Injection moulding clamping

Wall sections in foam moulding are thicker than in solid material. Longer cycle times can therefore be expected due to both the wall thickness and the low thermal conductivity of the cellular material. In contrast, however, the injection pressures in foam moulding are low when compared with conventional injection moulding. This means that less clamping force is needed per unit area of moulding and mould costs are less because lower strength mould materials may be used. 

Since the reactants have a low viscosity, the injection pressures are relatively low in the RIM process. Thus, comparing a conventional injection moulding machine with a RIM machine having the same clamp force, the RIM machine could produce a moulding with a much greater projected area (typically about 10 times greater). Therefore the RIM process is particularly suitable for large... 

The container shown at the top of p. 341 is injection moulded using a gate at point A. If the injection pressure at the nozzle is 140 MN/m and the pressure loss coefficient, m, is 0.5, estimate (i) the flow ratio and (ii) the clamping force needed. 

It may be seen from the above analysis and that in Chapter 4 for the calculation of clamping force on an injection moulding machine the Mean Effective pressure (MEP) across the cavity may be obtained from... 

Though its production, e.g. in an injection moulding machine, requires special tricks, the injection pressures and the mould clamping forces required are much lower than with a solid product. 

ABS" Closure-piercing devices, roller clamps Injection moulding Good To 1000 kGy Rigid, most often translucent/ opaque... 

The two main parameters for machine size are, the maximum shot size that can be injected in a single forward movement of the screw, and the maximum mould clamping force / damp- The shot size is usually quoted in terms of the mass of polystyrene that can be injected. The clamping force, typically in the range from 100 kN to 100 MN, restricts the maximum projected area A of a moulding onto the mould parting plane (Fig. 5.24). A typical average melt pressure p in the mould is 20 MPa, and the condition... 

Ah electrical fitting, injection-moulded in PES, will operate at 150 C. It will be bolted to a steel support, and the total clamping force must not fall below 10 kN after 10 seconds. Washers with inside and outside diameters of 10 mm and 20 mm, respectivety, will be used. The maximum allowable strain for PES at 15(PC is 0.7%. Calculate the number of bolts needed, using data given in Hgures 8.13 and 8.14. 

The basic principle of injection moulding is to inject molten polymer into a closed, cooled mould, where it solidifies to give the product. The moulding is recovered by opening the mould to release it. An injection-moulding machine has two principal parts the injection unit the clamp unit, or press. This is illustrated in Fig. 1.1. 

The injection moulding machine is an 80-ton clamp Negri-Bossi. Temperatures in plasticizing and injection sections are 185 C. The mould cooling water is at 70°C. 

The extruder feeds one of two presses from an overhead gantry. Presses are of the hydraulic upstroking type with a clamping capacity of 150 tonnes - a compact injection-moulding press producing the same-sized mouldings would need a locking force of approximately 1500 tonnes. Press platen area is 2.15 x 1.5 m (7 x 5 ft). 

In conventional injection moulding, a polymer melt is prepared in a heated barrel, using a compression-type extruder screw the melt is injected under high rates of shear into a cooled mould, which is clamped closed by a (high) force, sufficient to resist the hydraulic pressure of the injecting melt. 

Injection moulding, 1 clamp unit, 1, 2 control features in, 24 cores, 14, 18, 20 gate, 2. 10... 

Resin injection moulding is a cold moulding process applied at medium pressures (approximately 450 kPa), where mould surfaces are enriched with release agents and gel coat before GF reinforcement is placed on the bottom of the mould, allowing the plastic to extend beyond the sides of the mould. Then the upper mould is placed in its place and it is clamped to stop followed hy injection of activated resin under pressure into the mould cavity (Figure 9.11). By using this technique, it is possible to obtain a fibre/matrix ratio of 65 wt%. 

A silicone rubber can be bonded to a solid substrate if it is clamped into or onto it. A very good example is the baby soother. The silicone nipple is injection moulded by a common LR process and then post cured. After that the nipples are clamped into a plastic construction or even overmoulded by thermoplastic. 

Energy savings resulting from the lower clamping force required from the injection moulding machine... 

Moving the central nozzle away from the mould axis causes an asymmetrical mould structure, asymmetrical loading of the ejection system and an asymmetrical stress distribution in the injection machine columns. The effective mould clamping force is diminished. 

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