CAD Advice

abledog · Post by **abledog** » Wed Apr 04, 2012 1:26 pm

To some of you GK producers out there. CAD software and rapid prototyping are fast becoming a new standard in kit production. I'm currently playing with/ learning Rhino using Youtube lessons for now.

As I understand it, for Rapid Prototyping to work your surfaces cannot have intersecting poly's. I have some experience using Lightwave, but is nurbs modeling different enough that RP'ing doesn't have an issue with intersecting surfaces?

Thanks,

AbleD

WarpeD · Post by **WarpeD** » Wed Apr 04, 2012 3:31 pm

The trick to RP is what's called a "watertight mesh."

NURBS modeling is terrific, but in the end you will have to "mesh" the model bits before you can export to .stl for RP. You can't RP from NURBS.

Rhino will tell you if your polysurfaces are "closed" or "open." "Closed" is what you want.

When you go into the mesh tool, be sure to set density to 1.0 and go for a low aspect ratio polygon.

Bottom line, lots of polygons is a good thing.

You can't have intersecting objects with RP. Think of it sort of as an attempt to transport Dr. McCoy into solid rock.

You can RP parts that fit together, however. Why it's cool to prototype parts in their assembled state is something I don't understand, though.

abledog · Post by **abledog** » Wed Apr 04, 2012 3:57 pm

Thanks for the quick reply.

I definitely want to build sub-sections, and understand that it has to be watertight. I guess I need to really take my time and learn the construction/ interface techniques to get the results I'm looking for.

It's probably my most difficult hurdle, is the interface for Rhino... I'm so used to Lightwave that my mind keeps wanting to do things that way...

AbleD

WarpeD · Post by **WarpeD** » Wed Apr 04, 2012 4:18 pm

You're welcome.

One of the tricks is getting used to slicing surfaces - making other surfaces to serve as tools. That, and object snap. You can do some really nice precision stuff.

If you think the Rhino interface is hard, try Blender!

(Then again, maybe it's more like Lightwave. Dunno. Blender is free, but if you already own Rhino...ouch.)

I've been using Rhino for about 15 years now. Can't imagine a sweeter interface. YMMV!!

abledog · Post by **abledog** » Wed Apr 04, 2012 4:42 pm

No I don't own Rhino, (very pricey!!), just using the trial. Is Blender useful for rapid prototyping too?

AbleD

G-man · Post by **G-man** » Wed Apr 04, 2012 5:00 pm

Warp, you know that you can have intersecting surfaces in your base model, but you have to take the stl into Magics' or a like program and run a unify command right?

Its so much easier to model that way then to try and cut all the greblies into your surface and keep it all one mesh in your chosen modeling software.

There are also some RP technologies that will print intersecting surfaces and save the step of unification of the mesh, Not all of them will but some.

Though in magics the unify command takes ...less then a minute even on a very dense mesh so i run it anyway.

George

abledog · Post by **abledog** » Wed Apr 04, 2012 5:22 pm

Oh that's good to know! Is Magics a plug in, or stand alone that works with CAD software?

The initial issue for me was, how to model surface detail on something like a spaceship without being able to cut into and pull out of a surface like I can in LW. I was thinking based on the handful of tutorials I've seen, is that you intersect separate shapes, then edit out the curves you don't need... pretty involved depending on the model.

Sounds like Rhino & Magics is something to look into.

Thanks!

AbleD

WarpeD · Post by **WarpeD** » Wed Apr 04, 2012 5:37 pm

Magics wraps the model in a completely new polygon mesh that exactly conforms to the original outlines, and covers voids. Kind of like a wetsuit for a 3D model.

I'm aware of it, I saw Tony's (tonzye) presentation at Wonderfest a few years ago. I have no problem with that approach, but it's an extra step and does cost even more money. Good modeling practices in Rhino can produce the same mesh for the amateur.

http://www.materialise.com/Magics ...if you want to know more. There is a free demo, but I'm neither familiar with it nor aware of whatever limitations it may work with.

Blender is very capable, and can export in .stl format among many others. It is, however, freeware, and you get what you pay for sometimes. Rhino is my rock.

abledog · Post by **abledog** » Wed Apr 04, 2012 5:45 pm

Thanks guys!

I agree that having a solid foundation in the primary software is the way to go. The extra software would be convenient, but it allows for other potential problems down the line.

I'm convinced that Rhino is well worth the investment, so I'm going to focus on that, start saving my money to purchase.

