1st project - Need help with a few peculiar dimension-based questions

Rhino Rhino for Windows
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I am a new user to Rhino. I am attempting to utilize it to create a 3D-printed casting mold for ceramics. First I am creating the piece I want to cast, then I will subtract it from a mold cylinder or rectangle, slice it in 3 (left/right/top) and print it hollow.

This is what I am trying to create: https://www.youtube.com/watch?v=ypxer6we47I (the white plaster mold)

Now I know that Hammerly Ceramics does this process with Rhino as well, so I know it is possible: https://www.pinterest.com/pin/78672324727996552/

He just seems to 3D print the mold semi-solid: https://i.imgur.com/zVOTkX7.png

So here is what I am trying to make, like the YT video, a mold for my bowl which requires a top piece: https://i.imgur.com/RWQtmj1.png

My questions are:

  1. Is there an easy way to orient a top down sketch line 90 degrees right side up? I managed to somehow rotate it by dragging, but I am concerned it is not aligned properly. I imported a background sketch, traced the lines in the top perspective, then I rotated it.
  2. Is there a way to properly orient an object straight upward so it is not tilted?
  3. Is there a way to discern the width of this edge? I tried measuring the linear dimension to no avail https://i.imgur.com/9EPJTGx.png
  4. Dimmension is really important since I have to make sure this is exact. I need to make the top outter edge exactly 8.62 cm, is there a command I can input that will proportionally scale the whole object to that diameter? Keep in mind, this isn’t the outter most edge, but the top-most edge which tapers inward a little.
  5. Is there a way to adjust the thickness of the outter wall at the top (where the yellow lines are in a the previous photo) to a smaller size, or perhaps am I able to soften the slope?
  6. Is there a way to do something, like add a triangular bump and have it copied radially at this point?
  7. Is there a way to add or subtract something from the edges and snap at an equal distance to each quarter?
  8. Is there a way to add a guideline near the top so I know where to cut off the mold at for the top piece? Like radially around the upper outer wall?

I realize a lot of these questions might be answered in basic tutorials but I haven’t found the answers to the specifics I am looking for. Any and all help is appreciated. Thank you.

2

Most of your questions are covered in rhino level 1 training manual but anyways to get you started:

Many ways but one is using the Gumball : click on quarter circle of the Gumball and enter 90

Rotate —> pick first point, second point, drag up while holding shift

Measure both radii and substract from each other assuming you’ve modeled everything concentric.

Use Scale —> pick first point (quad), second point (oppositie quad) and then enter your desired dimension

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Since your shape is a simple revolved shape make sure to model it as a profile that you can revolve around the y axis. Revolve can make use of history recording. Then you can edit the curve while the revolved shape gets updated.
Or set it up in Grasshopper

ExtractIsocuve

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make sure to model it as a profile
I actually started it as a profile and then revolved it as a FullCircle

So I just edit the profile curve in front or right perspective?

Thank you very much for all your help!

One last question, I am attempting to create the mold:

1375Ă—856 103 KB

But even after inserting the bowl, it won’t let me select it for a Difference or Booleon.

I think this is because after I revolved the profile, it is still hollow.

So how can I successfully subtract the bowl from the rectangle to create this mold?

Mesh Booleon Difference doesn’t seem to work either.

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Adding a file helps others to check what’s wrong. It looks to me like you did subtract it from that box but didn’t delete the object to be subtracted. Try moving the shape away from the mold to see if it created the cavity. If it didn’t, post your file so we can see what is wrong.

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If the BooleanDifference didn’t work, it could be that the revolved object is not closed - check in Properties.

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Besides of the boolean command you can use split or intersection command.

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having the surface seam right at the point of intersection is a good way to make boolean difference fail in many cases. To investigate a boolean fail: run Intersect and check if the resulting curve is a closed curve