March 2007 Mechanical Engineering Departments: Tech Focus, Pt. 2

This section was edited by Associate Editor Alan S. Brown.

Technology Focus part 2:
Power Transmission and Motion Control

Linear Actuator Slides on Plastic Guides
by Alan S. Brown

Igus Inc., the East Providence, R.I., company best known for plastic bearings, has launched its first linear actuator. The DryLin ZLW is a lightweight unit designed to position small loads quickly. It combines a hard-anodized aluminum profile with a self-lubricating plastic linear guide and sliding elements to achieve maintenance-free operation.

"Most companies that make similar actuators design them around linear metal ball bearings that require maintenance and hardened shafting," said Igus DryLin product manger Matt Mowry. "This part is a low-cost solution when compared with ball bearing systems and it's maintenance-free."

A linear actuator with self-lubricating plastic bearings and an aluminum track lowers maintenance.

In the past, Mowry explained, engineers used steel ball bearings in linear applications because that was all they had available. The bearings had to run on very hard shaft surfaces. This ensured that they would fail before the shaft, which costs more to replace.

Companies generally solved that problem by treating stainless steel shafts with carbon in order to harden their surfaces. Unfortunately, this created a problem for food, pharmaceutical, personal care, and other industries that must wash down production lines before switching products. Carbon treatment makes stainless steel more vulnerable to corrosion.

Igus solved the problem by molding plastic bearings that lubricate themselves with a dry lubricant as they move. "Since plastic is much softer than steel, it doesn't erode the shaft," said Mowry. "You don't need surface treatment, and you can use a relatively soft but highly corrosion-resistant stainless." Not only is the shaft cheaper to make, but it aligns far more simply than conventional ball bearing systems.

Igus's DryLin ZLW linear actuator builds on the plastic linear bearings and an aluminum track. "Aluminum is lighter and less noisy than steel," Mowry said.

The system comes in two configurations. The ZLW 01 is a lightweight design that eliminates the need for any oil or grease. ZLW 02 requires some external lubrication, but operates at speeds of up to 20 feet per second.

Acquisition in India
by Peter Easton

Cleveland-based Parker Hannifin Corp. is beefing up its presence in India. The company has acquired SSD Drives India from the UniDEL India Group, a privately held automation and technology company, for an undisclosed amount.

SSD Drives, which had fiscal 2006 annual sales of approximately $7 million, will be integrated within Parker's Automation Group as the SSD India business unit.

Headquartered in Chennai, SSD Drives designs, integrates, and sells low-voltage ac, dc, and servo-drive systems to power and control continuous and discrete manufacturing processes. The company has seven regional sales offices throughout India.

"We are particularly excited about their capability as a systems integrator," said Roger Sherrard, president of Parker's automation business. "India is among the fastest growing manufacturing economies in the world. Our existing strong relationship and SSD India's outstanding local engineering capability will enhance our ability to increase the productivity and profitability of our served customers through complete automation solutions."

Joe Vicic, president of Parker's Asia Pacific Group, said, "SSD drives will be a valuable addition to our customer offering in India."

With annual sales exceeding $9 billion, Parker Hannifin is a leading diversified manufacturer of motion and control technologies and systems. The company employs more than 57,000 people in 43 countries around the world.

Fine-Tuning
by Harry Hutchinson

In our age of MEMS, microsurgery, nanotechnology, and general pursuit of minute mechanical marvels, even the smallest vibration can become a big nuisance. For instance, people in quality control actually have to examine the microchips and tiny accelerometers that factories turn out.

Aiming to get a bigger piece of the action, the marketer of a passive vibration-canceling system has struck a deal with a manufacturer of isolation workstations to offer a product that will combine both companies' abilities.

Low profile: Minus K publishes a graph that compares the low-frequency, vibration-canceling curve of its half-hertz negative-stiffness isolator with the profile of a pneumatic system tuned to about 2.5 Hz.

Minus K Technology Inc. in Inglewood, Calif., has a passive system that isolates equipment from low-frequency vibration. It is collaborating with a maker of vibration-canceling workstations, Kinetic Systems Inc. in Boston. Their products are used in laboratories and by manufacturers.

Kinetic Systems has been making electronic and pneumatic vibration isolation workstations since the 1970s, according to senior sales engineer Larry Shaver. The new workstation, designated MK26, is the company's first to use the system from Minus K.

David Platus, president of Minus K, said his company has been selling its vibration-canceling system to manufacturers of other devices, such as atomic force microscopes, and has been offering it in a workstation for some time. Platus pointed out that this will be the first time the company has marketed its negative-stiffness isolator as part of a general-purpose workstation with a choice of either honeycomb or other tabletop and the variety of options that are available for the MK26.

As Minus K describes it, its vibration damping system uses a spring that supports a load in concert with a negative-stiffness mechanism to cancel vertical vibration. Beam columns combined in series cancel horizontal vibration.

Steady work: The MK26 workstation, a joint product from two vibration-isolation companies, is designed to cancel very low-frequency vibration—about 99 percent of a 5 Hz interference.

The natural frequency of the system is usually tuned to one-half hertz. As a result of the low resonant frequency, the surface of the workstation is isolated from 99 percent of a 5 Hz vibration and from 99.7 percent of 10 Hz. A video on Minus K's home page showcases a desktop product, called 25BM-4, which is tuned to half a hertz. Two wine glasses are on a table subject to a 5 Hz vibration with an amplitude of about a millimeter, the company says. One, almost still, is isolated; the other, almost spilling, is not. There are also a couple of coins balanced on edge on the vibration isolation platform.

The Web site also has a "Technology" section that explains how the company's isolation systems work.

The MK26 workstation consists of a Kinetic Systems frame with a tabletop resting on the Minus K vibration isolation device. The product is sold by both companies.

The stations are available in two sizes—30x36 inches and 36x48 inches—and in a range of weight capacities up to 650 pounds. They can come with options, including enclosures, guardrails, monitor stands, and Faraday cages to block electromagnetic interference, which will raise the price. The basic workstation starts around $7,000.