I am starting to develop my own ideas and i really want to do a good job, specially in the modeling side of things. My primary 3D design tool is Alias Automotive and i have a bit of experience with Class A surfacing stuff from scan data and alike. I would like to ask the big boys with more experience than me in this issue regarding surface quality settings for modeling.
Seems to me that when settings are more demanding (like general CAD and Inventor settings), surface output suffers a bit. More forgiving settings, while not as accurate, are sure to give you better surfaces; no need to use smaller patches and no multi-span surfaces, which leads to cleaner geometry.
While stricter tolerances are logical to small items (watches or surgical equipment), i believe it becomes overkill when someone models things like car surfaces, a train exterior or exhibition space. Of course avoiding blatant sloppiness, the bigger the geometry the more important it becomes to have smooth, clean surfaces with good transitions… do you guys think this to be a fair tradeoff for a bit of mathematical accuracy?
I believe this to be, when it come to modeling, the most important part of our Alias settings, regardless of other CAD software we might use to open surface geometry.
Unless i am simply wrong in this (quite possibly), i think i might develop 3 modeling settings regarding product size where surface output makes sense for the product’s size:
What do you guys think? Hope this leads to a discussion where we can all benefit.
When it comes to tolerances, there’s no absolute. (Tolerance joke, I’m sorry).
The main thing to consider with surfacing and tolerances is where is your data going AFTER Alias. Chances are if you are shipping it off to Catia, Pro E, NX, etc that each one has a set of tolerances and construction options it likes (using the Alias Defaults is always a good place to start) and beyond that you can tweak your settings based on what you expect your manufacturing to hold.
If you’re building a car, fitting to .001mm is overkill, but not on a small CNC’ed component.
Ultimately you need to decide if the tradeoff is OK in conjunction with your engineers and manufacturers. Assuming the engineers have worked with surface data before, they should have a good idea of where to start.
So it’s more of a CAM and exporting thing to think about?
I think NX does a great job of stitching geometry to make it engineering and CAM-ready, but others WOW they really do a horrible job at that. I guess this also depends on how the other CAD’s settings are.
Anything will turn foreign geometry into garbage if it is allowed to. Finding and dialing in tolerances that work the best is half science half art. That’s why trying to invent the wheel yourself is usually not worth it, most vendors or engineers should be able to give you an idea of the tolerances they need to get clean imports without corruption of the design intent.
If your tolerances in ALias are to loose then CAD packages will not stick becasue it has the potential to cause corrupt geometry. the software tries to fill the gaps which can be ugly sometimes.
I will make this statement… Everyone who has ever complained to me about how ALias surfaces are horrible and CAD packages wont turn them into solids, where extremely poor surface modelers and thought since it “looked” good on the screen then it was the softwares fault for not letting it turn into a solid…
Building surfaces in Alias to import into software such as Proe SW, and others is a skill set and requires a fair bit of technical understanding of the software
Thank you guys for your thoughts, it helped shape my modeling preferences a lot.
I have used CATIA and also NX at some stage in product development, and i still prefer by far to use Alias when it comes to surfacing. I find i have more control over each step towards building geometry. But to each his own i guess.
I believe that as Alias surfaces are dependent on the quality of the curves from which they are built upon, same goes for external CAD systems; if Alias data is crap, other software will do a bad job of “fixing” it