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

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 isnâ€™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 havenâ€™t found the answers to the specifics I am looking for. Any and all help is appreciated. Thank you.

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 â€”> pick first point, second point, drag up while holding shift

Measure both radii and substract from each other assuming youâ€™ve modeled everything concentric.

Use Scale â€”> 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:

But even after inserting the bowl, it wonâ€™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 doesnâ€™t seem to work either.

Adding a file helps others to check whatâ€™s wrong. It looks to me like you did subtract it from that box but didnâ€™t delete the object to be subtracted. Try moving the shape away from the mold to see if it created the cavity. If it didnâ€™t, post your file so we can see what is wrong.

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

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

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