Lofting with 3D Guide Curves - Fails

[kcoffield]

The attached file is a bit of a mess, but it was all done to generate the 3D spline guide curves for the sweeps and lofts. I used the method in this video which teaches using the edge formed by the intersection of two surfaces and then project to sketch to capture the curve.

One difference for my file from the video is I don't want to use any of the spline construction geometry for the actual model, only to generate the guide curve, thus my suppressing everything before the 3D spline guide curve. I was (pleasantly) surprised that the guide curve still existed without error after suppressing all the features that created it. You can see I eventually got there with the fully generated file, but now I'd like to experiment using guided lofts using the same 3D guide curve.

Though in 3D sketch I can select all, there is no copy function so it appears there is no way to copy a 3D sketch feature like the guide curve and paste it to a new sketch. Is that correct?

So I thought I'd just delete the sweeps so the 3D spline guide curves were available for re-use and to my surprise, the only items in the entire DE unavailable to be deleted are the sweeps. Why? So then I unsuppressed everything thinking that may have something to do with it and still cannot delete the sweeps. I can suppress the sweeps and think I could go back and use the projection from the intersection of the two surfaces to duplicate the guide curve, but the sweeps appear to be forever imbedded in the file. I have never encountered this before.

A bit frustrating because the guide curves are the only features I care about in that whole file and I can't access them to further edit and develop the file. What did I do to create such a problem?

Best,
Kelly

 

[Stu3d]

So I thought I'd just delete the sweeps so the 3D spline guide curves were available for re-use and to my surprise, the only items in the entire DE unavailable to be deleted are the sweeps. Why?

Delete the Shell and Mirror at the bottom of the DE you can then delete Sweeps.

 

[kcoffield]

Delete the Shell and Mirror at the bottom of the DE you can then delete Sweeps.

Thanks Stu. Easy fix. It never occurred to me that something later/farther down in the Un-generated DE could control and earlier feature like that. Thank you.

Best,
Kelly

 

[kcoffield]

So having gotten by the simple part thanks to Stu, I tried centerline lofting with the 3D guide lines and the lofts fail. I did find a small error in the outer guide curve position and fixed that on the updated file attached below but it did not matter. When I created the 2D geometry used to construct the intersecting surfaces that defined the 3D Guide Lines, I included short straight segments at the ends of each curve/spline to maintain perpendicularity to the plane of the sketches and also applied continuous tangent constraints where the splines/curve connected to those straight segments.

I can successfully sweep along the either of 3D guide curves from any of the of the round or D-shaped sketch features on the respective guide lines, so I assume that means I succeeded in making the sketches perpendicular to and touching/intersecting the planes of the sketch geometry. But if I try to loft between the sketches on those guide lines, they fail with error message:

ACISERROR_NON_CONTINUOUS_GUIDE_CURVE: Guide curve is not continuous.

I don't know how to analyze a 3D spline/sketch for problems like is available for 2D sketches. Is there such a function in Alibre? Any help on how to remedy would be much appreciated.

As an aside, being able to do guided lofts and sweeps is probably the single most important CAD skill for me to master and try as I may, I still suck at it.

Best,
Kelly

 

[Stu3d]

ACISERROR_NON_CONTINUOUS_GUIDE_CURVE: Guide curve is not continuous.

In your 3d Sketch, Outer Runner CL, there are two circle sketch figures representing the positions of Outer Runner OD at Carb and Outer DPort No Offset aswell as your guide curve . These would make your guide curve not continuous? I assume you did a Project to Sketch to bring the circles into the 3d Sketch but as sketch figures instead of reference figures. There doesn't seem to be a way to change them to reference figures so you may need to go back a stage.

 

[kcoffield]

In your 3d Sketch, Outer Runner CL, there are two circle sketch figures representing the positions of Outer Runner OD at Carb and Outer DPort No Offset a swell as your guide curve . These would make your guide curve not continuous? I assume you did a Project to Sketch to bring the circles into the 3d Sketch but as sketch figures instead of reference figures. There doesn't seem to be a way to change them to reference figures so you may need to go back a stage.

I did not (intentionally) bring those other features into the 3D sketch for the 3D guide Lines, and although I see what you are referring to, I'm not certain they are actually part of the 3D sketches. When I globally toggle off sketches, and activate/edit 3D Sketch for Inner or Outer Runner CL, I can see still see every other sketch in the file as a very light blue ghost, and I can highlight them but even though I can select/highlight them, I can't delete or edit them in any way. The 3D guide line is the only feature that shows as an active red line when the 3D sketch is active, and furthermore, if I use "select all" while the 3D sketch is active, only the guide line is selected/highlight and can be deleted, but none of the other suspect sketch features.

