non-contact 3d surface roughness measurement
non-contact 3d surface roughness measurement
(OP)
I'm trying to find a company/lab to do some 3D surface roughness measurements for me. I'm looking for some specific parameters and having trouble finding someone who can measure what I need for a model that has been developed.
The tricky parameter is the standard deviation of peak distribution.
I have found several labs that use non-contact white light interferometers, but they do not know how to interpret the data to give me the standard deviation of peak distribution.
Can anyone give me any tips to find the standard deviation of peak distribution?
The tricky parameter is the standard deviation of peak distribution.
I have found several labs that use non-contact white light interferometers, but they do not know how to interpret the data to give me the standard deviation of peak distribution.
Can anyone give me any tips to find the standard deviation of peak distribution?





RE: non-contact 3d surface roughness measurement
Is there another surface texture factor that you can use as a proxy?
= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection
http://www.trent-tube.com/contact/Tech_Assist.cfm
RE: non-contact 3d surface roughness measurement
http://www.michmet.com/
RE: non-contact 3d surface roughness measurement
RE: non-contact 3d surface roughness measurement
My advice to you is to _always_ get the raw or massaged data (say if your lab records voltages, but you want some distance recorded. the raw is the voltage, the massaged is the distance).
RE: non-contact 3d surface roughness measurement
If anyone knows a lab that has the capability to perform non-contact 3D surface roughness measurements and can give me standard deviation of peak distribution please advise me.
RE: non-contact 3d surface roughness measurement
RE: non-contact 3d surface roughness measurement
TTFN
Eng-Tips Policies FAQ731-376
RE: non-contact 3d surface roughness measurement
RE: non-contact 3d surface roughness measurement
= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection
http://www.trent-tube.com/contact/Tech_Assist.cfm
RE: non-contact 3d surface roughness measurement
I am now looking for software to do the following:
Locate all peaks (points higher than their nearest neighbours (4 or 8))
Work out the curvature of each peak, from the heights at the peak and the 4 or 8 neighbours
Obtain the total number of peaks in the sampling area. Scale to unit area.
Produce a list of peaks and their heights, or a distribution (number of peaks in each height range ).
Calculate average curvature (Ssc parameter)
I believe most of these calculations are done internally by profilometer software in order to calculate Rpm etc, but may not be accessible to the user.
Peaks, summits and asperities mean the same or similar. There may be differences due to an exclusion zone etc.
There should not be a lower cut-off (ie a peak whose height is less than zero is valid - but it is a peak, not a valley, ie like a mountain under the sea!)
I expect to have to do any further analysis using Excel or similar package.
The peak distribution would be fitted to a Gaussian curve. The mean value is the "mean peak height" - from all the peaks, not just the top 5 or 10. The standard deviation is a measure of the width of the distribution. The magnitude of the curve is related to the total number of peaks.
Contact pressures are low, so the true area of contact will be very small - I estimate around 0.001% of the nominal area. So very few peaks in the sampled area will come into contact. The statistics of most of the peaks are irrelevant as they do not come into contact.
A fit can always be forced, but the important thing is to get a close fit to the highest peaks in the sampling area, say the top 100. This distribution can then be used to extrapolate to the very highest peaks on the surface, which are unlikely to appear in the sampling area.
I would therefore use the goodness of fit to the top 100 peaks only in fixing the parameters of the Gaussian distribution, even if the fit elsewhere is poor.
As a final point, it would be useful to have the curvature of each peak listed, or some way to link the curvature to the height. I think there is often a correlation between the two - higher peaks have greater curvature.
RE: non-contact 3d surface roughness measurement
RE: non-contact 3d surface roughness measurement
http://www.digitalmetrology.com/
We had a PhD intern that work on some wear problems we were having with out high speed equipment and about the only thin I remember was the he considered the peaks to conical in most cases.
Another approach might be Fractal Geometry. Sometime back I ran across a paper extolling the virtues of describing surface roughness and topography by means of fractal Geometry. For some reason I didn't mark the site.
RE: non-contact 3d surface roughness measurement
I get an idea of what you are after, I wasn't thinking of low contact pressures. You are going to need to do this optically. Otherwise stylus geometry will limit you data.
= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection
http://www.trent-tube.com/contact/Tech_Assist.cfm
RE: non-contact 3d surface roughness measurement
Their Infinite Focus Instrument is capable. I use one regularly.
RE: non-contact 3d surface roughness measurement
www.veeco.com
RE: non-contact 3d surface roughness measurement
Thanks for the tip, I hadn't heard of them. Does anyone know a metrology service that has an Alicona Infinite Focus? I found one company in Manchester (ISS Group), but their email address doesn't work and I'd like to find a company in the states. Thanks.
RE: non-contact 3d surface roughness measurement
Get in touch with Paul Beaulieu or Chris Rinaldi at Excel Technologies (Enfield CT; www.extec.com )
They should be able to place you with someone.
good luck.
RE: non-contact 3d surface roughness measurement
RE: non-contact 3d surface roughness measurement
RE: non-contact 3d surface roughness measurement
htt
RE: non-contact 3d surface roughness measurement
RE: non-contact 3d surface roughness measurement
Please believe me that I have done extremely similar work before, GW model, etc - I would not say exactly same. Anyway, I will just give you what I gained before:
1) You insist non-contact imaging, so the tapping mode of AFM can be used;
2) When you have 3-d surface topography from AFM, you have to do the calculation youself to find/define the peaks. 2 years ago, the AFM I was using does not support this calculation automatically.
3) Actually I think I wrote a program to calculate this offline before - find the peaks and fit into whatever distribution. It is not hard at all. I do not understand why the labs won't take this.
4) You have to be quick because I always wanted to write a paper on this, but have been lagging after I left school. Just kidding, if I pick it up again, it will be purely numerical as I have no more access to AFM.
RE: non-contact 3d surface roughness measurement
Is it any local maxima, regardless of its position? Then you would have to count a small bump in the bottom of a pit.
Is it only local maxima? Then you would not count a "ridge".
These topics are being wrestled in ISO TC213/WG 16 and some definitions are falling in place.
Try Digital Metrology Solutions (www.digitalmetrology.com) to have something developed. Otherwise, Michigan Metrology (www.michmet.com) could get raw, ASCII data to you and you can process it yourself.
Good luck!