Abstract:
A method and system of comparing a part to a computer model of the part obtains coordinate data for a plurality of points on a part, compares the coordinate data to a computer model of the part to obtain comparison data, reports the comparison data corresponding to a selected surface of the part, and excludes comparison data for all surfaces other than the selected surface.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention relates to inspection of parts, and more particularly to comparing a physical part to a computer model of the part. 
         [0002]    When designing, developing, or optimizing a product, such as a part for a vehicle, it is common to create a computer model of the part. In some cases, computer-aided design (“CAD”) software tools are used to create a computer model. A computer model of a part typically has a plurality of surfaces. For example, a CAD model of a cube would have six planar surfaces. However, in more a complex CAD model, such as a casting for a turbine engine, there will be many more surfaces, and it is likely that not all surfaces will be planar. In one example, a designer operating CAD software and the CAD software itself determine what constitutes a surface within a computer model. A typical CAD model may comprise hundreds or even thousands of individual surfaces. 
         [0003]    Once a part is actually created, it is desirable to compare the part to an associated computer model of the part to verify that the part has been created accurately as part of an end of line quality control process. In the past this was achieved through mechanical inspection via a surface plate using a height gage, rotary tables, and handheld inspection tools. However, an example part may have hundreds or thousands of surfaces, and mechanical inspection is slow and does not provide sufficient data to obtain accurate measurements. 
         [0004]    More recently, scanners have been used to scan a part with a laser to obtain detailed coordinate data for a plurality of points on the part. Some scanners are able to obtain coordinate data for up to 400,000 points per second. Software may be used to compare the coordinate data to an associated computer model of the part. Comparison data may then be reported in a visual display. Existing software reports comparison data for an entire area of a part. This is undesirable because an area of a part may have hundreds of different surfaces that are being reported simultaneously. When comparison data for so many surfaces is displayed simultaneously, isolating and diagnosing problematic surfaces becomes very difficult. There is a need for an improved system for part inspection. 
       SUMMARY OF THE INVENTION 
       [0005]    A method and system of comparing a part to a computer model of the part obtains coordinate data for a plurality of points on a part, compares the coordinate data to a computer model of the part to obtain comparison data, reports the comparison data corresponding to a selected surface of the part, and excludes comparison data for all surfaces other than the selected surface. 
         [0006]    These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  schematically illustrates an example scanning system. 
           [0008]      FIG. 2  is a flow chart illustrating an example surface review method. 
           [0009]      FIG. 3  schematically illustrates an example display of a first surface, a second surface, and a third surface an example part. 
           [0010]      FIG. 4  schematically illustrates an example display of the first surface of  FIG. 3 . 
           [0011]      FIG. 5  schematically illustrates an example display of the second surface of  FIG. 3 . 
           [0012]      FIG. 6  schematically illustrates an example display of the third surface of  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0013]    As shown in  FIG. 1 , an example scanner  40  scans an example part  42  using a laser  44  to obtain coordinate data for a plurality of points on the part  42 . It is understood that the laser  44  may move to contact various regions of the part  42 . In some cases a part must be prepared prior to scanning. Part preparation may include a process such as applying a coating to the part, removing a coating from the part, or applying stickers to the part. 
         [0014]    The scanner  40  stores the scanned coordinate data in memory. In the example of  FIG. 1 , the coordinate data is stored on a computer  46 , however it is understood that the scanner  40  would be able to store the coordinate data somewhere else, such as within its own internal memory. Also, it is understood that this invention is not limited to use with a scanner  40  that uses a laser  44  to obtain coordinate data. An example display  47  is connected to the computer  46 . The display  47  may be used to view a computer model of the part  42 , and to view coordinate data from the scanner  40 . 
         [0015]      FIG. 2  is a flow chart illustrating an example surface review method that compares coordinate data  48  of a part to a computer model  50  of the part. In one example the computer model  50  of the part is a computer-aided design (“CAD”) model. The coordinate data  48  and computer model  50  are imported in a first step  52 . In a second step  54 , a best fit is performed between the coordinate data  48  and the computer model  50 . This involves determining an orientation of the scanned part  42  and determining how points of the computer model  50  correspond to points from the coordinate data  48  so that the coordinate data and computer model can be correlated or aligned. In one example a best fit is performed manually. In another example a best fit is performed mathematically by software. 
