Motion Control

How To Make a Decision for Electrical Actuation

There are many factors that play a role in choosing the proper drive mechanism for your automation equipment. It can be overwhelming, even for someone with a controls background, but here is an important rule of thumb: “Keep it as simple as possible”. Let’s assume that you just need to move between two points such as open and close for a gripper. Without any other requirements given, the clear choice would be pneumatic actuation. It is very simple to implement and speed, stroke, and sensing can be manually adjusted. Pneumatic actuators are also low in cost and have a high force to size ratio. All of these features make pneumatics a favorite for integrators and maintenance personnel alike.

So why choose electric over pneumatic? There are many reasons, but let’s start with the simplest. What if you need the functionality of pneumatics such as point A to B or open to close, but you don’t have access to pneumatics? Perhaps compressed air is not allowed in the environment or it just isn’t accessible. SCHUNK has alternative mechatronic solutions for such applications that make it as simple as possible to integrate electric actuators. SCHUNK “alternative” mechatronic solutions run off 24 Volt DC power and they simply open and close based on two digital inputs. Essentially they are controlled just like a pneumatic actuator. SCHUNK offers the EGP series of alternative grippers for small parts. The PGN-plus-E gripper would work for medium to large sized parts. And for linear applications, the ELB series of alternative linear motors offers an unparalleled ease of integration.

The main reason to choose electric over pneumatic is for the added level of control and flexibility. If you need to go to several different positions or have precise control over velocity or force, then it is probably best to go electric. It is important to make the integration into the existing control system as easy as possible. SCHUNK’s line of adaptable mechatronic products does just that. By allowing the user to install any motor they want, it makes communication with the host controller as simple as possible. There is no need to do handshaking between control products from different manufacturers. SCHUNK offers adaptable mechatronic products for grippers, linear and rotary actuators. Some examples are: the EGA 2 finger parallel gripper for large parts; the ERM rotary actuator with 48:1 gear ratio and air feed through; and the ELS screw driven linear actuator.

Sometimes you need the flexibility of an electric servo system but you don’t want to deal with a high voltage drive or bulky power and encoder cables. Or maybe you just don’t have any room in the electrical cabinet for a servo amplifier. For those applications, SCHUNK offers an intelligent line of mechatronic products. Intelligent mechatronic products are a complete servo system in a single compact package. The actuator, motor, amplifier and gearhead are all integrated. They are powered by 24 Volt DC and controlled through a field bus. You only need to run electrical power and a communication cable to intelligent mechatronic products. They offer the full flexibility of a servo system without any of the hassle.

The SCHUNK PRH is an example of an intelligent mechatronic rotary module. The PRH includes a brushless servo motor, Harmonic gearhead, and servo amplifier all integrated in an extremely compact package. Communications methods for the PRH include Profibus or Canbus.

The WSG is an intelligent servo gripper with the ability to have a very delicate touch. The WSG has a brushless servo motor, amplifier, gearhead and belt driven gripper mechanism all bundled into one single package. It even has electrical connections on the base jaws for force sensing fingers. The information from the force sensing fingers can be processed directly in the WSG’s onboard controller. This makes integrating closed loop force control easier than ever. The WSG is capable of controlling grip forces below one Newton. The WSG communicates via Ethernet TCP/IP but Canbus and Profibus are also an option.

SCHUNK products span a broad spectrum of actuator types and control options. So whether you need a pneumatic actuator, simple electric actuator or a fully functioning servo actuator, SCHUNK has an appropriate solution. By using SCHUNK, you can meet application requirements while keeping the solution as simple as possible.

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