In Process: Nylon casting process does prototyping, mass production

A new method of creating plastic parts without dies allows prototyping service bureaus to expand and enhance current product offerings, and it lets manufacturers produce short runs without the sometimes prohibitive costs.

Called Compcasting, this process enables the molding of fiber-reinforced nylon 6 as easily as casting epoxy and urethane tooling plastics, using traditional low-cost rapid tooling molds. Compcasting is a patented rapid prototyping/production process for molding structural, fiber-reinforced nylon 6 and other thermoset resins. Compcast Technologies LLC (Barnegat Light, NJ) holds the rights to license the process from its creator, Matti Holtzberg.

The equipment to implement this process is currently available only from Gusmer Corp. (Lakewood, NJ). After obtaining a license and equipment, a plastics company or rapid prototyping service bureau can go from a CAD file directly to a fiber-reinforced nylon 6 structural production part in as little as one day using the rapid tooling Compcast process.

This quick turnaround begins with the building of a mold from a CAD file. A pattern is typically created (using SLA, SLS, FDM) in the same media traditionally used for casting urethane prototypes: rubber, plastic, plaster, and sand. Even lost-core technologies employing quick-melting, eutectic alloy cores can be used due to the lack of high injection pressures when making the part.

The next step involves the anionic polymerization method to manufacture fiber-reinforced nylon 6. A Gusmer Model RP-10, fiber-reinforced nylon 6 dispensing machine mixes the monomer caprolactam from which all nylon 6 is manufactured, using an activator. With the resultant slurry heated to 140 to 150C, fiberglass reinforcement then gets mixed in via the machine?s agitator. To initiate polymerization and the casting of parts in one operation, the catalyst is dispensed from a separately heated tank. The catalyst is automatically injected in the proper proportion into the stream of activated, fiber-reinforced caprolactam just prior to entering the mold.

As the materials are dispensed, gelation has already begun, and the mixture thickens to a denser slurry. Once in this state, the fiber reinforcement cannot fall out of suspension. The RP-10 dispenses fiber-reinforced nylon 6 into a mold, which has been preheated to a temperature of 140 to 150C. The fiberglass-reinforced nylon 6 then polymerizes into a structural part within seconds.

The flexibility of the process and the options available for the RP-10 dispensing machine allow single dispensing units for one-off rapid prototyping on up to full-scale production part manufacturing.

In all cases, a single-cast, fiber-reinforced nylon 6 part has identical properties to parts manufactured in a production run. Such nylon 6 parts are identical in form, fit, and function to those parts fabricated in a high-pressure injection mold. Additionally, rapid molds may now produce as many as 1 million to 2 million nylon 6 parts with the Compcast process.

As many as 30 duplicate molds can be set up on a single carousel, with the RP-10 machine continuously filling each mold as it passes the dispensing nozzle. With a shot capacity and rate of up to 1 lb/sec and the ability to feed multiple molds quickly, even large production runs of car parts can reportedly be manufactured 60 percent faster than with a traditional injection molding process.

For more information contact Gusmer Corp. at (732) 901-2752 or visit www.gusmer.com.

Multimaterial press, cube tool help molder get a handle on big project

Tackling any part program will require some investment, even if it?s just in worker hours, but taking on a job that demands 4 million parts per month can require far more than that. For McKechnie Plastic Components (Easley, SC) it required two new multimaterial machines, a 90° rotating stack mold, a specially designed preform conveyor, and when all that was added up, more than $1 million in capital.

The brand new machines, 450-ton Milacron (Batavia, OH) K-TEC multimaterial presses, now operate 24/7 using a Foboha 90° rotating stack mold featuring 32 cavities per side to produce two-shot screwdriver handles for Stanley?s redesigned Thrifty brand. Both shots are polypropylene, one black and one yellow, and the parts are allowed to cool at a hold station between the first and second shots. After both shots are completed, the handles are taken by tubular receivers on a special conveyor because they retain latent heat and could deform if mishandled.

The Milacron K-TECs themselves have 900 mm between the tiebars, and when fully opened, the platens reveal 2500 mm of daylight, which is more than enough to accommodate Foboha?s cube tool. The machine?s injection units have a capacity of 1031g, and the alternate material?s side unit features an electric drive for its screw.

For more information contact McKechnie Plastic Components at (864) 859-7548, www.mpcsc.com; or Milacron at (513) 536-2428, http://plastics.milacron.com.