I really appreciate the advice!!!

AbleD

WarpeD · Post by **WarpeD** » Wed Apr 04, 2012 5:52 pm

If you're a student, McNeel does offer an academic discount! Have fun. Rhino is more addictive than drugs.

abledog · Post by **abledog** » Wed Apr 04, 2012 6:00 pm

Darn... I wish I were... but still looking forward to it!

G-man · Post by **G-man** » Wed Apr 04, 2012 6:18 pm

I have thought of trying out rhino, but just don't have the time to learn another GUI and tool set. Plus i am not a fan of Nurbs modeling personally
I've been modeling in Maya for about ten years now and have learned to use it for Prototyped modeling, alot of people in the visual effects field ( my previous background) say that you cannot model to scale accurately in Maya, but i prove them wrong with each completed master.

Blender though is a very good Free substitute and you can get High quality meshes out of it.

Just be sure that you don't spend time modeling details on the mesh, that the end technology will not print out. Know what printer you will be using to print the object out in the end, and know the limitations of their resolution. If it will not show up in the end there is no reason to put eh detail in the mesh.
If they cannot bevel a grown corner at the bevel you need, because it is below their resolution capability, then do not add the bevel, Things like that are big time savers on your models. its a experimentation thing, you get a feel for it after a while. And you get to know what printer tech can do what after a while as well.

OT:
WarpeD i didn't know realize you used Rapid prototyping for master work? I am assuming that the Screen Name WarpeD coincides with the GK brand right?

George

WarpeD · Post by **WarpeD** » Wed Apr 04, 2012 7:52 pm

I've had some stuff grown for a personal project and parts of the long out of production SSC Christopher Columbus were grown as well. In the main, though, I'm nowhere's near a GK kit producer and have no desire to be.

I'm just a happy polygon pusher for flight sim, rendered images and video. WarpeD is a 15 year old nick started on SSM back in the day. My first serious use of Rhino was for the "Model the Logo" contest! Unfortunately, 3D models didn't count...

abledog · Post by **abledog** » Tue Apr 10, 2012 11:06 am

Hey guys.. I've been looking into my options while I'm learning Rhino. It looks like Magics can correct & convert LW files... but just how much is this software?

I can't seem to find a price for it on the manufacturer's site. That's a little concerning... (if you have to ask, you can't afford it?)

AbleD

G-man · Post by **G-man** » Tue Apr 10, 2012 3:21 pm

There isn't much of anything graphics wise used for modeling or prototyping that will cost you less then 1000$... and most of it costs more then that.

I think all together, just in software i have almost 9000$ tied up.
add another 4 grand for computer...you get the point.

George

abledog · Post by **abledog** » Tue Apr 10, 2012 3:30 pm

Yeah.. it's basically confirming that Rhino & probably T-Splines is the way I ought to go. After telling myself to be patient & forget what I know about LW, I'm finally beginning to grasp Rhino's way of doing things... exciting!!

AbleD

abledog · Post by **abledog** » Thu May 31, 2012 12:49 pm

Hi Guys,

As it turns out, I'm now taking a class in Rhino, which is great! But I just saw a video (curse you You Tube! ) on Solidworks, which seems like a more natural fit for producing kits... any of you ever use it for something like that?

I think I'm still gonna commit to Rhino for now, as I'm getting a good grasp of it, and I can purchase it at a student discount..

Just wondering if down the line Solidworks is a better fit.

Thanks!

AbleD

(Edit): Just did a little more research on Solidworks... way too pricey for my budget, and the student discount only gives you a 12 month license. Now I know I'm on the right software package.

Tankmodeler · Post by **Tankmodeler** » Sun Jun 03, 2012 12:37 pm

abledog wrote:Hi Guys,

As it turns out, I'm now taking a class in Rhino, which is great! But I just saw a video (curse you You Tube! ) on Solidworks, which seems like a more natural fit for producing kits... any of you ever use it for something like that?

I think I'm still gonna commit to Rhino for now, as I'm getting a good grasp of it, and I can purchase it at a student discount.. Just wondering if down the line Solidworks is a better fit.

Thanks!

AbleD

(Edit): Just did a little more research on Solidworks... way too pricey for my budget, and the student discount only gives you a 12 month license. Now I know I'm on the right software package.

