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I use Creo Parametric to model. I tried to model the pendant shown below, but nothing worked. I first made an extrusion of a circle. Then, I created the outer arc using sweep. I was able to get the shape of the pendant through 'pattern.' My original idea was to create a bend in the pendant, import two of the same part files, and then assemble them using Boolean operations. But, I am unable to get the curvature/convex bent-shape. When I tried spinal bend, it returns an error. How do I approach this correctly? Please help. The error is shown in the second figure.

The pendant to be modelled

Error in model

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  • $\begingroup$ This looks like three features to me - revolve (profile in your last picture) extrude cut to make one petal (per second picture) then pattern bodies. (And also add the ring at the top) $\endgroup$ Nov 28, 2021 at 20:11
  • $\begingroup$ @r13 - I understand this, that's what I was describing how to model! $\endgroup$ Nov 29, 2021 at 8:47
  • $\begingroup$ @JonathanRSwift No, I did not use revolve. I created an extrusion of a planar petal, then I used spinal bend to make it curved. Then I tried using pattern to make pattern out of it, but I got a regeneration error. Any ideas how to do it in Creo? Meanwhile I will try another software, if it works $\endgroup$
    – user35974
    Nov 30, 2021 at 7:16

1 Answer 1

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An elementary way to make it (or something resembling) is to make the surface by revolving an ellipse 180 degrees (or a half ellipse 360 degrees). Then one can extrude it to the normal direction to the wanted thickness. Many programs also allow creating a shell with wanted thickness around a solid. In the most simple programs one must revolve a profile which already has the wanted final thickness.

The holes can be drawn in plane and extruded to bars. Subtract them from the shell and that's it - add only the ring.

Another a little different approach is to make one petal and bend it. Bending a piece can be tricky or it's not at all implemented in simplest programs. I have a simple one which has a kind of bending .The next example is made there (=a low cost program named Moment of Inspiration, "MoI")

The bending in MoI is only a geometric trick. MoI is definitely not a valid metal engineering tool because it has not a slightest idea of how real metal would behave. That capability would need some real money to be purchased.

See the next image:

enter image description here

The planar petal is a XY-plane surface limited by 4 circular arcs which are joined. The curve in the right is a quarter of an ellipse. That will be rotated 90 degrees and used as the bending profile.

The ellipse arc is rotated to YZ plane and a corresponding reference line is drawn on the petal in XY plane:

enter image description here

MoI has geometric deformation named "Flow" which forces the piece under deformation so that the reference line becomes the wanted profile. Here's the result:

enter image description here

The original is still there. I keep (and hide) it for safety because the program is not a parametric CAD.

Extrusion makes this solid:

enter image description here

It's extruded to Z-direction. It's not physically realistic, it's jumping over where the fence is lowest; See NOTE1.

An upside down copy is made. The pieces are placed to overlap a little:

enter image description here

The final shape (minus the ring) can be made by making rotated copies and an union of them. I rotated 30 degrees/petal to make a little less dense version:

enter image description here

The edge strokes disturb. Without them one can see better how the surfaces fit:

enter image description here

Here's a high zoom into show the joints:

enter image description here

One can see that there's a little error at the joints. That's because the petals have only a single curvature, their overlaps cannot form a smooth continuous surface, there must be steps. The surface normals point to different directions where adjacent petals meet.

NOTE1: Extrusion to surface normal direction would be more realistic. The easy way to get it is to extrude the planar version and to flow (=bend) the already extruded version:

enter image description here

That makes easily exactly fitting cusps, but the crossings in the middle of petal edges have still the same steps as in the previous version:

enter image description here

That impossibility to make a smooth surface by joining rotated single curvature petals can be the cause of your error message. I cannot verify it (= no Creo nor other high cost professional CAD software available)

Making a smooth surface by joining rotated petals is possible if the petals have both needed curvatures. The easiest way to get it is to project the planar petal shape onto a revolved surface:

enter image description here

The circle is the reference surface. The dome below it is a revolved quarter of an ellipse. This is the result of the projection (project is a mode of Flowing):

enter image description here

Extruding and making rotated copies gave this result:

enter image description here

This is a smooth surface, as expected. High zoom in doesn't show any steps at the joints:

enter image description here

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  • $\begingroup$ Thank you for your valuable answer! I have tried the exact same thing in Creo (in Creo, the Flow option is called Spinal Bend). I am able to make a single petal with a bend, but when I extend it to a pattern of petals, the model shows some regeneration error. What do I do in that case? I have updated the erroneous model's image in the original question. $\endgroup$
    – user35974
    Nov 29, 2021 at 5:21
  • $\begingroup$ Thank you for the help! I will try to model it in MoI or some other software now. $\endgroup$
    – user35974
    Nov 29, 2021 at 7:34
  • $\begingroup$ If you are interested in freeware which can make the exactly fitting projected version I recommend to try Design Spark Mechanical. Here's one of my attempt's in DSM: i.stack.imgur.com/8ms6F.png That program is a decimated version of SpaceClaim. Many professional CAD file formats, sheet metal and making drawings are for ex. disabled, but the core of geometry making is still there, It's free and intended for hobbyists. $\endgroup$
    – user287001
    Nov 29, 2021 at 10:55
  • $\begingroup$ I will use DSM then, thank you so much! $\endgroup$
    – user35974
    Nov 29, 2021 at 13:35
  • $\begingroup$ I don't see any issues making this with Creo using the steps in my comment! $\endgroup$ Nov 29, 2021 at 21:30

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