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dhpeterson  
#1 Posted : Monday, May 23, 2011 8:34:09 PM(UTC)
dhpeterson

Rank: Junior Member

Joined: 5/21/2011(UTC)
Posts: 9

Hi there,

I'm brand new to ViaCAD (and somewhat new to CAD in general). I wish to model aircraft parts which are constructed in sheet metal. I wish to build up a 3D model of various Zenith aircraft - something along the lines of the below image:

http://www.zenithair.com/zodiac/ch650/gif/features.jpg

with each major part within the model being dimensionally accurate.

I have started by making a rudder spar model (attached), which I made by doing up the profile in 2D and then extruding a solid of the correct width (0.40 mm or so) for each piece of the part.


I would like to get some suggestions from the community as to best practics here - should I be modelling each part (spar, rib etc) as a 3D solid? Should I be modelling skins as 2D surfaces or 3D solids?

Should I be using the "bend feature" to try to make my flange bends - incorporating a bend radius (which is typically R3.2 on the spar or rib pars), or should I just be constructing this from 2D lines and then extruding out to get a rough 3D version, with no bend radius incorporated?

Final question - does ViaCAD support me maintaining each "component" or "part" (grouped from the sub-parts) in a separate file and then dragging them in to a single file to bring them together in 3D, or do I have to do everything in a single file? Is there any part or assembly inspector / explorer that I can use to drill-down the different parts in my model?

Sorry for all the questions but hey, I'm new ;)

Thanks in advance for your help and suggestions!

-- Dave


P.S. I should mention that if I can learn some of these things I intend to put together some screencasts (youtube or vimeo) to allow others to follow along. I think this will help the community around the product to grow.
dhpeterson  
#2 Posted : Thursday, May 26, 2011 10:49:47 PM(UTC)
dhpeterson

Rank: Junior Member

Joined: 5/21/2011(UTC)
Posts: 9

Nobody has any suggestions for me?
billbedford  
#3 Posted : Friday, May 27, 2011 1:42:38 AM(UTC)
billbedford

Rank: Senior Member

Joined: 2/19/2007(UTC)
Posts: 186

Originally Posted by: dhpeterson Go to Quoted Post
Hi there,
I would like to get some suggestions from the community as to best practics here - should I be modelling each part (spar, rib etc) as a 3D solid? Should I be modelling skins as 2D surfaces or 3D solids?

Whatever you feel most comfortable with. I model almost entirely in 3D solids, others use a mixture.
Quote:


Should I be using the "bend feature" to try to make my flange bends - incorporating a bend radius (which is typically R3.2 on the spar or rib pars), or should I just be constructing this from 2D lines and then extruding out to get a rough 3D version, with no bend radius incorporated?


Either of those, or build the spar from 3D primitives and use booleans to get the flange. You can use blends to get the bend radius in both 2D and 3D.
Quote:


Final question - does ViaCAD support me maintaining each "component" or "part" (grouped from the sub-parts) in a separate file and then dragging them in to a single file to bring them together in 3D?

Sort of, You can't drag and drop components from one file to another, but you can either import a component file or copy and paste between files. If you import you will get the whole history tree of the component, and you may wish to delete redundant layers from the history to keep the file size down. If you copy and paste you get an ACIS solid without a history tree. What you can't do is update a components file from the assembly file.

Quote:

Is there any part or assembly inspector / explorer that I can use to drill-down the different parts in my model?
Yep, Features in Concept Explorer
mlochala  
#4 Posted : Friday, May 27, 2011 4:02:15 PM(UTC)
mlochala

Rank: Senior Member

Joined: 9/1/2008(UTC)
Posts: 140

ViaCAD is an excellent way to model the Zenith. You can model every part of the aircraft very accurately using a variety or combination of methods. Sometimes you may have to try different approaches to see which works best for the component that you are modeling.

For the sake of accuracy, if I were modeling something I truly wanted to build, I would do every thing as a solid. I would only use surfaces for when I'm doing concept modeling, such as just trying to see how something would look or to create illustrations. Surfaces do not have volume or depth. If modeling a wing skin, for example, the thickness of it will be important to your dimensional data. Also, having it modeled as a solid (even though a very thin solid) will give you the volume information so that you can calculate the weight or density of that part.

When I'm modeling something with different parts or components, I usually create a folder for the project. Then, I model all parts individually as separate files and then import them into one file for assembly. Many times, I actually model all parts in one file and the copy them to separate files later. That's one thing that I love about ViaCAD is that I can model multiple parts in the same workspace.

You will find that ViaCAD is great for modeling just about anything. However, when modeling something as complex as an airplane or car body (http://forum.punchcad.com/showthread.php?t=3261), the design work requires a certain amount of strategy to figure out how to get from Point A (the idea in your head) to Point B (the 3D model). There are so many great tools featured in ViaCAD, you will find there may be multiple ways to create the same thing. The biggest issue will be to find the method that is easiest, fastest, most accurate, etc...

