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Scanning vs Touch Probes

slipper57
We are enquiring about a new CMM. I have been looking into 'scanning' probing, not so sure if this is what we want?? So, here I am, asking people with knowledge on this type of probing. I am NOT familiar with scan probes at all!
Some, if not a majority, of our inspections may be on sheet metal surfaces, which are NOT the same finish as machined surfaces. I , with no knowledge, would be concerned about the accuracy of scanning probes on an un-even surface.?? I also have heard, with as little of a 'crash' these probes can be problematic?

So, in closing, if you were to purchase a new CMM, would you include the scanning probe? To me it sounds too good to be true? Thanks!
  • In 35 years of doing sheet metal, I've yet to run across any instance where the INSPECTION of the sheet metal REQUIRED scanning, but we are not production, we are construction (we build the tools that do the stamping). BUT, scanning is useful in other aspects of what I do, but for 30 years, it was TTP scanning, and that is good enough for 99.99999% of what I need to scan. We do have scanning on the new machine we bought a few years ago, and we do use it, but not very often, and generally only for reverse engineering, never for inspection.

    So, yes, include it if they will pay for it, sooner or later it will be useful.
  • With the Renishaw SP25 range of probes you can switch between touch trigger probing, TM25/TP20 and Scanning SP25M/SH Module on the same machine and probe rack. Might be best to have both worlds available.
  • in reply to Liambo734
    Yes, we would have both options.
    I was/am just concerned about the accuracy/life span of these probe options vs the cost to include this.
    Our other CMM, which we are keeping, will not have this 'scanning' option....
  • in reply to Liambo734
    sounds just like here. We use the TP20 all the time on the new machine, EXCEPT when I need to do reverse engineering scanning, for reproducing details we didn't make or design. The SP25 stays in its box except for 10 days a year or so.
  • Scanning is useful, since it gathers thousands and thousands of points in a few seconds. This particular software is structured in a way that slows it down when scanned features are used liberally (seems to be a cubic function, double point density takes 8x as long to process).

    Be careful how you use it.

    Also, I have noticed that with extremely flexible (0.2mm-0.3mm) tips, something in the scanning calibration process can go haywire, where these will show non-existent ovalities, if a tip flexes along a specific vector.
  • Get scanning probe head dude even if you will barely use scanning. We have one Global with scanning head & it proves useful when tooling or engineering department need to check something but have no CAD or print to go by. And that's about what it does. Happens once every 2-3 years but it happens. The other an old B&S One has only TTP & while it's a great machine along with bug free 2016 software version it's useless when we need to reverse engineer complex contours for the toolroom or print-less engineering department. If you have a budget for new CMM might as well throw in little more dough & get full capability out of it. It's like buying a car. If you have a budget for an economy car it's worth to throw a bit more dough to get something much better & more capable.
  • in reply to Kai Kendall
    Yep. We have .5mm tip mounted on a 50mm styli & during calibration we noticed flexing too. We got around it by reducing touch speeds & also you can check Trax calibration box that makes CMM calibrate using touch points only.
  • in reply to Kai Kendall
    Yes, Trax, is another way to correct the it's-not-a-bug.
  • We have both TTP and Analog heads here. Be aware if you have high vibration in your shop it can affect your analog system as it is much more sensitive to vibrations. We found out the hard way!
    Scanning is fantastic for developing trim lines, reverse engineering details stuff like that. I think most companies can get by with just a TTP system but scanning capabilities are nice when you need them!
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