Use of surfaces

Mike,

Surfaces are used mostly for swoopy, curvy, industrial design type stuff. Also injection mold design.

If you design machines you may never need to use them.

regards

Mark

We ID guys use them often for creating more complicated geometry. You can use them to create complex curves in space (intersecting extruded surfaces) and many other things, such as surface offsets for stopping cuts or extrusions. If your world is primarily planar, there's not much need for them.

Jeff Mowry Industrial Designhaus, LLC

"GETRIDOFTHIS" from email address)

Mike wrote:

Count your blessings! But if you do want to find out about surfaces, check out Ed Eaton's Curvy Stuff Tutorials:

I think 101 talks a bit about some of the not-so-obvious reasons you might want to use surfaces.

Jerry Steiger Tripod Data Systems "take the garbage out, dear"

Without going to swoopy stuff, surfaces have their uses, and are occasionally indispensable. One example where surfaces are useful, even in prismatic design: Take, say, rectilinear gearbox housing for worm reduction boxes.

Say you have cooling fins on a face of the box, which are "cut extruded" across to a couple of upstanding faces, perhaps including an output bearing boss. An "Up to Surface" cut extrude will only allow you to pick one face. If you need the extrude to terminate at a collection of faces, pick those faces and "Insert/Surface/Knit" (Some old hands may not realise it is no longer necessary to first convert those faces to surfaces, by offsetting zero: Knit will automatically convert a face to a surface) Then, when you come to specify the extrude "Up To" surface, pick the "Surface-Knit" feature from the feature tree.

I should have mentioned:

If you get unpredictable results from the extrusion, check that you've picked ALL the faces the sketch projects across. It doesn't matter if you pick adjacent faces which are not currently capping the extrusion, in fact if you are designing a model which will represent several different sizes of gearbox (in the example I gave) you should err on the generous side.

Surfaces are great for modeling swoopy stuff, but that is not their only application. In fact, from the first day you started working on SolidWorks you've been modeling with surfaces. Solid modeling just automates a lot of functions that change that underlying surface model into a chunk of stuff.

What does it mean for you? Well, solid modeling creates lots of hidden faces in the model that you don't really need. For instance, if you us a rectangular cut to shave a model back, you actually are creating six faces inside the modeler to get the one you want in the model. Using surfaces, you can make that sort of thing directly, using only one face. I am not saying you want to do this with every cut, and of course using a solid cut with an open contour also streamlines the face count. But have enough features in the model (or a slow enough computer) and all that extra stuff that you don't see can add up (I've actually run some tests).

There are all sorts of other little things that pop up here and there where its just faster and easier to convert the model to a surface model (delete a face without patching it) then going back to a solid later, or use a surface to swap one undesirable face for a better one. And this is on stuff that's not particularly curvy. Surfaces are also really handy for repairing all those weird little glitches that can pop up when a cut goes too far or something doesn't quite line up like you want it, or you want to test a radical change to a model but don't want to deal with your feature tree erupting in blood.

If you are in the Texas area, I am going to head down to the all Texas user conference in July and give a talk on just this subject. Its called "Surfacing for 'Block-heads" and will try to answer just your question - what are surfaces and are they ever really useful?

This session will go into how SolidWorks operates behind the scenes, and explain how that knowledge can get you through modeling challenges and streamline the creation of all sorts of parts. The first half of the presentation will cover the BREP, the interchangeable use of Solids and Surfaces, and deconstruction of features into their behind-the-scenes processes. The second half of the session will show how this information can apply even to those folks who suspect that surfacing has no place in their lives.

If you ever have problems filleting, you will be very happy you came.