The method of fiberglass sprayup technology requires the use of equipment specialized for this work. Commonly called a “Chopper Gun,” this equipment meters the ratio of catalyst to resin, and chops the glass roving as the whole mixture is sprayed into the mold.
There are several techniques and styles of this equipment, but the normal components of the equipment are as follows. A center of the process is a resin pump which draws resin from buckets, drums, or tanks and delivers it out of a long hose to the operator”s gunhead. There is also a catalyst slave pump that is driven along with the resin pump and also has a hose out to the gunhead. An single air motor is mechanical force to operate these items. There is also sometimes a solvent tank at the equipment which has a line out to the gunhead for cleaning.
At the gunhead, the resin and catalyst meet one of two ways. There are internal and external mix gunheads, which each have pros and cons. The internal mix units have the solvent flush lines attached. There is also an additional airline or two feeding the gunhead for creating the resin spray fan. The gunhead has a glass chopper motor on the topside which turns continuous roving into chopped roving at a high rate.
So the gunhead has a bunch of hoselines running into it to result in a mixture of glass, resin, and catalyst coming out. Normally this equipment is completely run from a compressed air source. The only electricity required may be an electrical resin heater, though they are not really that common and can cause problems.
The adjustability of the equipment is one of its advantages. The catalyst-to-resin ratio can be set with on a sliding scale to hold the ratio from between .75% to 3%. There is an air manifold with regulators to control resin pump speed and resin pressure, as well as the refining air at the gunhead to develop a fan.
Safety is important with this equipment. There is not a lot of mass to the equipment, but there are a lot of pressurized hoses and chemicals. The movement of materials through hoses can create static electricity,
so the equipment must be grounded at all times. It must be inspected for worn or bulging hoses as well as leaking fittings.
The equipment is relatively straight forward and can be inexpensive, but does require a lot of understanding in how it works in order to achieve good results.