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November 2015

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Subject:
From:
Mike Fenner <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Mike Fenner <[log in to unmask]>
Date:
Mon, 16 Nov 2015 08:41:19 -0000
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text/plain (143 lines)
Even less my area, but I had a fleeting need to understand it some years ago
on a project.

I recall only two main things now

1)that there are a lot of different ways to quantify surface roughness none
of which have much to do with the others. So a number in one scale is fine
surface, but coarse in another. 
In other words the units of measurement peak to trough, profile of peaks and
troughs and frequency are all specified in different ways. 
2) sort of resolved it by having multi processed sample with different
roughness on and just matched the requirement by looking at it, bit like
using a colour chart to match paint. Got the sample from an engineering
company up the road. [I just walked in, told 'em I was next door but two and
asked them to help me out.]


So the moral of the story -if there is one - is sort out your units and
check out your neighbours to find someone better than me to ask!

-- 
Regards 
 
Mike 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bev Christian
Sent: Saturday, November 14, 2015 2:33 AM
To: [log in to unmask]
Subject: Re: [TN] Surface Roughness Sample Length

Richard, 
Not really my area of expertise, but couldn't one have a smooth surface with
a chemical coating that gave a surface energy of X and a rougher surface
with no coating or a different coating and still have the same surface
energy X? I don't see how you can equate surface energy necessarily to
roughness if you have not characterized the surface.  Maybe I'm totally
ignorant. If so, please educate me.

Eddie,
We have both types of systems Richard talks about if you want something
tested - before Nov 27th.

You may want to check out:
ASTM
-D7127
-F2791
-F1048
-A 480/A 480M
-D4417

Regards,
Bev

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: November 13, 2015 8:23 AM
To: [log in to unmask]
Subject: Re: [TN] Surface Roughness Sample Length

Or if you need a cheaper but effective method, you can purchase Dyne pens.
A set of Dyne pens can be used to measure the approximate surface energy to
determine appropriateness for direct dispensing of conformal coatings,
adhesives, paint, epoxies, etc.
If the surface energy as measured by the Dyne pens is too low, you may then
have to treat the surface prior to coating to provide a suitable surface to
bond to.
Dyne pens are relatively inexpensive, ranging from around $65-$125 for a
set. Here is one I use http://www.accudynetest.com/adtpen.html
I have not tried any others, so I cannot say this is the best or the worst. 
Others may recommend other Dyne Pen sets. 
My esteemed colleague and friend Dr. Pauls is someone whom I would heed a
suggestion from, as to a reputable source. I have copied him directly. He
may be quite busy at the moment writing something about half-rational
elements from the planet Boron or something like that, however.
dean

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bhanu Sood
Sent: Friday, November 13, 2015 7:09 AM
To: [log in to unmask]
Subject: Re: [TN] Surface Roughness Sample Length

One can measure surface roughness either by using a contact or non-contact
method. Some other optical microscope-based methods may be more qualitative.

Contact methods include using atomic force microscopy or surface
profilometry. Essentially, run a stylus on the surface and track the rise
and fall that corresponds with changes in the surface roughness. The
measurement would give you the heights of the valleys and the depths of
troughs. You can also calculate a root mean square roughness or RMS
roughness. 

Examples of non-contact methods include interferometry that uses white light
or discrete wavelengths. 

 The length of the scan essentially depends on the planarity of the sample
surface. At some point the global curvature of the sample is going to start
influencing the measurements.

I hope this helps.
Bhanu

> On Nov 13, 2015, at 7:52 AM, Eddie Hofer <[log in to unmask]>
wrote:
> 
> Wondering if anyone has more experience in the measurement of surface 
> roughness.  I am hoping to better understand the specifications 
> relating to surface roughness and specifically the nuances behind 
> determining sample length.
> 
> Appreciate any input you can provide.
> Thanks!
> Eddie Hofer
> 
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