path

Hi All,

Here the story,

I drew this solid (the yellow one) using Autocad 2004 a couple years ago. It's an circle profile extrude along a 3Dpline path (white path).

The reason I am using 3Dpline is because I can't extrude the profile along spline path (green path).

Today, I redraw this solid using Autocad 2008 (the white one) and using sweep command this time, because I can't extrude the profile along 3Dpline neither spline in Autocad 2008.

The problem is I have a little different result after compare with my first solid (made by Autocad 2004). They have different mass/volume whereas they made from same profile and same path.

The question is:

1. Why I can not extrude/sweep my profile along the spline path (both Autocad 2004 & Autocad 2008)?

2. What causes mass/volume difference between those two solids?

I hope it can explain what I mean, sorry if I have wrong grammar.

Thank you for help.

path.dwg

The green spline did not have a common tangent (G1 continuity) at the end points. In the attached, I hit “C” for Close to connect the spline to the startpoint.

With regard to differing volumes; unlike the Extrude command, Sweep will automatically orient the profile perpendicular to the curve. The profile may not have been perfectly perpendicular during the Extrude operation. Even so, those volume measurements are fairly close – equally valid for estimating material quantity given the likely discrepancy after tooling.

path2.dwg

Yes you are right SEANT,

I tried this to my own path and it work. So the point of using spline path is I have to close the connection by hit close option and set the tangent to 0.

Is that right?.

The result is prettier than using 3dpline. I like the idea using point for the path.

But I still curious, When I sweep the profile along the new spline path the result still different if I use extrude command.(see the magenta & yellow solids)

It make me wondering whenever I should choose to use sweep or extrude command?

path3.dwg

I would always go for the sweep command as it automatically aligns the given cross-section perpendicular to the extrusion path. Extrude command is a primitive version of sweep, use this for simple orthogonal extrusions only.

So sweep is the best choice for complex path than extrude right?