Influence of selected technological parameter to quality parameters by injection molding.

Dobransky, Jozef ; Hatala, Michal

Abstract: Paper deals with observation of influence of selected technological parameter to selected quality parameters by injection molding. During this observation was specified some technological parameters and next was selected technological parameter--injection speed. From product quality parameters was selected quality parameters--hole diameter and total weight. Based on measurements was made functional dependencies. This observation is used as preparation measuring for next work. After that we will made planned experiment.

Key words: speed, plastics, weight, diameter

1. INTRODUCTION

Injection molding is a major processing technique for converting thermoplastic materials. The basic concept of injection molding is the ability of a thermoplastic material to be softened by heating, formed under pressure and hardened by cooling. In a reciprocating screw injection molding machine, granular material (the plastic resin) is fed from hopper (feeding device) into one end of the cylinder (the melting device). It is heated and melted (plasticized or plasticated), and it is forced out the other end of the cylinder (while still melted) through a nozzle (injection) into a relatively cool mold (cooling), held closed by the clamping mechanism. The melt cools and hardens (cures) until it is set up. (Strong, 2005)

Injection molding process is usually divided to basic parts--process times.

[FIGURE 1 OMITTED]

2. SPECIMEN PRODUCTION

Specimens using for these measurements was made by injection molding machine DEMAG Extra 120-430.

Injection speed was changed from 20 to 206 [cm.sup.3]/s. Especially 20, 30, 40, 90, 110, 140, 160, 170, 190 and 206 [cm.sup.3]/s. Optimal injection speed was 160 [cm.sup.3]/s.

[FIGURE 2 OMITTED]

Specimens used for this observation was moving-machine safety cover (Fig.2). This cover was made from polypropylene (PP). Injection material contains 2% of coloring agent. It was made 6 specimens by every change of injection velocity.

After that, the specimen was measured. We measured hole diameter and total weight. Diameter was measured by Caliper Mitutoyo Absolute Digimatic 150. Total weight was measured by Exact Analytic Balance Mettler Toledo 1502-S.

Optimal diameter which is specified by purchaser was 6,08 mm and total weight was 69 g. Each of measured values was recorded into the PC automatically, because measuring equipments was connected on PC.

3. SPECIMENS EVALUATION

Specimens were evaluated by Statistica software. We observed dependency of injection speed and diameter for screw grip. Next we observed dependency of injection speed and total weight of specimen. During the change of injection speed we could observe change of cycle time and injection time.

3.1 Effect of injection speed change to hole diameter

[FIGURE 3 OMITTED]

Figure shows dependency of injection speed to hole diameter. Optimum injection speed by optimal production process is 160 [cm.sup.3]/s. As we can see in this figure hole diameter is changed from 6,037 to 6,077 mm. Experimental curve was translate by logarithmic function. Equation of this function is displayed in figure. Based on The Pearson correlation index was chosen appropriate function. All of these values are in asked tolerance. Based on these measurements we can say that injection speed has not eminent effect to hole diameter.

3.2 Effect of injection speed change to total weight

[FIGURE 4 OMITTED]

Figure shows dependency of injection speed to total weight. Required total weight by optimal production process is 69,1 g. As we can see in this figure at intervals of injection speed from 110 to 210 [cm.sup.3]/s is total weight unchangeable. Under the 110 [cm.sup.3]/s total weight is greatly going down and under the 40 [cm.sup.3]/s is total weight inaccessible. Experimental curve was translated by polynomial function. Equation of this function is displayed in figure. Based on The Pearson correlation index was chosen appropriate function.

3.3 Change of injection time

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Figure shows dependency of injection speed change to injection time. Injection time was changed with injection speed change. As we can see in figure by injection speed accumulation is injection time going down. Experimental curve was translated by polynomial function. Equation of this function is displayed in figure. Based on The Pearson correlation index was chosen appropriate function.

3.4 Change of cycle time

Figure shows dependency of injection speed change to cycle time. Cycle time was changed with injection speed change the same as well as previous case. As we can see in figure by injection speed accumulation is cycle time going down. Experimental curve was translated by polynomial function. Equation of this function is displayed in figure. Based on The Pearson correlation index was chosen appropriate function.

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5. CONCLUSION

Paper deals with observation of influence of selected technological parameter to quality parameters by injection molding. During this observation was specified some technological parameters and next was selected technological parameter--injection speed. Based on the all measurements we can say that injection speed influenced markedly to product quality. These analysis paper was visibled on all dependencies.

This observation is used as preparation measuring for next work. After that we will made planned experiment. Based on these planned experiments will made graphs of influence of technological parameters to product quality parameters by injection molding. It will be three types of graphs: Pareto graphs, graphs of Marginals diameters and 3D graphs of influence of technological parameters to product quality parameters.

6. REFERENCES

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

Dobransky, J. & Todea, M. (2007). Examination of production process capacity by monitoring of plastic part quality parameters, Proceedings of Modern Technologies in manufacturing, Technical university of Cluj-Napoca, Romania, in print

Dobransky, J. (2007). Observation of production process capacity by injection moulding. Scientific bulletin of International multidisciplinary conference, pp. 197-200, ISSN 1224-3264, North University of Baia Mare, Romania,

Strong, A. (2005). Plastics: Materials and processing. Prentice Hall, ISBN 01-311-4558-4, New Jersey