A hot runner systems supplier proves that upstream analysis helps to prevent a part project’s downstream paralysis.

One of the world’s leading manufacturers of irrigation equipment for golf courses and landscaping, Hunter Industries (San Marcos, CA), has a saying that it believes is fundamental to its success: “Customers come first—always.” It regularly coordinates customer feedback sessions, for instance, which it believes are vital to its growth and success.

In one recent case, a case involving the hot ­runner molding of a complex, micromechanical irrigation system component in a mildly hygroscopic engineering resin (acetal), Hunt­er succeeded because of its supplier’s willingness to put Hunter’s interests first.

Hunter sourced very small nozzles that are engineered for the runnerless molding of materials like acetal. They’re supplied by Thermoplay SpA (San Martin, Italy). Thermoplay products and resources are represented in the United States through Alba Enterprises Inc. (Rancho Cucamonga, CA).

The smallest nozzle Thermoplay has developed is 0.394 inch (10 mm) in diameter, the size Hunter’s application called for. Other factors influencing the selection of this nozzle included a production requirement—the need for hot-half ejection—and a key part design element: a minimum gate vestige of just 0.008 inch (0.2 mm).

Hard- and software testing

Alba and Thermoplay put Hunter Industries’ interests first, rather than just selling it an off-the-shelf product. They performed extensive upfront analytical work to ensure the project’s success.

After Hunter supplied Alba and Thermoplay with the application material for sampling purposes, Thermoplay ran a number of molding tests to verify the operational behavior of the small nozzles the project required. Also, since the part’s geometry was extremely critical, Thermoplay performed flow analysis to simulate moldfilling, and to determine whether or not the hot runner system it recommended for the application was suitable, especially with the minimal gating dimensions required.

“Using POM in a hot runner is very critical, as it requires the melt temperature to be consistent,” says a Thermoplay source. “Otherwise, the material degrades with subsequent filling and causes functional problems in the part.”

In addition, acetal is a high-density material, one that usually requires high injection pressures. “Normally, this is a problem for injection with small nozzles. But in the results of the analyses we made, we found that there were no particular problems warranting the use of high injection pressure,” says Thermoplay. “Such high injection pressures can cause the overheating of the material with this type of extremely small nozzle, even with a minimum gate diameter of around 0.031 inch.”

Through its upfront simulations, Thermoplay was able to work with Hunter’s engineers to ensure the delivery of systems incorporating a workable compromise, one that has resulted in this application’s successful launch.

Problem solved

“We were looking for a direct-gate solution to a small, complex acetal part with mechanical movement in the hot half,” says a source at Hunter Industries. “The recommendation of the Thermoplay F-11 nozzle gave us the size of hot runner system we required. And Alba and Thermoplay gave us the documentation, analysis, service, and follow-through to make the project a success.”

Today, Hunter is using five four-drop Thermoplay systems that are running with a fill time of 0.6 second. What’s more, they’ve recently ordered another one.

Thermoplay’s F-11 nozzles are designed and built for running both in restricted areas and in applications requiring gate feed on an inner part surface where long nozzles with very small diameters are required.

Alba Enterprises Inc. | www.albaent.com
Hunter Industries | www.hunterindustries.com
Thermoplay SpA | www.thermoplay.com