Best fit points to surface model in NX7.5 1

[twimer]

I have CMM data for a surface profile tolerance on a converging-diverging nozzle in the form of a .igs file. I would like to open the file in NX, drop in the CAD model of the surface that was inspected and then position the surface model so that it is best-fit to points in the .igs file (i.e. the largest variation from any point to the surface is minimized).

Does NX have an automated way that I can select the points I am interested in, select the surface, and have it automatically positioned to best fit?

Thanks.

 

[JohnRBaker]

First you have to get the points into NX as 'point' objects. If the IGES file is actually providing 'point' objects then that shouldn't be an issue.

Once the points are in the NX part file, your best bet is to try and use...

Insert -> Surface -> From Point Cloud...

Note that this function has been completely rewritten in NX 8.5 and is now known as 'Fit Surface'.

John R. Baker, P.E.
Product 'Evangelist'
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Siemens PLM Software Inc.
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[kapmnit123]

Hi Twimer,
As far as i know the iges file containing the point data will not be treated as point cloud data (it would be better if you get .stl format files for it but i suspect that CMM gives you point data only and not cloud data .Please correct me if i am wrong).
Had it been a case where you get the point cloud data (which will get faceted when imported inside NX) then you can directly use EDIT/ALIGN/BEST FIT.This will re-position your surface model as per the point cloud data [this utility doesn't support point data (only facet is allowed apart from solid and sheet) however as per my knowledge].
But in case you have only point data as input then you can use EDIT/ALIGN/POINT SET TO POINT SET.Since you have only surface and not the points for reference on it so you may be required to create some reference points on the sheet first (using point set) and then use this. I am attaching an image herewith.Not so straight forward but surely can be relied on.
Sorry i am using NX8.5 as of now so please re-check it at your end also (i guess the ALIGN utility was there in NX7.5 also)
Best Regards
Kapil Sharma

 

[Toost]

There are a few methods of aligning faceted bodies to surfaces that should do what you want. So i would rather say your best bet is to get the points into a facet format *, then use the Edit - align ...
* I Have no clues in how to convert the points into a faceted body...
Regards,
Tomas

 

[kapmnit123]

Hi Tomas,
Yes i completely agree with you.That is the reason why we prefer to have a stl file as an input. Edit/ALign/Best fit works on Facet data (apart from sheet and solid) only and in this case will be the best option to try.However i don't remember if the point data can be converted to .stl directly .My past experience is that we need to have sheet body or solid body data to generate the cloud data.So we get .stl files in case of rapid prototyping only and i suspect CMM will give point data only. May be i am wrong though.
Good day.
Best Regards
Kapil Sharma

 

[vrishraj]

Hi John,

I have checked NX8.5 Fit surface, it ask only point set or point group apart from facet body, how to get point group from cloud of existing points? am I missing some options here?. In previous versions I could select existing point in our file.

Raj
NX 7.5

 

[kapmnit123]

Hi vrishraj,
I may be slightly mistaken but as per my knowledge FIT SURFACE was introduced in NX8.5 only. Are you refering to some other utility?
Best Regards
Kapil Sharma

 

[vrishraj]

Hi Kapil,

previously I used
Insert -> Surface -> From Point Cloud... to use existing point to create surface but that option not there in NX8.5 now. I have searched in help file also. I thought it has been replaced with Fit Surface in NX8.5 as per Mr. John stated in this thread.

Raj
NX 8.5

 

[kapmnit123]

Hi Raj,
Ok.Sorry i rarely used it so cannot make any valuable comment on the same.I have always relied on taking sections and create smooth curves on these and then start surfacing.In case where i was required to do it fast i used rapid surfacing tool or create a four point surface and then use REFIT FACE.
As far as FIT SURFACE is concerned if you wish to use existing points for selection then you can create a GROUP of the existing points and then it can be selected for FIT SURFACE input.Not sure if this will help your case.
Best Regards
Kapil Sharma

 

[vrishraj]

Hi Kapil,

Thanks for the info, you have mentioned that "create a GROUP of the existing points" I could not find how to group existing points, pl let me know. Thanks.

Raj
NX 8.5

 

[kapmnit123]

Hi Raj,
Just select the existing points right click and select NEW GROUP.You will find the GROUP in your part navigator histoy below the CAMERA. So whenever you require to slect the points just select the group from part navigator.
I am attaching an image herewith.
Best Regards
Kapil Sharma

 

[vrishraj]

Hi Kapil,

Thank you for your detailed explanation, it works great. I hv learned new option today!! Nice star for you.

Raj
NX 8.5