I guess what I'm saying is that until you are fully proficient with ViaCAD, don't be surprised if you try modeling something one way and then end up trying again another way. That's normal. After you've had a lot of practice with ViaCAD, you will learn quickly the best way to model things.
zumer  
#5 Posted : Friday, May 27, 2011 10:29:27 PM(UTC)
zumer

Rank: Senior Member

Joined: 11/4/2007(UTC)
Posts: 515

Was thanked: 1 time(s) in 1 post(s)
Boolean interaction is what makes CSG useful. Addition, subtraction and intersection make it simpler to devise, determine and adjust contact areas and how parts fit together. In VC, skins and panels are probably most easily built with open profiles, 2D or 3D (creating zero thickness surfaces), then thickening imparts mass and volume properties to them after you've described a shape. VC Pro and Shark have the advantage of surface booleans, which can extend edges, loft and fillet between edges and surface intersections, and so on. That's possible in vanilla VC, but indirectly rather than being directly addressable parts of the toolset.
For flanges on ribs in VC, I'd extrude the rib profile, specify cutouts, blend the flange edge and cutout edges the radii wanted, then shell the extrusion to the sheet metal thickness, deleting the open face. I'd do so to allow rib shape and each parameter to be adjusted without having to redo the others, and use the same associativity in copies to create a family of parts from one parent.
VC's bend is linear, so if the flanges follow curves, bend isn't an option.
In CAD the "right" or "best" workflow and methodology is the one that you find easiest and fastest that works, especially in these days of retail CAD. It's often different from user to user, learned from experience and experimentation after picking up the basics, and then exploring the toolset.
dhpeterson  
#6 Posted : Monday, May 30, 2011 8:05:20 AM(UTC)
dhpeterson

Rank: Junior Member

Joined: 5/21/2011(UTC)
Posts: 9

Thanks to all three of you for some exceptionally useful advice. My apologies for the time it's taken me to respond - busy few days!

Thanks also for the specific tips on modelling the Zenith parts. I've tried a few of the techniques and had varying degrees of success from good to bad - each has been a learning experience!

For example, one thing I've noticed when trying the Bend Feature using the plans I have (which mark out the bend line) is that the bend feature uses the specified bend axis to correspond to the point where the bend first STARTS, rather than either (1) the outer point of the bend - i.e where it ENDS, or (2) the centerline of the bend. I can't see any options to tweak this?

What this means in practice for me is if I'm modelling a bend, say in 0.016" (0.4 mm) sheet with a 3 mm bend radius (for example), and I wish to bend the part to produce a 10 mm flange at 90 degrees, on a a 120 mm flat blank, I need to put bend axes at the following locations:

0 (start point) + 3mm (radius) + 0.4 mm (sheet) + 10 mm (flange) = 13.4 mm

and

120mm - 3mm (radius) - 0.4 mm (sheet) - 10 mm (radius) = 106.6 mm.

It's a bit of a hassle to do these calculations (in my head) each time! I'm not sure what the best way is, or whether I'm missing something simple, but the other option proposed earlier - creating a solid of the required external dimensions (including radiused edges) and then shelling out the interior to the desired thickness - sounds like it might end up being a superior approach ...


In terms of bends, I'm not sure how other products handle this, but it seems that it might be easier if we could specify whether the bend axis corresponds to the the inside tangent point (as current), the outside tangent point, or for the bend centerline. I think that might make it more powerful, and would be a simple enhancement, yes?


Obviously there's another whole discussion about being able to design in sheet metal (e.g. sheet aluminium in my case) and then "un-folding" the part to a flat equivalent - but I suspect that's a complex topic!


Thanks again to you all for your help ~ I've really been able to get started as a result (but still MUCH to learn). I have another question on how to simply align multiple parts but I will post it (and a model) in another thread. Cheers!

-- Dave
Albatrossflyer  
#7 Posted : Monday, May 30, 2011 9:05:40 AM(UTC)
Albatrossflyer

Rank: Member

Joined: 7/21/2008(UTC)
Posts: 47

Was thanked: 4 time(s) in 4 post(s)
Here's a primer on determining the bend allowance for flat pattern layouts.

[URL="http://www.sheetmetalguy.com/bend-allowance.htm"]http://www.sheetmetalguy.com/bend-allowance.htm[/URL]
dhpeterson  
#8 Posted : Monday, May 30, 2011 9:13:50 AM(UTC)
dhpeterson

Rank: Junior Member

Joined: 5/21/2011(UTC)
Posts: 9

cheers - that looks VERY useful! I've read of K-factor but haven't seen a worked example like that. Would be nice to get K-factor support in ViaCAD eh :)
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