![]() Airless spray guns are becoming popular because they provide more controlled spray patterns and reduced emission of volatiles. In the other type, the catalyst is sprayed through two side nozzles into the resin envelope. Gun mixing provides thorough mixing of resin and catalyst inside the gun and is preferred to minimize the health hazard concerns of the operator. Resin/catalyst mixing can take place inside the gun (gun mixing) or just in front of the gun. The spray gun chops the incoming continuous rovings (one or more rovings) to a predetermined length and impels it through the resin/catalyst mixture. ![]() Once the gelcoat hardens, a spray gun is used to deposit the fibre resin mixture onto the surface of the mould. The gelcoat is left for two hours, until it hardens. In this process, the release agent is first applied to the mould and then a layer of gelcoat is applied. The processing steps are very similar to those in hand lay-up. The length of the mould is shortened or lengthened using inserts and mould secondaries such as windows, air vents, and propeller shaft tunnels. Several different hull sizes can be made using the same mould. The mould is made by taking the reversal of a male pattern. The outer shell of the mould is stiffened by a wood frame. In the boating industry, a single-sided female mould made from FRP ( fibre-reinforced plastic) is used to make yacht hulls. To make shower bathtubs, a male mould is used. Steel, wood, GRP, and other materials are used as mould materials for prototyping purposes. In filled resin systems, fillers replace some of the reinforcements 5 to 25% filler is used by weight. The most common fillers are calcium carbonates and aluminium trihydrates. The resin often contains a significant amount of filler. Fast-reacting resins with a pot life of 30 to 40 minutes are typical. The most common resin system used for the spray-up process is general purpose or DCDP polyester isophthalic polyesters and vinyl ester resins are also sometimes used. The weight fraction of reinforcement in this process is typically 20 to 40% of the total weight of the part. Continuous strand mat, fabric, and various types of core materials are embedded by hand whenever required. The most common material type is E-glass, but carbon and Kevlar rovings can also be used. For improved mechanical properties, a combination of fabric and chopped fibre layers is used. The basic reinforcement material for this process is glass-fibre rovings, which are chopped to a length of 10 to 40 mm and then applied on the mould. Bathtubs, swimming pools, boat hulls, storage tanks, duct and air handling equipment, and furniture components are some of the commercial uses of this process. The part is then cured, cooled, and removed from the mould.Īpplications include making of custom parts in low to medium volume quantities. ![]() Wood, foam, or other core material may then be added, and a secondary spray-up layer embeds the core between the laminates. Workers roll out the spray-up to compact the laminate. The resin and glass may be applied separately or simultaneously "chopped" in a combined stream from a chopper gun. Spray-up is an open-moulding composites fabrication process where resin and reinforcements are sprayed onto a reusable mould. The difference comes from the application of the fibre and resin material to the mould. It is very different from the hand lay-up process. Corvette fenders and boat dinghies are commonly manufactured this way. This method is used often when one side of the finished product is not seen, or when large quantities of a product must be made cheaply and quickly with moderate strength requirements. Spray-Up also known as chop method of creating fiberglass objects by spraying short strands of glass out of a pneumatic gun.
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