Variable frequency drives convert AC input voltage to DC, and then back to pulse-width-modulated AC voltage with variable frequency. These AC voltage pulses are controlled by insulated gate bipolar transistors (IGBTs). IGBTs have a fast switching time (also referred to as “rise time” or “dv/dt”—rate of change of voltage over time), which reduces energy losses […]
What limits linear bearing speed? (Part 2)
In part 1 of this series on bearing speed, we looked at the factors that limit the speed of linear recirculating bearings. In this segment, we’ll look at the factors that limit the speed of linear plain bearings. Linear plain bearings operate with sliding contact between the two bearing surfaces, so the limitations encountered with […]
Precise, rigid, high load Slide Guides from NB
SGL Slide Guides from NB Corporation are high-precision, high-rigidity, high load capacity linear bearings with low friction, non-stick or slip mechanisms that provide smooth linear motion even under high loads. SGL Slide Guides are available in lengths from 160 mm to 3000 mm. Six types of blocks are available depending on the mounting space and […]
Dissipating static electricity in urethane rollers and wheels
Contributed case study courtesy Plan Tech || Dissipating static electricity in urethane rollers and urethane wheels by using an anti-static additive. Static electricity is an invisible field of protons, neutrons, and electrons found in anything that has potential to move. Each atom has its own properties and characteristics. One of these properties is an electrical charge. […]
What limits linear bearing speed? (Part 1)
High-speed motion is a requirement for applications where throughput is a critical factor, such as packaging and electronic assembly. These systems typically use linear motors or steel reinforced belt drives in conjunction with recirculating linear bearing guides for good stiffness and high load capacity. But the speeds demanded by these applications can pose a challenge […]
New brochure from Thomson explores benefits of smart actuation
Thomson Industries, Inc., a leading manufacturer of mechanical motion control solutions, has published a new brochure that educates industrial automation users on the emerging role of smart actuators in meeting their demands for greater connectivity, application flexibility and cost efficiency. The brochure explores, with help from 10 pages of detailed 3D application renderings, the unique […]
How are servo system velocity control loops tuned?
Servo systems typically use a combination of three types of control loops: current, velocity, and position. The velocity control loop serves two purposes—it enables the system to respond to changing velocity commands, and it allows the system to resist high-frequency load disturbances. But the velocity loop by itself can’t ensure that the system maintains a […]
Environmental challenges for linear bearings, and how to address them
“Environment” is a difficult parameter to quantify when selecting recirculating linear bearings or ball screws. Unlike load, stroke, or speed, there are no programs or calculations that help you choose the right bearing based on environmental factors. But environmental conditions can have a big impact on the performance of linear bearings and ball screws. Because these components operate […]
What are the differences between slotted and slotless motors?
The original brushless DC (BLDC) motors were designed with slotted stators, and the majority of BLDC motors are still made this way. But this design produces cogging torque, which makes it difficult to achieve smooth motion, especially at slow speeds. To eliminate this effect, a new design was developed, eliminating the slots in the stator (which […]
FAQ: What are recirculating linear bearings?
Linear ball and roller bearings can be broadly divided into two categories—recirculating and non-recirculating—depending on whether or not the rolling elements actually flow (or circulate) through the bearing housing. In order to understand what a recirculating linear bearing is, let’s first take a look at bearings that don’t recirculate. Non-recirculating linear bearings Non-recirculating bearings have […]
7 Twitter accounts that make science fun!
It’s probably safe to say that those of you who follow this site (myself included) are science geeks. Whether it’s archaeology, astronomy, or biology, we’re fascinated by the latest discoveries across all realms of science and technology. And for staying on top of these developments, there’s no better platform than Twitter. Most leading scientists and […]
FAQ: What are ways to avoid torque ripple in DC motors?
