For a while, the phrase "paradigm shift" seemed to appear way too often in literature and lexicon, though the term has been heard less frequently since the dot.com meltdown. But leave it to one of the backbones of American manufacturing, the plastics industry, to come up with a true paradigm shift in a new method of creating plastic parts that blurs the distinction between prototyping and production runs -- hence spawning a new term, ProDotyping™. By avoiding the expensive and time-consuming process of creating an injection molding die, a brand new process and its associated machinery lowers plastics prototyping and production costs while dramatically speeding time to market.
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. Until now, rapid tooling processes have been reserved for making prototype parts or models out of tooling plastics. Yet Compcasting, and its associated machinery, makes it possible to go from a CAD file to creation of full-scale, production Nylon 6 parts in as little as a day. The significance of this new technology is that prototyping service bureaus can flow right into the production end of the market, and manufacturers can produce very short runs if they so choose. At least for Nylon 6 applications, this is a major development.
The Problem With Previous Technologies
As one of the most common polymers used for fibers and in injection molding, Nylon 6 finds numerous applications in the automotive parts industry (intake manifolds, valve covers, water pumps, radiator fins, fan shrouds) as well as for power tool handles, appliance parts and enclosures. However, as with most plastics, the creation of Nylon 6 production parts has traditionally begun with a trip to a rapid prototyping service bureau with a CAD file. These bureaus then translate the design file into an STL file, and ultimately into a prototype model via a choice of Stereolithography (SLA) Selective Laser Sintering (SLS), Laminated Object Manufacturing (LOM) or Fused Deposition Modeling (FDM).
Convinced of the potential by a prototype model, plastics manufacturers then had to swallow hard and take the next big step: create an injection-molding die. For decades, though, plastics manufacturers have sought to find a way around commissioning these highly expensive dies that often represent a six-figure investment. For small- or medium-sized manufacturers, the cost was prohibitive.
These molds are expensive because they must be designed to withstand extremely high pressures. With injection molding, plastic pellets are melted and forced under very high pressure into the die cavity. Once solidified, the properly shaped product is then de-molded. Production quantities are achieved, but at quite a price in terms of cost and time. Plastics injection machines and their complicated ancillary systems such as hot runners (including nozzle tips, heaters, manifold thermocouples, piston and valve stem assemblies) are also prohibitively expensive to purchase and maintain, putting them out of reach for smaller, startup operations.
Clearly, the high cost of bringing new injection-molded products to market has limited expansion of the use of plastic parts. Even the alternative of metal rapid tooling (directly from a CAD file) has, until now, proved suitable only for small quantities of injection-molded parts.
Understanding the New Process
Compcasting, developed and licensed by Compcast Technologies, LLC of Barnegat Light, NJ, is a patented rapid prototyping/production process for molding structural, fiber reinforced Nylon 6 and other thermoset resins.
The equipment to implement this process is currently available only from Gusmer Corp of Lakewood, NJ, a leading supplier of plural-component mixing, proportioning, and dispensing equipment. This equipment is integral to the success of the Compcasting Process; it cannot be accomplished without the correct dispensing machinery.
Once the proper license and equipment are in hand, 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 building 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 using quick melting, eutectic alloy cores can be used due to the absence of high-injection pressures when making the part.
The next step simply involves the traditional 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, with an activator. The resulting slurry is heated to 140-150°C, and 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 right 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 directly into a mold, which has been pre-heated to a temperature of 140-150°C. 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.
Time and Money Savings
The capability of making a part using rapid tooling, as opposed to metal injection molds, dramatically reduces the time and money it takes to lead a product from the drawing board to market.
Using the RP-10 Nylon 6 dispensing machine, rapid prototype and production molds can be created quickly, skipping the tremendous expense and typically long wait (occasionally months) for the milling of metal injection dies. Additionally, rapid molds may now produce as many as 1-2 million Nylon 6 parts with the Compcast process.
Compcasting also eliminates the need for injection molding pellets. In the case of fiber-reinforced Nylon 6, a preceding compounding step involves heating the Nylon until it softens enough to add fiberglass. This not only saves time, but also production costs, since the compounder -- who traditionally adds his fee -- can be completely sidestepped.
Because of the efficiencies built into the Compcasting machinery, production runs can be executed at an accelerated pace over injection machines. Since Compcasting molds are significantly less expensive to make, it becomes far more cost effective to have multiple molds with this 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 size" as large as one pound per second, and the ability to feed multiple molds quickly, even large production runs of car parts (such as intake manifolds) can be manufactured 60% faster than with injection molding machinery.
The savings extends to cost-per-part, as well. At a minimum, molds can be developed at 80-90% of the price of steel dies. Additionally, Compcasting machinery costs up to 66% less to purchase than heavy, high-pressure injection molding machines. In some applications, the overall Compcast Process has proven 50% less expensive, by conservative estimates, than conventional injection molding, even in high production runs.
In many cases, the efficiencies and cost benefits afforded by the Compcast process can spell the difference between bringing a product to market or scrapping the project in the first place, especially when dealing with production quantities of less than 100,000. In such relatively small quantities, the up-front cost of creating a robust, high-pressure injection die can sometimes never be amortized over the production run. In effect, this new ProDotyping way of doing business really has created a paradigm shift for those plastics manufacturers who wish to profit from innovation.
