Wrap 2d shape to 3d curved solid

[rafael.tavares.costa]

Hi everyone,

This is my first post here, and I don't know if my exact issue is already posted here.

Here's my problem. I was given a 2d shape with a "shell" shapped pattern (see attached) wich I have to model to a curved panel with the same dimension as the one given.

The intended result is to wrap the 2d on the 3d, and convert the "shell" shapes into holes, each one perpendicular to the curved panel. 

I have seen this done on Inventor, with the bend command, and other similar cad softwares, but my company is using good old autocad (currently 2018 version), so I'm kinda stuck on how to get the end result.

Any suggestion?

Thanks in advance.

[john.vellek]

Hi @rafael.tavares.costa,

I am not sure that I totally understand your question with out seeing an actual drawing file but it sounds as if you are looking for the PROJECTGEOMETRY command in AutoCAD.

If not, please attach a sample so I can get a clearer idea of what you are trying to do.

Please select the Accept as Solution button if my post solves your issue or answers your question.

[Kent1Cooper]

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@rafael.tavares.costa wrote:

.... I was given a 2d shape with a ... pattern ... wich I have to model to a curved panel ....

The intended result is to wrap the 2d on the 3d....

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I don't think PROJECTGEOMETRY is going to do it for you.  In this simplified example of the distortion it makes when projecting onto a curved [in this case] Solid [but likewise if a Surface]:

The green is a Circle, and to demonstrate the distortion clearly it's only slightly smaller in diameter than the width of the half-cylinder grey Solid.  Its plane is parallel to the flat back of the Solid.  The cyan Spline on the Solid's surface is from PROJECTGEOMETRY-ing the Circle onto it.  Clearly that doesn't look like a Circle "wrapped" onto that curved surface.

The yellow lateral Arc on the Solid surface is the same in length  as the Circle's diameter.  I would expect that to "wrap" that Circle onto the Solid, you would want a result that's the same distance along the surface in that direction as the width of the Circle, which is what that Arc represents.  From that yellow Arc I determined the necessary width of the red Ellipse inside the green Circle, which when projected onto the Solid results in the yellow Spline on the surface.  That more accurately reflects "wrapping" the Circle onto the Solid, but it requires the intermediary Ellipse, and it works only with a regularly-curved surface, and with the Ellipse "centered" in relation to it.

But it's highly dependent on the particulars of the curvature of the surface in relation to the size of the element(s) to be projected.  In a case like your pattern, such a chore would need to be performed separately for each element of it.  And a given element in the pattern, when centered in relation to the curved surface, would need to be handled very differently where it's off toward the side.  And assuming the Solid gets Subtracted from to make a constant-thickess curved "sheet," converting the assorted Splines [resulting from projections of the pattern elements onto the surface] into something by which you could cut out holes in the sheet is another challenge, if at all possible.

Is that pattern made up of only Arcs [or Polyline arc segments] of different radii?  [If so, it seems at least possible to do similar projections, but for each Arc or arc segment separately.]  Or is it wholly or partially of something else, such as Splines?  If it's a Hatch pattern, it's necessarily made up of only short straight  segments, which may need to be dealt with in a different way entirely.

[Johanna_Esteban]

Hello @rafael.tavares.costa, 

I understand what you need, take a test as simple as possible to show you the method, however, the result can be affected by the dimensions of the curved panel and the pattern.

I took as reference the image that you attached to generate the shell in 2d, later using PEDIT to turn it into a closed polyline to have no problem to extrude it, then with polar ARRAY I created part of the pattern in a circular direction, I exploited the array and extruded the shells.
I used two extruded circles, subtracting the internal to simulate a hollow cylinder and finally with SUBSTRACT removed the shells to the cylinder.

I hope it gets closer to what you need, if you need additional or detailed information, I will be there to help you.

Greetings.

[rafael.tavares.costa]

@Kent1Cooper, you nailed exactly on what I'm trying to do. If I was working with Inventor or other similar software, I could just do this as if it was a metal sheet, model the sheet with the holes and then bend the solid to the desired radius. Unfortunatelly Autocad does not have the bend command...

Thanks for your reply.

[rafael.tavares.costa]

@Johanna_Esteban can you share your result with a screenshot?

Thanks

[rafael.tavares.costa]

@john.vellek Hi,

The projectgeometry command is not suitable for this problem. I already tried it before posting my issue, and as @Kent1Cooper showed on his reply, it gives out a distortion that we can't work with...

I have to model some GRC (Glass Reinforced Concrete) panels to apply to a curved wall, so the panels have to follow the same curvature. Also, this 3d model would have to be used to make the casting mould, so it has to be accurate...

See the file attached, and hopefully, it would help get to a solution.

Thanks

[beyoungjr · Accepted solution]

Hello,

Thanks for providing your dwg!

AutoCAD does not have a native function to "wrap" 2D profile objects to a surface or solid face.  Inventor handles this very well, as you indicated.

My approach to this would be to determine the center of your curved wall (5.1 radius) and rotate objects around that center by the necessary arc length.  The simplest result is in the attached file that I created.  I copied my steps so that you might understand my process.

The outcome is a curved pattern of your shell objects subtracted from the wall.  The shell objects had to be created at a slight distance (.2) off of the inner face and then rotated, so that they would protrude through the innser and outer faces of the wall.   They were PressPulled and thus remained straight.  This yields tapered webs.  If you want to maintain constant web thickness you could taper the shells before subtracting.