Also, if you select one of the Inner/Outer CL 3D sketches and use it as the path for the sweep with any of the other circular or D shaped sketches constructed on the path/guide line, they all successfully sweep. If those other sketch features were actually imbedded in the Inner/Outer Runner 3D sketches, wouldn't the sweeps fail as well for the same reason as the loft?

Best,
Kelly

 

[HaroldL]

Check the Status of the Loft (RMB>status) to see what message you are getting.
From what I saw it appears the guide curve is not aligned properly.

Here are some of the things I repaired...




And this is the result



I think there is still some work needed on the guide curve.

 

[kcoffield]

Check the Status of the Loft (RMB>status) to see what message you are getting. From what I saw it appears the guide curve is not aligned properly.

Here are some of the things I repaired...

And this is the result

I think there is still some work needed on the guide curve.

Thanks Harold, I appreciate the reply.

When I check (failed) loft status I get the same status as the error message. I guess I didn't make the connection with the error stating the line wasn't continuous with it not being aligned properly to the lofting faces. You certainly got farther than I did, but I must say, if you actively edited a 3D spline in 3-space/3D sketch mode, you're a far better man than me. I can connect straight lines between reference points in 3D sketch mode but when it comes to trying to insert a 3D spline by the spline command and selecting/placing nodes in 3-space, I have no luck at all getting the nodes anywhere near where they're supposed to be so I never get a chance to apply the tangent continuous constraint.

I guess the thing I failed to realize about the method of projecting a 3D guide line from an edge of two intersecting surfaces, is even though the 2D guide curves used to create the surface geometry are perpendicular to the lofting faces, that doesn't constrain the line created at their intersection to be so. Also, apparently, I was mistaken about the sweep path needing to be normal to the sweep cross section sketch geometry and that's why the sweeps work and lofts do not. Sweeps are ok and I can vary the cross section from end to end with draft but not change the shape....must have loft for that.

Think I need to take a break and fix the dent where I've been beating my head against the wall.

Best,
Kelly

 

[dwc]

I can't open your files as I have an older version, but am wondering if it would produce a better result to loft round to round and then afterwards cut the portion you don't want to create the flat side.

 

[kcoffield]

I can't open your files as I have an older version, but am wondering if it would produce a better result to loft round to round and then afterwards cut the portion you don't want to create the flat side.

I decided that learning to build better 3D lofting guide lines can wait for another day. Sweeps are far more tolerant so I did a thin sweep of a round profile on the 3D centerlines, then added the D-shaped floor with another guided sweep with draft, then mirrored the features. -Moving on.

Best,
Kelly

 

[HaroldL]

Creating 3D sketches are a real trick. Take a look at the video @Ex Machina posted for 3D sketches.

Rookie to Rocking it: A Masterclass in 3D Sketching in Alibre

Here's a video with all the tips and tricks I use to design using 3D sketches in Alibre. I also show how I switch planes and continue sketching from the same place. I hope you enjoy it and I'd love to hear comments or additional questions on 3D sketching. P.S. Here's the Pneumatic cylinder...

www.alibre.com

That said, I had another go at this one and got the centerline guide curve to be accepted. Here are some screen shots...









And now it will Shell.

 

[kcoffield]

Thanks Harold. I think I've watched that video of Konstantino's a half dozen times now. Your loft looks excellent. The thing that was a big bonus was there didn't seem to be any twist. Any twist can potentially pose a problem for the next steps.......splitting it on the parting line and mounting it on a surface made from the parting line for two-sided machining.....like in the attached pics. I added a fillet to the D sketch. And it still shelled! Well done. Dog-gone you.......I may have to have a go at the other runner.

Best,
Kelly

 

[HaroldL]

I got the technique for the tangent arcs from this video by Alibre Schwiez

 

[kcoffield]

I got the technique for the tangent arcs from this video by Alibre Schwiez

That variation is useful and similar to the method ExMachina teaches for continuous tangent on 3D splines. I'll need to keep learning and practicing making useable 3D guide lines and gives me a few more tools to work with. It's a skill central to almost every project I do. As always, thanks for your help.

Best,
Kelly