More and more, medical device manufacturers are replacing traditional components with smaller, lighter-weight options that have sufficient life and reliability for “life-critical” applications. One such example comes from manufacturers of ventilators, who are using voice coil actuators to control the valves that deliver air to a patient who’s unable to breathe on their own. Ventilators are […]
What are rail brakes and when should you use them?
The servo and stepper motors that drive linear motion systems often include a braking function, or, in the case of stepper motors, detent torque that helps prevent the motor (and, therefore, the load) from moving when powered off. But in some applications, a secondary brake is required — either to provide redundancy and meet safety requirements […]
How to reduce the effects of stiction (stick-slip) in linear guides
Unless you’re playing the violin, stiction, or stick-slip, is an unwanted condition caused by the difference between static and dynamic friction between the two surfaces. When stiction occurs in linear guides, it can lead to chattering (“jerky” motion), seized motion, fluctuating torque requirements, or a loss of accuracy in the form of overshooting. What causes stiction? […]
What are some alternatives to L10 bearing life?
If you work with linear ball or roller bearings, you’re familiar with the L10 bearing life equation, which states that bearing life is equal to the bearing’s rated dynamic load capacity, divided by the applied load, raised to a power of 3 (for ball elements) or 10/3 (for roller elements). Introduced in 1947 by Gustaf […]
What are differential roller screws and how do they differ from planetary designs?
Traditional roller screws — sometimes referred to as planetary roller screws — can produce axial forces comparable to hydraulic cylinders, with the speed and precision capabilities of ball screws, at a price point that falls between the two. A variation of the planetary roller screw — referred to as a differential roller screw — reduces some […]
Synchronous belt materials: What’s the difference between urethane and neoprene?
Synchronous belts for linear motion applications — such as general transport conveyors or high-speed gantry positioning — are available in a wide range of materials suitable for virtually any application. The most common synchronous belt materials are neoprene and polyurethane, but specialty materials and backing surfaces are also available to address requirements such as temperature extremes, […]
What makes a linear guide suitable for high temperature use?
For most recirculating ball and roller linear guides, the allowable operating temperature range is -10° to 80° C, with some configurations rated up to 100° C for brief periods. But not all applications fall within this temperature range, and each component in the linear bearing assembly (housing, rail, balls, seals, etc.) has a different maximum […]
What options are there for integrated motor and screw designs?
Ball and lead screw assemblies are often driven by a motor connected in-line with the screw shaft via a coupling. While this mounting arrangement is simple and easy to service, the addition of a non-rigid mechanical component (the coupling) can introduce windup, backlash, and hysteresis — all of which affect positioning accuracy and repeatability. The […]
Acme or trapezoidal? What’s the difference between lead screw designs?
In power transmission applications, there are two primary types of screw drives: those that use recirculating balls or rollers, for applications that require high rigidity, excellent positioning accuracy, and high duty cycles, and those that rely on sliding contact, for applications that require corrosion-resistance, self-locking operation, and customizable nut designs. The second category — screw […]
Electromagnetism basics for mechanical engineers
Electromagnetism — the relationship between electricity and magnetism — is the underlying principle for the operation of electric motors, as well as generators and transformers. And even though most of us aren’t designing motors (or generators or transformers) from scratch, it’s helpful to have a basic understanding of the concepts and laws that drive their operation. […]
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