Motion in Motion: A Reference Guide with Case Studies and What’s to Come

As with other aspects of mechanical engineering, the use of standard types of motion in countless applications will remain in use but at the same time, will continue to evolve. Machine Design has therefore created a quick motion reference guide, highlighting new application examples that reflect the growing trend of customized solutions for specific industrial, medical and manufacturing problems. 

Rotary Motion     

Definition: Rotation around a fixed axis

Rotary Motion Example: Sorting packaged products

A manufacturer of small consumer packaged goods needed to sort products into three categories coming out of a descrambler. “They devised a gate with rails to support each side of the package, and the rails were to pivot to one of three positions to direct the package into corresponding chutes,” explains Norman Lane, president of Rotomation. “Their initial plan was to use a three-position rotary actuator to drive each rail. Being on close centers, the actuators would have to be very small. Rotomation proposed its A032 miniature three position actuators, but the inertia of the gates slowed their performance.” Rotomation therefore designed a customized version of its much larger A22 three-position actuator, incorporating two pinion shafts being driven by a single set of racks and pistons.

Lane reports that this solution proved to be much more capable while significantly reducing system cost and complexity. The number of magnetic position sensors and flow control valves was cut in half, and the four rotation adjusters were eliminated due to the improved accuracy of the larger actuator.

Rotary Motion—A Second Example: Lock testing

A manufacturer of door locks needed a versatile actuator for testing operations. This customer wanted to be able to use the same test fixture for testing its full line of locks. Rotomation supplied a highly versatile three-position rotary actuator that rotates 360 deg. from a central position. “In addition, special rotation adjusters were incorporated with a range of 360 deg.,” says Lane, “so that the rotation in each direction could be adjusted from 0 to 360 deg.”

Rotary Motion: What’s Ahead

In an online Researve article, Dr. Wei Zhang recently noted that rotary systems that integrate linear actuators mark “a significant advancement in various engineering applications” across robotics and more. She states that “linear actuators allow for precise control over motion, which when translated to rotary systems result in improved stability and accuracy. This is particularly beneficial in scenarios requiring incremental adjustments, such as in CNC machines or automated assembly lines.” 

READ MORE: Actuators and Drives: Foundations of High-Performance Motion Systems

Linear Motion      

Definition: Linear motion is the straightforward movement of an object along a straight path

Example Application: High-precision lithography

In a semiconductor etching application, Thomson and Nook (a Regal Rexnord company) specified miniature stainless steel bearings with high-fit tolerances and optimized surface finishes. “These bearings were chosen for their compact size, corrosion resistance, and ability to maintain dimensional stability under thermal cycling (up to 600°F),” says Pablo Olachea, product marketing manager, linear motion division of Regal Rexnord. “Integrated into the lens alignment subsystem, they provided ultra-smooth linear motion with minimal stiction, enabling precise repeatability in optical sensor positioning. This was critical for maintaining beam path integrity and achieving the resolution required.”

Linear Motion – A Second Example Application: Concrete slurry dispensing head in 3D construction

The concrete slurry dispensing head for the automated “printing” of walls to construct residential homes required an actuator with specific speed, stroke and thrust requirements, explains John Fenske, director of marketing and product management at Tolomatic. For this customer, Tolomatic modified its RSA32 electric linear rod-style actuator, which features a planetary roller screw. It was also chosen for its high duty-cycle design and IP67 environmental protection to achieve a long lifespan during outdoor operation in the elements.

Linear Motion – Third Example: Clean environment battery manufacturing 

A dispensing head for filling battery cells with electrolyte needed to move in both X and Y directions. The successful solution combined a ball screw-driven actuator slide and linear motor actuator coupled with THK America’s “caged ball technology” to meet the demanding high speed, high precision and clean environment required in battery manufacturing lines, explains Yoshinori Murakami, corporate engineering manager at THK America.

Linear Motion: What’s ahead

Olachea reports that linear motion systems (lift columns and linear guides) are becoming more compact. Matsui notes this trend as well, along with greater customization. Olachea also points out that linear systems are becoming “smarter” through innovative integrations of components and software. “These systems not only move but also sense and adapt in real time,” he says, “which is critical for applications where precision and safety are paramount,” such as cobot transfer units.

