Full Version: Cutting template for frustum

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Merry Christmas All!

The attached file has a shape I plan to make out of sheet metal. For this I need to create a cutting template. I know how to do it the old fashioned way of extending the two vertical lines to a point, drawing 2 circles, using the distance between intersections multiplied by 3.14.

As there are two horizontal holes in the object, I don't know how to position them in this template.

Is there a way to kind of unwrap the whole object to automatically create a template for cutting?

Thanks in advance :)

Attachments:
Bucket ring.3dm

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Slicer for Fusion 360 (its free, and a standalone app despite the name) should be able to handle this with relative accuracy. Although Its designed for unfolding paper, if the segments/facets are small enough (lets say 0.090 along the circumference), and there are no sharp bends to stretch the material it should be pretty close.

If you are CNC cutting this you'll want to redraw the flattened curves as arcs, the segments don't work well.

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Hello gunter and Merry Christmas,

there was a similar discussion here it works also vice versa: http://moi3d.com/forum/index.php?webtag=MOI&msg=8745.1

Have a look, if it works for you!
Karsten

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That's awesome, don't need another app.

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Gunter, here is another set of posts on unwrapping cones/frustums.
The script that I did was called ConeUnwrap, but I have it in customui as UnwrapCone...

http://moi3d.com/forum/index.php?webtag=MOI&msg=6175.1

- Brian

Script for unwrapping curve on a cone/frustum is possible, but I think Flow can do it.

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Thanks much for all your help!

Wishing you all a Happy New Year!

Gunter

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Brian,

I'm not a technical guy so a lot of mathematical info goes over my head!

You mentioned a script you did called ConeUnwrap.. could you tell me where I can download it?

Many thanks!
Gunter

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Hello Gunter,

follow Brians link. His script can be found in the following posts!

Have a nice day
Karsten

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Hi Karsten,

The file I see in his post is unwrap-cone.3dm

Isn't that just a 3dm file rather than a script? I'm under the impression that a script is something your download, unzip and add to the contents of your moi3d programme. Am I missing something?

Thanks!
Gunter

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Hello Gunter,

follow the posts or click here: http://moi3d.com/forum/index.php?webtag=MOI&msg=6175.22

A nice day to all
Karsten

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Hi Karsten,

Thanks so much. I've installed the script but am still unclear how to work it.

Step 1. Do I select the top tip of the cone?



Step 2. Which face do I select?



Step 3.Presumably this is the circle at the base of the cone..



Step 4. Not sure what this is for and also there is only a cancel option. If I click Enter, nothing happens.



Holes on sides of frustrum - If I work on this model, will the holes be reflected in the unwrap?



I apologize for being a pain, but this is all rather new to me!

Many thanks!
Gunter

Image Attachments:
Screen Shot 2017-12-26 at 16.26.16.png  Screen Shot 2017-12-26 at 16.26.26.png  Screen Shot 2017-12-26 at 16.26.41.png  Screen Shot 2017-12-26 at 16.26.52.png  Screen Shot 2017-12-26 at 16.27.47.png 

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Sorry Gunter,

I've never used the script and I can't uncompress the archive - I'm working under Linux - 7z archives are not supported.

It's a question to Brian.

-Karsten

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No worries Karsten, thank you for your help!
Gunter

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Hi Gunter,
I wrestled hard to make understandable user prompts, but fell short of the mark:-)

The prompt "Select unwrap center point" should be "Select any point in the view, to become the apex of the unwrap."

The prompt "Select Cone Face" should be "Select face of the cone, or face of the Frustum. A frustum is a cone with the top cut off. The face is the surface of the cone or frustum"

The prompt "Select Base Circle" should be "Select the Base Circle of the cone or Frustum"

The prompt "Uncheck Box for Cone, THEN select slant seam" should be "For a Cone, Uncheck the checkbox, then select the slant seam of the Cone. For a frustum, just select the slant seam of the Frustum. A slant seam is the edge of the cone or frustum which connects the Base circle to the apex of the Cone, or the top circle of the Frustum."
(A better way would be to have the user select either a cone or a frustum from the outset, and have separate menus.
But I find that the .htm is very difficult to write. MoI's stock commands, for example Circle, have XML code to pop up separate menu's for each circle type.
I find that some of Michaels examples of .htm are very complex. I am currently wrestling with combining two similar scripts into one. It is difficult for me.)

I did not write code to unwrap a curve or hole in the cone/frustum, even though it is possible using a bunch of curve points, because FLOW should accomplish that.

- Brian

(Note that a mathematical cone has two halves. In common talk, a cone is just half of a mathematical cone... The definition of a frustum, how to spell it, and
the meaning of a "slant seam," or "face," are not commonly known.)

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Brian,

Thank you ever so much for taking the time to explain this in detail.

I'm happy to say it worked really well for my frustum!

All sorted thanks to your script!

Happy New Year :)
Gunter

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Sorry Brian, about using FLOW to transfer the holes in the cone to the unwrapped curves.

I'm not clear how to get that done. Would you mind telling me how?

Thank you!
Gunter

Attachments:
Bucket ring.3dm

Image Attachments:
Screen Shot 2017-12-26 at 18.29.43.png 

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Hi Gunter,
I have been unable to get flow to work on this :-(

- Brian

(with Planar)

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Hi Brian & Gunter, to use Flow you'll need to build a flat surface through these curves but you need to use either sweep or network to do it so the "underlying surface" has its UV structure going in that direction. Don't use Construct > Planar for this case because that will make a large 4 point plane that's trimmed, and Flow will use the structure of the underlying surface to do its work:


If you turn on the surface's control points it should look like this with the control points hugging the curve contours, if you make it using Construct > Planar and turn on those control points you'll see it looks different with there being a large plane made up of just 4 corner points with the curves being trim curves rather than being part of the underlying surface's structure:



Also you'll probably need to cut that in half since your cone surfaces are cut in halves too.

- Michael

Image Attachments:
gunter_flow1.jpg  gunter_flow2.jpg 

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Please check and read the description in the posted theads.

Have a nice day
Karsten

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Thanks Michael,
So that is why Karstens sweep worked for the wine bottle lable, while I could not do it using unwrap/Planar/Flow.

After applying Planar to the ConeUnwrap, the flat surface has Iso's going at an angle, which is no good for FLOW.
But the ConeUnwrap can be used, for the Sweep. First trim off the two straight sides. and use the straight side to do a sweep, with the two arcs as rails,
(which I think is equivalent to Karsten's sweep). (Then use FLOW. I have yet to try it.)
(I spent an hour doing it wrong this morning:-)

- Brian

(The bucket frustum has only one (outer surface) seam, I think.)

EDIT:
FLOW works well!
Select the two outer edges of the roundish cutouts on the cone/frustum, as Objects to Flow.
Select the surface of the frustum near Base circle, near seam, as Base surface.
Select flat swept surface of unwrap, near longer arc, near left straight edge, as Target surface.

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