Torque ripple—variations in torque production during shaft revolution—is an undesirable effect that occurs in permanent magnet motors, preventing smooth motor rotation. Torque ripple is generally defined as non-linear torque production of an energized motor. Cogging torque—a phenomenon similar to torque ripple—is torque produced by the attraction between the permanent magnets of the rotor and the […]
ETEL expands linear motor lLine
As engineers expand their range of machines to a point where a larger payload is required, an upgrade of their linear motors may be necessary. So, to make their design process easier, ETEL has added extra ironcore linear motor lengths to each of their different widths. These new lengths are compatible with existing 50, 70, […]
Servo motor or stepper motor? How to choose
The overwhelming majority of linear motion applications (with the exception of pneumatically-driven types) use either a stepper motor or a servo motor to provide torque to the driving mechanism, which is typically a ball or lead screw, rack and pinion, or belt and pulley system. And unlike other components involved in linear motion, when choosing a motor, […]
FAQ: What are typical drive-based safety functions?
Functional safety standards EN/IEC 62061 and EN/ISO 13849-1 ensure safety via electronic solutions, unlike traditional safety systems, which used electromechanical components to achieve safety. And while functional safety applies to a machine and its control system (not to individual components), the drive lies at the heart of the safety implementation. In fact, functional safety specifies that monitoring […]
Linear actuators: belt driven vs. rack and pinion driven
Belts and rack and pinions have several common benefits for linear motion applications. They’re both well-established drive mechanisms in linear actuators, providing high-speed travel over extremely long lengths. And both are frequently used in large gantry systems for material handling, machining, welding and assembly, especially in the automotive, machine tool, and packaging industries. Timing belts for linear […]
FAQ: What are functional safety standards for servo drives?
Safety is a serious concern for machine builders, system integrators, and end users. Not only do they have a responsibility to provide a safe production environment, they must also meet regulatory requirements for machine safety. And of course, all of this should occur with minimal impact on operational efficiency and productivity. Fortunately, functional safety features […]
New Profile Rail Linear Recirculating Bearings from Lintech
Lintech’s MR, ARC, and HRC Profile Rail Linear Recirculating Bearings incorporate two or four rows of recirculating balls arranged in a 45 degree contact angle with the raceway. The rigidity under moment and torsional loads is increased by this design. Larger ball size is used to enhance the load capabilities. This design offers equal loading in all […]
How to estimate your linear actuator needs with minimal application data
Choosing linear motion components during the development phase of a project has been a source of frustration for designers and application engineers for decades—especially when it comes to complex subassemblies such as linear actuators. Consider for a moment the influence that a linear actuator has on the overall machine design. First of all, in an actuator, […]
FAQ: What are Hall effect sensors and what is their role in DC motors?
DC motors can be either brushed type, which are mechanically commutated, or brushless, which are commutated electrically. In brushless DC (BLDC) motors, Hall effect sensors are used in place of a mechanical commutator and brushes. Hall effect sensors are solid-state, magnetic field sensors. They work on the principle that when a conductor with current flowing through […]
When do you need a ball screw?
The gap is narrowing between applications that require ball screws and those that are suitable for lead screws, and it’s becoming more difficult for engineers and designers to determine which technology is best for their machine. Advances in lead screw designs and materials have given them higher load capacities and better positioning accuracy, making them a sound choice […]
FAQ: Can DC motors run at lower than nominal voltage?
In a DC motor, the relationships between voltage and speed and between current and torque are straightforward. When the load (torque) on the motor is constant, speed is proportional to the supply voltage. And when the supply voltage is constant, speed is inversely proportional to the load (torque) on the motor. Specifications for DC motors include […]
FAQ: What are PID gains and feed-forward gains?
Gain is the ratio of output to input—a measure of the amplification of the input signal. A common example is the volume button on a stereo. This button controls the ratio of the input signal (received from the radio station) to the output signal (how loud the sound is from your speakers). When the volume is […]
The top 5.5 linear motion stories of 2016
As a writer and editor, it’s always fun (and sometimes surprising) to look back at the end of the year and see what articles our readers were most interested in. And for you, our readers, it offers the chance to take a quick look at what are, at least to some of your peers, important topics […]
FAQ: What is a pulse rectifier and what kinds are there?
Variable frequency drives are made up of three primary sections: a rectifier, which converts the supplied AC voltage to DC; a DC bus, which stores the DC voltage; and an inverter, which converts the DC power back to AC at the voltage and frequency required by the motor. The most common, and simplest, rectifier designs use […]