Twisted surface using Through Curves

[kadego]

Hi Everyone
I have a series of closed profile curves(sketches) which need to be lofted together to form a tubular shape.
The supplied profile curves have differing start points so I end up with a twisted surface when using Through Curves.

How do I align the start points of each curve?

TIA
Dave

 

[gieter]

You need to take this into account before making the sketches. I found the best thing to do is to work with at least 2 curves in a section and to choose the starting point so that every section's origin can be alligned.

This means: when you have a circular section, don't use a circle, but make it out of 2 arcs.

I hope however, that someone will prove me wrong and have a solution that will work with single curved sections

 

[Xwheelguy]

Use the By Points Alignment method when creating the surface. If you have documentation installed, it covers this pretty well. If not, then I'll try to explain a situation where it is used:

Creating a surface that passes through 3 curve strings; the first set of strings being a square, the middle set a triangle; and the last being a square. Imagine we are viewing these strings at an ISO point of view, with the first set of strings being in the lower left hand corner of the view 'window' & the last set of strings being in the upper right corner.

Select the first set with the bottom curve of the square being the first curve selected. Continue in any direction until you have selected all 4 curves. Next, select the triangle with the base of the triangle being the first curve selected & be sure to select in the same direction as the first set of strings. Finally, select the bottom curve of the square & continue in the same direction as the first 2 set of strings. Now all red vector display arrows should be pointing in the same direction.

Next, select the By Points Alignment method & for EACH string, choose ONE point to align. So on the first set of strings (the first square) we select the upper right hand corner of the square; for the second set of strings (triangle), we select the peak at the top & for the last set of strings (square #2) we select the upper right corner of the square. This should force the resulting body to converge at the peak of the triangle then taper back out as it approaches the final set of strings.

I realize this is probably a much simpler example than what you may be working with, but it's a good place to start. Should your cross sections be different, try joining and/or splitting the section curves so that their start & end points are more closely aligned (to prevent the twisting). You might even be able to define a spline that intersects each section string, then use that spline to define a plane that is perpendicular to it (the spline). If you can do that, then you can align your WCS to the plane & split/join the curves more precisely.

Tedious, but should get you closer to the results you desire. Another option is to use Swept, should you be able to define a guide somehow.

Tim Flater
Senior Designer
Enkei America, Inc.

http://www.enkei.com

 

[Enduro99]

Gieter,
Place datum of sketch plane using CSYS Constructor's "X-axis Y-axis Origin mode" with the filter setting "At Angle". This will let you place a circle instead of separate arcs to align orientation.

 

[gieter]

Enduro99,

I will certainly try that one. The trouble is that the sections in our case are not always in a single plane.