Autodesk Inventor T-Splines Troubleshooting


Autodesk Inventor 2015’s Freeform T-Spline modelling tools bring us some great new options for modelling complex, organic shapes. In this post we will troubleshoot a couple of the common issues you may come across while learning this new toolset.

Inventor’s T-spline tools allow us to create smooth shapes with complex curvature without having to spend a lot of time and effort constructing a surface model. T-spline surfaces are created in the Freeform modelling environment.

To convert your T-spline model into a Brep (Solid) model you simply need to leave the Freeform environment and Inventor will do the conversion on the fly. This sounds easy, right? but there are a few ‘Gotchas’ you will need to look out for.

Autodesk Inventor 2015 Freeform T-splines

Non manifold surfaces

Autodesk Inventor 2015 can’t create open T-spline surfaces (yet!). Each T-spline surface model you create will be a ‘manifold’ surface. Manifold means that the surface is completely watertight. The model is one complete lump and there are no gaps between the edges of the surface model.

I like to think of my Freeform model as a rubbery balloon. When I leave the Freeform environment, Inventor fills my balloon full of  concrete which sets instantly… (kind of, it’s only an analogy).

A non-manifold surface may have gaps, or in this case, overlapping edges that the T-Splines plug-in inside Inventor can’t use to calculate a solid volume.

Inventor 2015 constantly checks your T-Splines surface for non-manifold conditions. You will know when you have a problem because Freeform will pop up a little triangular yellow warning dialogue.

Autodesk Inventor 2015 Freeform T-splines

Note: The constant checking is a blessing and a curse, because the processing takes a lot of power and it is happening while you  perform direct edits. This may slow down Inventor on your computer.

If you see this warning DON’T PANIC! Use the ‘back’ button in the dialogue to undo your direct edits until the warning goes away.

Autodesk Inventor 2015 Freeform T-splines

To avoid seeing this warning in the first place, I highly recommend switching to ‘Cage’ mode frequently – this makes it much easier to see if your cage nodes are overlapping.

Tip: Select on the warning sign on the floating toolbar, then select on the links to get some handy advice on what the problem with your surface is.

T-Splines for Inventor troubleshooting - Non manifold  error message

Creases and start points

Edge creasing in Inventor’s Freeform tool set allows us to ‘sharpen’ an edge. To use this tool, simply right click on any given edge and chose CREASE.

Autodesk Inventor 2015 Freeform T-splines

before you do this though, count the number of edges you have between the edge you want to crease and your nearest Starpoint. Every creased edge will effect the next TWO edges.

If one of these edges hits a starpoint, the crease will shoot into the starpoint and radiate out in all directions.

Autodesk Inventor 2015 Freeform T-splines

To crease an edge that is near a Starpoint, you’ll need to subdivide the intervening faces to put two clear edges between your crease and your starpoint.

You can see more in this excerpt from my Video tutorial series ‘Mastering Inventor T-splines‘.

More Autodesk Inventor T-Splines tutorials


Over to you

Have you come across any other issues while creating T-Spline surfaces with Autodesk Inventor’s Freeform toolset?

For more on Autodesk Inventor T-splines read:

What are T-Splines? And how can I use them?

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