PolyWorks 3D Aids Corvette Racing Team

By John R. Anderson

This image illustrates the scanning process for new body panels for the Corvette Racing Team.Designers start with production body panels (black) and modify their shape using clay (tan).

At Pratt & Miller Engineering & Fabrication in New Hudson, MI, automotive designers and engineers use point cloud data in reverse engineering applications to take new ideas from concept to reality quickly and efficiently.

  Since its founding in 1989, Pratt & Miller has developed a full range of sophisticated automotive design, engineering, fabrication, and race-program management services. The company offers complete vehicle kinematics and compliance testing, seven-post ride analysis, full and fractional scale wind-tunnel development, and vehicle dynamics and evaluation testing.

Critical to the overall efficiency and accuracy of the company’s test and evaluation programs is the use of computer-generated models to provide engineering insight into design concepts. In order to create these models, it is necessary to digitize certain shapes, primarily the curved body parts, and use this dimensional information to create MCAD models. In the past,  Pratt & Miller technicians would build a model using individual data points and create curves manually from that data.

Point cloud of the front fascia of the Corvette.

Scan alignment in PolyWorks IMAlign module.

Polygonal model of the front fascia.

A curve network is extracted to fit NURBS.

“That was an extremely time-consuming process,” says Blair Sonnen, a Pratt & Miller engineer, “and didn’t give us the precision and accuracy we needed. If we had to redesign a part to improve its performance, we would have to build another model the same way. In order to reduce the time spent in this process, and improve accuracy, we would sometimes hire an outside company to come in and collect dimensional data using the scanning process, or create curved surfaces from the discrete point data we collected, but that was not a cost-effective way of creating models.”

  To help solve that dilemma, the company recently expanded its engineering capabilities by adding PolyWorks 3D metrology software from InnovMetric Software Inc., a full-featured metrology solution that automates and streamlines many of the operations associated with gathering and comparing dimensional data with design intent. In concert with a FARO Titanium Arm scanning device equipped with a FARO Laser Line probe the company already owned, Pratt & Miller is improving the efficiency of its reverse engineering program for the GT-1 champion Corvette Racing Team, run in conjunction with General Motors.

“PolyWorks software is a key piece in our reverse engineering program because it allows us to quickly digitize models and get the design into our analysis programs much faster than in the past. That allows us to evaluate the design more quickly so we can incorporate necessary design changes immediately and go into production faster,” says Sonnen.

  Putting Advanced Engineering to Work
In practice, the company’s design engineers create a clay model of an automotive body part, such as a fascia. The model is then scanned using PolyWorks software in conjunction with the FARO arm and probe capable of collecting dimensional data at a rate of up to 19,200 points per second.

  The dimensional scan of the clay model is taken using the IMAlign module of the software. Once the data have been collected, Sonnen downloads it all to his personal workstation where he uses PolyWorks/Modeler to create a precise model of the part. PolyWorks/Modeler is a comprehensive program for creating accurate and smooth polygonal models and NURBS surfaces from high-density point cloud data. This software can create class A polygonal models for three- and five-axis milling operations and aerodynamic simulation.

  One of the features of the PolyWorks/ Modeler software is its full-featured alignment toolbox.

“I’ll use the IMAlign module again to create a best-fit alignment of the multiple scanning paths,” says Sonnen. “Then I export the aligned scan paths to the software’s IMMerge module to create a polygonal mesh that graphically defines the shape of the scanned part.”

  At that point, he goes through an iterative process,  combining models. The combined model is then imported to the IMEdit module to correct imperfectly digitized geometry using flat and curvature-based hole-filling procedures. From there, the model goes to curve network creation and automatic NURBS surface fitting. The rapid-surfacing methodology delivers optimized and usable NURBS surfaces to the company’s NX MCAD program.

  According to Sonnen, PolyWorks software excels at polygonal modeling and rapid surfacing, procedures that can significantly reduce the time and cost of less-automated methods when creating models for analysis.

Using the MCAD model, Pratt & Miller engineers can subject the virtual part to a full complement of performance evaluations including advanced computational fluid dynamics (CFD) tools using an in-house solution called Raven CFD to analyze the aerodynamic impact and flow field structures of vehicles. At this point, engineers will also use the company’s proprietary automated dynamic analysis of mechanical systems (ADAMS) model for virtual track simulations. Based on the evaluations, part design can be improved incrementally before production tooling is produced, resulting in a significant savings in time and costs as well as a dramatic improvement in vehicle performance.

  It seems to be working. The Corvette Racing Team has scored successive championships in the American Le Mans Series and scored impressive finishes in the Rolex 24 Hours at Daytona as well as the 24 Hours of Le Mans. In the process, Pratt & Miller has created an engineering approach to performance design that has applications for original equipment manufacturers in the automotive, aerospace, and marine industries.

More Info:
FARO
Lake Mary, FL
faro.com

InnovMetric Software Inc.
Quebec, QUE
innovmetric.com

Pratt & Miller
Engineering & Fabrication
New Hudson, MI
prattmiller.com

Robert McNeel Associates
Seattle, WA
rhino3d.com

Siemens PLM Software
Plano, TX
siemens.com/plm

  John R. Anderson is a freelance writer and marketing communications consultant based in Rhode Island. You can send comments about this article to [email protected].