Help me understand how/when to apply an evaluation filter (Gauss) to a 2D Curve

[[Ni...]]

Hello,

I am hoping to get some input on how best to use, or when to use a gaussian low pass filter on a 2D Curve. For some context, my organization does a lot of profile controls - for example all unspecified surfaces are typically controlled by a profile of .020 to DATUM A/B/C. The vast majority of our profile measurements are captured through 2D or 3D curves that are a combination of linear surfaces and radii. (Screenshot of feature below is an example of what our strategy may look like.) Up to this point we have not applied filter/outlier elimination to the features themselves, and typically just insert the raw data into a Line or Surface profile characteristic.

After reading up a bit on the Gauss low-pass filter setting that can be turned on/off on our curves I believe it may be appropriate for us to start utilizing that setting at times. So here is my understanding of the usage.

-The filter is used to smooth a profile to compensate for surface finish/roughness of material

-A minimum of 7 points is required (question here from me is this per wavelength based on the Lc setting, or for the entire curve length?)

-The wavelength cutoff setting (Lc) should be selected based on the expected roughness of the surface? (is the surface roughness conversion chart I have in a image below a good resource for selecting 'Cut-off length / Lc?'

-What is the 'connect segments' setting is under the filter

-In the third image below, is it appropriate to use this filter, on this specific curve when measuring it as a profile, and what should the specific settings be? The maximum allowed surface roughness is 125 (microinches) but will likely fall between 30-62 (microinches.)

-Any suggestions on how or when to appropriately apply the Gauss, low-pass filter to a 2D curve feature that is measuring surface profile would be greatly appreciated..

 

 

Edited June 4

[[Ze...]]

I believe you should be using a Spline filter for open curves/features and Gauss for closed loops. I'll let others respond on the best settings. 

[[I...]]

only Gauss always...

[[Jo...]]

My company has been using 2d curves for ages. They strictly use spline, and it seems to work for them. I have not deviated from this to avoid impacting production.

I have questioned the Lc value, though, and am interested in others' thoughts. 

[[M1...]]

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That is not always the case and I suggest to look at the post from Klaus-Dieter here: 

https://qualityforum.zeiss.com/topic/24879-rules-of-thumb-for-2d-curve-evaluations/#comment-141085

Especially the files he sent.

Edited 5 hours ago
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