The study of parametrs process of the injected parts by thermoplastic material.

Crai, Alina ; Iancau, Horatiu ; Grozav, Sorin 等

1. INTRODUCTION

The injection molding process involves the injection of a polymer melt into a mold where the melt cools and solidifies to form a plastic product. It is generally a three phase process comprising filling, packing and cooling phases. Its popularity is typified by the numerous products produced in this way at the present time. The introduction of simulation software has made a significant impact in the industry where in the past, much was unknown about the injection process itself (Chang & Yang 2001).

Injection molding is the most widely used process for the industrial forming of plastic articles. Its applications are of an extreme variety and the products range from large parts, such as used in the automotive industry (fenders, dashboards, hatchbacks), to much smaller objects like electromechanical components (electrical switches or contact breakers) (Advani, 1994). A major advantage of this manufactures technique may be found in the capacity of forming fairly complex shapes at a high production rate, in view of the cyclic nature of the process.

2. SIMULATION OF INJECTION MOLDING

The part of study is a icecream box. We'll have a part product like in figure 1. The software package chose for obtain the 3D part is called SolidWorks (www.solidworks.com).

[FIGURE 1 OMITTED]

The selected material for injection parts is a sorts of Acrilonitril (ABS), Produce brand name BASF under commercial name TERLURAN HH-112:BASF, material find in MOLDFLOW database programs (www.moldflow.com).

The therimis specific features processes of injection are furthered presented.

[FIGURE 2 OMITTED]

In order to analyze the flow of plastic material during it's injection in the mold it's necessary to cover several stages (Seow & Lam 1997).

1. The import of 3D models of the part

The geometrical model of the piece (figure 3) to be analyzed can be realized directly in MoldFlow, using the module MPI/Modeler or in the CAD 3D program, afterwards imported in MDI/STUDIO module as a file STL or IGES.

2. The discretization of geometrical model (New Mesh)

[FIGURE 3 OMITTED]

It's a very important stage of the simulating process, because it can appear various deficiencies of the mesh, for example: breaches, superposition of the elements, unorientated elements. This deficiencies doesn't permit the realization of the simulating and appear messages of errors.

3. The selection of the boundary conditions

In this stage we choose the point of the injection. The place ill be represented by a yellow knot on model surface.

4. Stualysis Preparation Wizard

In this stage take place the choice of the material for the piece from the data base of the soft, the choice of the analysis type (Flow, Optinum profile analysis, Cool, Warp or Stress).Choosing the Flow option, further will choose theoprion Filling only and the necessary parameters for the injection.

SIMULATION RESULTS

Study of flow was made for parts which thickness of the wall was 1,5; 2; 2,5; 3; 3,5 and 4 mm.

* The fill time

The diagram of fill time(figure 4) shows the flow front position at regular time intervals during the mold fill.

The outlines represented by the same colour show the part f the mold filled in the same time. At the beginning of injection the result it's red and at the end is navy blue. If the injection time is too short, the part of the piece unfilled isn't coloured.

[FIGURE 4 OMITTED]

* The time to freeze

The time to freze (figure 5) presents the additional time needed after finishing the fill (fill analysis) or after compacting (compacting analysis) for cooling the plastic. Time for freeze typically for the process of refrigeration is a partial partial time from one of cycle of injects. Technology of injection involves to obtain time which assure the quality parts.

[ILLUSTRATION OMITTED]

[FIGURE 5 OMITTED]

The values obtained from simulations program were entered in table 1

For each study of were represented a diagram depending on wall thickness of the part the figure. 6,7.

[FIGURE 6 OMITTED]

[FIGURE 7 OMITTED]

4. CONCLUSION

After simulation made whit Moldflow we achieved the optimization parameters of injection- the fill time and the time to freeze depending of wall thickness study. Results that the value for all three parameters for study decrease whit walls of parts study.

5. REFERENCES

Advani,S.G. (1994). Flow and Rheology in Polymer Composites Manufacturing, Elsevier Science, London.

Chang, R.Y. & Yang, W.H. (2001). Methods Fluids, Int. J.Number 37, 125

Seow, L.W. & Lam Y.C. (1997). Optimizing flow in plastic injection molding, Journal of Materials Processing

Technology, Vol., 72, ISSN 333-341 http://www.moldflow.com, Accesed: 2008-06-12 http://www.solidworks.com, Accesed:2007-09-23

Tab. 1 The values obtained from
simulations program

 Part's
thickness Parameters for study
 (mm)
 Fill Time to
 time (s) freeze (s)

 1,5 1,468 8,095
 2 2,284 12,91
 2,5 2,948 19,12
 3 3,287 24,91
 3,5 3,466 33,41
 4 4,210 42,91