For a machine designer, flexibility means highly configurable and adaptable components that can allow for slight variations without demanding major design changes. When applying these demands to your electromechanical actuator, what are the specific markers for flexibility to look for?
Stroke length and performance will determine the speed and precision of the required actuator in your machine. Is a variety of stroke lengths accommodated as standard? In your machine, would the stroke length affect the performance?
It helps to consider an array of drives. For instance, ball or lead screw drives are often limited to lengths of less than two meters while belt drives can achieve very long stroke lengths with consistent speed, but don’t offer the precision of a screw-driven product. In contrast, linear-driven actuators offer scalable stroke increases, with motors without speed limitations at longer strokes and precision repeatability maintained over the full stroke.
Look for an actuator manufacturer with a deep product line. The availability of multiple frame sizes and widths benefits your design in several ways. Product price is usually tied to size. If your application is too big for one product, the jump to a larger size could add a proportional increase in your cost. Having a family of products from which to choose allows you to select just the right size without overkill.
Multi-axis applications with different loading for each axis? You’ll get consistency in look, feel and performance by selecting from a manufacturer’s family of linear actuators.
Drive train options
Multiple drive train options within the same form factor can be useful to a machine designer. With the thrust density you get from a screw drive or the speed of a belt drive, you can tailor your drive train to your need. The flexibility to choose can avoid the need for serious rework to your machine’s layout.
Electromechanical actuators are usually connected to other actuators or mechanical devices. It is critical to machine builders to combine linear actuators into XY, XZ or XYZ assemblies quickly and effortlessly. Most components are designed to be bolted together without transition plates for XY systems. For stability, plates are often unavoidable for the Z or vertical axes.
Larger size doesn’t always translate into better performance. Highly compact actuators or stages give designers room to add end effectors and tooling. Performance factors such as thrust or rated load per height-by-width are important metrics to consider in comparisons for a given application. When cost is critical, optimizing extrusion profiles, bearing technology and drive trains is crucial.
Selectable resolutions and encoder types
A variety of resolutions and encoder options assures good servo control. An actuator should have 5–10× more resolution available than the repeatability of motion required. Some modern encoder products can change resolution with a simple hardware change.
Flexible encoder technologies have long included the popular optical encoders that use glass scales, but competitive resolutions and costs are now available in other technologies. Magnetic, inductive and absolute encoders serve varied speed, precision and environmental applications.
Most of these encoders were once designed with proprietary signals embedded, so your design had to use a limited list of manufacturers, based upon the signal. With the advent of BiSS-C and other open standard protocols, you can use any number of manufacturers’ drives or controls.
Thanks to 3D CAD models, products are now designed and digitally tested before the first piece of metal is machined. Finite element analysis software allows evaluation of thermal or magnetic variations and deflection characteristics. Simulation cannot yet predict performance with absolute certainty, but it is increasingly useful in expediting design development.
Metrology is increasingly employing digital capture, using optical, non-contact methods such as laser interferometry to provide much higher resolution and more repeatable results. With the strenuous application tests now available, having a design partner who understands and tests to your mission-critical requirements is imperative.
Integrated and optimized complementary products
Most modern component manufacturers offer simplified standard cable configurations and connections. Newer drive and encoder technologies allow the drive to recognize motor data parameters automatically. Once connected and powered up, the drive collects the data from the encoder, adjusts for payload and auto-tuning, and the machine is ready for motion.
The days of waiting months for design, configuration, and delivery of a machine have passed. Now, automation suppliers can deliver components quickly, with flexibility in stroke capacity, scalable performance, drive train options and modularity. Resolution and encoder protocols offer choice, so you are no longer limited by a manufacturer’s drives or controls. The design is virtual, metrology is digital and integrated, and optimized complementary products are the norm.
If you want a twenty-first-century electromechanical actuator supplier who carries a product family that is flexible, scalable and integrated, connect with us. We understand your day-to-day design hurdles and have systems in place to allow the rapid development of your machine.
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Article contributed by Electromechanical Division, Parker Hannifin Corporation.
Much of this content was first published in April 2016 as “Machine Design in the 21st Century” by e-Drive online.