Cabriole Leg - Proof of Concept

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Cabriole Leg - Proof of Concept

Postby dealguy11 » Sun Feb 06, 2011 2:16 am

A couple of weeks ago, Tim MC posted a video of a commercial machine making a cabriole leg, and asked if it's possible to make a similar part in Aspire. This seemed like a worthwhile challenge (and maybe something to sell) so I thought I'd give it a try. Here is the result. This is in pine (because it's cheap) and it would need some more sanding if it were commercial work.

This was entirely designed and toolpathed in Aspire - didn't export to anything else. I didn't use any wrapping or unwrapping, so it could be done on any machine with enough z-clearance. It was machined on 3 sides, and I used my indexer to make it easier to flip and keep registered. You could do it on a flat bed machine if you built a cradle. I can post more pictures of the Aspire part and cut sequence if anyone is interested.
Attachments
IMG_0370.JPG
IMG_0371.JPG
Steve Godding
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Re: Cabriole Leg - Proof of Concept

Postby GripUs » Sun Feb 06, 2011 2:34 am

Okay...I am suitably impressed. Great work!

Joe
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Re: Cabriole Leg - Proof of Concept

Postby jam1962 » Sun Feb 06, 2011 3:22 am

If it was a challenge it looks like you are victorious. I would like to here more.
Thanks for sharing...
Jay Morris...
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Re: Cabriole Leg - Proof of Concept

Postby tmerrill » Sun Feb 06, 2011 3:32 am

Steve,

Very impressive. I would like more details also.

Tim
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Re: Cabriole Leg - Proof of Concept

Postby myozman » Sun Feb 06, 2011 3:50 am

Excellent Work, Now that's what I'm talking about.

I would still like to see this done with a wrap.
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Re: Cabriole Leg - Proof of Concept

Postby dealguy11 » Sun Feb 06, 2011 3:54 am

I would like to do it with a wrap, too, because it would mean less sanding. Unfortunately, I couldn't find a way to do it easily in Aspire. Not saying it can't be done, just that I wasn't clever enough to come up with one.
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Re: Cabriole Leg - Proof of Concept

Postby dealguy11 » Sun Feb 06, 2011 4:40 am

This post describes the Aspire files used to create the leg. There were 3 files.

Imagine the leg cut in half down its front, so you have 2 symmetrical parts. 2 of the files are the right and left side of the leg. The 3rd file is a front view of the carving.

The first picture shows the vectors for 1/2 of the leg. X and Y zero is set to the center of the drawing. The basic shape of the leg is three 2-rail sweeps. The first is the block on the top, using the upside-down vee vector on the top left. The second 2-rail sweep starts with the upside-down vee and goes to the rounded shape in the middle. If you wanted the leg to bulge out a little more in the middle, you could widen the middle shape. The last 2-rail sweep starts with the middle curve on top and ends with the small pointed arch.

I purposely designed this with the x-axis going through the center of the block on the top to make it easier to register the 2 sides. Also, I was concerned that it would move in the indexer if the part was off-center. This does waste some wood. You could move this down (i.e., in a negative Y direction) to save some wood, but then you have to make sure the part is moved up exactly the same amount in the other file.

Once the basic shape is in place, export the shape to an STL file. Import this into a component in the 3rd Aspire file, flipping it on its back to give a front-view of the leg (see the second picture). Then the component is mirrored, and the 2 mirrors are baked into a single component representing the front of the leg. The carving is added on top of this (see the third picture). Outline the carving, and use the outline in Create Shape from Vector to make a flat blank into which the leaf is carved. Next, create a finish toolpath of the flat blank, then do a Create Component from Toolpath Preview, and clear the area of the component outside of the outline of the leaf to create a component just of the leaf blank. Export this to STL format, and import into the first file, flipping it on its side. The next picture shows the 1/2 of the leg with the leaf blank in 3d. Create toolpaths using a 1.25" core box bit to rough it out, and a 1/4" ball nose for the finish cut (or whatever your tools of choice are)

Finally, on the front view, hide the leaf blank, turn on the leaf, and toolpath just the leaf with a 1/8" ball nose finish cut.
Attachments
Side View Vectors.JPG
STL Import.JPG
Front View with Leaf.JPG
Blank to be exported to STL.JPG
Side View with Blank.JPG
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Re: Cabriole Leg - Proof of Concept

Postby dealguy11 » Sun Feb 06, 2011 4:49 am

The next pictures show machining. This leg is 20" long. I started with 4" x 4" x 24" blank, positioned in the indexer with 1 edge pointing up. Next, cut relief cuts at each end to keep the collet from hitting the waste (these weren't deep enough - really needed another 1/2 inch and ended up pausing the program to knock out some wood with a chisel).

I roughed and finish cut one side, then did the other. If I were doing a bunch of these, I'd rough both sides, then finish both sides. Finally, I cut away the waste from the front, flipped the leg 90 degrees and carved the front. Last step is to remove from the machine, cut off the waste at the top and bottom and sand.

Total cut time was about 2 hours.
Attachments
IMG_0357.JPG
IMG_0358.JPG
IMG_0359.JPG
IMG_0363.JPG
IMG_0367.JPG
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Re: Cabriole Leg - Proof of Concept

Postby tmerrill » Sun Feb 06, 2011 12:56 pm

Steve,

Excellent explanation - detailed but easy to follow and understand.

Thanks for taking the time to post this.

This was your proof of concept, where do you see yourself taking it from here?

Tim
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Re: Cabriole Leg - Proof of Concept

Postby dealguy11 » Sun Feb 06, 2011 2:50 pm

I'm adding the sample to my bag o'samples that we show customers. People have asked if we could do these in the past - the answer is now definitely "yes". It would be fun to do a Queen Ann style piece using them, but won't be for home because my wife is not a fan of that style.
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Re: Cabriole Leg - Proof of Concept

Postby mtylerfl » Mon Feb 07, 2011 2:41 pm

Excellent work, Steve! I really enjoyed reading about your technique and want to thank you for taking the time to share it with us!
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Re: Cabriole Leg - Proof of Concept

Postby JamesB » Mon Feb 07, 2011 5:06 pm

Steve - good stuff, interesting way to make it work. Keep up the thinking outside the box.
Cheers,
James
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Re: Cabriole Leg - Proof of Concept

Postby dealguy11 » Mon Feb 07, 2011 5:37 pm

Thanks, everyone. This was fun to figure out.

Although it would be nice to do this leg as a wrapped part, I don't think it's possible to make it come out well in Aspire. That's because things close to the center-axis of rotation in the wrap can become distorted - you're trying to wrap geometry around a very small volume. If you import an STL file, the triangles near the center get very elongated and pronounced. In addition, if the part ends up with all of the part on one side of the center line (for example, imagine if the leg had a more pronounced curve, so one part of the "S" curve went totally on one side of the centerline), then Aspire has trouble figuring how how to "heal" the place where the wrap comes together. I tried this with several different shapes, some developed outside of Aspire and imported in, with disappointing results. Vectric did tell us directly at the user conference that wrapping was not an approach to make cabriole legs, and from my experiments it seems they are right.
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Re: Cabriole Leg - Proof of Concept

Postby esteeme1 » Mon Feb 07, 2011 6:12 pm

Steve,

Thanks for all the info. This is exactly why I'm on this forum.This is definatly a challange I would like to persue. I will just have to find a cutomer to push it onto.

Thanks again, well done and outstanding work.
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Re: Cabriole Leg - Proof of Concept

Postby Fleming » Mon Feb 07, 2011 6:32 pm

Excellent work Steve! Thanks for telling us the details and the approach.
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