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Profits in motion
Linear motors decrease downtime, while increasing precision and profits
By Laurie Toupin, Contributing Editor -- Design News, March 26, 2001
Every day, companies ask engineers to make their machines run more reliably and efficiently. Less down time means more throughput, higher yield, and increased sales. To meet this goal, many integrate linear motors into their designs of cutting machines, inspection stages, pick-and-place devices, wire bonding, and screen-printing machines.
Linear motors provide precision, accuracy, reliability, and quickness with extremely smooth motion, says Robert Novotnak, division manager of the motion control division for Aerotech Inc. (Pittsburgh, PA), developers of motion control devices. The motors also greatly simplify design by eliminating the need for rotating parts, and require little to no maintenance.
But don't take our word for it. Just ask these engineers who've turned to linear motors to increase their companies'profitability.
About six years ago, Brian Sawatzky, electrical engineer for Lacent Technology (Alberta, Canada), had the task of finding a new technology for the company's industrial laser cutters. Lacent's machines appear throughout the North American textile industry, cutting jeans material for Levi's, airbags for the automotive industry, and water filters for water treatment plants.
Originally, Lacent used stepper motors. "But this was the wrong technology for our application," says Sawatzky. "They couldn't produce the force we needed and they had no feedback system. We knew we had to update our process."
Sawatzky considered ball screw, belt-driven, and linear motor technology.
The Lacent 1000 OR L1000 cuts material by focusing a reflected laser beam onto the material. Sawatzky needed to find a technology that could move both the optics that re-direct the laser beam as well as the nozzle assembly used to channel the light onto the cutting surface in a basic "H" configuration. The technology also had to enable the machine to cut 1 m/sec. (40 inches/sec) at 11/2G acceleration (580 inches/sec 2 .)
Sawatzky chose LM310 and LM210 linear motors from Trilogy (Webster, TX), primarily because of the low maintenance required. "Our machines run 24 hours a day, 7 days a week," he says, "and we wanted to insure that the downtime and maintenance would be at a minimum." With no gearboxes to fail or belts to stretch, linear motors need next to no upkeep. This makes them extremely reliable as well, he adds. "At one of our installations, our customer told us that our machine has the best uptime by a factor of 2 compared to his other cutters," Sawatzky says.
With Trilogy linear motors, Lacent also significantly increased the precision and tolerance of their machines. "This increases our customers'ability to be competitive," says Cory Smith, marketing manager for Lacent. In addition, because part repeatability is near perfect, Lacent's customers see anywhere from 5 to 10% material savings. In some instances, Lacent's half- million-dollar laser cutter pays for itself within a year with the amount of money saved from material loss, says Smith.
What does this mean in terms of profitability for Lacent? Loyal customers, repeat and increased sales, and new markets.
"In the past 18 months, when we've competed head-to-head with our major competitors, we've landed the sale," says Smith. "Linear motors are one of our big competitive advantages." Lacent is the only textile laser-cutter manufacturer that uses linear motors. The company's competitors use belt driven machines. "But their machines cannot achieve the same level of performance as ours," says Smith. "This is our big bragging point."
Now that the North American market is well in hand, Lacent hopes to expand in Europe with its first CE-certified machine hot off the production line, complete with Trilogy's linear motors.
Customer satisfaction
Bayside Motion Group (Port Washington, NY), developers of motion control devices, had a customer who manufactured precision thin-film inspection equipment used for inspecting wafers in the semiconductor industry. The customer needed an XYZ motion platform to inspect the thickness and identify irregularities of the thin-film substrates that are placed on the wafer. In addition, they had to process 300-mm wafers at a better constant velocity and higher throughput than their present system. The customer also required extremely smooth motion and a constant velocity, with an accuracy and repeatability better than 2 microns.
For such a complicated project, Bayside engineers integrated a number of motion control solutions. But to get the uniform, constant velocity, accuracy, and repeatability required, they relied on linear motors for the scanning axis. For this axis, they designed a High Accuracy Luge linear motor stage with crossed roller bearings and an ironless linear motor. This prevented z-axis jitter, common in the customer's previous stage, while supporting a high constant velocity and the accurate straightness/flatness specifications. Constant velocity was tested at 0.03% uniformity. For the x-axis, they designed a Micro Plus positioning stage with ballscrew drive and integral motor. For the z-axis: a ballscrew drive and integral motor.
New markets
Another example: "With a 5020-4 linear motor from California Linear Devices (Carlsbad, CA), we've been able to provide a cost- effective system with the responses that our customer required," says Steven D. Atkins, senior systems engineer with Teems Automation (Ringgold, GA). "This new system makes us viable in a market where we've had no previous presence."
A customer asked Teems to design a system with which they could move a 50-lb mass with a position tolerance of five-thousandths of an inch, and at a thousand 0.200-inch- moves/minute. Also, the operator had to be able to change the move profiles of the system quickly and efficiently.
Simulating manufacturing processes saves time and money
A division of Boeing wanted to streamline its manufacturing process for producing spars for jet airplanes. Much like the human rib cage, these spars shape the body of the aircraft, holding the belly of the plane together. Using MSC.Software's manufacturing simulation code, Boeing reduced the number of steps required to manufacture the spars from seven to three. By streamlining this single manufacturing process, Boeing saves millions of dollars per year.
"We not only help manufacture the product, but we help engineer the manufacturing process, " says Reza Sadeghi, senior director of MSC.Software's manufacturing and nonlinear products.
MSC Software enable do this by examining a company's manufacturing process using a physically accurate and mathematically precise simulation of that process. Engineers can visualize the exact flow of the material while MSC packages recommend ways to minimize the work required to transform this raw material into its final shape. MSC programs also predict possible manufacturing defects that may otherwise cause in-service expenses and difficulties, as well as potential solutions.
Among MSC.Software's flagship products is MSC.Marc. This general coupled physics simulation program allows engineers to simulate a variety of manufacturing processes including welding, machining, bulk forming, and sheet forming. MSC.Software engineers are also developing and marketing applications for specific manufacturing markets such as hot forging, super plastic forming, rolling and cutting, and machining.
Simulation of these kinds of processes requires fast and powerful computers. But this type of power does not exist in a single machine. MSC.Software products enable users to network their existing workstations to perform these complex simulations using numerical techniques such as parallel processing and domain decomposition, which increase the solution speed an order of magnitude or more.
"Investing in our products and services create impressive returns for companies willing to replace physical prototyping with simulation, not only in arriving at better and safer designs but, more importantly, more affordable and more reliable ways to manufacture. It is too expensive, too time consuming, and sometimes not possible with trial and error," continues Sadeghi.
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