I think this approach may satisfy your needs?  Please have a look and let me know if my understanding is not quite right.

Cheers,

Blaine

[Johanna_Esteban · Accepted solution]

Hello @rafael.tavares.costa,  

Mira:

[rafael.tavares.costa]

thank you @Johanna_Esteban and @beyoungjr for your demonstration.

In the lack of a proper command like Inventor's "Bend" command, I will have to follow one of your solutions, that are similiar to each other.

I appreciate the help provided. If someone knows any other solution, or third party app that can speed up the process, please fell free to share with me and the community.

Kudos people.

[Patchy]

There was, but I don't know it works with newer Autocad.

https://apps.autodesk.com/ACD/en/Detail/Index?id=5135633357254081302&appLang=en&os=Win32_64

[rafael.tavares.costa]

@Patchy Thanks, I will check that out and give you some feedback.

[leeminardi · Accepted solution]

The two posted solutions suffer from the same shortcoming.  Neither addresses the need to make a radial taper of the solid that will be subtracted from the cylindrical shell. The straight projection used will create a wall thickness between shell cutouts that varies.  @beyoungjr mentions that a taper could be applied to help compensate for the required radial taper but the AutoCAD taper that is an option when extruding a 2D shape is uniform in all directions.  This would be alright if the solid were to be subtracted from a sphere but in the case of a cylindrical surface the taper should only be in the tangential direction and NOT the transverse direction. 

I took the 2D shell outline created by @beyoungjr and imported it into 3ds Max and then applied an extrude modifier followed by a bend modifier resulting in the following.

This provided the bend in the radial direction but not the axial direction. The file was saved in Max as a .dwg and then opened in AutoCAD.  I added top and bottom surfaces and then used surfsculpt to create a solid that could be arrayed and subtracted from the cylindrical shell.

Although no dimensions were provided by the OP I think the attached solid could be used (uniformly scaled if necessary) to create the desired 3D model. 

[rafael.tavares.costa]

@leeminardi Thank you for your time and attention to my issue.

What you say it's completely true. Autocad is lacking in some tools that are standard for other Autodesk family softwares.

The Radial taper is something that both solutions don't solve, not by lack of knowledge from both replies, but due to software limitations, as you correctly said.

I will give a go to your solution.

Thanks

[Johanna_Esteban · Accepted solution]

Hello @leeminardi,

You're right, it's an important detail, and it's easily solved. Attach dwg file with the step by step process for it.

Basically the extrusion is done and the subtraction of the pattern to the cylinder, which will now be a surface, not a solid (the same eater works).

When the holes are already in place, using THICKEN, a thickness is assigned to the surface and already.

Regards, 

[leeminardi]

Hello @Johanna_Esteban,

I like your solution in that the walls of the holes are radial. It also avoids the need to export/import the shape with Max. There is some small error introduced with your "surface model/thichen" solution due to the initial linear projection of the 2D shell shape onto the cylindrical surface but this distortion is minor and should not affect the integrity of the solid model.

[Johanna_Esteban]

Hi @leeminardi, 

Yes, besides that when importing and exporting, the type of entity can be more affected by software "compatibility".

The distortion is of the initially spoken, everything is subject to the dimensions of the pieces, if the cylinder is huge and the very small patterns will be minimal.

Regards, 

[Kent1Cooper]

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@leeminardi wrote:

The two posted solutions suffer from the same shortcoming.  Neither addresses the need to make a radial taper of the solid that will be subtracted from the cylindrical shell. The straight projection used will create a wall thickness between shell cutouts that varies.  @beyoungjr mentions that a taper could be applied to help compensate for the required radial taper but the AutoCAD taper that is an option when extruding a 2D shape is uniform in all directions.  ....

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Another way to get a radial taper, without the top and bottom also tapering down and up, and without exporting to other software, would be to not EXTRUDE the shape of a hole, but LOFT from it to a very narrow rectangle of the same height, at the center of the plate's curvature.  You can't LOFT to a Line, which would give you greater precision, or to a closed Polyline made up of only two line segments that coincide, but a very skinny  Polyline rectangle may give acceptable results.  Then ARRAY etc. that as in other solutions to make the pattern of pieces to SUBTRACT from the curved-plate Solid.  [Yes, my shape is slightly different, but should give you the idea.]

[SEANT61]

Generally, the Vector Mapping routine, mentioned by @Patchy in post #11, maps WCS coordinates to a surface’s UV coordinates.  This is not guaranteed to have a 1 to 1 length correspondence.  The one exception is with geometry based on a circle/cylinder.  With the posted file, though, the arc bend is so slight, there is only about a 0.1 % distortion compared to a straight projection.

In any event, here are some screencasts of that app in use.

https://knowledge.autodesk.com/support/autocad/learn-explore/caas/screencast/Main/Details/dedada19-2...

https://knowledge.autodesk.com/support/autocad/learn-explore/caas/screencast/Main/Details/894d4a0e-9...

https://knowledge.autodesk.com/support/autocad/learn-explore/caas/screencast/Main/Details/1d47a745-4...

[SEANT61]

Incidentally, I notice that the perimeters of the flat shells in the original “Curved Panel” drawing are not all the same.  Compare a shell in the middle column with one of those next to it.  Is that by design?