Spray-Up also known as chop method of creating fiberglass objects by spraying short strands of glass out
of a pneumatic gun. 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 without regards to strength.
It is very different from the hand lay-up process. The difference comes from the application of the fibre and
resin material to the mould. Spray-up is an open-moulding composites fabrication process where resin and
reinforcements are sprayed onto a reusable mould. The resin and glass may be applied separately or
simultaneously "chopped" in a combined stream from a chopper gun. Workers roll out the spray-up to
compact the laminate. Wood, foam, or other core material may then be added, and a secondary spray-up
layer embeds the core between the laminates. The part is then cured, cooled, and removed from the mould.
1. The mould is waxed and polished for easy removal.
2. The gelcoat (a smooth, hard polyester resin coating) is applied to the mould surface and is
given time to cure before re-applying. Usually two coats of gelcoat are used.
3. The barrier coat is applied to avoid fibre print and a rough surface through the gel coat.
4. The barrier coat is cured in an oven and left to cool to room temperature.
5. After curing, calcium carbonate and aluminium trihydrate fillers are added using a high shear
6. A wax-like additive is added into the resin to reduce styrene discharge by 20% during
7. A fibreglass chopper is mounted on the spray gun.
8. The mixture of catalyst, resin and fibreglass is then sprayed evenly in a fan-like pattern to
assure even coverage.
9. A roller is used for compaction after each layer has been applied, this removes trapped air.
10. Where desirable, wood, foam, or honeycomb cores are embedded into the laminate to
create a sandwich structure. Corner and radius coverage is also checked.
11. The part is cured in an oven and left to cool to room temperature.
Manufacturing Process12. The mould is removed and is ready to be waxed and polished for the next manufacture
13. Finishing is done by trimming edges of excess fibreglass and drilling holes as needed.
14. After the part is assessed by quality control personal, it is weighed, structurally checked, and
the surface finish is inspected prior to packing and shipping.
It is a very economical process for making small to large parts.
It utilizes low-cost tooling as well as low-cost material systems.
It is suitable for small- to medium-volume parts.
The processing steps are very similar to those in hand lay-up. In this process, the release agent is first
applied to the mould and then a layer of gelcoat is applied. The gelcoat is left for two hours, until it hardens.
Once the gelcoat hardens, a spray gun is used to deposit the fibre resin mixture onto the surface of the
mould. The spray gun chops the incoming continuous rovings (one or more rovings) to a predetermined
length and impels it through the resin/catalyst mixture. Resin/catalyst mixing can take place inside the gun
(gun mixing) or just in front of the gun. Gun mixing provides thorough mixing of resin and catalyst inside
the gun and is preferred to minimize the health hazard concerns of the operator. In the other type, the
catalyst is sprayed through two side nozzles into the resin envelope. Airless spray guns are becoming
popular because they provide more controlled spray patterns and reduced emission of volatiles. In an airless
system, hydraulic pressure is used to dispense the resin through special nozzles that break up the resin
stream into small droplets which then become saturated with the reinforcements. In an air-atomized spray
gun system, pressurized air is used to dispense the resin.
Once the material is sprayed on the mould, brushes or rollers are used to remove entrapped air as well as to
ensure good fiber wetting. Fabric layers or continuous strand mats are added into the laminate, depending
on performance requirements. The curing of the resin is done at room temperature. The curing of resin can
take two to four hours, depending on the resin formulation. After curing, the part is removed from the
mould and tested for finishing and structural requirements
Contact: Sia Yi
Add: Rm 909-910 Buiding B3 Biguiyuan xinggang international park Yingbing Road Huadu District Guangzhou City,Guangdong Province China.