Unfolding A Curve

[Chally72]

We have a 2d sketch of an airfoil section. For in-process verification, we need to be able to check the part in the flat state. (These airfoils are formed from a flat blank.)

How can I straighten a curve in SE while keeping its length the same? Will I be able to maintain a relationship between the curve and a specific point on the curve, so as to repeat this unwrap "around" the same point through multiple sections?

Thanks to anyone who can help with any part of this.

 

[beachcomber]

The only suggestion I can make is to try creating a sheet metal part from each profile. You might be able to unfold it, but I doubt it as I don't think spline curves will flatten. You would also need to check the flattened length with the spline curve length.
The other problem is the profile would have to be broken, so if you have a closed one you will need to split it.

bc.
2.4GHz Core2 Quad, 4GB RAM,
Quadro FX4600.

Where would we be without sat-nav?

 

[Chally72]

I came up with a better way of doing this, I think.

Picture an airfoil cross-section with a bunch of cut lines perpendicular to the concave curve of the blade. Say, 20 or so cuts between the leading and trailing edge. If I can measure the length of the curve in between these cut lines, and knowing the length of each cut line, I can "unfold" the concave side of the blade to make it flat by drawing flat sections the length of each curve section, with cut lines off of each, and then regenerate the convex side as a curve through the tip of all the cut lines.

The problem I have is that the only way I can find of measuring the length of a curve is the Total Length inspection option, which only displays the length until you click off of it. Meaning I can't use it in goal seek, and I can't even display more than one arc length at a time. If I could use it in goal seek, for example, it would be simple to make a canned flat-section generator that I could drop any airfoil section into and relatively quickly "unfold."

Thanks!

 

[beachcomber]

Don't know if it would help but the AREA command creates a set of variables which includes perimeter.
If you could create a closed area from each segment you might be able to do something with it.

bc.
2.4GHz Core2 Quad, 4GB RAM,
Quadro FX4600.

Where would we be without sat-nav?

 

[HDS]

It is hard to follow exactly what you want to do. Are you considering the stretch of the sheet metal as it is bent?

The curve can be broken up. You might be able to do something using expressroute because it will give straight lengths and can output a file.

It sounds like what you really want to do is calculate the flat pattern of the sheet metal parts. This is what the sheet metal models are for. The help explains the calculation used and how to change it for your material.

 

[Chally72]

This isn't a sheetmetal part and doesn't behave like one. I think I can get these pictures to upload. This will be a crude sketch of what the flat pattern should look like.

 

[Chally72]

And here is a sketch of what it is coming from. These parts stretch very little when they are formed. Enough that it doesn't matter for our tolerances when laying out the flat pattern from a cut of the form.

I don't have expressroute, so no-go there, but an interesting thought that I didn't consider.

Perimeter wouldn't really work. I can do it faster just manually writing down the segment lengths using the total length option.

It looks like I can't create a generic unfolding template in SE without more input than I want.

Thanks for the suggestions.

 

[beachcomber]

HDS - I only suggested sheet metal as a way of flattening the curves to get the correct lengths.
Chally - Looking at the pictures now I think I see what you mean.
The actual section has a curved base but you want to recreate it with a flat base that has the same length as the curve, so you can check you have the correct material length?
If you don't have XPressRoute have you tried Frames?
The funcionality is more or less the same and you should be able to get cut lengths as variables. The only drawback is I don't think you can create a frame that is closed. ie a complete 'hoop'

bc.
2.4GHz Core2 Quad, 4GB RAM,
Quadro FX4600.

Where would we be without sat-nav?

 

[Chally72]

Yeah, basic idea is to be able to check the thickness distribution while in the flat state, to ensure that even before forming, LE, Max, TE thicknesses will be in, assuming a good form.

I have not tried Frames and am not even aware of anything in SE called that, but I will research on my own and see what I can do with them.

The way I hope to do it, I won't need closed hoops, so all is good there.

Thanks!