A new twist on a mirrored Loft

[OTE_TheMissile]

Unfortunately, it sucks.

Apparently I burned up all my good fortune with Lofts when I did the model for our electric horn, now they're back to cause me issues. You'd think the term "mirror" is pretty self-explanatory, but for whatever reason Alibre decided to screw up one end of a flattened tube when I Mirrored the features I did on the other end.

I'm gonna take a shot in the dark and guess that Guide Curves would help me out here, but I've got no idea how to use them. Any help?

P.S.: This model worked just ducky 10 minutes ago, then I moved Plane <2> to make the tube 1" longer and that's when it flipped out on me.

 

[OTE_TheMissile]

While y'all are at it, change Plane <2>'s offset distance to 1.125". Overall length should be 14"

 

[NateLiquidGravity]

Edit Loft<3> and select Specify Tangent for both sketches. Then change Tangent Magnitude to .1 or some other number that is small for both sketches. OK. Regenerate and Enjoy!

 

[OTE_TheMissile]

Sweet! Not sure what that did, but as long as it works. 8)

Last time I modeled a flattened tube was at my last job where they used thinkdesign. Worked pretty much the same way as Alibre but thinkdesign asks you to pick a point (or to use Alibre terminology, a Node) in each Sketch to serve as starting points, so the resulting geometry doesn't get twisted like that.

 

[NateLiquidGravity]

Yeah, i think Solidworks uses a similar method of snapping to points on each sketch too.

 

[MilesH]

Yes, it works ok if you use a circle, rather than 4 arcs, for the Loft Sketch.

 

[OTE_TheMissile]

Yes, it works ok if you use a circle, rather than 4 arcs, for the Loft Sketch.

That's what I tried when I first did the model, but Alibre got mad because it couldn't match one continuous circle to the 4 sketch figures that made up the shape of the flattened tube. I kinda expected that to happen, but thought I'd give Alibre a shot at it. Wouldn't be the first time it surprised me 8)

I also tried Lofting both the inner and outer diameters of the tube at the same time, no bueno. So I have one Loft Boss and one Loft Cut.

 

[MilesH]

Hi Mike,

I deleted your 4 arcs and substituted a circle and it worked fine, for me.....

 

[MilesH]

File

 

[OTE_TheMissile]

~sigh~

I think Lofts & Sheetmetal are out to get me :roll:

EDIT: And as further proof that Lofts & Sheetmetal are evil, this is Post #666 :shock:

Anyway...Miles, both our Lofts still have some twist to them, but strangely yours is a little more severe & in a different direction. Weird.

 

[MilesH]

Yes, you're right, I didn't look at it closely enough.

Anyway, nice to know that it discriminates in a subtle way :lol:

 

[idslk]

hi ote,

this is not the straightest way....and has a little bug inside...but looks symetric
(sorry, i've used random dimensions...)

greets
Stefan

 

[BernardK]

Mike / Miles,

My version attached (Note V10!). No problem with changing tube length or transition length.

I notice the distorsion too. Its similar to Miles. I've also added some cross sections through the transition which shows how the distortion develops. Seems like its caused by the curve fit process that isn't clever enough to realise that the section is symetrical.

 

[JordanCClark]

EDIT: And as further proof that Lofts & Sheetmetal are evil, this is Post #666 :shock:

Yep! The work of the AntiCAD. :mrgreen: