Page 22 - MetalForming February 2017

Servo-Driven Presses
Mechanical presses serve ably and have applications where they are the ideal choice. But servo-driven presses often get the call in demanding applications and bring whole new levels of flexibility. When choosing, consider this input on energy use and ROI.
BY LOUIS A. KREN, SENIOR EDITOR
There’s no doubt that North Amer- ican manufacturers have become educated on the basics and nuances of servo-driven stamping presses. But we’ve noticed that there are some questions related to energy management and cost of ownership as compared to traditional mechanical presses. With that in mind, MetalForm- ing reached out to an industry expert, Shrinivas Patil, product manager for Aida-America (www.aida-global.com) for his perspective. Here he details energy management and return on investment (ROI).
MetalForming: Metalformers have expressed concerns about energy usage and how servo-driven presses compare in energy management. Can you address how press builders have lever- aged technology to reduce energy usage, especially energy demand dur- ing peak rate periods?
Patil: Mechanical presses use fly- wheels to store energy and then provide it during forming operations. On the servo-driven-press side, there are a few alternatives. Some press builders employ a flywheel-based energy-man- agement system (EMS). For our part,
Answers on Energy Management and ROI
20 MetalForming/February 2017
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Servo-driven presses employ technologies such as capacitors and smart systems that efficiently manage energy use, helping to provide improved returns on investment.
we choose a capacitor-bank EMS, where capacitors store energy in DC form, with capacitor sizes based on a user’s speed and stroke requirements. Here, the capacitors are charged con- tinuously, and when the servo motors need excess energy, such as when drawing or coining, the capacitor banks bump up the supply. During the non- forming cycle, incoming electricity charges the capacitors so that they can supply extra energy when needed.
A good analogy is that of a hybrid automobile, where during city driving braking action supplies energy back to the batteries, and when accelerating the cylinders supply energy with extra energy supplied by the batteries.
A proprietary smart EMS studies
press speed and the amount of energy stored in the capacitors and knows how much energy is required. With all of that data, the system routes energy back and forth into and out of the capacitors to help smooth the peak- energy curve and lower the amount of electricity needed from the incoming line.
With a system such as this, energy requirements can be less than 50 per- cent of that for typical servo-drive systems.
With the ability to store energy and use it as needed, servo-driven presses save a large amount of electricity as compared to similar-sized traditional mechanical presses. In addition, servo-press users have benefitted from