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Stopping the Loft Twist
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* July 25, 2019, 05:59:25 AM
Hi All,

When lofting to a polygon to a circle is there a way to stop the loft twist? The minimize loft twist check box helps but it does not make the resulting loft symmetrical because there is no resulting construction vertice that divides the loft in half. Often times the loft tool will fold in this edge resulting in a notch in that will divide the two halves if you try to mirror a slice down the center.

Any ideas that could help to get a symmetrical loft when lofting from a polygon to a circle?

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TurboCad Platinum Pro 19,20,21, 2019


* July 25, 2019, 07:26:52 AM
#1
Whoa I have to add two guide lines to fix this, then I have to mirror the better half, then I have to retrace the polygonal profile afterward!

Is there anyway to avoid having to do that to get a symmetrical loft part?!

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TurboCad Platinum Pro 19,20,21, 2019


* July 25, 2019, 08:03:50 AM
#2
And so after the chaos of having to add guide lines, then slicing down the mirror plane, then reconstructing the profile from the loft (for instances where I have had to loft from circle to polygon), then relofting neighboring lofts that are simply polygon to polygon, then creating solids that add between the lofts to add the last remaining unneed line in the lofted solid that turbocad created from the reinforcing guideline I have endup with this bunch of parts to sum. This is way beyond yesterday and should produce a way better solid.

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TurboCad Platinum Pro 19,20,21, 2019


* July 25, 2019, 08:55:38 AM
#3
Even in this amount of activity and utilizing all snaps between profiles and building profiles snapping to other profiles I still have bad edges being produced. Could this be rounding errors? The act of slicing and mirroring and summing from the profiles that are snapped together seems to introduce error at Precision 5. this is at maximum zoom.
« Last Edit: July 25, 2019, 09:41:25 AM by MicheliDE »

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TurboCad Platinum Pro 19,20,21, 2019


* July 25, 2019, 09:55:39 AM
#4
So I have begun the process of assembling objects one at a time and checking every corner. It is unbelievable that turbocad has moved my objects by the tiniest amount. At maximum zoom I can see this slight adjustment that needs to be made to the lofts. I certainly didn't move them. This must be the difference of snapping between profiles and snapping to objects!?

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TurboCad Platinum Pro 19,20,21, 2019


* July 25, 2019, 11:21:27 AM
#5
At maximum zoom I just moved a 2D poly line that I created with the rectangular tool and it created a 3D edge problem!  >:(

It also destroyed one of the surfaces that I was trying to join but were still individual solids!

I've never seen anything like that before

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TurboCad Platinum Pro 19,20,21, 2019


July 25, 2019, 11:46:39 AM
#6
I don't hve the time to experiment, but you might try rotating one of the 2D profiles before lofting.  TurboCAD has to decide where to start and that depends on where you originally clicked to create the objects.

It just occurred to me that, if you duplicate the polygon and apply the Fillet2D command judiciously, you might be able to create a reasonable-enough approximation of a circle for your needs, then loft between the two objects.


Jeff

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* July 28, 2019, 06:00:38 AM
#7
Hi Jeff,

That is not a bad idea, I did try using the 2D fillet  for profiles before lofting in this post, page 1 mid way down somewhere:
http://forums.turbocad.com/index.php/topic,25957.0.html

I think that I am having a lofting twist profile where guide are needed to make the object mirror however when I add them it creates a not square edge even though the profiles that I am lofting between have a single square edge.

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TurboCad Platinum Pro 19,20,21, 2019


* July 28, 2019, 12:14:01 PM
#8
Hi All,

When lofting to a polygon to a circle is there a way to stop the loft twist? The minimize loft twist check box helps but it does not make the resulting loft symmetrical because there is no resulting construction vertice that divides the loft in half. Often times the loft tool will fold in this edge resulting in a notch in that will divide the two halves if you try to mirror a slice down the center.

Any ideas that could help to get a symmetrical loft when lofting from a polygon to a circle?

Maybe. Please post a .tcw containing just the polygon and the circle.

Henry H

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