Rib Builder Help.

Hi Guys

I need help with a rib builder I'm trying to build. I know there is the grillage fabricator out there but i want mine to behave a little differently. And i promise to share the definition once i've finished.

So my problem is;

I have divided the geometry in the x and y as curves. So i have these curves and i want to lay them out flat on a sheet in the x & y plane. But for some reason i can't get it to work.

So i need help with this. Any ideas.

I want to lay out these curves first and then i plan on offsetting them, closing them and then adding the notching. I think this way is better because it will enable me to chop up any free form surface and make a rib type construction with the laser cutter.

So your help would be most appreciated. Attached is a model file and also the start of the definition.

Cheers

Attachments:

Section Ribs.ghx, 267 KB
Ribs Example.3dm, 30 KB

Replies to This Discussion

Permalink Reply by Material Raum on November 22, 2009 at 2:24pm

Ok so my attempt at getting the curves along the x and y plane attached.

Any ideas how to get this to work.

Attachments:

Section Ribs.ghx, 239 KB

Permalink Reply by taz on November 22, 2009 at 2:26pm

If you're interested the grillage fab definition I made would, I believe, still work for you.

The was done making a closed polysurface from your master surface.

Here is a guide if you wanted to work with my definition and keep your master surface interactive.

Permalink Reply by Material Raum on November 22, 2009 at 2:44pm

Hey Taz

Thanks for that.

Good idea. Just one question, how did you make a closed ploysurface from the master surface.

Thanks

Permalink Reply by taz on November 22, 2009 at 3:19pm

_Offset surface from master surface
_Duplicate border of master surface and offset surface
_Loft the border curves
_Join the surfaces

You could set up a routine to do this in GH too...

Permalink Reply by Material Raum on November 23, 2009 at 9:05am

Taz

I think your grillage fabricator would work better if you set such a thing up. Or at least a version of your grillage fabricator that can do this…because sometimes when i use your fabricator if it is just a free flow surface with no depth / thickness the rib components are not quite what you want.

What you think?

Permalink Reply by taz on November 23, 2009 at 10:59am

I agree with you, but I was attempting to make the definition as generic as possible.

This issue is this:

If you want to create a rib/waffle/grillage from a polysurface with a constant offset, Rhino/GH will only offset each individual surface and these surfaces may or may not intersect. Rhino/GH doesn't do "Shelling".

This becomes problematic (for me anyway...) when taking sections (curves for cutting) and determining notch locations (from intersecting planar surfaces created from the section curves) .

Extruding is much nicer/easier since it will automatically work with polysurfaces and produce a closed BRep.

So for the general case (if a constant offset is required) its easier if the user manually offsets all surfaces, cleans up the geometry, and then slices-and-dices a closed BRep.

I could set up an offset option for the special case of a single surface, but that could still produce problematic conditions that would have to be solved on a case by case basis.

I'm not sure if that makes sense, but the summary is this: Since Rhino/GH doesn't do shelling it would be a lot of work to put together a definition that would always work for any polysurface.

-taz

Permalink Reply by Material Raum on November 23, 2009 at 1:02pm

"So for the general case (if a constant offset is required) its easier if the user manually offsets all surfaces, cleans up the geometry, and then slices-and-dices a closed BRep."

Ok so this seems the way to go then.

Thanks for your help Taz

Permalink Reply by Material Raum on November 26, 2009 at 5:16am

Taz

Sorry but again i'm having troubles with your rib builder using the following surface which is just a loft of 4 curves.

Any ideas?

Attachments:

Square frame view.3dm, 145 KB

Permalink Reply by Material Raum on December 2, 2009 at 3:46am

Hey Taz

A quick question with the rib builder. Is the notch width slider in Inches or what?

Thanks,

MR

Permalink Reply by taz on December 2, 2009 at 1:09pm

The units should all be relative to your Rhino units...

I think the default notch thickness I have is either a 1/16th or 1/8th of an inch (0.0626 or 0.125) with a rib spacings of 1 or 3 inches.

If you're using metric units the default settings wouldn't make much sense.

Permalink Reply by Nathan Miller on November 22, 2009 at 3:10pm