High cycle rates, short cycle times

NSK introduces the advanced HTF-SRM series, a high-speed, heat-resistant version of its ball screws for heavy-duty drive applications. This innovative new product is ideal for electric injection molding machines that need to produce thin-walled products with high cycle rates and short cycle times. The HTF-SRM ball screw achieves the highest speed and heat resistance ratings in the industry thanks to NSK's newly developed "RM Recirculation System" and heat resistant materials and parts.

Electric injection molding machines need high cycle performance to improve productivity and meet the increasing demand for plastic products - a demand driven by the growing global population and rising living standards in emerging markets. They also need to be able to mold thin-walled parts to reduce plastic consumption and reduce the environmental impact on the planet in line with the United Nations SDGs (Social Development Goals) and climate neutrality initiatives.

With this in mind, there is a demand for electric injection molding machines equipped with heavy-duty ball screws to enable both higher cycle speeds and the molding of thin-walled parts. However, high cycle speeds also mean higher operating speeds, which in turn require countermeasures to manage the associated heat build-up.

NSK has overcome this challenge with the SRM (Smooth Return Metal Coupling) recirculation system. One of the technical challenges associated with higher speeds is the increased impact force on the recirculating ball bearing guide, which leads to damage to the recirculating ball bearing guide and ball screw shaft components. NSK found the solution by using its Digital Twin technology to optimize recirculating ball bearings.

The resulting SRM ball recirculation system offers smooth ball recirculation and improved heat resistance, breaking through the limitations of conventional plastics. This innovation is supported by the use of heat-resistant materials for the ball screw seals and resin components.

Thanks to these advances, the permissible d-n value (shaft diameter x speed) is 200,000, a 40% improvement over NSK's conventional HTF-SRC high-speed ball screws. In addition, the maximum operating temperature is 90°C and the short-term maximum temperature is 100°C, both 20°C higher than NSK's conventional products.

Importantly, the external dimensions of the screw and nut match those of the HTF-SRC ballscrew, allowing for an interchangeable design that requires no changes to the injection molding machine when upgrading.