Solid Vs surface modeling

[bbrannerud]

How do you think about using solid or surface modeling when starting on a project?

You can make the surface thicken and shell och the solid so how do you think about it?

If we would for example model this:

http://www.justdrones.co.uk/media/wysiwyg/cx-20-drone.png

A drone would you make its chassi in solid or surface and why?

http://s3images.coroflot.com/user_files/individual_files/original_585147_gtumngl_ix6cawtw6rhxenwbk.jpg

The same with this helicopter propeller blades?

[JonathanHodgson · Accepted solution]

In general, solids work fine for shapes made by prismatic machining (milling and turning), and for relatively smooth shapes (coil springs, for example).  The rotor blades you show would probably be OK in solids (I imagine making the main blade shape with a swept blend, perhaps along some control curves, then using simple revolves and extrusions for the root detail).

For complex shapes, especially cast or moulded ones, with lots of detail and intersecting, angled surfaces (I'm guessing that the chassis is injection moulded and has things like stiffening ribs and fixing screw bosses), surfacing is definitely the way to go.

Another way to look at it is that if you want Boolean operations (merge, subtract etc) then in Creo you need to use surfaces.  If you can do everything with simple protrusions and cuts, then solids will do.

As BH OOI said in your duplicate thread Solid modeling vs surface modeling :

"whatever we need to do on solids, we are able to accomplish it surface modeling" - but if you don't need the capabilities of surfacing, then solids may be a little simpler.

[bbrannerud]

Thank you for that answer!

That are some good points you had! So you would split this uop making rotor blades in solid, the chassi for the drone in surface, and the "legs" for the drone in surface?

(btw what is protrusion?)

I accidentally made two posts, so I put this as an correct answer so this thread ends but the other one is still open.

[JonathanHodgson]

Way back before Wildfire, 'protrusion' was the opposite of a 'cut' (IIRC) - i.e., protrusion - either revolve or extrude - adds material.

Remember that solids or surfaces is not an "either/or" choice - sometimes if a machined part has some complex milled geometry, I'll model most of the part in solids, but use surfaces to define the 'tricky' bit (finishing with a Solidify).  Equally, you could start with a surface, Thicken it, then add some solid features.  They're all just tools in the toolbox at the end of the day.