Mould closure

A special design of injection presses (from Husky) is used to mould hinged, flip-top lids for wet-wipe containers that are folded during mould closure. When compared to conventional systems, this new device can lead to a 10% to 15% increase in output and a 15% to 25% reduction in floorspace. 

Mould closure pushes Resin injechon into the gap resin into preform may deform preform... 

Meanwhile, other developments, especially at the Shoe and Allied Trades Research Association (SATRA), led to the emergence of injection-moulded shoes in various thermoplastics, especially plasticized PVC. More recently thermo-plastic rubbers have become important. In the most important of these processes, the sole is directly moulded on to the shoe. The lasted shoe forms the mould closure, and the PVC compound is injected to give the completed shoe, which subsequently requires only trimming and minor finishing operations. 

More recently, an alternative system has come into use. In spite of the good performance of the single-shot polyester product, difficulties have been encountered, often related to the design characteristics of different patterns of sole (see also Section 13.8). The two-shot system has been developed in which a first shot of a tough, harder skin compound is followed after about 1 min by a shot of soft low-density foam. A temporary mould cover, with a blank, ensures correct location of the skin, and is replaced by the normal mould closure, or lasted upper for the second shot. 

A larger quantity of parameters must be defined to specify a filling process. Along with the selection of where to inject and vent, a decision is required on how far open the mould will be during injection. How should secondary mould closure be controlled, specifying a constant closing speed or application of a specified force ... 

A fireman s helmet (a) finite element mesh, (b) SimLCM output for normal stress distribution during mould closure. (Source Reprinted from reference 38. Copyright (2009), with permission from Elsevier Ltd.)... 

A variant of low-pressure moulding is catalysed resin injection into matched moulds in which the reinforcement has been preplaced prior to mould closure vacuum applied before resin injection assists mould filling. All these techniques depend on the easy flow of the prepolymer and good wetting of the reinforcement, but preclude the addition of much cheap particulate filler. 

Applications Technical mouldings. Closures caps. Crates boxes. Houseware. Storage waste bins. Pallet boxes fish crates. Food containers. Packaging (household chemicals, food stuffe). Fuel tanks. Containers for hazadous materials. Pipe. ... 

Closure liners of pulpboard or cork, unless specially treated with a preservative, foil or wax coating, are often a source of mould contamination for liquid or semi-solid products. A closure with a plastic flowed-in linear is less prone to introduce or support microbial growth than one stuck in with an adhesive, particularly if the latter is based on a natural product such as casein. If required, closures can be sterilized by either formaldehyde or ethylene oxide gas. 

Fig. 2.6. The diagram shows the essential features of the PTFE taps, but it is not a representation of any one firm s model. A is2i shaft of PTFE or of some other material covered with PTFE. It is driven by rotating the plastic cap B which engages the screw-thread of the glass moulding C. The seal against the atmosphere is provided by the bulge D. The valve closure at E is the more reliable of the two seals.

Closures made with a liner (or wad)-type sealing system break the seal faster, thereby allowing more time to vent the carbonation gases. The technology of liners has developed significantly over recent years. This development has improved the reliability of the seal across a wide range of bottles, both glass and plastic, and offers the potential for an improved barrier in the closure. All this has meant that most closures in the soft drinks and juice market today have liners of one form or another. There are two types of liner a loose liner pushed into the cap after the cap is moulded and a moulded-in liner, which is formed at the time the closure is made. 

Plastic closures can be made by injection moulding, where the mould has two parts - a core which has the inside features of the closure and a cavity which has the features of the outside of the closure. Molten plastic is injected into the mould, which is water-cooled. The plastic solidifies, and the mould opens and the completed closure is ejected. If the closure is a two-piece design (i.e. fitted with a loose or flowed in-liner), then this is added later. Another technology for moulding plastic closures for the beverage market is compression moulding. A hot pellet of PP is positioned in a mould, similar to the cavity of an injection mould. As the mould closes, the pellet is squashed and defoimed into the shape... 

Fancy closures for bottles for perfumes or other luxury items can be moulded from plastics and coated with precious metals like gold containers of this kind are required to be especially attractive in appearance, and to remain so over the whole life of the contents. 

Chemical additives on the surfaces of container closure system component fabrication machinery, such as mould release agents, antistatic and antislip agents, etc. 

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

PF is made by the condensation polymerisation of phenol and formaldehyde. Due to the volatile and toxic/irritant nature of formaldehyde, this is usually fixed with ammonia giving hexamine. Polymerisation of hexamine and phenol not only produces phenol formaldehyde but may release residues of phenol, formaldehyde or ammonia. In certain cases some residues may remain in the moulding and be released into the product. As with UF, PF is mainly used for closures but due to the fact that the material is naturally dark, it is used for dark or deep colours. PF is generally more resistant to heat and moisture than UF. Both UF and PF are used with a range of fillers, e.g. wood flour, synthetic fibre. Density 1.25-1.45. General pharmaceutical applications have now reduced. 

Thermoset resins are normally moulded by compression, compression transfer or, more recently, injection moulding. Two-part resin systems are used for adhesives, coatings and lacquers. Pharmaceutical applications include closures (reducing), adhesives in laminations, protective lacquers, and enamels. 

Expanded low density polyethylene is found as either a cross-linked foam or a noncross-linked foam, with significant developments being initiated in Japan. It has been offered as a replacement moulding material for closure wadding either with or without an additional facing. When used as a wadding material, densities can be varied to give different levels of compression. 

Although the above are the major moulding processes for thermosets, injection moulding can now be used for the selected thermoset moulding operations. The major use of thermosets still remains with screw closures. These are made on either a multicavity platen tool (up to 96 cavities) or a rotary type press which resembles a rotary tableting machine. 

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