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Technical Discussions
Shah'Zan
Shah'Zan
12:54 Aug-26-2012
Eddy Current - Polymer Overlay Thickness


Dear All

I wish to receive recommendations from experts regarding the application of eddy current measurement technique for the measurement of polymer (actually this is polymer base nano composite material) overlay thickness. The overlay phase is applied on a rough non-ferrous substrate.

Main problem being faced by us is 15-20 % offset from actual overlay thickness as determined by microscopic methodology.

Maybe, some one from NDT industrial sector could provide the contact of his/her organization for further discussion. We wish to apply the selected measurement device for our production lines globally.

Regards

Shah'Zan

 
 Reply 
 
Dave Utrata
R & D,
Center for NDE, Iowa State University, USA, Joined Feb 2000, 37

Dave Utrata

R & D,
Center for NDE, Iowa State University,
USA,
Joined Feb 2000
37
17:22 Aug-27-2012
Re: Eddy Current - Polymer Overlay Thickness
In Reply to Shah'Zan at 12:54 Aug-26-2012 (Opening).

Various issues would seem to be presented here, those being the anticipated film thickness range and accuracy needed for measurements, the roughness of the substrate, and whether the probe may contact the polymer layer. At least I think these are the main issues, unless I am missing part of the challenge description.

In some measurement work we did recently, commercial devices such as the Positector 6000 worked well. (We do not recommend any particular device; this is simply the one we used on our tests). The challenge on the rough, and that is a relative term, surface was that multiple measurements had to be made and an average used for thickness testing to produce anticipated trends. The other issue in that work was that it was unknown if the thickness of the test layer precisely followed the surface profile or if it filled in the "valleys" on the topography of the substrate and left thinned layers over the "peaks" in the profile.

The end result was a that fairly straightforward measurement could be utilized but multiple readings had to be made, and that preconceived notions of film distribution had to be reevaluated.

Regards,
Dave

 
 Reply 
 
Shah'Zan
R & D,
Germany, Joined Aug 2012, 1

Shah'Zan

R & D,
Germany,
Joined Aug 2012
1
14:22 Aug-29-2012
Re: Eddy Current - Polymer Overlay Thickness
In Reply to Dave Utrata at 17:22 Aug-27-2012 .


Thanks Dave for your expert view.

The most important criteria for us are accuracy & close resemblance to data generated by microscopic investigation.
The film thickness is finer than 15 µm & Rz of the coated surface profiles is in the range of 5-7 µm. The coating process deposits a layer that follows macro-profiles of rough substrate and relatively thin layer over the peaks, as you said.
Additionally, we wish to measure the wet-coating thickness using some other suitable measurement technique /process. The idea is to determine in-process (online) coating thickness to generate data for an optimized control of the process parameters. Any technical feedback /company brochure will be highly appreciated.
Regards

Shah’Zan

 
 Reply 
 

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