Close-range Laser Scanning for Reverse Engineering

The audience for LiDAR News usually reads stories about long range spherical laser scanners capturing large buildings, bridges, or boats. There are plenty of other applications for laser scanners and our roots at Direct Dimensions are actually from a much smaller scale of such problems. A similar concept of 3D scanning has been developed and utilized for more or less a similar number of years as spherical scanners aimed at more mechanical components, such as aircraft and automotive parts. While these are relatively smaller scale objects, the tolerances are also relatively much tighter very often in the +/- 0.1mm or less range. As such, the usual tools for scanning buildings simply do not apply here.

Another class of 3D measurement equipment, which many of us refer to as close-range scanners, is aimed at this world of industrial 3D metrology. Such tools include patch-based laser scanners, a variety of projected light-based optical imaging systems, and laser line scanners manipulated by either fixed or portable means, such as an articulating arm coordinate measurement machine (CMM). Because there is such a wide variety of applications for close-range industrial metrology, there are a dozens of OEMs making a plethora of 3D scanning solutions. We see new concepts develop and enter the market almost every month. In fact, I just wrote about a new one in my last submission to LiDAR News, called the F5 from Mantis Vision in Israel.

This story below is about how one of these tools, a portable articulating arm with a laser line scanner, that was used to capture the complex shape of a snowmobile engine. Our customer was a group of engineering students from a nearby university hoping to win a racing challenge with a new idea. But before they could start the actual race, they soon realized another challenge how to reverse engineer the new engine so they could incorporate it into their car.

Direct Dimensions, and our toolbox full of 3D technologies, to the rescue!

Each year a select group of students in the Mechanical Engineering program in the A. James Clark School of Engineering at University of Maryland in College Park, MD compete in the Formula SAE (Society of Automotive Engineers) competition. The FSAE competition requires the team of students to design, build, and race their own open cockpit race car.

The University of Maryland team, called Terps Racing, consistently finishes in the top 10 against 80 to 120 other school programs annually. Aiming for a first place finish in the upcoming races, the team is experimenting with a new engine design.

The small autocross cars, usually weighing between 300 and 500 pounds, typically run on modified motorcycle engines. But this year the student engineers at Terps Racing are experimenting with a snowmobile engine for the races this year.

During the design phase for a new gearbox for this style of engine, the students realized they needed a 3D CAD model of their particular snowmobile engine so that they could accurately and efficiently design within the tight tolerances necessary to the mounting points. While they have a shop full of conventional measuring tools, they had nothing that could accurately capture the complex 3D relationships of the engine.

Terps Racing approached Direct Dimensions for help creating the CAD model to aid in their design and we were happy to help!

Here is a review of the major steps in this process:

Laser Scanning: Using the integrated combination of a Platinum FAROArm Portable CMM and laser line probe (V2 LLP), Direct Dimensions engineer Michael Lent scanned and digitized the complex casting shapes and critical geometric interface features on the engine. The FARO system is a great fit for this type of project because it provides both a contact probe for high accuracy geometric features, such as attachment holes, and a non-contact laser scanner for the complex contoured surfaces. The system is manually manipulated and provides real-time feedback to the operator to assure complete capture. The entire capture process took only a couple of hours including set-up. The resulting data is a dense 3D point cloud with all the laser scan data and various geometric features including circles, cylinders, and planes. All data is coordinated together in a common reference frame, usually established initially based on the geometry of the part.

Reverse Engineering: By utilizing a variety of software, including PolyWorks, Geomagic, Rapidform and SolidWorks, the Direct Dimensions engineers merged and modeled the 3D digitized data with the laser scanned point clouds into a hybrid of a parametric solid-based feature model with the watertight complex NURBS surfaces. The casting surfaces are converted into a mesh of polygons and then into rapid NURBS. The geometric entities are converted into editable solid geometry features. These two styles of models are then merged together into a watertight solid CAD model with the critical features as smart geometry features and the complex cast surfaces as dumb. This file can be exported via IGES and x_t (parasolids) interchangeable formats, or as an SldPrt native SolidWorks file. Either file type is readily usable within most mechanical CAD software products, such as SolidWorks, for the subsequent re-design effort by the Terps Racing students.

History repeats itself: But talk about reverse engineering, it turns out this isnt the first time Direct Dimensions helped a racing team at the University of Maryland with our 3D technology. The first official project that I ever performed upon establishing Direct Dimensions in April of 1995 used the FARO Arm to align the wheels of the University of Maryland solar-powered car prior to a critical race. Over the years weve helped this school and many others in our area with similar challenges. No question that the best part of these projects is working with the students and introducing them to our world of 3D scanning and digital modeling technologies and capabilities. I am quite sure weve influenced more than one to consider a career in our field.

Meanwhile, as you begin planning for the new year, consider opening your mind as these students did, by learning more about close-range 3D industrial metrology and how it relates to what you do. The 28th annual conference dedicated to this technology and its applications, called the Coordinate Metrology Systems Conference, or CMSC, will be held in New Orleans in July 2012. Our Call for Papers will be announced very soon and I urge you to consider submitting an abstract or at least attending. I wrote about the CMSC conference and related others in my February 2011 submission to LiDAR News. Include learning more about close-range 3D in your new year and come to CMSC!

About the Author

Michael Raphael

Michael Raphael ... Michael earned a BS degree in Engineering Science and Mechanics from Virginia Tech, followed by a Masters of Engineering Administration from George Washington University. During his 10 years at Lockheed Martin as an engineer responsible for solving aerostructures manufacturing quality problems, Michael co-developed the FaroArm portable CMM and became the first user on the planet! In 1995, he founded Direct Dimensions, Inc., providing rapid solutions to 3D problems!

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