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Scanner Inconsistencies

pelli85
Hi,

I have been trying to verify the accuracy of my scans. To do so, I take a part, fix it to the table, and run my scan program. I then print the report. Next, I re-execute the same program on the same exact piece (without even moving it from where it was for my first execution). When I compare the two reports, some points are basically the same measurement, however I do get at least 25%-40% of the measurements that end up 10-30 thou different from the same point on the previous scan. I have tried everything, from ensuring that the scanner is checked to trying different angles and fixtures. I am not sure if the issue is my program, my scanning technique, or if my expectations/standards of the scanner's consistency are too high. Either way, I am kind of at a loss of ideas to improve these scans because it feels like I have tried everything. Any suggestions or advice helps, even if you don't know. I have an absolute arm 85 with an RS6 scanner for reference.
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  • Well, if the scanner is out of calibration (all probes & scanner must be calibrated at the same time, and it's done in the RDS, not Pcdmis), I can see that much error showing up.

    Ya gotta remember, there are 7 (7?) very small circular disks, one in each joint that pivots, that are the scales for that thing. Doesn't take much calibration error to throw an arm WHY out into left field, as it were. I mean, think about it. A 3" disk scale is responsible for 24"? 36"? of arm segment accuracy.

    When you tried re-scanning, did you hold the pistol grip in the same orientation (exactly.... mostly) for the second scan that you did for the first scan?

    If I remember right form the training class all those years ago, the best results are when the camera is perp to the surface you are scanning, NOT the laser emitter. Also, when scanning a radius, they told us that the laser should make the 'circle' of the radius, not the axis of the radius (so the laser line wraps around the radius, not on the same axis as the radius).
  • in reply to Matthew D. Hoedeman
    Okay. I'm going to try to re-calibrate the arm. Everything u said makes sense. I definitely was paying no attention to the consistency of my scan angle across both scans (so I doubt I held the same orientation both times). Also I've never had any formal training on these arms and how to use them so that last paragraph definitely gives me some pretty good insight on my issue.
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  • in reply to Matthew D. Hoedeman
    Okay. I'm going to try to re-calibrate the arm. Everything u said makes sense. I definitely was paying no attention to the consistency of my scan angle across both scans (so I doubt I held the same orientation both times). Also I've never had any formal training on these arms and how to use them so that last paragraph definitely gives me some pretty good insight on my issue.
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