Both LVDTs (linear variable differential transformers) and resolvers are measuring devices that convert displacement into an electrical signal. As its name implies, an LVDT is used for linear measurement, while a resolver is used to measure rotary, or angular, displacement. In terms of construction and operation, the most significant similarity between an LVDT and a […]
Ultrasonic sensors for linear position and distance measuring
In nature, some animals — such as bats and dolphins — analyze the echo of a sound or call (a process known as echolocation) to navigate or to find prey. In industrial applications, ultrasonic sensors use the analysis of echos from ultrasonic waves to determine the presence, position, or distance of an object. Ultrasonic waves are […]
Three easy ways to specify application requirements for linear motion systems
The first step in any automation project is to clearly define the objective — what process are you trying to accomplish or what output are you trying to produce? Once the process or output is defined, it’s time to dig into the details of the application so you can choose the right components or systems […]
What are capacitive sensors and where are they used?
Linear position feedback devices — also referred to as linear encoders — typically measure travel distances ranging from a few dozen millimeters to several meters. But when a positioning system has a very short travel — a few millimeters or less — traditional linear encoders are often too bulky or don’t provide the required measuring resolution. […]
What factors contribute to air bearing stiffness?
According to the American Society of Mechanical Engineers (ASME), stiffness is: The capacity of a mechanical system to sustain external loads without excessive changes of its geometry (deformations). When we think of stiffness in traditional bearings with rolling elements, we’re typically considering the deflection of the carriage when a load is applied. For air bearings, […]
When should you use a bronze lead screw nut?
Lead screw manufacturers offer nuts in a wide array of materials, including various plastics and grades of bronze. And while plastics garner a lot of attention for their versatility and range of suitable applications, lead screw nuts made of bronze are especially well-suited for applications with high loads or extremely high (or low) temperatures. Plastic […]
What are low outgassing materials for linear motion components in vacuum applications
Outgassing — the release of gas or vapor from a material through desorption, sublimation (the transition of a material from solid directly to gas), or evaporation — is a critical parameter for materials used in vacuum environments. These gasses and vapors can affect the pressure (or level of vacuum) in the vacuum chamber, and outgassed compounds […]
How to make linear motion systems cleanroom compatible
While we often talk about the importance of keeping contamination out of linear motion components such as linear guides and screws, when these systems are used in a cleanroom, the goal is just the opposite — to keep these components from introducing contamination into the environment. What exactly is a cleanroom? According to ISO 14644-1:2015, […]
How do miniature profiled rail guides compare to their full-size counterparts?
The basic distinction between “standard” and “miniature” profiled rail guides is the width of the guide rail: profiled rails with a width of 15 mm or less — and the carriages that fit on them — are generally considered “miniature” by bearing manufacturers. (However, some manufacturers also produce 15 mm rail guides in standard versions, as we’ll […]
When is encoder resolution specified in bits, and what does that tell us?
Absolute encoders — whether rotary or linear — track the position of an axis by assigning a unique value to each position on the encoder, so that no matter where the axis being measured is located, its exact position can be determined. And because each position is uniquely identified, this holds true even if the […]
The top 10 linear motion articles of 2020
Suffice it to say, pretty much everything about 2020 has been out of the ordinary, and our recap of the top linear motion articles for this year is no exception. For the first time in recent history, only one (1!) of the top 10 articles is about ball or lead screw technologies — a topic that usually […]
What’s the difference between minimum incremental motion (MIM) and resolution?
