Molding Machine Builder Breaks the Mold

Wilmington Machinery was founded more than 35 years ago to produce structural foam injection molding machines. Although its specialty is structural foam plastic products, Wilmington has expertise in gas-assist molding, solid molding and various other injection molding techniques. As well as structural foam machinery, Wilmington builds a highly successful line of continuous rotary extrusion and coextrusion blow molders for very high-volume production of polypropylene and polyethylene bottles.

Wilmington Machinery systems are sold globally with machinery located in Mexico, South America, Europe, Canada and the U.S. Sales are accomplished via a team of international sales and service representatives combined with a high level of direct sales assistance from our office in the U.S. “Manufacturing is done at our 65,000 ft2 facility located in Wilmington, N.C., which has one of the larger ocean ports on the east coast,” explains Jeff Newman, vice president, sales and marketing. “We employ on the average 25 to 30 employees.”

Foam Mold, Anyone?

The structural foam machinery is designed for several specific industries which include the broad category of material handling—pallets, collapsible bins and crates—underground boxes and drainage control and a category of miscellaneous that could include battery boxes, outdoor storage units, automotive, brush handles, construction and playground equipment. “The structural foam machinery requires a wide variety of automation controls including temperature, position, speed, sequential and operator interface screens, alarms and machinery/operator safety, to name a few,” says Newman. “The controls are PLC-based and utilize extensive digital networks to interface drives, remote I/O and operator stations. The machinery is highly customized for individual applications, which allows them to serve a wide variety of markets.”

Primary machine control utilizes commercial components and software only, while some other components with custom programming for things like temperature control, closed CE-based OIT and MACO smart cards also are used, says Newman. Machines can be hardwired or connected to a digital network such as DeviceNet, Modbus Plus or EtherNet/IP. “All machines are designed to meet ANSI/SPI safety standards,” says Newman. “This includes the use of door and e-stop safety interlock relays as well as two-hand control and presence sensing. We also use Allen-Bradley safety connection systems.”

Future Tech

Web-enabled controllers and distributed systems for remote diagnostics/configuration/SPC are at the top of Wilmington’s new technology list for investigation, says Newman. “The size of the components, ease of application, speed, features, cost, technical support and improving safety are what drive our innovation,” he says. “And today’s use of remote I/O with digital networking is standard given the large physical size of the machinery. It has reduced our cost to build the machines. Innovation in improved offering in the operator interface station is very important since, to many customers, the simplicity and ease of the operating screens translates to the quality of the machine control.”

Some other predictions from Newman include increased robustness and safety in wireless control, more green technology, improvements in remote I/O devices and in drive, sensor and heater technologies.

“There also will be a larger selection of hardware with Ethernet compatibility, eliminating the need for pulling wires,” says Newman. “And the size of components will continue to be reduced to allow smaller control panels, especially as it relates to large hp motor drives. Faster processors, more compact controllers, wireless communications and the use of more user friendly operator controls all will be required for the future. Each new generation of machine design will have greater connectivity options that are easy to implement, friendlier human interfaces, easier ways to troubleshoot problems, especially remotely, more reliability, more value, a smaller footprint, better energy-efficiency and more safety for the end user.”

Big Machines for Big Jobs

Wilmington’s structural foam machinery is based on a large platen injection molding system. “The system utilizes large 32:1 L/D extruders with special screw and barrel designs to accommodate the injection of gas, typically nitrogen, into the barrel to create the foam,” explains Newman. “The material is extruded and stored in a large accumulator that can handle as much as 150 lb of molten plastic and gas. The material is quickly shot through a manifold and nozzle system into the mold where the foam is allowed to decompress and expand to the shape of the mold. The machines can be quite large with multiple platens each weighing as much as 80,000 lb each.”

The extrusion, manifold and nozzle system also require precise heat control and sometimes as many as 100 zones of temperature control for both heat and heat/cool scenarios, says Newman. “The speed and positioning of the accumulator and large platens must be precisely controlled to produce the highest quality parts. The same is true for the speed of the extruder melting the plastic.”

In the design and build of such large complex machinery a team of mechanical, electrical, control and design engineers are utilized to understand, document, design and validate the successful completion of each large machine at Wilmington. “It’s not unusual for the engineering hours to match the labor hours required to assemble,” explains Newman. “The engineering team and service engineers work closely together during the final assembly and validation of the machine prior to customer acceptance and shipment. The R&D team is the same team that implements the design along with key managers from purchasing, assembly and sales. This allows for a greater contribution of creativity and to make sure we are including the latest component design and technology. Presently we have 10 people in our technical department including mechanical engineers, controls engineers, process engineers, designers and technicians. The R&D team is made up of a combination of the above. Size of projects will dictate who and how many.”