Scan to CAD, Reverse Engineering, laser scanning, Metrology

Jan 01 , 2017

DESIGN INTENT OR "AS IS", SCAN TO CAD Part 2 of 3

Don’t let your scanning source tell you that you cannot have editable models from your scan data.

Dumb Solids vs Smart Models

So why is one dumb and one smart? One has a feature tree, one doesn't.  If your scanning source cannot supply a native file for your CAD software; then find someone who can.  Don't just blindly pay for a dumb solid (Import body), unless that is what you want.  Most often a dumb solid will be cheaper, but get what you need the first time.  A lot of scanning service companies today only offer an obj or an stl. Don't fret, their are companiesthat can. You don't have to fire your valued vendor.

Shameless plug...if they can't, we can.  Other companies out there can too…

With today’s import diagnostics, feature recognition, and import tools, often you can get by with just a dumb file (No feature tree).  Often though, it is nice to have the tree to be able to edit as needed.  If you are cutting a replacement tool, dumb surfaces are probably fine, but if you need drawings or need to make significant product development changes, being able to quickly modify the intended design my hold huge benefits.

Dumb Surface tree                                       Smart model tree

 

 

                                                Dumb Solid.png           Feature Based.png

 

 …but Nathan, I want my cake and I want to eat it too. What if I only want to modify a couple of features, but the rest must stay “As is”? What if I want to modify a couple of holes in mold tool, but do not want to pay for the whole tool assembly to be parametric?

No problem, as for a hybrid model. Use pictures and annotations to explain what area is important for your needs.  We reversed a side mirror for a client; we were able to create a dumb solid of the main body, but gave the C’bore holes as intelligent features for the customer.

Do you want a very organic surface, or just  a place holder? Sometimes, A NURBS surface is all you need, and will save you a ton of time and money.  There are down sides though, so be careful with these models.  This is kind of a shrink wrap, so the edges are typically rounded off.

  1. Nurbs:
    1. Non-uniform rational Baize spline model.
    2. This is a series of curvature continuous knitted surfaces wrapped around the point cloud. This type of model gives the closest fit to the actual scan data, but has significant draw backs.
    3. This method is organic; NOT feature based, so there will be no cylinders, planes, cones, etc. No reference geometry such as axis to mate to

 

NURBS Surface         Traditional CAD model

 

 nurbs.png      CAD.png

 

At Garrett Engineering, we excel and specialize in converting physical objects into digital models. Have an idea how to use this technology to improve your process? Get a hold of use today.  We are always looking to help

I have been doing this a long time, and this is just the tip of the iceberg. Let me know if you have any questions. I would love to help you understand this field better. The more you know, the better we can all use it.

I am always looking for interesting things to post about, so check back often, leave a comment, or suggest a subject.

Thanks for your interest!

 

 

Nathan Garrett

About Nathan Garrett

Nathan is a seasoned design engineer with a deep understanding of how to make a product great. He has been using Solidworks for 20 years and Geomagic for 6 years.