Analysis eases assembly, cuts cost

Rockford, IL--Scott Riddle, design engineer for Ingersoll Milling Machine Co., had to strengthen a new design of a universal head case bracket for an automotive engine-block transfer line. The assembly consisted of the bracket bolted to a slide assembly and the head case bolted to the front of the bracket. Riddle tested different materials such as steel, cast iron, and nodular iron, along with various wall thickness and configurations. The new head bracket would have to be able to work with many different heads, cutting forces and tolerances. Because of the varying uses of the new part, Riddle analyzed it with the heaviest thrust forces the head would see and held to the least amount of deflection allowable. Riddle used COSMOS/Works 4.0 from Structural Research & Analysis Corp. (SRAC, Santa Monica, CA) to analyze different combinations.

His solution: a head bracket cast of nodular iron with an extra support rib. The head gets bolted to the bracket and the bracket gets bolted to the slide. "Because this bracket design is more modular than our previous design, we can use it in many places," says Riddle. "This increase in quantity has decreased the average cost per piece. This makes it easier for manufacturing, assembly, and alignment, and cuts down on the total cost."

At the time, COSMOS 4.0, the newest release of the company's integrated design analysis program for SolidWorks (Concord, MA), was still in beta testing.

Riddle varied the design and material type for each analysis, all the while staying in the SolidWorks environment. He loaded, restrained, meshed, and analyzed the assembly, looking at deflection and stress plots. He says, "For instance, in the final design, if the thrust load on the head was 18,000 lbs, the deflection plot would show a deflection of 0.00228 inch. This is one of the more important criteria I have to design to. If a machine deflects too much under cutting loads, you can end up with a cut that is not to the given dimension and tolerance and a possibility of chatter in the cut surface and vibration of the machine."

He continues, "The fact that COSMOS/Works 4.0 interfaces with SolidWorks is great. There is no need to export data to other analysis software and this saves model integrity and time. A model can be modified and reanalyzed with just a few clicks of the mouse."

One structural assembly may consist of 1 to 150 individual parts, each of which could be out of different material types. "Before, I had to work on one piece or group at a time. COSMOS/Works 4.0 allows me to do entire assemblies," he says. "We used to use a mainframe program with older software and it would take three days to complete an analysis. Now we can do the same analysis in under an hour."

COSMOS/Works 4.0 lets design engineers perform analysis of complete SolidWorks assemblies, says SRAC. The company also offers a new Assembly Analysis module that users can add to COSMOS/Works Basic for $1,500. The Assembly Analysis module works only with SolidWorks 98 and later versions of that software.

Release 4.0 also helps design team members communicate all pertinent design information through the office or the world by means of design reports that can be reviewed and distributed via the Internet in HTML, VRML, AVI, or TXT files, says SRAC. In addition, the company says the new release will identify the model geometry and apply appropriate loads and boundary conditions automatically. It will also automatically identify differences between solid and shell elements, used for thin-walled structures made of sheet metal and plastics, and apply loads and boundary conditions to them.

Riddle says he found the program to be very user friendly. COSMOS/Works 4.0 also features a new postprocessor for visualization of analysis results. "We can dynamically zoom and rotate the design without timely repaints of the shaded model," says Riddle. "A special feature allows an engineer to cut a portion of the part away and look at the analysis results inside the part." Doing so, Riddle can view inner plates and high stress points that may not be evident with the outer shell covering them up.

"Another plus is I don't need a high-end workstation," says Riddle. COSMOS will operate "on a relatively inexpensive desktop PC and it will still run well." Riddle has a Pentium II 300 with Windows NT, 512 Mbytes of RAM, and dual processors.

COSMOS/Works 4.0 began shipping in March.