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Need a crash course on Unfold Face
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March 04, 2011, 01:44:44 PM
Hi All,
I need a crash course in, how to unfold a duct transition piece, as I cant get the Unfold Face tool to select the transition piece between the circle and the rectangle.

I have attached the dimensions (thickness for the duct material is 2 mm).

Please write the instructions in easy understandable steps.

Thanks for your help!

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Thanks!
Best regards,
Lars
www.lm-illustration.dk

(TurboCAD PRO PLATINUM v2018 64bit)


March 04, 2011, 03:35:52 PM
#1
Unfold Face will only work with flat surfaces that have properly-defined fillets.

The biggest problem I see with your structure is that it doesn't have any gaps between the two adjacent sides, so TurboCAD won't know where to split.

I don't currently have TurboCAD on my system (I am building a new one), so I am limited in my ability to advise you.

What you could do is create a flat surface and than add flanges to each edge with a bend radius and length (in your case, height).  After you have the desired height, add more flanges to the vertical edges to build the overlap that can be welded to the adjacent face for actual construction.

You should be able to unfold this structure.

However, TurboCAD has a glaring (to me, at least) drawback in that it will not properly mark the points where a bend should start.  There are two ways to deal with this.  One is to insert holes before unfolding that will mark the desired bend lines.  The other is to make your flanges a bit shorter than the entire edge so that there will always be discontinuities that will identify the bend points.  In either case, you will have to enter the desired bend radius into any drawing you submit for manufacturing.

Jeff

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* March 04, 2011, 03:41:47 PM
#2
Jeff is entirely correct, but there are other ways to draw the object. The attached screenshot shows the transition piece built by using the Prism tool (nearly the same as Loft) on pairs of parallel lines lying in the plane of the top of the transition and in the plane of the bottom. Resulting "prisms" were zero-thickness objects, which I 3D-Added, then filleted the joints, then shelled. Cut a vertical slit in one face and unbent.

Henry H


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March 04, 2011, 04:06:54 PM
#3
Another way...
Part below is two 24 side polygons lofted. One is node edited to make a sqare(ish) shape. Use another much smaller 24-side polygon in each corner to vertex snap nodes - that keeps each face flat.
Fillet the sides and shell outwards, omitting top & bottom faces. I couldn't Unfold this object but Unbend did work (once a thin solid was subtracted to slice the sheet)

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Julian

TC18 / 38.5 Platinum, AL5. XP, Core2 Duo E6750 OC'd 3.0Ghz, Render test: 3mins 3sec.


* March 04, 2011, 09:17:42 PM
#4
Unfold face and unbend sheet will only work with ruled surfaces.  Unbend sheet's additional compulsory criteria is cylindrical curvature.  Loft mostly DOESN'T use ruled surfaces, and prism's ruled surface is only guaranteed if the profiles are both polygonal.  The simplest way to guarantee usable ruled surfaces is using the cone tool.  My workflow is:  Start with the end profiles, and the cone tool with "2D entity for the base" and the "base for object height" parameters checked.  For this example, most common in my experience, the rectangular base is coned to each quadrant of the circle.  Then the circle is coned to each vertex of the rectangle, and the result of these is eight solids.  Stalactites and stalagmites.  Add them all, and you get the simplest ruled surface for the transition.  Unfold face will give you eight patterns to lay out.
Cone can also make unbend sheet a bit easier, too.  Another story...  
« Last Edit: March 04, 2011, 10:45:38 PM by murray dickinson »

