Extrude along path

[David Sassano]

I am trying to extrude a channel shape along a path that represents a stair stringer. I cannot get the final output to be perpendicular to the ground plane. The channel always want to extrude at an angle.

[M.CH]

Have you tried using multiple extrude?

[David Sassano]

I don't understand how that helps.

I have a stair with several landings. So the stringer has to turn as it rises.

[AndiACD]

David, i unfortunately have similar difficulties with the Extrude Along A Path command. i have only very rarely been able to get it to do what i expect of it, usually because EAAP puts the profile where it wants to on the path, and any attempt to adjust it's position on the path gives very unexpected and undesirable results.

Theory suggest that you should create the desired path, make sure it's a 3D object, move the elements of the path that are required to a different plane(landings, hoping the starting point stays put) and continue until the required path is obtained. Hit OK and Voila!

At this point one would imagine that the extrusion you desire should appear before your very eyes. Personally, i have never had any such luck and even simple flat objects get me no closer to anything i have dreamed of(See Ads and start up screen).

As a result i end up having to use the simple Extrude command and glue the various parts together once they've been moved, rotated, added, subtracted and adjusted to get what i want.

Once again i am probably missing something somewhere along the line, but that's because they're so well hidden . . . . . .

Good Luck anyway.

[michaelk]

In my experience Extrude Along Path works very well for objects (and predictably, once you get the hang of it) that don't change in Z value.

For those objects, one just has to keep in mind that the extrude will be created with the profile object running along path object on its center point. Edit the profile and move it in relation to the 0,0 and THEN hit OK and Voila!

(One thing I keep meaning to put on the wish list is the ability to create extrude along path objects in views other than Top/Plan. You can create them, but as soon as you hit OK and before the Voila, VW drops the new object on the floor.)

Have you tried using the loft tool? It is more predictable when creating objects that move about in all 3 dimensions.

michaelk

[islandmon]

Loft is definitely the procedure of choice for those stringers.

The problem with ExtrudeAlongPath is that the bezier is derived from the declination angle which

then produces a tangential control point 'weighted' Z value which is dihedral to the plane

based on the central angle, ie. twists the profile around the bends like a motorcyclist leaning into the curves .

[GWS]

I have found that if the path is converted into a NURBS line first then the extrude seems to stay where the path was in 3D space.

[cad@sggsa]

And who said books are better than the net??

all the info you need right here as that you would not find printed, but posted....

Thanks GWS

[michaelk]

I have found that if the path is converted into a NURBS line first then the extrude seems to stay where the path was in 3D space.

True that. I alway remember that just after I hit OK and before I say "Voila".

michaelk

[jeffroyer]

A little late on the discussion but...

I also find that the sweep command works great for stuff like complex stringer shapes. You have to monkey around with the pitch a bit but it produces a shape that is quite good. Doesn't have all the funky faceted surfaces that extrude along path does when the path is a curve.