One of the most popular subjects on this site is ball screws—especially the topic of how (and when) to select a ball screw. This is not surprising, because screws, and ball screws in particular, are workhorses of linear motion, with a range of styles, sizes, and performance capabilities that covers just about any application an engineer or designer […]
How to reduce jerk in linear motion systems
The most common move profiles for linear motion systems are trapezoidal and triangular. In a trapezoidal move profile, the system accelerates from zero to its maximum speed, travels at that speed for a specified time (or distance), and then decelerates to zero. Conversely, the triangular move profile accelerates from zero to maximum speed and then […]
What is quadrature encoding?
As an incremental encoder turns (or travels linearly, in the case of a linear encoder), it generates a precise number of equally spaced, square wave pulses. The number of pulses generated for each rotation (or unit of linear distance) determines the encoder’s resolution. For rotary encoders, resolution is expressed in terms of pulses per revolution […]
Robots that are saving the environment
Earth Day was celebrated this weekend, and it’s probably not a stretch to say that most of you participated in some way, whether it was joining a local cleanup, planting trees, or just pledging to make better use of your reusable water bottle and grocery bags. A 2010 study by Trucost estimated that environmental damage caused […]
What happens when a bearing reaches the end of its life?
Determining the expected life a recirculating ball or roller bearing is fairly straightforward when the applied loads and duty cycle are known. Just use the bearing life equation: for recirculating ball bearings OR for recirculating roller bearings Where: L = bearing life C = bearing dynamic load capacity F = applied dynamic load These equations give the […]
Telescoping slides: Extending the reach of linear guides
Traditional round shaft and profiled rail linear guides can be joined in sections to provide virtually unlimited travel. But some applications require a linear guide that can extend into and retract out of the work area, and with profiled rail and round shaft guides, there’s not a simple, easy way to do this. For these […]
How to specify linear actuator travel
One of the most important criteria when selecting a linear actuator is how far it needs to travel. The travel, or stroke length, can dictate the type of drive mechanisms that are practical (screw, belt, rack and pinion, or linear motor). But more importantly, specifying the wrong stroke or travel can leave you with an […]
What are linear stepper motors?
Like most linear motors, a linear stepper motor is essentially a variation of the rotary design, cut radially and laid out flat. Similar to their rotary counterparts in operation and performance, linear stepper motors are typically run as open-loop systems and are capable of providing high resolution at high speeds and accelerations. The linear stepper motor almost exclusively […]
Which linear guides are interchangeable?
The need to replace a linear guide in an existing machine or assembly can arise for any number of reasons: to improve the stiffness of the assembly by changing to a bearing with higher preload, or to accommodate unforeseen space constraints by using a different bearing type or style. And sometimes, a linear guide needs to be replaced […]
What is back driving and why is it important?
Power transmission screws—ball screws and lead screws—are typically used for converting rotary motion to linear motion. But when a load is applied axially to the nut, they do the opposite and convert linear motion to rotary motion. This is known as back driving, and is generally an unwanted effect. Although it can occur regardless of the […]