When we talk about the positioning capabilities of a linear motion system, we typically talk about accuracy and repeatability, and in some applications — especially those driven by stepper motors — we may also be concerned with resolution. But accuracy and repeatability define a system’s ability to reach its commanded position and to do so over […]
Linear bearing seals: Types, options, and applications
Seals for recirculating linear bearings serve two functions — keeping contamination out and keeping lubrication in — to ensure the system operates properly without premature wear or failure. Because sealing is so critical to linear bearing systems, manufacturers offer a variety of sealing designs and materials to meet a wide range of applications and environments. […]
Ball screw seals: Types, options, and applications
Ball screws are used in a wide range of applications, many of which expose the screw and nut assembly to harmful contamination in the form of dust, chips, or liquids. And like any bearing that uses metal balls (or rollers) on metal raceways, ball screws can experience abrasive wear when exposed to solid contaminants, while […]
Belt driven actuators for a wide range of applications
Belt driven actuators are the workhorses of the electromechanical world, offering longer stroke lengths and faster speed capabilities than screw driven designs, with less inertia and better resistance to contamination than rack and pinion drives. And although linear motors boast better positioning accuracy than belts, the price-performance ratio of a belt driven actuator is difficult […]
How to size a spline shaft: Shaft strength in bending and torsion
Choosing a shaft for a traditional linear ball bushing is relatively easy — choose the appropriate diameter, material, and hardness, check the dimensional accuracies and tolerances, and if the shaft is unsupported, perform a beam deflection calculation. But because spline shafts can withstand both radial and torque loads, it’s important to ensure the shaft strength […]
How to calculate bearing life for a ball spline
A ball spline is much like a linear ball bushing and shaft, but with axial grooves along the outer diameter of the shaft and the inner diameter of the nut. These grooves prevent rotation of the bearing (referred to as a spline nut) and allow the ball spline to transmit torque. Because a ball […]
What is stepper motor resonance and how can it be avoided?
The discrete, step-by-step movements that give a stepper motor its accurate positioning capability can also lead to some undesirable performance characteristics — namely, vibration and audible noise due to resonance. Stepper motors naturally exhibit small vibrations with each step, due to the inertia of the moving rotor, which causes the motor to slightly overshoot (or, […]
What are the differences between incremental and sine-cosine encoders?
Encoders that provide incremental position measurements (whether rotary or linear) output two signals, or channels, typically termed “A” and “B,” to provide position and direction information. These output signals can be in the form of analog sine and cosine waves or in the form of digital square waves. Those that produce digital output signals are typically […]
How to calculate linear ball bushing life (and how it differs from other life calculations)
The standard life calculation for linear ball bearings is widely known as: L = bearing life (m) C = rated dynamic load (N) F = applied dynamic load (N) But linear ball bushings often experience operating conditions that aren’t accounted for in the general bearing life equation. To account for these adverse conditions, the life calculation […]
How does shaft hardness affect the life of a linear ball bushing?
A linear ball bushing riding on a round shaft is often compared to a radial ball bearing, with the bushing acting as the outer race of the bearing and the shaft acting as the inner race. But in linear bushing assemblies, the surfaces of both the ball and the shaft are spherical, so contact between […]
What are stroke ball splines and how do they differ from standard ball splines?
Standard ball splines use balls that recirculate within a nut, or housing, similar to that of a recirculating ball linear bushing. But the mechanisms and geometry required for ball recirculation result in a spline nut that is relatively large in diameter compared to the diameter of the spline shaft. For a more compact assembly, several […]
What’s the difference between a ball screw spline and a traditional ball screw?
A ball screw spline is a combination of two components — a ball screw and a rotary ball spline. By combining a driving element (the ball screw) and a guiding element (the rotary ball spline), a ball screw spline can provide both linear and rotary motion, as well as spiral motion, in a highly rigid, […]
How to make sure you get the right linear bushing interchange
Linear ball bushings are one of the few interchangeable product types in linear motion, with industry-standard sizes and styles, so that a product from one manufacturer can often be substituted with a product from another manufacturer that has very similar dimensions and technical specifications. And most linear bushing manufacturers offer several product lines that are […]
Tips for mounting linear ball bearings: Pillow block housings
Linear ball bearings and round shafts are often used in applications that call for ease of use and simple mounting requirements. For example, where profiled rail guides require full support along their length, linear ball bearings, or bushings, can be used in many applications with shafts that are supported only at their ends. However, unlike […]