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Renishaw SP25

Big John
Hello,
At the moment we have a couple of CMM's with Renishaw PH10M heads and either a TP20 or a TP200 module.
We are thinking about buying a new CMM. We are planning to scan some products.
Hexagon recommended their own rotating head type HP-L. This looks quite fancy, except that I have heard that for calibration it needs 25 hits for each angle being used. If that is so, then we will lose plenty of time calibrating instead of measuring. At the moment we calibrate using 5 hits on the calibration sphere. (Minimal I know, but it seems to work for us)
The difference is 5 times longer!!

I have 3 questions:

Is the 25 hits correct?

If we were to buy a Renishaw SP25 how many calibration hits are needed on the sphere? I asked Renishaw, they replied that it is up to the software.

Concerning the HP-L or the SP25

Is it not possible to calibrate the first position with 25 hits, then the other angles scan the sphere?

Regards
John
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  • in reply to Big John
    Another consideration with the SP-25M, which we use, is that depending on the release version of PC-DMIS you use, the later versions have a tick box option to use partial scan only. That being said, once an initial calibration for a new tip has been completed you can check that box and a calibration will be completed with only 5 touch hits on the sphere. The software stores and remembers the scan data and ties it to the touch hit data during calibration For us, once I upgraded from V4.2 to 2009, I was able to reduce our calibration time from 6.5 hours to 1.5 for our rack of probe tips. Hope this information helps.
  • in reply to Big John
    It is true, you can use the reduced calibration method that only takes 5 points but this only updates the calibration values for touch trigger probing. If you are performing any type of scanning operation within your programs you need to do the longer calibration or the scanning parameters will not get updated.
  • in reply to Neil Challinor

    I guess it's time for me to wake a zombie thread... (but hey, I searched the forum!) (sorry, no actual advanced search options exist here)

    We are in the process of coming back online with our machine, which uses a SP-25...
    Managment has asked some questions about our calibration process, since we have a "new and different" machine now. Rather than move forward with the default "that's how it's always been done" answer I shall humble myself here on these great forums and hopefully get something more in depth to report. 

    Seems that the response above is what I was looking for, but just to be clear... (assuming after round 1 new probe calibration has been performed)

    To use the system with the best accuracy for scanning features, you must run the default calibration of 5 TTP hits and 8 or so scans per tip angle. 
    To use the system with the best accuracy for TTP measurements, running a "patrial calibration" that skips the scans and uses 13-25 TTP hits per tip angle will be best. 
    And these two forms of "calibration" only ever add to each other, not cancel each other out by choosing the wrong option? 

    99.9999999995% of our programs are TTP only so they understandably care most about that function of the machine. 

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