long probe repeatability issues

[[Ma...]]

Howdy, I have a 425mm long probe mounted horizontally. Ive been getting some weird repeatability issues on this bore and im looking for some advice on how to make this program more repeatable. 

The length of the measured bore is around 337mm long and we have to use a line scan for the given geometry. You can see the crest at the end of the bore indicated by a 20X mag of points and the cylindricity plot.
Every time i run the program the crest is either in a different location radially or not there at all. Any ideas of what could be causing this and how to avoid it.

Scanning direction is pulling (is it more stable to scan in a push direction?) at 7mm/s 
DK10 L425 
Contura 
Vast XTR. 

[[Ma...]]

I would say pull will be better.

Due torque of probe tip weight will tip go down, so pulling would help instead of a push. But counter weight could help more.

Is it needed to be measured by scan? Couldn't it be measured from both sides so you could have shorter probe?

[[Ri...]]

Turn down your probing dynamics, if the setup isn't very rigid, it will be vibrating on the initial hit. 

 

Also pay attention that you have no filter applied - since you are performing linear scans, you will need to use wavelength instead of UPR.

[[Jo...]]

Are you using the recommended Filter?  Is there a reason you have to scan instead of using single points? 

(Its a quick easy check to change a strategy to single points to see if scanning dynamics are affecting your measurement. )

[[Ma...]]

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I suppose I could use single points but were trying to keep cycle times down and we feel like scanning is faster. What would you recommend for a point count if we moved to single points. 

Im worried about increasing the magnitude of error on the measurement by going in through both sides. Historically, in our experience measuring from 2 sides has lead to more discrepancies in our results than good.  

[[Ma...]]

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I did not know this! Thanks for the nugget of wisdom. 

Rigidity is at 1.263, so pretty poor... by probing dynamics is at 30%, measuring force is at 200mN, Qualifying in Tensor. After playing around with it this gave me the best sigma value. But im open to try new qualification settings if you've had better luck. 

[[Ma...]]

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I depends on what you need from that feature. Wouldn't 3 circular path with 8 points be sufficient? For Accura i saw approx 1s for a point