Super-smart composites molding.

With intensive computerization and instrumented molds, this is like no other RTM you've ever seen.

For production of composites in the low- to medium-volume range - anywhere from 100 parts at a time to 20,000 a year - RTM has been gathering momentum as an alternative to labor-intensive open molding and capital-intensive SMC compression molding. However, RTM, as practiced in all but a handful of aerospace or automotive shops, has remained much as it was two decades ago - more art than science, more craft than rationalized industrial process. It remains a method in which the molder has relatively little real-time information on what is happening in the process and few "handles" by which to control it.

Gene Kirila is trying to do something about it. He is CEO and co-founder, with Jim Lapikas, of Pyramid Operating Systems in Greenville, Pa. Kirila seeks to elevate RTM to a new level of sophistication through an integrated "work cell" concept that incorporates computer monitoring and control of every facet of the process. His firm has also developed innovative tooling with in-mold sensors to give real-time data about the process.

Although Kirila does not like to call it RTM - his term is "Virtually Engineered Composites" or VEC - the basic process is still that of pumping liquid resin and catalyst into a closed mold that is laid with reinforcements. And the benefits are those that have always been cited for RTM: low tooling and labor costs and high quality and consistency. However, VEC has an ace up its sleeve that reportedly can reduce tooling costs and mold-changeover time well below those ever seen before in open or closed molding. The VEC system uses a novel "floating" mold design, in which the mold halves are actually empty pressure vessels filled with water and sealed with laminate skins that form the core and cavity.

Pyramid Operating Systems started out in 1984 as a manufacturer of physical-rehabilitation and fitness equipment. The company has since sold that segment of its business and has concentrated on developing and marketing its VEC system. Pyramid started VEC development in 1989 out of dissatisfaction with the variable performance and high cost of the composite parts it was purchasing from outside suppliers.

Today, Pyramid considers itself to be the only single source of a fully integrated system for molding large, complex structural shapes in low to medium volumes. The heart of Pyramid's system is its VEC 5.5 controller, or "operating system," which runs on a Windows NT platform. The rest of the work cell includes the floating mold, tanks, pumps, hydraulic power unit, heating/cooling unit, and air-filtration system.

The 24 x 24 x 18 ft cell module can be installed in three days in any factory space equipped with electricity and compressed air, Kirila says. The system is offered in a rental arrangement by which Pyramid becomes a long-term partner with its customer, supplying services in resin formulation, mold design, training, and troubleshooting. Pyramid provides off-site monitoring and technical support 24 hours a day, seven days a week. A digital hook-up allows video conferencing with the cell operator for instruction, preventive maintenance, or repair. Pyramid expects to install its first VEC system in a customer's plant during this second quarter.

"Basically, if you are a composites shop producing more than $5 million worth of product - typically 5000-7000 parts - per year, this system is for you," says Kirila. He claims that an open-mold composites operation that converts to the VEC system can lower its cost of materials, labor, and overhead by as much as 20%.

Big Brother is watching

Pyramid's VEC 5.5 "operating system" manages over 500 control inputs and outputs and uses "fuzzy logic" to adjust the many variables on a real-time basis so as to maintain reproducibility over time. The system manages and records parameters such resin storage, mixer, and mold temperatures, as well as flow rate, mass density, gel time, and peak exotherm - all on a real-time basis.

Although almost fully automated, the VEC system was never conceived as a "lights out" molding system, says Kirila. The VEC controller provides a variety of alarms, reminder lights, e-mail messages, and digital screens to help the operator manage the work cell.

The operator display is based on a pictorial representation of the cell. During the process, screens scroll down to guide the operator through each step. On top of each screen is a series of alarm buttons to signal non-conforming variables such as resin flow, temperature, or viscosity. Alarms require operator acknowledgment and automatically alert Pyramid's remote monitoring center to provide technical support. After the part is molded, the operating system prompts the operator to input quality-related data such as the hardness and gloss of the finished part. Those data are archived and displayed on a graph of performance over time.

Kirila says the VEC system is a help to molders who are seeking ISO 9000 quality certification because it reports all real-time processing parameters, as well as essential quality data and basic operational documentation.

One VEC system can control several molding cells. Additional cells can be added and networked together as the operation expands. Typically, one operator can handle molding operations for two parts, Kirila says.

