Flattening a Non-linear Conical Surface in SolidWorks. Is it Possible?

by Josh on December 15, 2009 · Comments

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So, last week I was bending up strips of sharp sheet metal with nothing but loud screams and occasional spewing of coffee from my nostrils when I got an email from a very cool ID chap asking about flattening an imported conical surface in SolidWorks.

I thought, this should be a cinch, opened it up in SolidWorks, hit a very large wall and spewed some more coffee… the surface was non-linear. Non-linear, meaning curved. Now what? Well there is an easy way to flatten this shape, but you may not like the results if you want a curved surface.

So, I ask you. How would you approach it? Here’s the sample part and the solution I came up with to flatten the conical surface very fast.

Download the Non-linear Ring (SolidWorks 2010) and try for yourself.

One solution…

So,this surface has less edge than Ian MacKaye after Minor Threat, but we can still get a flat pattern out of it. My first thought was to use a Loft Bend sheetmetal feature. The only problem is, this feature doesn’t allow you to specify guide curves and you can only use a maximum of 2 sketches to define the loft.

There are likely multiple ways to tackle this and, really, the curve is so slight, the curve could be formed after the flat piece is bent into shape, but if you had to do this for a part that had a more drastic curve, how would you tackle it. Is it even possible?

(2 votes, average: 5.00 out of 5)

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Comments

Tagged as: formed parts, imported parts, non-linear surfaces, sheet metal, surface design

ckeen

Good luck figuring out a k-factor or bend deduction.

88_2c_MiXage

While I haven't checked out your model Josh (not on 2010 yet!) I think its asking a bit much trying to get the software to flatten something that's curved in two directions... The lofted bend feature is pretty powerful but remember it is assuming that you want to form this in some kind of brake. Where would it put the bend lines!?

There are myriad of things that are made with sheetmetal that potentially will never be recognized with sheetmetal CAD features, and when you are making these parts using complex forming operations and tooling is there really any need??

Josh M

We gotta ask a lot of the software!! :) Really though, thanks. It's true, something like this likely has a form operation along the way, but there's still a flat pattern needed to start from right.

The lofted bend feature is interesting. It's set up to allow multiple profiles, but the functionality now only allows two profiles max and no guide curves. It will be interesting to see if that feature develops to bring in more typical loft functions.

anyway, for this example, my suggestion is to add some material on the top edge so it can be formed after cut from the flat and 'bent.' With a curve this slight that should work, but if you had a cone with a larger curve in it, e.g. a stretched aluminum panel for a satellite dish panel or a admantium shroud for a prosthetic leg, you're gonna have a much harder time getting a flat to work with. know what I mean?

88_2c_MiXage

Normally forming operations, like drawing or coining, stamping (english wheel?) are followed by a trimming operation to remove the flash so no you don't need a flat pattern, but you do need to work out the blank size to save material.

If you loft from more than two profiles then you are forcing curvature into the direction of the loft as well as the in the profiles, a two profile loft is basically just joining straight lines to the profiles and creating a surface in between.

Forming something like this (body panels on cars etc) obviously involves severe plastic deformation, complex FEA is needed to simulate the material flow. For a simple bend (or dividing the piece into simple bends like the lofted bend does) the software only needs to know the location of the neutral axis (K factor) and it does the addition and subtraction of the inner and outer surfaces based on that, (I'm guessing by some means of an offset), and even that is an approximation.

I agree with you 100% that we need to ask a lot of the software! I just think in this particular case we are stepping outside the realms of sheetmetal CAD. Maybe Solidworks will prove me wrong and I hope it does!

loughnane

This reminds me of a similar problem I've seen a few people have.

You have a simple spline, extrude it as a surface, and thicken it. The result is a constant thickness (read: sheetmetal-able), but there are no bends to speak so it can't be easily flattened.

The tedious workaround is to manually measure the edge lengths and use those to build a flat pattern.

It seems the functionality should exist to do solve both my own and Mr. Owens' problem.

88_2c_MiXage

You can do this using the Lofted Bend feature. It won't give you angles on the bend lines but you can choose how many bend lines to show to give the sheet metal worker something to go by. Very sweet feature, especially for doing square to rounds!

bowfin

I had this problem last week with a die cut on a plastic decal. I settled for an approximation which fits but frustrated me tha I coiuld not make it exact.

bcourter

Here you go: http://twitpic.com/tmelk. If you want to unfold something that's doubly curved, it's time to have a heart-to-heart with your tolerances and manufacturing process. SpaceClaim doesn't do this directly, but I have techniques...

Josh M

you must share your secrete techniques with us oh wise one...

bcourter

Well, you need to figure out whether your manufacturing technique involves stretching, shrinking, whether you want to approximate it as a developable surface, or whether you want to approximate it by tessellating it and having lots of little edges to bond. For example, here's what happens if you crank up the tolerance:

http://twitpic.com/tno1h

Those lines are little hair-like cracks!

I do all of this with custom code that I've generated to create my sculptures. It takes several different algorithms to get the results I want, and I've also written code to create special lofts that guarantee that they can be unfolded. I want all sorts of manual control over tolerances, which I do very carefully on a case-by-case basis. There are a lot of manual steps. Lets just say it takes a lot of love.

Some results here: http://www.coroflot.com/bcourter

Now, which it comes to serious unfolding, there are two apps to check out:
http://touchcad.com/
http://www.vistagy.com/products/fibersim-compos...

I have used neither.

Sean Dotson

Josh, just an FYI, Inventor has been able to do this for sometime now.

Josh M

Thanks Sean! I see Inventor has been able to unfold conical surfaces, but this is conical and also non-linear, so it's a curved cone, so to speak. Can Inventor also do this? I'm thinking, like Blake says below that there are techniques but I've not seen the capability in 3D modeling programs.