2D comparison

[[Ba...]]

Hi,

Could you please help me. What's the best way to compare a 2D profile loaded as a .iges or .stp file with a cloud of points imported from a CMM scan as a .txt file?

I am a beginner and have been trying to approach it for several days but I can't find a solution

[[Se...]]

Hi Bartłomiej,

What do you want to achieve exactly? Is the CMM scan point cloud the entire surface or just the 2D profile?

In the second case, the best way would be to import the CMM scan data as curve -> https://techguide.gom.com/en/article/cmd_sys_import_ascii.html

Then you can link the imported nominal and actual to perform the checks.

If airfoil inspections are intended, sections are required.
This can be achieved by projecting the imported curves on the section plane ->  https://techguide.gom.com/en/article/cmd_cad_project_points_on_plane.html

Hope this helps.

Best regards,
Sergio

 

[[Ba...]]

Thank you Sergio. I would like to achieve map with distance deviations between actual and nominal curves or shape deviation. 
The scan is dedicated to 2d profile (2 axis values).
I can import data to GOM but the problem is how to link nominal and actual profile. I can do only shift actual curve to nominal by manual transformation. 
What kind of measurment principles shoud I use?

Regards,
Bartek

[[Se...]]

If curves are already imported (not sure it was done in your case, ASCII import as curve can be used for example, see https://techguide.gom.com/en/article/cmd_sys_import_ascii.html), they can be linked by the measuring principle "link to actual element"

Select the nominal curve, apply the measuring principle. On the uncoming dialog set the actual curve to be linked.

Furthermore, to be able to use the  airfoil profile inspection functionality (more information here https://techguide.gom.com/en/article/general_get_started_blade_Inspect.html?serial=0), a section is needed.

You can create it by using the "Project Element On Plane" command on the nominal curve and applying referenced construction on the actual curve.

Hope this helps. Best regards,

Sergio

[[Ba...]]

 Hi,

thanks again for your help. The problem is that I cannot import  it as a curve because as you can see in attached 2a 20st.txt there is no full profile and aproximation to curve could give me wrong results. 

I would like to ask if anyone can give me instruction what is the best way to import nominal data from .igs and actual from .txt. 

The problem is also with aligments, could you advise how to do this if I do not have characteristic points.

 

I attached 3 files. Two with scanned data from laser line sensor and one nominal cad profile. 

 

0 stopni 2a unj .txt 2a.igs 2a 20st.txt

[[Se...]]

Hi,

To import nominal data, you can just drag and drop it. To get a section out of it, it can be projected into a plane:

To inspect the measurement of complete curve, it can also be imported as a section. Again drag and drop, choose "Ascii text format" and Add to part.
Template "curve" already exist, but in this case separators are commas. You can create a new template that handles this, and imports a section directly:

Then you need to apply the measuring principle "Link to actual" to link both.
For the alignment, a prealingment like "3 point alignment" and finally a better alignment like:

For the incomplete section it is a bit more tricky. Could be imported as point cloud. Data is quite noisy already.
I did it again as a section, perform a similar alignment, then do a Section deviation check with large point distance (to prevent points on the segments that close the non measured gaps to be part of the inspection) and a small search distance.

Hope this helps.

Sergio

[[Ba...]]

Great! Thank you 🙂

You have written that you imported noised profile as a cloud of points but I am not sure. Is it really point cloud or curve?

I tried to do it as a points but in this way I cannot do the section as well as I cannot link nominal with actual data. How I can define cloud of points as an actual data and link it with nominal curve?

I can import noised profile as a curve but it do not look good as you can see on the second picture.

Maybe can I delete some noised points and after that generate curve? But the problem is I do not know how to do this in GOM. 

Regards,

Bartek

[[Se...]]

Hi,
I mentioned that it could be imported as point cloud, I imported it however as actual section.
To get rid of the noise, I created a 3D deviation (Actual section) with (see screenshot in previous post):
- Max distance set to a meaningful value (this is how far the check looks for checking the distance)
- Point distance larger than the artificial segments created between measured points, such that the check does not create additional points on them
 VG,
Sergio