SITE Manufacturing (Redding, Calif.) has taken knowledge acquired during more than 23 years of producing hi-tech carbon composite components, such as telescope housings (for Celestron, see story on p. 20), and applied it to the sport of paintball. "One year around Christmas, we decided we wanted to do something else,"
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SITE Manufacturing (Redding, Calif.) has taken knowledge acquired during more than 23 years of producing hi-tech carbon composite components, such as telescope housings (for Celestron, see story on p. 20), and applied it to the sport of paintball. "One year around Christmas, we decided we wanted to do something else," quips SITE plant manager Dave Weir. "So we cleared the table and spent the next three months designing and developing an all-carbon-fiber composite paintball gun barrel." The result was the ST!FFI, a tournament-quality barrel with a stepped bore (0.002 larger at 5 inches) available in one of a variety of bore sizes in 10-, 12-, 14- or 16-inch (254 mm, 305 mm, 356 mm or 406 mm) lengths or as part of a ST!FFI SW!TCH kit (with nylon carrying case) containing a 0.695-inch bore barrel with four interchangeable sizing breeches (0.685 to 0.691 inch, in 0.002-inch intervals) used to adapt the barrel to slight differences in available paintball ammo.
Barrels were designed with the aid of SolidWorks 3-D design software from SolidWorks Corp. (Concord, Mass.), using woven carbon prepreg impregnated with a toughened hi-tech polymer epoxy resin, supplied by Bryte Technologies (Morgan Hill, Calif.) with fiber-to-resin ratio controlled to within ±3 percent resin content. Plies of prepreg are precision cut to within ±.005 inch (±0.127 mm) on a programmable computer-controlled cutting table from Eastman Machine (Buffalo, N.Y.), then table-rolled onto a tubular polished metal mandrel (precision ground to within ±.0005 inch) and vacuum bagged. SITE claims that barrels are molded to a tight ±.0005-inch tolerance on the bore size.
The bagged parts are then autoclave-cured at 121°C/250°F. Following cure, the barrel exteriors are precision ground to a fine satin finish, drilled and ported for noise reduction. Then a black anodized aluminum collar, threaded to fit the desired brand of gun, is bonded to one end, using a high-grade bonding agent supplied by 3M Co. (St Paul, Minn.). Weighing only 53g/2 oz, the ST!FFI barrel is three to seven times lighter than metal barrels and shoots straighter, due to its glass-like interior surface and dimensional stability (courtesy of carbon's zero co-efficient of thermal expansion). A new variation is the MAMBA ST!FFI SW!TCH kit, featuring a carbon/Kevlar outer weave in colors red or black. Prices for single barrels (factory direct) run $109 to $119 (USD). Kits begin at $209, including a single barrel and four sizing breeches.
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Composite parts are formed in molds, also known as tools. Tools can be made from virtually any material. The material type, shape and complexity depend upon the part and length of production run. Here's a short summary of the issues involved in electing and making tools.