Hand moulding

The major process today is the hand lay-up technique in which resin is stippled and rolled into the glass mat (or cloth) by hand. Moulds are easy to fabricate and large structures my be made at little cost. 

Machines with actual moulds similar to hand moulds,... 

Very occasionally bricks are still made by means of hand moulding. A lump of clay is forcefully thrown into a mould and then the surplus clay is removed. The result is a lively and variable product. When large quantities of bricks are produced the process does not differ much from that of hand moulding. However, now the clay is pressed into a mould and a rather uniform product is the result, e.g. the common brick. 

In the industrial world bricks are mostly made in an automated production process. After the raw materials have obtained the correct composition and plasticity, the forming process follows. In The Netherlands hand moulding, press moulding and extrusion moulding are applied in coarse ceramics. Occasionally the stamping press is still used, mainly in the manufacture of roof tiles. 

Hand moulding is the oldest method. Wooden moulds with six or seven compartments of the desired size are used. First these are cleaned and then lubricated with sand to prevent the clay from sticking. A lump of clay is then rolled through sand or sawdust and forcefully thrown into a compartment. With a piece of wire, excess clay is removed from the top of the mould. Next the mould turned upside down and the shaped bricks fall out and are ready for transport. The baked bricks are characterized by an non-uniform texture. Nowadays handmoulding is often done mechanically. 

Hand moulding It is carried out in wooden boxes and is cheaper than machine on a jobbing basis. 

Machine moulding Machine-moulded refiactories have higher strength and density than hand-moulded relfactories. Machine moulding can be used for semi-plastic mixture using moderate moulding pressures. 

Sandstruck Brick. A brick (hand) moulded at 20 to 30% moisture, in a mould coated with sand to prevent sticking. 

Slop Moulding. The hand-moulding of building bricks by a process in which the clay is first prepared at a water-content varying from 20 to 30% depending on the clay. The wet clay is thrown into a wooden mould, pressed into the corners, and the top surface is finally struck smooth with a wet wooden stick. The filled mould is set on a drying floor until the clay has dried sufficiently to maintain its shape the mould is then removed and the drying process is completed. 

Wauk. A US term for a plastic clay body rolled and beaten to the rough shape of the mould, before hand moulding. 

Isomerised and cyclized rubber are chemically modified NR produced by the rearrangements of the bonds. Of these only cyclized rubber is available commercially. It is used in shoe soles, hand mouldings, heavy-duty industrial rollers, adhesives, bonding agents, reinforcing resins, corrosion-resistant surface coatings and printing inks. 

Method of manufacture Spray-suction Hand-moulded premix Extruded premix Pressed premix... 

The application of the colloidal method is certainly not new to ceramic powder preparation, for example, ancient applications include the cigeing of clays for hand moulding. In addition, colloidal methodology has been applied for more than one hundred years to prepare clay slurries for casting into porous moulds, usually plaster-of-paris, to form thin walled, complex shaped bodies. Colloidal methods are also commonly used to fractionate ceramic abrasive media to obtain a desired narrow particle size distribution, however their use prior to consolidation of a ceramic body to eliminate or reduce in size the common heterogeneities associated with ceramic powders, such as agglomerates and inclusions, is relatively rare. 

Slides Cars steel-pressing plant car assembly line hand lay-up of GFRP polymer moulding plant. 

Injection moulding - Elastomers Compression moulding - Composites Hand/spray lay-up - Composites... 

Polymerisation casting involves mixing monomer or low molecular weight polymer with a polymerisation initiator, pouring the mix into the mould and allowing polymerisation to occur in situ. A variation is to impregnate fibres with initiated monomer or other low molecular weight material and polymerise to produce composite structures. The main problem is due to the heat of polymerisation. Unless heat transfer distances are kept short or unless the reaction is carried out very slowly it can easily get out of hand. 

Polymers of a-methylstyrene have been marketed for various purposes but have not become of importance for mouldings and extrusions. On the other hand copolymers containing a-methylstyrene are currently marketed. Styrene-a -methylstyrene polymers are transparent, water-white materials with BS softening points of 104-106°C (c.f. 100°C for normal polystyrenes). These materials have melt viscosities slightly higher than that of heat-resistant polystyrene homopolymer. 

The cross-linking reaction is carried out after the resin has been applied to the glass fibre. In practice the curing is carried out either at elevated temperatures of about 100°C where press mouldings are being produced, or at room temperature in the case of large hand lay-up structures. 

For mass production purposes matched metal moulding techniques are employed. Here the preform or mat is placed in a heated mould and the resin poured on. The press is closed and light pressure ( 501bf/in ) applied. Curing schedules are usually about three minutes at 120°C. It is possible to produce laminates using less resin with pressure moulding than with hand lay-up techniques and this results in better mechanical properties. 

The resins are also used for coating on to moulds to give a good finish that is to be used for polyester hand-lay up operations. 

The Manual processes cover methods such as hand lay-up, spray-up, pressure bag and autoclave moulding. 

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