Making a mold from imported .step

LH STEP no holes 1 v6.step (10.4 MB)

Hello all! I have an imported surface model attached that I am trying to make a mold from that can be machined from a solid block. My aim with this model is to extend the edge loop by 20mm, and then create a further loop parallel to the ground plane, and to finally close the whole beneath of the model with a box that can then be the body of the mold.

So my first thought is to ‘extend surface’ but I can only complete this after exploding the part, and then can only extend 1 surface body per time… slow, painful, and doesn’t always work.

So to speed this up, I’d like to create a sketch or curve (I’m new to Rhino!) from the edge loop… is this possible? If so, can anyone help me find the tool to do it?

Or am I looking at this all wrong?

Effectively I am trying to do exactly what is shown in this video Mold Making Tools: new in Rhino 7 - YouTube except I only need the bottom part of the mold and it must follow the edge line where the surface is cut?

Any and all help is appreciated!

I am trying to do the same thing in inventor, but find that some faces the direction seems to flip. But effectively I would like to recreate this from an edge loop, and then outwards at 90 degree, then down to create the block that we feature is machined into…

If the cross sections of the 20 mm extension are to be somewhat parallel to the ground plane, you can follow steps shown in How to Make a Partition Surface in Rhino 3D - YouTube , but particular to your model:

  1. Do not explode the model.
  2. Set the viewport’s CPlane to be parallel with the ground plane. In this model, it may be _CPlane with option _World then _Back. (Words with underscores are commands and options, and are not needed in English language installs of Rhino.)
  3. _DupBorder to obtain the perimeter as a single polycurve.
  4. Follow the aforementioned video on how to use _RibbonOffset on the curve from #3.

Thanks for this, I will give it a try later this evening. The 20mm extension needs to be simply a continuation of the already existing surface. Then an additional surface parallel to the ground plane, making a block similar to the video in the original post.

Ok I’m a bit stuck still, I’ve managed to create the 20mm run off parallel to the cplane, but when he tells you to select the outer curve and scale to 0 giving a flat surface that is the body of the mould I can’t get it to work? He’s getting a flat projection of the perimiter line but I can’t make that happen and he doesn’t show what hes doing at this point? Can you help? Thanks!

He is using the Gumball. Be sure that it is enabled in the status bar.

  1. He makes a copy of the curve, and with one of the 2 curves selected,
  2. He clicks the Gumball’s Scale Z control (blue square / #12 bubble on the help page) and a textbox control appears.
  3. He enters 0 in the textbox and presses Enter.