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Centerline Lofting along 3D Spline

kcoffield

Member
Hi all,

In the attached file I was attempting to loft (Loft 7) the filleted rectangle (Port Window) to the circular sketch (Carb Opening) along the 3D Spline (Runner Centerline). It fails and I get the error "SKIN_PATH_PROFILE_NO_PERP: Profile plane and tangent of the path are not perpendicular". The tutorial doesn't explicitly say so, but I note I have no option to select tangent or angle in the lofting command with the spline selected as the centerline guide. As the error suggests, must the spline be perpendicular at the intersections with the lofting profiles? I had a heck of a time with shape of that spline and was hoping to be able to manipulate it achieve the desired transition. If so, I don't understand how to constrain the guide spline perpendicular at the intersection of the sketches. -All help appreciated.

Best,
Kelly
 

Attachments

  • Runner Loft.AD_PRT
    250 KB · Views: 3

HaroldL

Alibre Super User
I have no idea what the error/status message means but, I changed the guide curve to Tangent and it created a Loft.
1670285904550.png
From the appearance of the guide curve I wonder if the loft could follow the path, it would have some bends that may preclude the loft from completing.:(
I think this needs another pair of eyes on it.

And as you hinted, 3D sketching is no picnic especially if splines are involved. I can never get them to go where I want.
 
Last edited:

kcoffield

Member
Thanks for that Harold. It lofts for me with those settings too. The goal is a .25" wall transition from the port window to the carb opening, and along a guide path if/when possible.

I tried to shell the resulting loft outward with .25" wall but it would not execute the command. So then I added a couple sketches with a larger perimeter to achieve .25" wall, lofted those (Ext Runner Surface) with the same settings, and then used the previous sketches to try to loft cut to achieve a .25" wall tubular transition but loft cut prompt with the same parameters/settings as the previous loft (with the inside sized sketches) will never enable the OK/Execute command? Hmmm, I'm just a noob but lofted tubular transitions will be important features to me so I need to understand it well. Thanks in advance for help.

Best,
Kelly
 

Attachments

  • Runner Loft with Wall.AD_PRT
    415 KB · Views: 1

HaroldL

Alibre Super User
Kelly, I haven't looked at your last model but did make an attempt with the loft using a recreated 3D sketch path and a Face-to-Face loft.

This video should explain the steps I took.

And here's the model. I hope you can open it. You should put your version of Alibre in a forum signature.
 

Attachments

  • Runner Loft with Shell.AD_PRT
    593.5 KB · Views: 4

kcoffield

Member
Harold,

Wow, thanks so much for that and taking time to do that and for the video explanation. It was very helpful and looks very good. I'm running out of gas tonight, but I'll see if I can apply the same methodology to other examples and make sure I understand the all the nuansces. I use these models to make cnc cut lost foam patterns for casting aluminum intake manifolds and being able to define the centerline path and transition from face to face of the tubular runner is fundamental to the performace of the part.

Alibre Pro V25. I'll imbed in my sig.

Best,
Kelly
 

kcoffield

Member
Harold,

I’ve experimented a bit, understand, and can replicate the approach. Without the video I doubt I would have known to enable maintain association when the face extrusions were removed.

The transition is suitable for this particular runner and I can use it to complete the design. I’m sure I’ll be back to this thread for future intake manifold projects……maybe before I’m done with this one.

For many, there just won’t be any option other than to be able to control the loft along the centerline. It’s also beneficial if the cross-sectional area can be driven formulaically to increase linearly along the path. That’s above my head now but maybe as my Alibre skills increase and I get centerline guide figure out.

I did follow what you did to constrain perpendicularity and coincidence at the lofting faces. Puzzling why that didn’t work?

I’d appreciate it if you could leave the video in place for a while. I didn’t see a way to download it.

Many, many, thanks,

I attached a picture of a similar runner, that I split, did 2-sided machining, then reassembled. This model was provided to me by a friend. Also attached is another intake manifold (both the lost foam pattern and resulting casting) I did without CAD or CAM........If you look closely you can tell it was made from many pieces and a lot of hand work. Today, I would do the vast majority of it in two pieces as an upper and lower half that are glued together.

Best,
Kelly
 

Attachments

  • CNC Foam Runner.jpg
    CNC Foam Runner.jpg
    198.2 KB · Views: 18
  • 48 Pattern Two.JPG
    48 Pattern Two.JPG
    167.8 KB · Views: 20
  • 64.1 Clean Casting.JPG
    64.1 Clean Casting.JPG
    194.2 KB · Views: 19
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