Laser Scanning Accelerates Data Acquisition

Engineering firms manage more data today than ever before and because of this, laser scanning has by and large become the new currency in the competitive world of engineering. Among the new currency being brought into circulation by various companies is a 3-D digitizer series from Minolta (Mahwah, NJ) - a portable, non-contact surface and texture digitizer designed for workplace and remote location uses.

Digitizer Details

The system runs on 256MB of RAM and supports both Windows NT and SGI computer platforms with data export capabilities to a wide range of applications and industries - including 3-D animation, rapid prototyping, CAD/CAM, CAE, industrial design, reverse engineering and Internet development. It can be used with a number of software systems - including Alias/Waterfront Maya, 3D Studio Max, Raindrop Geomagic, SoftImage, Lightwave, RapidForm 2000 and OpenInventor, to name just some. In a phrase, laser scanning has accelerated data acquisition.

"If you think of it, the digitizer is really a 3-D copy machine," says Martin Chader, 3-D business unit manager at Minolta. "What we give you is a watertight polygon mesh. It looks like a fine fishnet and if you imagine taking that fishnet and stretching it around the object you are digitizing, that is what we are giving you - connectivity instead of a whole bunch of dots on the surface. The software supports running a turntable with it to automatically index the part - you take a shot then repeat it. Then you take this fishnet system and lay them over each other so that they coordinate properly. You can do it that way or use it free hand and move it around to wherever you want. When that's all done, what you have is this watertight mesh, which means it has no seams. The digitizer also has the ability to export both image and shape data to a CAD or directly to a CAM application to make molds or recreate the part."

Triangulation, Pulse and Modulated Beam Lasers

But there are several other laser scanner variations out there that should be mentioned.

For example, for large scale scanning, the pulsed laser is an excellent alternative; it can produce up to 1,000 individual dots in each columnar sweep then measures time of flight for each point. In using time of flight, what you are trying to do is measure airplane-sized volumes over very large distances - measuring rotations from side to side (i.e., azimuth) and up and down (i.e., elevation) and dividing each rotation up into tiny angular increments. As the laser source is swept over the area, the scanner simply shoots a pulsed laser out and measures how long it takes to get back.

Amplitude modulated beam laser scanners sweep a continuously varying beam via rapidly rotating mirrors and capture the return via a receiver that deflects the reflected energy. The receiver matches the return waveform to the output modulation and calculates the distance of the object. In each category, the scanners capture four pieces of information for each individual dot (surface geometry measurement), the X, Y, and Z coordinates and a return intensity, which they can use to map a color or grayscale over the cloud. The image that appears on the computer screen is a 3-D cloud, which, depending on the scan density and technologies used, can capture minute details. Point clouds refer to information that is gathered by 3-D laser scanning. Conversion software then turns the point clouds' data into a 3-D model or 2-D drawing that can be put into your CAD software. Until scanners were developed, the only way to depict 3-D objects was to use traditional one-point-at-a-time capture methods plus a CAD system capable of 3-D modeling.

Reworking an Exhaust System With the Digitizer

For the best possible results, the reflective metal surface was treated with a spray to dull the surface. Only one scan was required to capture the targeted area using the Vivid utility software to view and prepare the data for export. The data was then imported to CAD software for analysis and the raw scan data was surfaced. The finished IGES file was then delivered to the customer, which was imported into their CAD software, and analyzed and processed to obtain a standard mass production exhaust muffler.

Before all of this could take place, the Rosenheim team needed to know the precise area of the bike's exhaust. It is much more economical to accurately fabricate all of the bike's parts, then ship the bike out. Any mistake or mismeasurements would prove costly. Placing the scanner in different locations allowed multiple scans to be stitched or registered together to create one, single 3-D representation of the exhaust in relation to the motorbike frame and other exhaust components. The scans were captured in minutes, and engineers took two weeks to convert the scan data into a 3-D CAD model, perform further analysis and fabrication plans for the new part.

"There are two places the laser process is used," says Chader. "One is the design process where the majority of industrial designers still prefer to work in conceptual models. Some still work onscreen, but most will create conceptual models, then take that information and put it into a CAD system. The other is where you have physical parts and one standard - usually a digital standard - and you want to inspect the part to make sure that it matches your design intention. These are the two classical places - capturing the design from the physical and the inspection. There is so much more communicated by having a 3-D object in front of you than trying to stay on the screen throughout the entire process. Design is definitely moving from a geometrics world to a much more organic, sculpted and interesting one."