Hot Runners Pages 35 to 50 Five Ways a Hot Runner Is Key to Processing Reinforced Materials By Tony Brodzeller Here are ive considerations that a hot runner supplier and a moldmaker/molder should discuss when using iber-reinforced materials, such as those with glass iller, wood ibers (lignite in biomaterials) and wool ibers: . Tip selection: The key with tip selection is maintaining appropriate heat as close to the gate as possible, while maintaining a reasonable pressure drop through the tip and balancing the gate vestige requirements. In addition, tip composition can greatly impact tip durability and longevity. For example, some carbide tips are warrantied for ive years (regardless of shot count) against normal wear caused by contact with abrasive and corrosive polymers. . Nut selection: The nut detail is how the hot runner inter-faces with the tool design. Does the gate detail have to be in the tool steel or can it be in the nut of your hot runner sys-tem? If you can live with the witness line on the part (from the temperature variation on the face of the nut relative to the surrounding tool steel), keeping the gate detail in the nut will allow much easier gate size adjustments or future service. If a molded sprue is allowed, consider tipless nuts. . Valve gates: Valve gates It’s important to manage the are frequently used, so it is important to con-expectations of supporting sider service-friendly the specifi cation, tool design, designs, pin hardness, installation and service of a parallel/cylindrical gate detail and premium hot runner system. guided carbide tips for durable systems that guide the valve pin before it enters the cavity, ensuring long gate life and clean vestige. . Gate size and gate land: An important relationship exists between the tip and gate detail, along with the cooling in the mold design. A long gate land will lead to high pressure and gate processing issues. A short gate land can leave a thin Image courtesy of Mastip. Torpedo Tip -Open Nut Torpedo Tip -Bush Nut Torpedo Tip -Sprue Nut Open Tip -Sprue Nut Tipless Sprue Nut Valve Gate -Open Nut Valve Gate -Sprue Nut Examples of tip and nut confi gurations. Nozzle Selection and Specifi cation Get your hot runner supplier involved early in the discussion and know the answers to these questions: • How are you planning to gate: directly to the part or with a short cold runner? • What is the exact material grade, total shot weight and material fl ow length? • What is the recommended processing temperature and is the material residence time-sensitive? • Does the molder/moldmaker understand gate size, expected fi ll time and allowable gate vestige? For high-temperature applications, use a larger nozzle body to get more steel mass in the nozzle body and a higher watt density heater to help maintain the higher temperature if you’re running PEEK at >700 ° F, for example. steel condition and fast gate wear. Discuss gate life, cosmetic requirements and resin concerns. . Manifold design and construction: The flow channels distribute the molten plastic to the individual nozzles, so carefully consider precise heater control and balanced flow, especially with an engineered-grade application. If long glass ibers are involved, keep the iber orientations in the same direction and allow a larger, smoother radius from the flow channel into the nozzle body. FOR MORE INFORMATION Mastip / 262-644-9400 tony.brodzeller@mastip.com / www.mastip.com Tony Brodzeller, Senior Technical Sales Manager, Mastip 50 M MoldMaking g Technology T — — JULY JU 2022