High Power, High Speed, All Electric Injection Molding System from Moog Offers New Options for Machine Builders

by Burkhard Erne, Business Manager, Moog ProControl; Choonman Kim, Plastics Market Manager, Asia Pacific; Sunil Murthy, Marketing Manager, Americas

Today’s injection molding machine manufacturers are experiencing rising resin costs driven by high petroleum prices, increasing demand for thin walled parts from the electronics and automotive markets and growing environmental regulations mandating clean and quiet factory floors.

These market drivers combined with increasing competition are requiring Injection Molding Machine OEMs around the world to look for avenues to add value and to differentiate their machines from their rivals.

These trends are prompting Injection Molding Machine OEMs increasingly to favor more electrical motion control solutions in their new machines. Electric motion control solutions offer benefits such as higher productivity and increased precision together with the advantage of oil free operations and lower noise levels than the existing hydraulic designs.

Moog has been a leader in providing high performance motion control solutions to plastics machines OEMs for over 30 years. As experts in hydraulic, electric, and hybrid technologies, Moog is uniquely able to recommend the best solutions for machine builders based on their specific needs. In the last issue, we featured our newest hydraulic solutions and this article focuses on a specific electric motion control solution developed by Moog that improves precision and energy consumption of injection molding machines with the direct benefits of reduced resin usage, lower energy costs and improved part quality.

Moog High Power, High Speed, All Electric Injection Molding System

In 2005, Moog acquired Switzerland-based ProControl, a company with great expertise in motion control solutions for injection molding machines. ProControl and Moog have had a very successful partnership since 1991, marrying the building block products from Moog and the application expertise of ProControl. Moog ProControl has vast experience in the marketplace to help address the challenges faced by the injection molding OEMs as they create new all electric machines.

This Moog ProControl collaboration has resulted in a truly innovative approach to precise control of the injection axis: the new High Power, High Speed, All Electric Injection Unit. This unique alternative uses a non-linear actuator and direct drive servomotor to drive the injection screw vs. traditional ball screw and timing belt arrangements. The resulting solution offers impressive results in higher productivity, greater efficiency, and lower maintenance, while being scalable and versatile in adapting to many machine sizes and different applications.

Various OEMs have expressed interest in the All Electric Injection System and Moog has collaborated with an industry leader in Asia to develop 2 machine sizes (60 ton and 110 ton) initially with an All Electric Injection System. This customer has sold the two machines to an end user in a mobile phone application and placed additional orders with Moog. The customer plans to extend his range of machine sizes based on the All Electric Injection System concept.

How Does It Work?

Injection Actuators Nonlinear Characteristics

The High Power High Speed Injection System consists of an injection and a plasticizing unit. On the injection axis, a High Torque Direct Drive Servomotor works together with a planetary gearbox and a nonlinear actuator to provide the translational movement of the injection axis. Another High Torque Direct Drive Servomotor rotates the plasticizing screw. Closed-loop injection speed is based on the feedback of the angle of the nonlinear actuator and its angular velocity. A load cell is used to control force in a closed-loop.

Benefits of the Moog All Electric Injection Molding System

• Tailored for Thin Wall Applications: Machines for molding thin-walled parts require higher injection speeds, response, and injection pressures to fill complex molds in a mere fraction of a second. The Moog All Electric Injection System uses a non-linear actuator and High Torque, Direct Drive Servomotor to drive the injection screw. This reduces overall inertia and maximizes energy efficiency, making more power and higher speed available in a shorter time compared with the ball screw/timing belt arrangements widely used on all-electric injection molding machines.

• Higher Productivity: Moog’s All Electric Injection Molding System is designed to improve productivity. By reducing the inertia of key elements in the system, injection rates have been significantly improved, which leads to faster fill times.

• Greater Efficiency - More Shots for the Same Energy: A high power density Direct Drive servomotor is used to drive the plasticizing screw, providing the best energy efficiency.

• Low Maintenance - A Key to Higher Up Time: The Moog All Electric Injection System is a truly robust solution for molding of thin walled parts on small-to-medium-sized high performance machines. Its non-linear actuator is designed to be low-friction and durable for reduced maintenance burden and total cost of ownership. The MTBM (mean time between maintenance) is 30,000 hours.

• Higher Precision Leading to Lower Material Costs: The low-friction design of the Moog All Electric Injection System, which keeps system heat lower, combined with Moog’s patented method for superior pressure control during the transfer between injection and holding phases, allows the Injection System to maintain tighter tolerances on shot weight to reduce raw material costs.

• Versatility - Easy Adaptation for Different Applications: The Moog All Electric Injection System also can be used to produce thick walled parts such as lenses. The non-linear characteristic of its actuation system closely matches the molding process for thick wall parts where only force or speed is required at one time. This allows longer hold-on time at higher pressure, with minimal power consumption. In contrast, the linear actuation typical of most all-electric machines requires hold-on pressure to be reduced very quickly to avoid overloading the injection axis servomotor and drive.

• Scalability from 50 tons to 4000 tons: The actuator system of the All Electric Injection System may be scaled up and down easily for various speed, torque, and power requirements for small-and-medium sized machines. With some additional modifications to the gearbox the All Electric System can be scaled up to 4,000 tons.

Demonstration Unit Data

The 200 - 250 ton demonstration unit of this solution has been tested for over one year and has produced injection speed of 600 mm/s, acceleration time of 35 ms, injection power of 300 kW, and 80% holding pressure (unlimited time).

Summary

The All Electric Injection System is one example of how Moog applies its motion control expertise to help companies achieve high performance and differentiate their machines from others in the marketplace. Our ability to collaborate with our customers and deliver solutions tailored around their unique needs, is illustrated here by effectively embedding application-specific knowledge in a high performance combination of motion control software, drives, motors and mechanical actuation. Moog’s long time leadership in motion control for plastics machines now includes many unique electric, hydraulic, and hybrid solutions that are offering new options for machine builders contemplating future designs.

Burkhard Erne is the Business Manager for Moog ProControl, the Switzerland-based company focusing on Motion Control Solutions for the plastics industry. He has joined the ProControl team in 1984. He has a Bachelors Degree in Mechanical Engineering.

Choonman Kim, the Plastics Market Manager in the Asia Pacific region based in Korea, is responsible for the plastics engineering team in this region and for the development and support of solutions for specific customer requirements in the plastics market. He has worked at Moog for 18 years, mostly in the plastics machines industry. He studies Electronics Engineering at University.

Sunil Murthy is the Marketing Manager for Americas. His previous experiences have been in the semiconductor manufacturing, software and automotive industries. He has an MBA in Business Management and Ph.D. in Electrical Engineering.