Simulation of using injection channels by injection molding.

Dobransky, Jozef ; Fabian, Stanislav

Abstract: Paper deals with simulation of using injection channels by injection molding. Task of this simulation was review using injection channels into injection mould by injection molding. Simulated plastic was Mowing-machine safety cover. It was compared using one or two injection channels into injection mould. In this time is using one injection channel for this plastic part production. This work is a partial solution of dissertation work.

Key words: injection, plastics, simulation, molding

1. INTRODUCTION

It would be difficult to imagine our modern world without plastics. Today they are an integral part of everyone's lifestyle with application varying from commonplace domestic articles to sophisticated scientific and medical instruments. Injection moulding is a major processing technique for converting thermoplastic materials. The basic concept of injection moulding is the ability of a thermoplastic material to be softened by heating, formed under pressure, and hardened by cooling.

Simulation serve the purpose to determine based on some aspects which method, technique or process is better or preferable.

2. SIMULATION DESCRIPTION

Simulation was made on moving machine safety cover, which is represented in fig. 1. This plastic is made from Polypropylene with manufacturing identification Borealis BC 142MO with added 2% colouring agent. Plastic is made by injection machine DEMAG EXTRA 120-430.

[FIGURE 1 OMITTED]

Task of this simulation was compared two alternatives of using injection channels into mould and evaluated which alternative is better. In this time is using one injection channel for this plastic part production. During simulation were compared indicators:

* injection time

* injection pressure decomposition

* injection pressure loss

* temperature decomposition

* welded lines occurrence

* air bubbles occurrence

At first was created real 3D plastic model in Pro-ENGINEER (Fig. 2). In these figures is also represented injection channels location.

[FIGURE 2 OMITTED]

Next was made injection simulation with one or two injection channels in subprogram MOLD FLOW. Based on this simulation were compared individual indicators.

3. EVALUATION OF INDIVIDUAL INDICATORS

3.1 Simulation of injection time

In figure 3 is represented simulation of injection time by one or two injection channels.

a) one injection channel, b) two injection channels

As we can see in this figure, by injection with one injection channel is injection time 1,57 seconds and by two injection channels is injection time 0,94 s. Individual injection time section is color coded. Red color represents beginning of injection and blue color represent end of injection.

[FIGURE 3 OMITTED]

3.2 Simulation of injection pressure decomposition

Figure 4 shows simulation of injection pressure decomposition by one or two injection channels.

[FIGURE 4 OMITTED]

As we can see in this figure, by one injection channels in needed to produce injection pressure 174,65 MPa and by two injection channels is needed injection pressure 83,50 MPa. Injection pressure process is color coded. Blue color represents zero injection pressure and red color represents maximal pressure which is needed to make for maximal filling of mould cavity with melted plastic. The biggest injection pressure is by the feeder mouth. Its value is going down with running inside to mould.

3.3 Simulation of injection pressure loss

Figure 5 shows simulation of injection pressure loss during the injection process of plastic.

[FIGURE 5 OMITTED]

Running of injection pressure has the reverse character as by previous case. Injection pressure decomposition is color coded. Blue color represents zero injection pressure and red color represents maximal injection pressure. As we can see in this figure, zero injection pressure is by the feeder mouth.

3.4 Simulation of temperature decomposition

Figure 6 shows simulation of temperature decomposition by one or two injection channels.

[FIGURE 6 OMITTED]

As we can see in figure of temperature decomposition, the biggest temperature 230 [degrees]C is by the both cases in the injection mouth zone (red color). By one injection channels is maximal temperature on the opposite end too. By two injection channels is maximal temperature in the middle of plastic.

3.5 Simulation of welded lines occurrence

Figure 7 shows simulation of welded lines occurrence by one or two injection channels.

[FIGURE 7 OMITTED]

Welded lines are represents by red lines. By one injection channel is a couple of small welded lines. By two injection channels are considerable welded lines in the middle of plastic. This is by reason of material consolidate which is flowing to the middle of plastic from two sides.

3.6 Simulation of air bubbles occurrence

Figure 8 shows simulation of air bubbles occurrence by one or two injection channels. Determine air bubble occurrence and quantity is very important for plastic part production. We have to know how many air bubbles will be in the plastic that we will know what strength will be certain.

[FIGURE 8 OMITTED]

Air bubbles are represents by azure blue color. By one injection channel are air bubbles situated in the feeder mouth zone, in the middle of plastic and the opposite side of plastic. The biggest occurrence of air bubbles are in the middle of plastic by reason of flowing material.

3. TOTAL EVALUATION

Using of one injection channel has more benefits and less disadvantages as using of two injection channels, for all that is using of one injection channels is better and economical preferable. There are some benefits and some disadvantages of using two injection channels.

Benefits of two injection channels:

* smaller injection time

* smaller injection pressure needed to make for maximal filling of mould cavity

Disadvantages of two injection channels:

* needs to more cooling channels into mould

* more material needs to make a mould

* welded line in the middle of plastic can be effect less strength of plastic and quality anomalies

* more air bubbles occurrence

4. CONCLUSION

Paper deals with simulation of using injection channels by injection molding. Based on this simulation we can determined conclusions which are important to make an injection mould and plastic alone. During this simulation we are followed many aspects which could be influence on final plastic. It was compared injection molding with one or two injection channels. Based on this simulation we can say that using of one inection channel is preferrable than using of two injection channels.

5. ACKNOWLEDGEMENTS

The authors would like to acknowledge the support of Scientific Grant Agency of the Ministry of Education of Slovak Republic, Commission of mechanical engineering, metallurgy and material engineering, for their contribution to project 1/2209/05.

6. REFERENCES

Campo, A. (2006). The complete part design handbook: For injection molding of thermoplastics. Hanser Gardner Publications, ISBN 1-56990-375-1, Cincinnati

Dobransky, J. & Mandulak, D. (2007). Analyze of effect of switch point change to choosen quality parameters, Proceedinds of Modern Technologies in manufacturing, Technical University of Cluj-Napoca, Romania, in print

Fabian, S. (1997). Reliability of complex production systems. ELFA, ISBN 80-70993-014, Kosice

Harper, Ch. & Petrie, E. (2003). Plastics materials and processes. John Wiley and sons, ISBN 0-471-45603-9, New Jersey