OPEN MOULD

PRESS OPEN MOULDING EJECTED FORKED STRIPPING TRAY IN... 

Parifton plochad aa it amaroaa from die and then stretched between two ha 68 of open mould... 

Heated sheets placed between open mould halves... 

This method is often used for heavy mouldings. Inserts in a mould cavity tend to be displaced as they are positioned in an open mould. Often used for metal inserts. Better adhesion of rubber to metal or fabric is obtained. Specialty elastomeric compositions are to be designed to make high quality products. 

To form a plastic object by pouring a fluid monomer-polymer solution into an open mould where it finishes polymerising. Forming plastic film and sheet by pouring the liquid resin onto a moving belt or by precipitation in a chemical bath. 

Slush moulding utilises heated open moulds which are inverted to remove excess plastisol. Layer thickness is controlled by the rheology of the paste, timing and... 

A series of five nanocomposite elastomer systems were prepared for this study incorporating 0, 1, 2, 4 and 8% (on total resin mass) of the organically modified montmorillonite clay Cloisite 6A. The appropriate level of Cloisite was dispersed in a starting resin blend of OH terminated PDMS (M -77,000 and Mn -550 g mol in a 3 1 ratio) by a combination of mechanical mixing and ultrasonic processing to give a nano-dispersion of clay platelets. The blend was subsequently crosslinked with a stoichiometric level of tetrapropoxysilane (TPOS) in the presence of 5% diphenylmethylsilanol (DPMS) chain terminator and 5% tin(II) 2-ethylhexanoate catalyst, cured in an open mould at 65°C for twenty minutes, then removed from the mould and post cured for a further fifteen hours at 65°C to give an elastomeric mat. 

Open-mould processes are thermoset moulding processes with open moulds in the male or female form. In this process the mould is made from a pattern and the reinforced thermoset is applied to the mould to reproduce the shape and finish of the mould. Typical examples would be boat hulls made from fibreglass-reinforced gel coats. Figure 6.10 shows the basic contact-moulding process. 

Open-mould processes have traditionally developed through trial-and-error processing and have not been modelled formally, unlike the similar case of process modelling in the metal industry, as reviewed by Thomas (2002). 

The technique allows a reduction in the usage of both water and the release agent. This results in a lower amoimt of waste water and reduced emissions of steam containing oily particles. The active compoimds of the release agent are comparable to the traditional ones. Emissions due to decomposition of the release agent (and upon opening the die to get the casting out) therefore are comparable in nature to those with the open-mould technique. 

Hand lay-up Individual plies of reinforcement placed in open mould and impregnated with catalysed resin by hand tool, e.g. roller unidirectional tape can be used Large structures, e.g. boat hulls, chemical tanks... 

Spray moulding Chopped fibres and catalysed thermosetting resin sprayed simultaneously onto open mould and cured at ambient temperature As for hand lay-up. More rapid but short fibres provide less reinforcement... 

Pour Formulation 1 polyol 1 and isocyanate recycle through the mixing chamber s piston grooves and are poured in the open mould... 

The pouring operation can be executed in an open mould without fear of collision with the upper mould half. 

The system requires the presence of an open mould where the film-holding frame can be inserted to position the film prior to the vacuum-forming phase. Obviously, this technology is more easily applied to new equipment and new moulds since, most of the time, existing moulds must be modified to provide the vacuum and hold the frames. When one surface of the part is covered by an aesthetic or functional layer (carpet, plastics, etc.), obviously the film is only applied to the opposing side where the foam would be in contact with the mould (see Figure 3.19). 

Figure 3 J.1 Open-mould co-injection of PU and glass fibre is executed at high speed and in a clean working environment, with an InterWet machine.

The development of a proper device to carry the mixing head during the pouring operation over open moulds required relatively short time. Basic requirements were multi-axes capacity, speed, precision and easy programming. 

In extrusion-blow moulding (see Figure 7.44(A)), the extruder extrudes a parison into the open mould. (The extruder ceases to extrude whilst the test of the ( cle takes place.) The mould closes and the parison is inflated (B). When the parison has taken up the shape of the mould (C) the mould is cooled and finaUy the mould opens, and the bottle is removed (D). The extruder then extrudes another parison (A) and the < le is repeated. 

These thermosetting resins contain a urethane prepolymer in methyl methacrylate monomer. Although they are cured in a similar fashion to polyesters, their initial viscosity is much lower and the cure reaction is more rapid. The speed of cure along with the odour of the monomer preclude the use of open mould processes, but these resins are especially suitable for fast processing by methods including pultrusion and resin... 

The process uses an open mould which is generally itself FRP previously produced from a timber pattern. 

The spray-up machine consists of a gun for spraying catalysed/accelerated resin and a unit which chops continuous glass fibre. They are simultaneously sprayed on to an open mould coated with a releasing agent. The laminate is rolled and then allowed to cure, after which the moulding is released and trimmed to size. The properties and applications are similar to hand lay-up but the use of the spray machine produces a much faster lamination time. 

General polyesters are usually orthophthalic acid based resins, which are used in applications based on open moulds and hand and spray lay-up moulding. Resins with a low level of styrene emission are ideal for these applications. 

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