topic Betreff: Model an reversed curve that twists along another curve in Inventor Forum

Model an reversed curve that twists along another curve

jonathan.westerlund — Sun, 16 Jan 2022 16:27:21 GMT

Hi!

Sorry for the somewhat whacky title on this post, but I hope you´ll understand what I mean in the text below.

So, I have a splitter for a car (improves aerodynamics/downforce) that I want to model.

It has got a quite funny shape; a reverse curve that follows a path (radius) and also twists. It sort of leans in the end.

I need some help on some sort of workflow or a way to model this and get a decent result.

This is how I attacked the problem so far;

1. I measured the real part and took a bunch of reference measurements along the path of the part (roughly 50 mm a part).

2. I drew the path/curve of the part on the XY Plane in Inventor.

3. Every 50 mm I made a workplane perpendicular to this curve and drew the profile of the part from my earlier measurements.

4. I used loft to sweep these different curves along the path. So far so good!

5. I drew the main profile of the splitter on the XZ Plane and used 3D-sketch to project this curve to my twisted surface. I could have skipped this step because I could not find a way to remove the material on the projected surface from the 3D-sketch.

6. I just extruded the main profile straight through the part. The result is quite bad. The last extrusion left some angled surfaces and I can´t seem to find a way forward. I want to create a lip that follows the upper curve perpendicular to the twisting surface.

So, I want some help to achieve a good result. I dont really like loft in cases like this because the wall thickness is most likely not equal throughout the part, which would be good.

Is there a better workflow that allows me to use my measurements and create what I want?

I have attached two parts in this post:

Part "Example of end result" is a simplified curve that shows what I want the end result to look like (but with the twisting curve of course). Here you can see the lip that follows along the upper edge.

Part "Loft error" shows my current workflow which leave a whole lot to desire. This contains the actual measurements that I took of my real part. You can see it on the various sketches under "Loft1".

Thankful of any advice that could help me!

Best regards

Jonathan

Betreff: Model an reversed curve that twists along another curve

WHolzwarth — Mon, 17 Jan 2022 12:15:49 GMT

Perhaps this way? You can wrap Sketch 13 on the loft for splitting, as an alternative. (2022 IPT)

Betreff: Model an reversed curve that twists along another curve

jonathan.westerlund — Sun, 23 Jan 2022 17:48:15 GMT

Thanks for the suggestion! The end result looks good! But, I don´t really follow on how you got there? All I see is a derived part with an empty sketch.

How did you use loft to split the curve?

Betreff: Model an reversed curve that twists along another curve

WHolzwarth — Sun, 23 Jan 2022 18:51:37 GMT

Oh! You've used Inventor 2021. I didn't realize that.

Perhaps a screenshot helps.

Betreff: Model an reversed curve that twists along another curve

jonathan.westerlund — Sun, 30 Jan 2022 16:09:48 GMT

Thank you! Now it worked! I missed the part were you could make a new solid with Thicken/Offset and the delete the remaining surfaces.

Now it´s just one step left, to make the "lip" that follows the upper curve with an width of appr. 20 mm. It needs to be perpendicular to the surface along the curve. I have tried two different solutions;

Sweep. The lip won´t be perpendicular to the surface.

Shell. I tried to make the entire part 22 mm thick, and then use shell to remove material only leaving the lip. This did not work. Inventor can´t seem to comprehend the different surfaces to make an meaningful result.

Any tips or ideas would be much appriciated!

Best regards

Jonathan

Betreff: Model an reversed curve that twists along another curve

WHolzwarth — Sun, 30 Jan 2022 17:12:40 GMT

Here's an attempt. Take it as it is. I couldn't get it with 2021, and I had to use tricks in 2022, too.

Betreff: Model an reversed curve that twists along another curve

jonathan.westerlund — Sun, 30 Jan 2022 17:36:23 GMT

I have access to 2022 so it´s fine.

But I can´t seem to backtrack your steps (?).

Did you use "thicken" to make the lip? Without any sketch?

I want to make the lip only across the upper curve.

Thank you

Betreff: Model an reversed curve that twists along another curve

WHolzwarth — Sun, 30 Jan 2022 17:51:04 GMT

No big deal. Split with an offset face.

Betreff: Model an reversed curve that twists along another curve

jonathan.westerlund — Sun, 06 Feb 2022 18:39:11 GMT

I´m not sure on how you mean. Could you lay it out step by step?

Thank you.

Re: Model an reversed curve that twists along another curve

johnsonshiue — Wed, 16 Feb 2022 19:18:36 GMT

Hi Jonathan and Walter,

If I understood the request correctly, there should be a much simpler way to do this. Use Ruled Surface command -> select the top loop -> Normal or Tangent depending on your selection -> set a distance. After that, Thicken it to merge it back to the solid.

Many thanks!

Re: Model an reversed curve that twists along another curve

jonathan.westerlund — Mon, 21 Feb 2022 12:17:45 GMT

This worked out great, thanks!

Inventor had some issues with the thickening process after Ruled Surface. I couldn´t just choose all the surfaces (got different error messages) and thicken them, I had to to a couple at a time. But it worked out good!

Best regards J