Replicate Vacuum Mold

I am wondering if there is a way to replicate a vacuum mold on an object in Rhino?

I have tried the drape, but it does not give the result I am looking for.

Attached images of what I am trying to achieve and what I am getting so far


The sample you’re showing is not a ‘drape’ of any sort, it has tons of undercuts, it’s basically just the 3D model with some modifications.

Hi Jim,
yes exactly, the pictures body shell is made using a vacuum pull on a warmed up sheet of plastic.

I am trying to replicate that in Rhino but I only find the drape which does not recreat the same effect, and Im wondering if anyone might know better how to achieve the result Im looking for :+1: :+1:

Probably going to need something like:

  • Silhouette from the Top view
  • CurveBoolean to get just the outermost projected outline of the object
  • Extrude that closed curve upward to some point above the object
  • Start intersecting and trimming the the object and the extruded shape to each other so that it basically eliminates the undercuts.

That will give you a model with 0 draft. A more challenging thing would be to try and incorporate draft into the vertical walls, I guess it might go something like the following:

  • Make sure you have a joined single object
  • Run DraftAngleAnalysis and set max draft angle to the angle you want
  • Check “Add max draft curve” and then “Create draft curves”
  • Hopefully these curves will form a continuous outline
  • Extrude tapered the curves with the same draft angle to below Z0
  • Trim off anything below Z0
  • Try to trim the original object with the draft curves and join to extruded object.

Good luck…

1 Like

If you use the right materials, you can get the vacuum formed part off the mold despite having undercuts.

I have not done this myself but here’s an interesting video:


Using an Innovative Silicone Tool to Vacuum Form an RC Car Body (

1 Like

So are you trying to actually make a vacuum mold, or are you trying to ‘drape’ a surface over your model?

For the former, the mold is obviously not a ‘draped’ surface, it’s just…the model, it’s full of intricate detail and undercuts.

For the latter, that’s not gonna work for any real purpose, sorry.

thanks so much for the feedback, I will give these steps a go!

Thanks Martin!

Hi Jim,
im not sure how to explain this but I want to take complex model as the Urus base, and ‘simplify’ them to a simplier shape which will have an abstract resemblance of the original car.

Then I will use that model to 3d print a mold for an epoxy pour

Not sure if all this makes sense