on software ANSYS R14.5 following values of total deformation and equivalent stress is obtained as given below.

Fig-2 3 D Model -Mesh – Image

1. Inputs Provided To The Ansys R14.5 Software For Analysis Of Reciprocating Screw:

   TABLE 1 PROPERTIES OF MATERIAL

   Materials	SAE52100 (EN41B	SAE4340 (EN24)
   Youngs modulus (PA)	210×10^9	205×10^9
   Poisons Ratio	0.3	0.292
   Density (kg/m³)	7810	7850
   Thermal Expansion	11.9×10^-6	12.3×10^-6
   Yield Tensile strength (PA)	9.1×10^8	470×10^6
   Ultimate Tensile Strength (PA)	672×10^6	689×10^6
   Specific heat J/g-K	0.475	0.475
   Thermal conductivity W/m-K	46.6	44.5

2. Testing of coupling:

As this is industrial based sponsored project we have carried out testing of this project in Industry. First of all we have connected the coupling in between gearbox and reciprocating screw, it is observed coupling can sustain the torque occurring in the injection process, if process goes normally without any hurdles. Then we have stop heating by switching off a heater. Because of which melting of material will be stop, After some time it is observed that coupling broken up instead of reciprocating screw.

TABLE 2 E24 ANALYSIS REPORT

Fig-4 Model -Static Structural -Total Deformation-Image

Fig-5 Model – Static Structural – equivalent stress – Image

From above obtained results it observed that failure of reciprocating screw is confirmed. In equivalent stress analysis it is observed that failure threads are confirmed and which takes at maximum equivalent stress value which is equal to 2502Ma. And it is too much high. So it is not possible reduce the failure of reciprocating screw.

1. Analysis results for material EN 41

   After analysis on software ANSYS R14.5 following values of total deformation and equivalent stress is obtained as given below

   TABLE 3 ANALYSIS REPORT FOR EN 41

   ANSYS R14.5 software analysis report for EN 41
   Total Deformation in mm	0 Min	0.0091867Max
   Equivalent stress in MPa	1.6567	26.695.0 Max

   Fig-6 Model > Static Structural > deformation > Image

   Fig-7 Model – Static Structural -equivalent stress- Image

   From above obtained results also it observed that, this material; EN 41B gives better results than EN24, it has less chances of failure, But failure of reciprocating screw is confirmed. In equivalent stress analysis it is observed that failure threads at the end part is confirmed and which takes at maximum equivalent stress value which is equal to 2502MPa. And it is to much high. So it is not possible reduce the failure of reciprocating screw.

2. Thermal Analysis

   For this material EN 41B we have done thermal analysis also it gives clear idea of different temperature zones in reciprocating screw. By analysis we can get idea of how the temperature varies and temperature at any point.

   TABLE 4 MOULD TEMPERATURE

   MOULD TEMPERATURES (° C)
   MATE RIAL	T1(Meteri ng Zone	T2(Compressio n Zone)	T3(Feed Zone)	T4(Dri ve Zone)
   EN 41B	190	170	150	60

   Fig-8 Variation of temperature

3. Analysis of Coupling

In analysis of coupling we can observe that, coupling shows maxim possibility of failure than reciprocating screw. And maximum value of equivalent stress is obtained is also to much higher than reciprocating screw which is equal to15721 MPa compared to 2502.0 MPa.

TABLE 5 ANALYSIS OF COUPLING

Fig-9 Model – Static Structural – total deformation

Fig-10 Model -Static Structural -equivalent elastic strain

Fig-11 Model – Static Structural -equivalent stress

III. CONCLUSION

For reciprocating screw of material EN24 (SAE4340). of injection molding machine Static structural analysis performed on screw using ANSYS R14.5 software analysis applying torque at the end on motor side and keeping whole surface of screw as fixed support side, it is found that reciprocating screw has more chances of failure. In the same way For reciprocating screw of material EN-41B (SAE 52100) of injection molding machine Steady state Thermal analysis & Static structural analysis performed on screw using ANSYS R14.5 software analysis applying torque at the end on motor side and keeping whole surface of screw as fixed support side, it is found that this reciprocating screw also has more chances of failure. For reciprocating screw of material EN-41B (SAE 52100) also has done thermal analysis and it has shown variation of temperature along the full reciprocating screw length and it also can give temperature of material at different point.

In analysis of coupling we can observe that, coupling shows maximum possibility of failure than reciprocating screw. And maximum value of equivalent stress is obtained is also to much higher than reciprocating screw We can say from analysis of coupling as shown in figure and reciprocating screw, coupling is weaker one than reciprocating screw and it will really fail before or we can say avoiding the failure of reciprocating. The coupling is the better solution for reducing at least torsion failure of the

reciprocating screw by making coupling element than reciprocating screw in injection molding process.

REFERENCES

1. Nagsen B. Nagrale, Dr.R.N.Baxi, Finite Element Analysis of Reciprocating Screw for Injection Molding Machine, Nagsen B. Nagrale et al. / International Journal of Engineering and Technology Vol.3 (3), 2011, 191-199

2. Vikas.R.Rajoria, Prof.P.K.Jadhao, Finite Element Analysis of Reciprocating Screw for Injection Molding Machine, International Journal of Innovative Research in Science, Engineering and Technology Vol. 2, Issue 7, July 2013, ISSN: 2319-8753

3. Bc. Martin Pindak , " Design of injection mold including cooling system optimization ,TBU in Zlín, Faculty of Technology

4. Shahrir Hashim, Process Control in Injection Moulding Machine,

   ISSN 0128-0740 Buletin FKKKSA 7(2): 34, 1993

5. Muhammad Arshad Bin Zainol Abidin, Analysis Of Filling Stage For Injection Molding

6. Danian Zheng, Iterative Learning Control Of An Electro-Hydraulic Injection Molding Machine With Smoothed Fill-To-Pack Transition And Adaptive Filtering, Thesis Urban-Champaign, 2002

7. S. Rajalingam, Awang Bono, Jumat Bin Sulaiman Identifying the Critical Moulding Machine Parameters Affecting Injection Moulding Process by Basic Statistical Process Control Tools International Journal of Engineering and Physical Sciences 6 2012

8. Timothy W. Womer, Basic Screw Geometry , ANTEC 2000, The Annual Technical conference of the society of plastic engineers Inc.

9. C. P. J. M. Verbraak, H. E. H. Meijer, Screw Design in Injection Molding, Polymer Engineering And Science, Mid-April 1989, Vol. 29, No. 7

10. Jonathan M. Newcome: SPE Tech Pap Reg Tech Conf. PIONEER VALLEY SEC (77 june 8/9) 45 78

11. V. B. Bhandari, Design of Machine elements

12. P.C. Sharma, Production process

13. Daniel John Berkery Process monitoring for plastic injection moulding

14. Kirubel Bogale Simulation and design of extrusion dies Degree thesis Plastic Technology 2011

15. Oyetunji, A. Development of Small Injection Moulding Machine For Forming Small Plastic Articles For Small-Scale Industries Journal of Engineering Science and Technology Vol. 5, No. 1 (2010)