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FEA in a Snap PUBLIC ACCESS

A Toolmaker Finds that Finite Element Analysis isn't the Beast it Once Was.

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Associate Editor

Mechanical Engineering 123(07), 60-62 (Jul 01, 2001) (2 pages) doi:10.1115/1.2001-JUL-3

This article describes application of finite element analysis (FEA) in snap tool, developed by Snap-on Inc. in Kenosha, Wisconsin. FEA has been finding its way down the engineering chain with the help of easy-to-use software. FEA is the use of a complex system of points—called nodes—that form a grid, or mesh, across a model. The mesh contains the material and structural properties that define how the part will react to certain load conditions. Snap-on has discovered that if engineers analyze their products as they design them, they understand their products better and face fewer project delays. Engineers who use FEA have found that analyzing as they design parts saves development time. The Snap-on power tools group's move to integrated design and analysis should be complete by year's end. Mechanical failure often results from a variety of forces, including motion, stress, thermal and fluid-flow effects, and vibration. Multiphysics applications give engineers the ability to run all these analyses at the same time, to determine how the tower would withstand real-world conditions that occur simultaneously.

Five years ago, the power tool product-engineering group at Snap-on Inc. in Kenosha, Wis., began using a three-dimensional solid-modeling software package for product design. After the seven designers and seven engineers in the group became comfortable using the software for daily design, some of them began to realize that their new technology upgrade could easily be expanded to include finite element analysis capabilities, said John Fuhreck, product engineering manager for power tools at Snap-on.

Snap-on makes tools for use in a range of professions. Product lines include hand and power tools, diagnostics and shop equipment, tool-storage products, and diagnostics software for transportation, agriculture, and industry.

"We have everything you'd need to service an automobile-from the equipment to lift it off the ground to the chargers, to the power tools that we design in our group," Fuhreck said.

The designs of his power tools group include wrenches, pliers, and screwdrivers.

With the switch to 3-D design came a growing awareness that with the rapid changes in engineering software development, engineers and designers no longer needed to build prototypes for the first tests, or send their designs to Snap-on FEA specialists to be analyzed before they were built. If the engineers and designers who work with power tools could learn how to design in a new software package, why couldn't they also take advantage of the FEA capabilities integrated with the computer-aided design software?

FEA is the use of a complex system of points-called nodes-that form a grid, or mesh, across a model. The mesh contains the material and structural properties that define how the part will react to certain load conditions. In essence, FEA is a numerical method used to solve a variety of engineering problems that involve stress, analysis, heat transfer, electromagnetism, and fluid flow.

Once the purview of specialists and run only on mainframe computers, the analysis method over the past decade has been finding its way down the corporate engineering chain via the advent of easier-to-use software. Many engineering technology vendors are now marketing simplified analysis, which walks users through a series of steps that let them define the analysis they want to run and then interpret the results.

Snap-on has discovered that if engineers analyze their products as they design them, they understand their products better and face fewer project delays, according to Fuhreck. They also spend less time rebuilding and redesigning parts, because the kinks have already been mostly worked out of the designs, thanks to the ongoing computerized analysis.

Snap-on uses Pro/Engineer software from PTC in Waltham, Mass., for CAD design and is now moving toward giving designers and engineers access to Pro/Mechanica, PTC's FEA package that works with its CAD software. The two software packages are integrated or, to put it another way, can talk to each other. Thus, when engineers design a part in the CAD system, they can run an FEA analysis of the entire p art or of a subassembly without needing to translate any CAD information.

"Now that we have 3-D modeling and FEA software so well integrated, we're trying to stimulate the use of more and more FEA in our group," Fuhreck said.

FEA has been finding its way down the engineering chain with the help of easy-to-use software.

Grahic Jump LocationFEA has been finding its way down the engineering chain with the help of easy-to-use software.

The group's move toward integrated design and analysis. is ongoing, Fuhreck said. He credits the process to Joshua Beer, a project engineer and computer-aided engineering administrator in the unit, as the catalyst for investigating the cost and time savings associated with desktop FEA. When the CAD modeling software was introduced, Beer volunteered to be the FEA project leader. Three years ago, he loaded the integrated FEA pack age onto his computer and offered to run analyses of projects that the engineers and designers were working on.

"That kind of whetted their appetite," Beer said. "It worked well, and the teams have learned that analysis is worth the time and effort it takes to do it while you design. It solves problems as you build, so you end up with a better product at the end."

Prior to Beer's involvement, an FEA specialist rebuilt the group's designs in another software package not integrated with the design software. The FEA software resided on one workstation specifically devoted to manually recreating designs for FEA and then analyzing them. Because of the tedium and work involved, analyses were run only when absolutely necessary. Usually, products were de- signed, and a prototype built and tested. Design flaws were found in the prototype stage and the product was then redesigned to correct the problems, Fuhreck said.

Snap-on's experience mirrors that of many engineering departments over the past several years, said Bruce Jenkins, vice president of Daratech, a Cambridge, Mass., marketing and research firm. The FEA field has seen great change over the past decade, with a jump in the number of computer technologies available to all levels and types of engineers, he said.

Until the pas t few months at Snap-on, Beer did all the FEA analysis for the group's designs. Now engineers in the group do much of their own analysis. Beer is currently teaching the designers how to use the software.

"Our next step is to have everyone using it," Fuhreck said. "We don't want Josh or anyone else dedicated to just doing analysis. In the not- too-distant future, FEA capabilities will be pushed down from engineers to designers.

"When the designers are modeling a part and they're trying to decide whether or not to put a rib in, we'd like them to run a simple analysis of the part both ways—with and without the rib- to help them decide," Fuhreck said. "We're finding that running FEA on simple parts is very helpful."

