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# Reverse engineering through surface modeling

Pioneer

Not sure if this is the right forum section for this but I've got some questions regarding surface modeling.

We're working a lot with scanned objects in STL file format. Having never worked with surface modeling before, our usual work-way is to create section curves on the facet model. Then use those curves as a reference to model the part. And use GOM inspect for a final surface comparison check.

To my understanding the more accurate way is to get into surface modeling (specifically for 3D-impellers).

Usually I can get a lot of information from youtube or google regarding methods I haven't worked with yet. There's not much I can find about reverse engineering STL files though. Is this something that can be self-taught? And if so, can anyone point me to any in-depth guides / tutorials explaining how..

4 REPLIES

# Re: Reverse engineering through surface modeling

Gears Phenom

I've used "Rapid Surfacing", for some tasks here.  between the help files, youtube, and trial and error, I got it.

-Dave
NX 11 | Teamcenter 11 | Windows 8.1

# Re: Reverse engineering through surface modeling

Siemens Phenom

Yes, you have the correct forum.

There are basically 4 methods of reverse engineering surfaces from facets plus another method of working.

Which method to use depends on a number of factors. How close to the scan data do you want the surfaces? What quality of surfaces to you require? How do you want to edit the geometry later?

Method 1 – curves to surfaces

Probably along the lines you are currently doing.

Create sections though the facet body. Fit/smooth a spline (or multiple curves) though the section data.

Create surfaces though curves

Place lines and arcs by points and extrude for planar and conical areas.

This method is useful when downstream and later edits you want to be from 2D curves.

Method 2 – fit surfaces to facet

Analyze facet body to identify forms. Split facet into areas

Use Fit Surface on areas of facet to create analytical and freeform surfaces

Can edit by direct editing the surfaces

With methods 1 and 2 use enlarge and extend surface and trim and attach to sew together to single body.

Method 3 – Rapid surfacing

Use the rapid surfacing command, draw surface sides on the facet and it fits surfaces to the network.

Useful if update to design will be a new facet body set. Quick method but quality of results will only be tangent continuous.

Method 4 – Direct surface modeling

Class A surface method of placing a surface by 4 points on the face. Create Dynamic Sections though facet and surface and use X-Form to manipulate the shape of the surface to fit. Use Match Edge to bring the surface curvature continuous to each other.

Will create the best quality results but does need experience to get good and accurate results.

Method 5 – do not reverse engineer but Convergent Modeling

Keep data in facet, create adjacent geometry with feature modeling. Combine the geometry to single facet body and use the new facet body in downstream processes.

Saves a lot of time as do not have to reverse engineer new geometry.

Steve V

# Re: Reverse engineering through surface modeling

Siemens Phenom

Just came across the following youtube video and recalled this thread.  It's not the in-depth guide or tutorial you were looking for, but it does show the Rapid Surface command creating a parametrically controlled nurb surface from imported scanned (faceted) data.

# Re: Reverse engineering through surface modeling

Pioneer

Thank you for the helpful post! And @DaveK @BenBroad thank you guys as well!

Based on this post I broadend my search on youtube for more information. I've gotten to grips with some surface modeling utilities in NX.. but as you said @BenBroad - they're not in-depth guides.

Are there webinars or courses to follow or something alike for NX?