I have started Robert Burke's tutorials on using GNU Blender for engineering projects. So far I have just begun his first tutorial on modeling 608 ball bearings. It can be found at
http://www.rab3d.com/tutorial.html This should work out as a suitable CAD alternative. If not, I'll let you know.
Posts
"...try to keep your models simple..." "Spatial visualization is very important and, fortunately, the Pro/E display is very easy to manipulate. Secondly, as with computer programming, with Pro/E you must do a considerable amount of thinking and planning ahead (some fast free-hand sketching ability will come in handy here!) in order to create a clean model of a part or assembly." - Pro | ENGINEER WILDFIRE tm 4.0 Tutorial by Roger Toogood
Therefore, I would recommend using Blender for sketching. You can see a rough 3D visualization of your part so you can plan how you will build your engineering model in another program. Your other alternative is to use a piece of paper, but then you get to learn how to draw in 3D. I have done this, but you can't just move the angle of the paper to get a different perspective of the model like you can in Blender.
With all of the engineering CAD(or CAE) programs that I have used(AutoCAD, CATIA, Pro/E), modeling has been the most difficult area of each program. I personally refuse to use AutoCAD unless it is forced upon me, even after taking 9 credit hours of it. Don't take offense if you like AutoCAD, but you need to make sure that you check out other programs that may be much better for your needs. AutoCAD is not an engineering program. It is a drafting program to be used by the technician or machinist you hire to manufacture your design. Give me a pencil and strait edge any day over AutoCAD. CATIA is hard to grasp, and hard to learn, but is a very capable program-if you are an expert with it. Pro/E is an amazing program, but to model with it, because everything has to line up properly from start to finish-almost as if the model was premade. Pro/E uses parent/child dependencies. So if you model the wrong dependency first, then try to enter a value conflicting with the first, you won't be allowed to make your model. Pro/E also has a great feature that automatically changes certain dependencies if they don't conflict, such as scaling the x-dimension of a part.
Some of the problems associated with these engineering programs I believe are caused by engineers not being able to program. Engineers suck at programing, because they tend to make specialized programs that they understand, but nobody else can. A good programming team made Blender, so even though Blender is not easy to learn, it is easy to use. It can be used to plan how to build models in the engineering programs. You will want to do this, because you need to have a good plan before modeling in programs like CATIA and Pro/E. These programs are necessary to have because of their engineering advantages, such as finite element analysis, but they are hard to model in. Good engineering practice is to have the computer tell you what you already know, so it doesn't matter what program you model the part in first. You just need to be sure that the part is safe, and that it does what it is designed to do.
It is clear that engineering is an expensive hobby. An engineer has to procure tools, raw materials, etc., but also has to accept the fact that the first prototype could (and probably will) fail, which costs money. These engineering programs help an engineer fail more quickly, so he can progress faster. In a business environment an engineer's time is money. He will have access to a machine shop, but machining prototypes is an expensive part of engineering. An engineer will use software to test his design so this machining cost is minimized.
An aspiring (but poor) engineer will better serve himself by purchasing inexpensive engineering textbooks from amazon.com, because old textbooks are still good, and they can even be better than the new ones. Then he should study them, to make sure that he knows his stuff. The best thing though, is to enroll in an engineering university. There are lots of student loans and scholarships out there now. To be a good engineer is going to take many years of work. In any field, the experts don't need gee-wiz, wiz-bang equipment. In fact, flashy equipment is often seen as a sign of a completely arrogant noob, who relies on his equipment to show how much better he is than the experienced ones. What is most needed is competence.
As a final conclusion, don't get caught up searching for the 'best' engineering program. The best tools used are often the ones that are at hand, or the ones that are good enough. That is not to say that someone should avoid getting the proper tools, but that an engineer knows what tools he needs. Blender is good for visualizing the engineer's mental design, finite element analysis is good for testing static stresses, fluid dynamics software is good for testing airplanes and boats. An engineer knows if a design is hokey, or if it could work and needs to be physically built and tested to see how it works. How was the Empire State Building engineered? How was the Spruce Goose engineered? They were engineered on paper, not some fancy engineering software.
Engineering software can be nice to have, but it is not what defines an engineer.
An engineer defines himself.
Dude that rocks. Would be very cool to be able to have a physical model of something I built in Blender. I could see sending a file over with a payment and having them print and mail it back would be very cool.
http://reprap.org/wiki/Main_Page
They also have a page with different CAD software that people use to do their 3D modelling, but anybody on Scifi-meshes will be able to use their pet software. All you need is modelling skill and the ability to export to STL.
http://reprap.org/wiki/Useful_Software_Packages
Alot of people post their 3D models (and photos of their prints) in STL form on Thingiverse.
http://www.thingiverse.com/