The right stuff

Pyramid works with the molder to provide the appropriate materials system for a particular job. Designed-experiment studies are performed to determine chemical interactions between resin, reinforcement, filler, and additives, in order to establish the best combination of ingredients to meet part requirements. "We are trying to provide a simple formula for the guy on the shop floor," explains Kirila.

If desired by the molder, the selected materials may be shipped without additives that might cause chemical drift. This approach allows separate preweighed additives package to be supplied for manual addition at the point of use, minimizing possibilities of drift or measurement errors.

Bulk resins are stored on the upper deck of the VEC cell. The computer transfers the right amount of resin into the temperature-controlled mixing tank, which is mounted on load cells. The additives package is then added to the tank. After the batch is complete, it is transferred from the mixing tank to the temperature-controlled day tank. During processing, the resin flow rate into the mold is monitored ultrasonically. A redundant back-up also measures flow rate and will kick in if flow is lost or filters become clogged with dirt. Flow is also measured to ensure proper ratios of resin and catalyst during gelcoating.

As an example of the system's "intelligent programming," Kirila cites the controller's ability to automatically vary the catalyst level during injection so that the inside of the part cures at the same rate as the outside, thereby helping to optimize cycle time.

'Floating' mold cuts costs

A good part of what makes the VEC cell special is the patent-pending floating mold, which lowers tool costs, increases production flexibility, and shortens time to market. The floating mold was developed around the principle that some fluids such as water are incompressible, especially in the low-pressure molding ranges utilized by this process. Therefore, pressurized water can substitute for the rigid support structures that are usually built into composite molds. Those support structures account for much of the time and cost of mold construction.

The A and B portions of a Pyramid mold consist of two empty pressure vessels, which are basically open-top tanks outfitted with special attachment flanges. To create the mold cavity, male and female rigid composite laminate skins are fabricated over a master model in the usual manner. Each skin is bonded with a liquid-tight seal to its own pressure vessel. Once the laminates are bonded, the vessels are filled completely with water. The mold is heated and cooled by heat exchangers submerged in the water in the vessels.

"The cost of making the skin laminate is insignificant compared to other tooling technologies," says Kirila. A floating mold for a personal watercraft body reportedly costs about $15,600, versus $750,000 for an SMC mold and $42,000 for a spray-up mold. Low tooling costs mean that products can be scaled up from prototype to commercial volumes rapidly without large capital investments, says Kirila.

The floating mold concept is highly flexible to accommodate part design changes. Retooling - which involves merely supplying a new laminate covering for the fluid chamber - costs as little as $1000. Mold skin laminates can be changed in as little as 10 minutes.

Kirila says the process and tooling economics are not proportional to part size, as they are with SMC. Pyramid has used its floating mold to make parts as long as 12 ft and is preparing to mold a 17-ft boat hull.

A semi-automated process

During actual molding, the upper mold half is raised and lowered by a hydraulic lift/pulley arrangement. Top and bottom mold halves are held together with multiple hydraulic clamps located along the mold flanges. As the part is filled with resin, the load is transferred from the fluid inside the mold chamber to the outside of the steel vessel. The attachment flanges and all the necessary molding hardware are molded into the laminate skins.

Injection pressure is monitored in real time and controlled to between 5 and 60 psi to avoid disturbing the reinforcing fibers in the mold during fill. The mold design allows pressure, heat, and proximity sensors to be placed in the laminate skin to detect flow patterns and temperature changes during fill. Those sensor data, in turn, prompt the VEC system to make real-time adjustments in the flow. Heat exchangers and baffles can also be placed within the tool to heat and cool locally. The part is demolded based on sensing the actual exotherm achieved inside the tool. This is a more reliable means of achieving consistent cure than using a simple timed cycle.

Although much of the process is automated, manual operations are still necessary for placing reinforcements in the mold, spraying gelcoat, and removing parts - though a robot can assist in the last step. Pyramid is currently evaluating injectable gelcoats as a means of automating this step in the process. (The company is also looking into powder coating the tool or molded part.) Injectable gelcoats require an insert to be placed in the tool to achieve the proper coating thickness. After the coating gels, the tool is opened, the insert removed, and the tool closed again to shoot the back-up laminate.