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* March 05, 2011, 06:57:23 AM
#5
To unbend:  I've used your file and represented the circular neck as a polygon.  I arbitrarily went with 16 sides as a tradeoff, you can get more fussy and edit the perimeter of the polygon to close to that of the circle.  The first picture inset shows the polygon coned, the big picture is both profiles coned and added.  Then I format the solid as a surface and remove the top and base with facet edit, removing the internal cavity's faces at the same time.  (It occurs to me now that facet edit, highlight external faces and format|surface|from faces will do it faster.)  If you leave the internal cavity faces there, they'll interfere with filleting and shelling.  The reason I don't shell and omit faces is because TC does surface booleans anyway, and there are less faces to have to work with at this point.  Next step is to cut out those vertices of the solid that have more than three faces intersecting ie the quadrant points of the circle and the corners of the rectangle.  Those intersections will stall filleting and shelling if something's been overlooked.  I've done it using spheres.  I've locked diameter at 20mm in the inspector bar and placed them at the multiple-face intersections.  20mm because the cutaways leave the intersection points that come with filleting and shelling well clear.  The spheres are subtracted from the transition, and because it's a surface, that process doesn't create more faces.   Then I've filleted all of the longitudinal edges 5mm, to leave room to make sure that I don't produce more multiple-face intersections.  Then I've shelled the transition 2mm and booleaned out a .005 thick slice so that the surface is discontinuous, after which it'll unbend.  If you look at the cutouts that the spheres leave in the unbent piece, you'll see that they're multiple arcs.  Looking at the last picture, you'll see how I've continued green lines drawn through the face vertices in the cutouts to their complementaries on the opposite edge.  Those are the bend centrelines that TC omits, but this method does make them quite easy to define without special consideration.
« Last Edit: March 05, 2011, 03:47:37 PM by murray dickinson »

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* March 05, 2011, 08:37:01 AM
#6
Wow! What a tutorial that was. Thanks guys. Mike.

OK. I just went to the unfold section of my new turbocad pro book. Im using 17.1.
It sais it's under Modify/Unfold. It's not there. Is this some kind of Add/On. I dont seem to have a 3D Modify menu.
« Last Edit: March 05, 2011, 08:50:01 AM by besc »

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March 05, 2011, 10:01:50 AM
#7
Outstanding "crash course" Murray

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* March 05, 2011, 10:36:48 AM
#8
That's a jaw-dropper, Murray.

Henry H

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March 05, 2011, 12:17:23 PM
#9
Thank you so much all, for these fine instructions! What a cornucopia of useful knowledge this forum is! :D

I will have to test all the methods, one by one, so I can be more familiar with Unbend and Unfold.

Murray: is there a particular reason why you made the sphere so big as 20 mm? Could it be smaller, so the final sheet metal will look more correct?
*EDIT* I guess you made the sphere so enormous, to make it easier to understand the trick with bending lines - right?
« Last Edit: March 05, 2011, 01:57:31 PM by Lars Maltha »

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Thanks!
Best regards,
Lars
www.lm-illustration.dk

(TurboCAD PRO PLATINUM v2018 64bit)


* March 05, 2011, 01:19:23 PM
#10
re: It said it's under Modify/Unfold. It's not there.

Besc, the Bend and Unfold tools are in the Platinum or Mechanical editions only. See the Modify Menu in the Wiki for where you would find them.

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John R.

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March 05, 2011, 01:42:34 PM
#11
... unbend sheet will only work with ruled surfaces...  Loft mostly DOESN'T use ruled surfaces...

tis why the same polygon is used to form top, bottom and corners. So long as Z axis isn't rotated, loft does generate ruled surfaces.

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Julian

TC18 / 38.5 Platinum, AL5. XP, Core2 Duo E6750 OC'd 3.0Ghz, Render test: 3mins 3sec.


* March 05, 2011, 02:17:42 PM
#12
Thanks guys.

Lars, I made the spheres that big because filleting and shelling create more faces, and if those faces are going to run into each other, it stops the processes working at least some of the time.  It's a drag having to figure out why, big clearances eliminate the possibility.  Once you've got the bend centrelines, it's trivial to eliminate the cutout.  Facet edit, highlight the cutout facets and delete.

Julian, you're right, but you gave the exceptional criteria yourself.  It isn't universal behaviour.
« Last Edit: March 05, 2011, 09:03:35 PM by murray dickinson »

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