Well, Solidworks isn't cheap. It's a full fledged engineering CAD package and will run something like 4-6 grand a seat. It also doesn't work as well with surfaces because it is a native 3D solids modelling package. It doesn't do illustration quality rendering and won't export good quality models to gaming or other graphics packages.

However, there are also no such things as "open meshes" and no need to check for open or closed surfaces. Everything it does is considered a full solid so exports to STL format are as simple as saving the file in that format. It allows you to build single parts and group them into assemblies for turning into model kit parts and allows you to build the model in full scale (per any drawings you have) and simply scale the entire thing to whatever scale, up or down, that you want.

The interface is simple and you could learn it yourself if you have experience with another solid modelling or engineering CAD package (Autocad, Catia, Unigraphics, ProE). If you are an illustrator then it won't come naturally as it's designed around the needs of engineers.

I've been using Solidworks for 10 years and it's a great engineering software package. But it's build around the language of engineering drawings and real life manufacturing processes. It is not a free form illustratator's or graphic artist's tool, it's an engineer's tool.

But it turns out precise RP files as naturally a breathing.

I love it. But then, again, I'm an engineer.

Paul

abledog · Post by **abledog** » Sat Jul 07, 2012 2:39 pm

I have a couple of questions for anyone that has used this for RP. What kind of tolerance do you use when creating your model? Also, do you prefer to work in inches, or millimeters.. or does it really matter, (aside from the tolerance numbers?).

Thanks guys!

Able-D

Tankmodeler · Post by **Tankmodeler** » Sun Jul 08, 2012 12:26 pm

abledog wrote:I have a couple of questions for anyone that has used this for RP. What kind of tolerance do you use when creating your model? Also, do you prefer to work in inches, or millimeters.. or does it really matter, (aside from the tolerance numbers?).

Measurement system doesn't matter at all and most high end CAD systems allow you to enter dimensions in both in the same model as long as you use the correct designation, i.e. you can mage the length of a cylinder 1" and the diameter 22mm and most modern systems are quite OK with it.

Tolerances are not used in making 3D CAD models. You always model things to exactly the nominal size you want. Tolerances only come into play when making drawings of parts for full size manufacture. At that point you are telling the manufacturer what variances from "perfect" you are willing to accept. This doesn't apply to RP parts. Those you always want as close to perfect as possible (Unless of course you are trying to replicate the effects of some out of nominal condidion in which case you build the 3D models to the off-nominal sizes you desire to test).

When sending 3D models out for making RP assemblies, you send the nominal sized model and you then live with the tolerances that the RP machine is capable of. If making RP scaled models, then you send the scaled CAD model out and, again live with the variances produced by the RP machine.

Paul

Hatewall · Post by **Hatewall** » Sun Jul 08, 2012 11:25 pm

I have been using Rhino since it was introduced.

It is capable of very precise tolerances for prototyping. Once you get the basics down, it is very fast and very accurate.

http://img94.imageshack.us/img94/4528/n1mesh.jpg

Tankmodeler · Post by **Tankmodeler** » Mon Jul 09, 2012 12:19 am

Hatewall wrote:It is capable of very precise tolerances for prototyping. Once you get the basics down, it is very fast and very accurate.

I'm not trying to be a knob here, but what do you meant that Rhino is capable of fine tolerances? Any CAD model should be exactly and precisely spot on for all dimensions input to define shapes. There are no tolerances when it comes to this portion of creating a model. Any errors between a declared dimension (i.e. what you tell the program a dimension is) and the dimension carried within the model are not "tolerances" they are the "precision" of the CAD engine that is the core of the program. These precisions for mid and upper level program generally run to better than 16 decimal places.

In other words, if you enter a dimension of 4.000" the machine can understand it as anything between:
3.999999999999999"
and
4.000000000000001"

That's not a tolerance as the machine carries one number as the absolute definition of that feature.

But these are not "tolerances". The definition of a "tolerance" is what dimensions you will accept when measured on a manufactured item as compared to the nominal dimension as called out in the drawing that defines the manufactured item. As such, the term has no meaning when it comes to CAD models. It has a meaning when applied to the RP parts/assemblies created from the CAD models and this tolerance is generally expressed as the resolution or the precision of the machine producing the RP parts.

HTH

Paul

Hatewall · Post by **Hatewall** » Mon Jul 09, 2012 8:04 am

I was referring to other 3d/nurbs packages where you would have to type in values in the transforms rather than keyboard entry of units as you draw.

