3D Drafting and Design Software Comparison

[JorgensenSteam]

Like Leucetius mentions, you can start with creating a large block to model with in a 3D program, and then subtract (cut) out the parts you do not want, which is exactly how you would machine a part from a solid piece.

I used this approach for a while, thinking it was the only approach that could be used, and also thinking that if I drew one piece and then added onto it, it would not be treated as one piece, but rather two pieces.

I later found out that it is much more efficient for me to break down a part into its component shapes, ie: a steam cylinder is broken down into a sleeve or cylinder barrel, then a flange is added to one end, then the flange is mirrored to the other end, then the steam chest is sketched on a plane in space and extruded up to the cylinder outside surface. It is very quick to model this way, and much to my surprise, the program treats the entire part as if it had been carved out of a solid block.
Same thing applies to eccentrics, etc., draw the center first, then add a flange and mirror.

The mirror function can be used both with sketches (such as mirroring a shape or hole) and also used to mirror entire extruded shapes such as bosses. The mirror function is probably the biggest time saver in the entire program, and using it generally means you only have to draw at most 25% of a model, if you use symmetry extensively.

My boss once said to me "Work smarter, not harder", and so that is what I try and do. I do sometimes model a part from a solid shape just to understand the steps I will need to machine it though, and there is much to be learned from that method.

Pat J

 

[panofish]

I having nothing bad to say about all these great 3d packages, but for me, sketchup is great CAD solution.
It is polygonal though, so you have to make sure things like your circles/cylinders have sufficient steps to create a virtually smooth arc.
If I needed true nurbs, I'd probably use Rhino. Not because its better, but because I am more familiar with it. It is an exceptional nurbs package though.

For CNC, I am more concerned with which CAM package is easiest for me. For that I like VisualMill. It takes dxf files from sketchup and uses them happily.

 

[Tin Falcon]

IMHO all machine and design skills are valuable and good. We are hobbyists. We are here for fun we promote craftsmanship and innovation. How one gets from a cool Idea to a finished engine is a matter of personal preference. if someone sketches out a design on paper and pencil(lovingly called Crap O Cad) COC for short that is fine. If you design with Solid works that is fine too if you can afford it. O have it for professional use.
If you make an engine with a hacksaw file sandpaer and a torch fantastic bless you. if you have cnc skills bless you as well. I will not or do I expect anyone here to down someone on how they make a part or an engine. manual machining skills are different than cnc . But I will not say one is better than another across the board for all uses for everyone. It is all good.
Tin