Injection moulding mould-filling

Hiebcr, C, A. and Shen, S.F., 1980. A finite element/finite difference simulation of the injection-moulding filling process. J. Non-Newtonian Fluid Mech. 7, 1-32. 

Now let s summarize the data on the viscosity of PVC plastisols. First, as concerning injection moulding (filling of thin moulds), both the plastisols (those showing and those not showing thyxotropic phenomena) may be considered as non-linear liquids with no characteristic times provided that the filling time is much larger than the characteristic time of the medium. 

BOBBIN PBT(30% FILL) INJECTION MOULDED WITH ITEM 5... 

Following the tolerance stack through the end assembly, the bobbin dimension of 22 mm from the outside face to the back face of the magnetic pole is analysed next. This characteristic dimension does not include the tolerance on the impact extruded pole. The pole is to be moulded into the bobbin and the pole face is considered to be part of a mould related dimension. The bobbin is injection moulded using 30% filled polybutylene terephthalate (PBT). The tolerance assigned to the bobbin dimension is 0.035 mm. 

The flow process in an injection mould is complicated by the fact that the mould cavity walls are below the freezing point of the polymer melt. In these circumstances the technologist is generally more concerned with the ability to fill the cavity rather than with the magnitude of the melt viscosity. In one analysis made of the injection moulding situation, Barrie showed that it was possible to calculate a mouldability index (p.) for a melt which was a function of the flow parameters K and the thermal diffusivity and the relevant processing temperatures (melt temperature and mould temperature) but which was independent of the geometry of the cavity and the flow pattern within the cavity. 

Some typical data for this mouldability index are given in Figure 8.8. One limitation of these data is that they do not explicitly show whether or not a mould will fill in an injection moulding operation. This will clearly depend on the thickness of the moulding, the flow distances required and operational parameters such as melt and mould temperatures. One very crude estimate that is widely used is the flow path ratio, the ratio of flow distance to section thickness. The assumption is that if this is greater than the ratio (distance from gate to furthest point from gate)/section thickness, then the mould will fill. Whilst... 

The early 1980s saw considerable interest in a new form of silicone materials, namely the liquid silicone mbbers. These may be considered as a development from the addition-cured RTV silicone rubbers but with a better pot life and improved physical properties, including heat stability similar to that of conventional peroxide-cured elastomers. The ability to process such liquid raw materials leads to a number of economic benefits such as lower production costs, increased ouput and reduced capital investment compared with more conventional rubbers. Liquid silicone rubbers are low-viscosity materials which range from a flow consistency to a paste consistency. They are usually supplied as a two-pack system which requires simple blending before use. The materials cure rapidly above 110°C and when injection moulded at high temperatures (200-250°C) cure times as low as a few seconds are possible for small parts. Because of the rapid mould filling, scorch is rarely a problem and, furthermore, post-curing is usually unnecessary. 

Isometric data from the creep curves may also be superimposed on the creep rupture data in order to give an indication of the magnitudes of the strains involved. Most plastics behave in a ductile manner under the action of a steady load. The most notable exceptions are polystyrene, injection moulding grade acrylic and glass-filled nylon. However, even those materials which are ductile at short times tend to become embrittled at long times. This can cause... 

The results of the above section show that the significant nonuniformity of the distribution of the filler particles in the thickness of sample is observed during injection moulding of the filled polymers. This nonuniformity must affect the electrical properties of CCM owing to the strong dependence of the CCM conductivity on the filler concentration. Although there are no direct comparisons of the concentration profiles and conductivity in the publications, there is data on the distribution of conductivity over the cross-section of the moulded samples. 

A method of injection moulding thermoplastics, which makes large-part moulding possible on injection equipment normally capable of moulding only small parts. The injection moulding machine fills the mould at relatively low pressures. See Injection Moulding. 

A twin-screw extruder is generally preferred for producing rubber-toughened, glass-filled PET compounds for injection moulding applications. The PET and impact modifier are added at the throat while the glass reinforcement is added downstream. The size of the rubber domains will depend on the amount of energy and the capability of the equipment used for dispersion. 

Apart from the injection step itself, which is identical to common injection moulding, there are three steps for mould filling and gas introduction ... 

A thermoplastic grille-opening reinforcement (GOR) for Ford SUVs is injection moulded from 40% mineral/glass-filled PET that can withstand on-line e-coating (210°C). HDT B (0.46 MPa) is 241°C and HDT A (1.8 MPa) is 212°C. PET GOR allows at least a 10% weight reduction and 15% cost reduction per part. 

INCREASING THE DIMENSIONAL STABILITY OF PRODUCTS MADE FROM FOAMED AND FILLED THERMOPLASTICS BY THE USE OF GAS COUNTERPRESSURE INJECTION MOULDING Piperov N L... 

The manufacture of products, e.g. containers and lids, made from filled foamed PE by gas counter pressure injection moulding was studied with special reference to the effect of production conditions on dimensional stability. Results obtained are discussed and evaluated. 7 refs. 

Fig. 30. Design principles of direct compounding injection moulding machine for processing highly filled polymer compositions...

In addition to the nature of particulate platelet orientation induced during injection moulding, the associated consequences on molecular orientation and crystalline order of the host thermoplastic matrix have also been reported with particular regard to various flake-filled polypropylenes [174], together with an attempt to interrelate these higher order structural parameters with physical properties of the composites [175]. 

Fig. 35. In-mould magnetization injection moulding technology for filled thermoplastics (a) constructional features of mould (b) magnetic flux generation in the radial direction [177]...

Fig.36. Variation in electrical conductivity (o) with molecular weight for polyethylene composites filled with 4% by volume carbon black, demonstrating the effects of orientation (I), degradation (II) and flow-induced segregation of carbon black aggregates (III). ( ) injection moulded (O) compression moulded (unoriented) [181]...

PET bottles are made from resin chips in a two-stage process (even if made on one machine). A preform is injection moulded and is sterile when formed this is then blown into the final shape. If the machine is enclosed in an HEPA-filtered environment and the bottles blown with sterile air, the machine produces a sterile bottle. The bottle can be transferred to the filler within an enclosed sterile ah conveyor and filled without further treatment, thus eliminating the need for rinsing and chemical treatment. Carbonated products can be filled if the carbon dioxide is sterilised. 

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