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Technical Section Phone: 516-328-3970 www.technocnc.com  19 Laser Scanning is the fastest system and generates the best results, but does have some limitations. First, you need a CNC machine to use it; the depth of scan is determined by the Z-axis height as well as the specific lens selected for a particular depth of field or readable area. Another limitation arises when objects to be scanned have contours under the top surface. In order to collect data on these contours during the initial scan, the end user needs a 4th axis to rotate the object so that it can be scanned from another angle. A digitizing arm, on the other hand, through its manual operation, can collect points under the top surface of an object. The digitizing arms also have an impressive work range and are available in numerous work ranges of spherical radii. It works in tandem with a CAD program, giving the operator complete control of how points, lines and surfaces are reverse-engineered.  The quality and accuracy of the final model depends on the skill of the operator, as does the time.  However,  the  end  result  is  a  NURBS  model,  a mathematical representation of a 3D surface, that is much more flexible and smaller than a point cloud created by the other tools. That being said, they are also the most reasonably priced digitizing systems, versatile in that they perform 2D or 3D scans and do not require a CNC machine to operate. If you do have a CNC machine and want a cost-effective digitizer, then you should look at a CNC digitizing probe. These probes share the same benefits of the laser scanners in  that  they  are  automated,  and  subsequently  faster  in collecting data than digitizing arms and are less prone to error. They are also a more economical option than the laser scanner. Although, what you save in money, you lose in the detail a laser provides. Also, a digitizing probe shares some of the disadvantages of the laser scanner. Because you need a CNC machine to generate a point cloud, you lose whatever shop time you would otherwise use your machine for. A probe will not be able to collect points from sharp, deep cavities or grooves located underneath the object’s top surface without rotating and rescanning, but it can quickly and easily do 2D scans. Access to reverse engineering tools and the advantages they  provide  is  abundant,  but  which  system  to  choose greatly depends on the nature of your application. Do you require  2D  or  3D  capabilities?  What  is  the  shape  and contour of the objects being scanned? Do you have or plan to  get  a  CNC  machine?  What  is  your  work  load?  How accurate does your scan have to be and what funds are available for this purchase? Finding the right match between your application and a particular reverse engineering system is just the beginning. It helps to know how the system works in order to garner the best results. For instance, the noncontact digitizing CNC laser scanner collects data that is reflected back, off the scanned object. The laser shoots a stream of light toward the object;  when the light reaches the object, it bounces back toward the scanner in waves (i.e., Diffraction Principle and Interference Patterns). Depending on the intensity and range of the waves, the laser’s sensor interprets the depth of the object. When the laser’s sensor is able to clearly interpret the reflected light waves, the resulting point cloud is extremely detailed. It is possible, however, for some aspects of the object to give a misrepresented reading of the surface area being scanned. The cleanliness of the surface, for one, can contribute to an inaccurate point cloud. Again, the laser’s scan is so detailed that even the smallest of debris can be recorded. Other laser scanning aspects to consider include the texture and color of the surface to be scanned. As mentioned already, the surface area needs to be clean and free of debris;  but  clean  should  not  be  confused  with  glossy. Objects that have shiny or transparent surfaces do not scan well  due  to  the  nature  of  the  scanner’s  reflected  data collection.  When  the  laser  scans  a  glossy  surface,  the reflected light that bounces off and back to the sensor is too strong and thus, misrepresented. On the other end of the spectrum, if the surface is at all transparent or translucent, then a portion of the laser’s light will be absorbed into the surface, resulting in too little information returning to the laser. Color  saturation  also  plays  a  significant  role  in  the quality of a laser’s scan. Darker colors tend to absorb the laser, while lighter colored surfaces reflect too much. There are  controls  to  manipulate  a  scan’s  range  of  intensity. Tweaking these controls can compensate for the amount of