Creating Parting line/surface + core and cavity for existing model

test.rar (1.4 MB)

Hope you’re all doing well. I’ve been having trouble creating a parting line and surface for my model, which has been preventing me creating the core and cavity. I was wondering if anyone could assist me in learning how to do this in Rhino? I watched the tutorial videos, but still had no luck with it using my model. I attached it to this post.

Thank you in advance!!


Any ideas on this one?
It looks like a candidate for the new parting line tool.

Hi Solomon - DraftAngleAnalysis should help here.



As pascal noted above, once you create your draft curves, you will use the new _RibbonOffset tool-

this will allow you to create the curves you will need to make your shutoff collar. Once you have your parting line and the offset, 2 rail sweep can be used to create the actual shutoff surface itself.

then it’s a matter of blending this surface into your mold halves-

see this video

and this simple video with the basic steps outlines-

Thank you! the parting line looks great! Unfortunately, when I try to use the ribon offset it does not allow me to select the new curve

My apologies. I am very new to Rhino

no worries, make sure your parting line curve is closed before running ribbon offset.

also note, you have some undercuts that need to be fixed-

test5.rar (1.7 MB)
Thank you and apologies for the late response. attached please find images of how far I got. Right now I am having an issue blending the 2 surfaces. it won’t let me select the whole surface created by the ribbon offset to blend

use the chain edges = yes option in the blend surface command line


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Thank you for the response! That’s what I’ve been trying to do, but unfortunately, it doesn’t seem to allow me to select more than 1 edge on the piece

send your file to or post it here, I’d be happy to take a peek and see what’s missing…