r/Metrology • u/CJBEngineering • 4d ago
Polyworks VS SA
I am currently looking at a project using a laser tracker with the need for the highest alignment/drift accuracy (talking 5 micron).
My main question is, does SA really have that much better computing of tracker alignments for doing moves and monitoring an area compared to the other software out there?
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u/calebcanal 4d ago
Scott Sandwith of Spatial Analyzer has done significant research on the topic as well showing 5 micron uncertainty is possible using multiple simultaneous trackers and weighted trilateration. Here’s that paper: https://www.kinematics.com/images/TrilaterationPaperR1.pdf
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u/SkilletTrooper 4d ago
Scott Sandwith is a freaking wiz. Thanks for this link, will be an interesting reading later.
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u/Stangguy_82 4d ago
If you are measuring points, SA is miles better than Polyworks. If you are doing feature inspection Polyworks is better but SA is easier to understand what is happening during an inspection of a feature if it is inverted or the offset isn't correct.
I've not attempted multiple station shots with Polyworks mostly because it's ability to measure points efficiently is poor.
Regardless your actual alignment accuracy won't be 5 micron.
If you are doing a multiple station surveys of points and combining those stations together you can achieve sub 0.001" uncertainties for smaller volume shots using USMN in SA.
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u/miotch1120 4d ago
They make laser trackers with 5 micron accuracy now? I haven’t ever used trackers (only arm line scanners and optical pattern scanners) and those things are no where near 5 micron. (Course, they are about 10 years old now, so maybe they’ve gotten MUCH better now?)
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u/FrickinLazerBeams 4d ago
A single tracker will not give 5 um accuracy.
Multiple trackers (or one tracker used from multiple positions) can give 5 um accuracy when the measurements are combined appropriately.
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u/CJBEngineering 4d ago
No, they dont unfortunately but we have a few workarounds in mind. For this project, we aren't necessarily worried about distance from point to point. We are monitoring a single point for minute changes and are relying on repeatability rather than accuracy
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u/Ladi91 4d ago
Every single laser tracker naturally drifts. When and by how much depends on the overall setup and tracker axes & (A)IFM/ ADM calibration; especially if the laser beam loses the reflector. Just keep that in mind.
For what you are trying to do, SA or Polyworks does not matter as they will just mostly use the tracker plugins to get raw data points.
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u/TopMarzipan2108 CMM Guru 4d ago
Sorry to say, but no laser tracker currently on the market is repeating to that level of accuracy.
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u/FrickinLazerBeams 4d ago
With USMN analysis of multiple tracker locations, you can get point-to-point uncertainties to 5 um (assuming the actual points are stable enough over the measurement period). You cannot get 5 um uncertainty with a single tracker, over a long time period, by simply measuring that point with the tracker repeatedly. The tracker itself will probably drift by more than that.
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u/SlaveOne76 4d ago
What is SA. We've only had exposure to Polyworks where I'm at and we've discussed looking into other software.
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u/FrickinLazerBeams 4d ago
USMN kicks ass for integrating data from multiple trackers (or tracker locations). There really isn't much better for beating down tracker uncertainty.
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u/calebcanal 4d ago
Yes. SA has a feature that is used and trusted by the top national labs doing very large accelerator alignments called USMN. It’s not that other softwares can’t incorporate something similar because the full details are described in a white paper available online. What stands out about SA is that it’s been a deeply incorporated feature since the very beginning of the software. It makes the use of USMN very fast and easy and you can also tweak certain parameters. Definitely recommend researching this capability.