         [0016]    In a third step  56 , the coordinate data and the computer model are compared to obtain comparison data. The comparison data includes how much each of the plurality of points in the coordinate data differs from a corresponding point on the computer model. This difference for each point is then stored in memory. 
         [0017]    In the scanning process it is possible that some erroneous points may be recorded. If a difference between a point and the computer model exceeds an error threshold, then it is possible that the point was not accurately scanned. In an example fourth step  58 , such erroneous points are identified and excluded from further processing. 
         [0018]    The coordinate data  48  may be broken into a plurality of groups, or point clouds, where each point cloud corresponds to a selected surface of a part. In a fifth step  60  a user selects a surface of the computer model  50  that the user wishes to review. In a sixth step  61  comparison data that does not correspond to the selected surface is excluded, and in a seventh step  62  comparison data for the selected surface is reported. Reporting comparison data therefore includes displaying the selected surface of the computer model, displaying a point cloud of comparison data associated with that selected surface, and excluding comparison data that does not correspond to the selected surface. In an eighth step  64  a user is able to select a new surface for display. 
         [0019]    In one example, a designer operating CAD software and the CAD software itself determine what constitutes a surface within a computer model. A CAD model would have a defined number of surfaces, and each surface may have an identification number. In reviewing comparison data for a part as outlined in steps  60 ,  61 ,  62 , and  64 , a user may choose to simply start with a first surface of the part and sequentially view performance data for each individual surface of the part until the final surface has been viewed. A user may also choose to view comparison data for a surface by entering an identification number of a desired surface or by clicking on the desired surface with a mouse. 
         [0020]    The comparison data may be used in a quality control process. For example, if a sufficient quantity of the coordinate data is within an inspection threshold, then the part may be considered to have passed an inspection. However, if a sufficient quantity of coordinate data is outside of the inspection threshold, then the part may be considered to be a faulty part. 
         [0021]    In one example, color may be used to show a level of difference between a point in the coordinate data  48  and an associated point in the computer model  50  as determined in step  56 . A color scale may be used to indicate a magnitude of difference between a point from the coordinate data  48  and the computer model  50 .  FIG. 3  schematically illustrates an example color scale  68  indicating a magnitude of difference between a computer model of an example part  70  and an actual part. Green, illustrated by parallel lines, indicates an area of little or no difference between points in the coordinate data and points on an associated computer model of the part  70 . Yellow, illustrated by crosshatching, indicates points from the coordinate data that are moderately raised above or moderately recessed in comparison to their corresponding points on the part  70 . Red, illustrated by hexagonal shapes, indicates points from the coordinate data that are even more raised or recessed than the yellow points. In an example part inspection, if there was too many red or yellow points, a part may be considered to have failed inspection. While the example color scale  68  of  FIG. 3  only includes three colors and uses the same colors for raised and recessed points, it is understood that more or less colors could be used, and that different colors could be used for raised and recessed points to illustrate a level of difference between a point in the coordinate data and an associated point in the computer model. 
         [0022]      FIG. 3  schematically illustrates the example part  70  having a first surface  72 , a second surface  74 , and a third surface  76 .  FIG. 4  schematically illustrates comparison data for the first surface  72  of the part  70 . The surface  72  has a green area  78 , shown by a series of hexagons. The green area  78  indicates little or no difference between points in coordinate data and points on an associated computer model of the part  72 . Comparison data that does not correspond to the selected surface  72  is excluded, thus portions of the part  70  that are not included in the selected surface  72  are displayed in wireframe. However, it is understood that portions of a part not included in a selected surface do not have to be displayed in wireframe, and could be displayed in another way, such as being shown in a shade of gray. 
         [0023]      FIG. 5  schematically illustrates comparison data for the second surface  74  of the example part  70 . The surface  74  has a green area  80 , indicating little to no difference between the points and an associated computer model of the part  70 . The surface  74  also has a yellow area  82 , indicating coordinate data that is raised above or recessed with respect to corresponding points in the computer model. The surface  74  also has a red area  84 , indicating coordinate data that is raised ever more above or recessed even more below corresponding points in the computer model. 
         [0024]      FIG. 6  schematically illustrates comparison data for the third surface  76  of the example part  70 . The surface  76  has a red area  86 , indicating points that are highly raised above or highly recessed below corresponding points in the computer model. Unlike the prior art, where comparison data for many surfaces is displayed simultaneously, the examples of  FIGS. 4-6  only display comparison data for a single selected surface and exclude comparison data that does not correspond to the selected surface. 
         [0025]    Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.