For instance, 3dsMax or Maya where precision is certainly possible but not nearly as intuitive as a program designed for prototyping.

abledog · Post by **abledog** » Tue Jul 10, 2012 11:45 am

Thanks guys for the response. I take it that it's not something I really need to worry about then? I'm likely jumping the gun here, as I'm just now getting a handle on some of the most basic modeling functions.

Right now I'm trying to figure out the best way to create intersecting panel lines..

A very complex, but flexible program... as much as I enjoyed modeling in Lightwave, this seems even cooler!

Able D

Tankmodeler · Post by **Tankmodeler** » Tue Jul 10, 2012 5:10 pm

abledog wrote:Right now I'm trying to figure out the best way to create intersecting panel lines..

For creating 3D RP models you normally done't represent the panels at all (not even a little bit). If your model needs panel lines that is the sort of thing you scribe in after the RP model is made _and_ cleaned up (i.e the jaggies smoothed out). Unless the scale is quite large the panel lines are generally too small (too narrow) to be effectively created by RP programs. Concentrate on getting the shapes right and to scale and then scribe the panel lines (if you need them) after you get the RP model in your hands.

Paul

Tankmodeler · Post by **Tankmodeler** » Tue Jul 10, 2012 5:20 pm

Hatewall wrote:I was referring to other 3d/nurbs packages where you would have to type in values in the transforms rather than keyboard entry of units as you draw.

For instance, 3dsMax or Maya where precision is certainly possible but not nearly as intuitive as a program designed for prototyping.

Ahhh, I see. OK, this may be called "tolerance" by the program, but this is _not_ the proper definition of "tolerance". It is closer to establishing the values for shape precision, which I understand is the nature of this sort of modelling package. A package where entering dimensions of objects can't be done directly _can_ be used to create exact and precise 3D models, but it takes a lot more work and isn't necessarily the right tool of that sort of work.

These sorts of tools are good for making 3D models for illustrations and CGI sort of work, but rapid prototyping methods arenot really meant to work with those sorts of programs. Getting the meshes to "close" can be a significant problem. On th eother hand, these sorts of surface modolling programs are are better at modelling complex, flowing, nonlinear shapes thatn true engineering CAD packages. Super high end packages (like CATIA and Unigraphics) can do both, but you're looking at 15K per seat and really steep learning curves.

Paul

abledog · Post by **abledog** » Tue Jul 10, 2012 8:37 pm

Thanks for the info... just saved me a buttload of a headache. I guess I should think more along a different way to call out the details I want. It should be easy with larger ship designs, but with smaller, (fighter) craft maybe the scribbing technique you talked about would be the best way to go... Just don't want to make a mistake on my RP master.

Patience will definitely be the key.

Able D

Tankmodeler · Post by **Tankmodeler** » Tue Jul 10, 2012 10:08 pm

abledog wrote:I guess I should think more along a different way to call out the details I want.

As a general rule, don't bother to model anything smaller than 3ish times the smallest feature the RP system can recreate. This depends upon the sort of rapid protoyping and the machine being used. Check with them before you waste time creating the details!

I.e if the smallest feature the system can capture is .005", then don't model anything that, in scale, will be smaller than .015". If you are modelling a spacecraft in, say 1:72 scale, then the smallest feature should be something like .015x72 or 1.08" in full scale.

If you are making something that will be cast in resin, then you might need to go larger still, depending upon the skill of the person doing the mould making and casting.

HTH

Paul

Tonzye · Post by **Tonzye** » Wed Jan 30, 2013 7:28 pm

Hi Guys ,
Just came across you blog ...
Have you had a look at Sketchup? http://www.sketchup.com/
Its a 3D creative software that has a free download available to test run and you can up grade to a fuller version.
Its very intuitive ...though ive never used it ...our shop has developed a plugin designed specifically for Sketchup called Cad Span.
http://www.cadspan.com/tools
Cadspan has all the tools to help you get your mesh ready to print.
Sketchup also has many more plugins that might be usefull to you.
http://www.sketchup.com/intl/en/download/plugins.html
If you need any further help feel free to contact me .
Tony

G-man · Post by **G-man** » Wed Jan 30, 2013 9:50 pm

Tonzye,
Most if not all rapid prototyping agencies, with exception to Sketch up, HATE receiving files that were created in Sketchup.
So many issues with that program when exporting to STL its not even funny.
Is it possible to work around them? Yes...
Is it worth the trouble for the work around?
Not in my opinion.

Just my two cents

George