New valve needle cylinder for hot runner system stability improvement
September 30 10:17:48, 2025
Ben Somme, Germany, October 2005 – In the field of long glass fiber injection molding, achieving greater product stability is a key challenge. As the length of the glass fiber increases, so does the structural stability of the final product. Each additional millimeter of fiber contributes to improved mechanical properties, such as strength, impact resistance, and dimensional stability. To meet this demand, Synventive Molding Germany, based in Bentheim, introduced an innovative valve needle cylinder for its hot runner system. This new design features a significantly larger stroke and an optimized flow path, allowing for better retention of long glass fibers during the injection process.
The development was driven by the need to maximize fiber length in applications where enhanced performance is critical. The use of long fibers is becoming more widespread, not only in fiberglass granules and fiberballs but also in filament yarn blending processes. These trends highlight the growing importance of maintaining fiber integrity throughout the molding cycle.
A major factor in fiber degradation is the metering device, which can cause shortening if not properly designed. Injection molders must focus on preserving fiber length, while the gate remains a critical stress point. By using larger gates, rounded corners, and runners that do not interfere with the valve needle, stress and shear forces can be minimized, protecting the fiber material more effectively.
The new Synventive HYC 4018 and PNC 7518 (Hydraulic / Pneumatic Drive) systems offer numerous advantages. They enhance the service life of valve pins and hot nozzles, reduce fiber breakage, and improve overall part quality. Benefits include reduced shrinkage, less warpage, better flow characteristics, and lower anisotropy. Additionally, the thermal expansion coefficient is minimized, leading to more consistent product dimensions.
Another significant advantage is the reduction in skin thickness, which makes products lighter and shortens cooling times, thereby increasing production efficiency. The new valve needle cylinder also includes features like height-adjustable valve stems, lockable and externally adjustable stems, and a patented needle bushing with effective cooling technology.
This advanced solution is ideal for industries such as automotive, household appliances, and electrical and power installations, where high-performance materials are essential. By focusing on maximizing fiber length per millimeter, Synventive continues to provide value to injection molders and manufacturers, delivering superior performance and long-term reliability.