Prior to FEA software implementation, engineers and designers had the idea that FEA was predominantly reserved for very intricate and complex analyses done on a full part, Fuhreck said. That concept is a holdover from the days when the process was performed only by trained specialists working on mainframe computers. And the idea that FEA is hard to do took hold when engineers saw analysts completely re- entering designs into a new software program before they could analyze them.

"But simple analyses are quick and easy, and they are very beneficial," Fuhreck said.

In an effort to get engineers thinking about analyzing as they design, as well as to introduce them to everyday uses for FEA, Beer said he's been urging them to analyze the computerized design of a simple part that has already been built. They can then take the actual part next door to the laboratory to run physical tests that confirm analysis results.

"So the person will analyze it, and they'll also do a physical accelerated life test to test the durability," Beer said.

To carry out an accelerated life test, a preproduction or prototype of the tool is run in the laboratory with a heavy load and a high-duty cycle applied, to essentially put a year's worth of wear on the tool in a week. Analysis and tests always match, Beer said. But the laboratory experiment had an unexpected side effect, he added.

During their initial forays into analysis, engineers carried out varied analyses on all aspects of their design.

However, after running a few analyses, they can now predict, for example, which subassemblies of the parts they're working on will see more use than other subassemblies. With that knowledge, they design the part to correct for these problems from the get-go. FEA makes for more proactive design, Fuhreck said.

By year's end, Fuhreck hopes to see almost all of his 14 engineers and designers analyzing as they design. Each group member will be getting the FEA software loaded on individual desktops.

The other groups within Snap don't use FEA as often as the power tools group, but managers are looking to the experiences of that group in anticipation of their own march toward FEA. The hand tools group runs very specific analyses that can be applied to any of its products, Fuhreck said. Engineers in that group, for example, will run a detailed FEA on the interaction between the screwdriver and the screw. These analyses are then kept on file to give engineers in that group a thorough familiarity with their product. The knowledge helps them design.

"Those types of filed analyses are useful when you're dealing with everyday interactions," Fuhreck said.

He is also interested in cataloging analyses so that engineers tweaking part designs or designing a part similar to one produced in the past could see how earlier examples performed under analyses.

"Even though we're still in the learning process, we want to put analyses in a database so someone could access an analysis done a while ago to see how loads were applied, for example," he said.

Engineers who use FEA have found that analyzing as they design parts saves development time.

Grahic Jump LocationEngineers who use FEA have found that analyzing as they design parts saves development time.

The Snap-on power tools group's move to integrated design and analysis should be complete by year's end.

Grahic Jump LocationThe Snap-on power tools group's move to integrated design and analysis should be complete by year's end.

As is the case with other forms of engineering technology, FEA software is quickly mutating: Vendors are racing to market with upgrades and changes to their existing software packages in an effort to capture wider shares of the market. And that's a race from which engineering firms may benefit.

One of the most recent trends in FEA is the simulation of an entire multi physics event instead of a single static structural analysis that only reflects mechanical behavior at one moment in time, according to Bob Williams, development manager at Algor, the Pittsburgh-based maker of mechanical engineering software. Software now on the market, or new to it, allows engineers to examine the effects of multiple physical phenomena interacting over time. The new software lets engineers simulate the entire part in action and run multiple simultaneous, real-time analyses of the part. If FEA is used to solve a variety of engineering problems, such as stress analysis and heat transfer, why not solve for all of them at once rather than one at a time, the vendors' reasoning runs.

"The biggest trend in FEA is linking various analysis packages and. tying them together as tightly as possible with the least amount of differing user interface," Williams said. With a common interface, engineers don't have to learn and remember different computer commands for the various types of analysis they want to perform. They can use the results of one analysis to carry out a second, all through use of the same interface, Williams said. Algor ties together these analysis packages under one interface in a package it calls Professional Multiphysics software.

Mechanical failure often results from a variety of forces, including motion, stress, thermal and fluid-flow effects, and vibration Since an electrical tower could be subjected to cold temperatures, high winds, and ice loading simultaneously, for example, engineers must consider all these factors when designing a tower, according to Algor.

Multiphysics applications give engineers the ability to run all these analyses at the same time, to determine how the tower would withstand real-world conditions that occur simultaneously.

By use of thermal analysis software, an engineer can determine the temperature of a material over a period of time. At the same time, the engineer can run another analysis that will show how material is affected by the temperature variations. The structural analysis would use temperature numbers returned by the thermal analysis. In this way, the engineer can more quickly select the appropriate material for the part, Williams said.

Another company, Comsol in Bern, Switzerland, makes Femlab, also a multiphysics software. It couples any number of nonlinear physical analyses and solves them simultaneously, according to the company. That software runs on top of Matlab, the technical computing program from Mathworks of Natick, Mass. A researcher analyzing a chemical reaction, for example, could solve for mass and heat of the reaction at the same time, rather than first running one analysis and then the other, according to Comsol.

It will be a while before the Snap-on power tools group branches into multiphysics. Meanwhile, Beer attends regular meetings of a group called the Chicago-Milwaukee Pro/Mechanica Users Group. The meetings bring together Pro/Mechanica users from Beer's region who discuss FEA issues they face at work.

"This is probably the best resource I've found," Beer said. "They got me interested in accuracy and convergence and important things that aren't really taught in school, it seems. We don't have a dedicated analysis person here, so I'm gaining from the user group's experience." Many of the group members perform FEA as their primary job function.

"It's nice talking with people who do analysis eight hours a day," Beer said.

Copyright © 2001 by ASME
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