READ MORE: The Back-and-Forth on Linear Motors

In addition, Fenske points to a growing trend toward electrification of linear motion, where fluid power is left behind for a much cleaner and more-consistent motion control. He stresses, however, that “there’s a tendency to over-estimate the force requirements when converting from hydraulics to electric. Customers often compute the force based on the hydraulic cylinder inlet pressure without considering the residual pressure in the outlet. A simple differential pressure test allows designer to know the true force requirements and right-size the actuator.”

Reciprocating Motion

Definition: A type of linear motion involving back-and-forth movement.

Example Application: On-demand cable wind/unwind

A traverse was required in an application involving wind-unwind of fiber optic cable (attached to a probe) inside a small drum located “within an autonomous rover,” explains Andrew Hess, sales application engineer at Amacoil, “with very little allowable space and facing extreme temperatures.” The Amacoil team modified its standard frame to reverse in both shaft directions to accommodate winding-unwinding using the Kinemax model Rolling Ring Drive from Uhing. Tubular solenoids were used to modify the reversal when the rover needed to retrieve cable length. 

Second Example Application: Slow pivoting applications with heavy loads

Heavy loads are standard across heavy equipment applications such as excavator bucket tilt and lifting arms, hydraulic tail lifts, scissor lift pivots, hydraulic plows, etc. For these applications, bearing strength is paramount. For these applications, igus has recently developed 2K mulit-layer injection-molded plain bearings (iglide Q3E and W300E). Their inner layer with optimized tribological properties helps limit wear and the outer layer provides unprecedented strength in higher-load applications to 19,580 PSI. This solution is corrosion resistant, and because the inner layer has solid lubricants, maintenance is reduced.

A Second Application: Wear testing

Amacoil also used a Rolling Ring Drive in a reciprocating motion application for wear testing of a custom prosthesis, simulating the attachment-detachment process. The drive was used to hold the prothesis as it moved back and forth several thousands of times into and away from a stationary simulated limb.

Reciprocating Motion: Looking ahead

Hess explains that standard drives, augmented by electronic control of pitch and direction, now can offer infinite pitch and directional changes in reciprocation scenarios. “Using sensors and servo/stepper motor controlled by PLC, the pitch/linear speed and directional travel can all be controlled by a program written for any application,” he says. “Mechanical hardware assisted by electronics and software is changing the precision and dynamic capabilities of the Rolling Ring Drive.”

Oscillating Motion 

Definition: Oscillating motion involves an object or system moving back and forth repeatedly around an equilibrium position, typically due to a restoring force like gravity or a spring. Oscillating motion is sometimes described as a combination of rotary and reciprocating elements. Pivoting can be considered a form of oscillating motion when it involves reciprocal rotation over a limited angle, for example in an equipment lever arm. 

Example Application: Vibrating conveyor

A customer’s vibrating conveyor features a drive moving an unbalanced shaft that induces an eccentric motion on the trough. The trough in turn is supported by a system of springs that alternately store and release energy, which powers the up-and-over motion of the solids being conveyed. “The conveyor in this case was using an extraordinary number of springs and bushings causing increasing amounts of downtime,” explains David Webb, an associate mechanical engineer at Eastman. In addition, it seemed likely that replacement springs had different coefficients than the original springs, causing an overstroke on the machine and excessive wear. “The solution,” reports Webb, “was to rebuild the whole spring system to ensure all the springs were rebounding at the same rate.”

Oscillation: A look ahead

Webb predicts that oscillating motion will enable more energy efficient, gentle, and precisely controlled conveyance in future by using tunable vibration profiles and resonance matching to move varied materials with minimal damage. “Integrated sensors and real-time control will adapt frequency and amplitude to changing loads and material properties, improving throughput and reducing blockages.”

READ MORE: Axial Flux Motors Are Reshaping Movement, Manufacturing & Power Generation

Readers should also note a recent review of “self-oscillating” actuators in the journal eScience. These cutting-edge actuators achieve autonomous motion and are being examined for use in “soft” robotics.

One way to achieve self-oscillation in actuators is through “self-shadowing-induced” negative mechanical feedback loops with light-sensitive materials such as liquid crystal networks or hydrogels. When one part of a mechanism made from such a material is exposed to light, it bends or twists, blocking the light from reaching other sections. These other sections, now in shadow, cool down on a molecular level and relax back to their original positions, blocking other sections. However, in their original positions, these ‘relaxed sections’ are again automatically exposed to light, restarting the cycle and enabling sustained oscillation without external intervention.