Lofting a Taper Along a Complex Path

Lansteys

Hi,

I am a bit rusty on this type of thing, but have had a few shots and it’s proving more difficult then I feel it should be.
So, I am hoping that someone has a simple solution for the following modeling dilemma:

 
What I want is a continuous tapered tube along a path. However, I get this varying profile, somewhat on the path in places.

I think I could solve this with a bunch of guides, perhaps some more profiles, etc.
Though I am sure I am missing something... A regular taper along the length of the path is all I need. Adding more guides and profiles will heavily impact how easily it is to iterate at this point, as the path crosses into multiple planes with bridging curves.

I’m interested to see how people would do this. Oh, and I am working on the iOS app on an iPad.


Thanks,
Lliam

konstantin_shiriazdanov

Variable section sweep is good for things like that

https://cad.onshape.com/documents/2d81c59d7fc5df36ecbaecf3/w/a2de18e932e02a4bd51d3af3/e/c17e4dc293d0b843fc524ca6

on this page you can find some description - https://forum.onshape.com/discussion/4322/featurescript-user-community-spotlight/p3 (i would be thankfull if somebody teach me how to create references to the certain post in this forum)

Lansteys

Thanks Konstantin,

I was able to modify the example file you linked to, to do what I was after.
However, I’m afraid I was not able to fully understand what each control sketch was doing.
Would you be able to provide some guidance on this?

Thanks!

konstantin_shiriazdanov

So control sketch should be drawn on XY workplane and should contain a dependency graph for a variable, which is used to define some sketch dimesion. You can use as many variables in the sketch as you need, and for each of them appoint corresponding control curve in the Variable section sweep feature. Along the X axis of control curve the length along the sweep path is represented by default, but there are several more options like the distance along some direction. And finally at the bottom of the feature dialog there is drop down list to control cross section orientation type

Lansteys

Thanks!

I think I got most of that, though I’m still not able to replicate this from scratch and I’m not sure why...

Could you please correct/answer the following:

“So control sketch should be drawn on XY workplane and should contain a dependency graph for a variable, which is used to define some sketch dimesion.”

So I can have all control info in one sketch and variables that drive each line.
These lines or ‘control curves’ are what in turn drive each aspect of the feature, twist, etc.

“You can use as many variables in the sketch as you need, and for each of them appoint corresponding control curve in the Variable section sweep feature.”

So how do I define what a curve does, whether it drives rotation or scale, etc.? And why does the feature have to reference the variables themselves if it is the control curve that matters? 

“Along the X axis of control curve the length along the sweep path is represented by default, but there are several more options like the distance along some direction.”

So is it scaled to the length of whatever control curve I draw in the direction of X. Or do I need to calculate the sweep path length and match this length in X?

Again, the goal is a simple taper, if any of the above is beyond the scope of this goal, feel free to ignor them in your response. All I need is control over the start and end diameter and the path itself.

Thanks again!

konstantin_shiriazdanov

Lansteys said:
So how do I define what a curve does, whether it drives rotation or scale, etc.? And why does the feature have to reference the variables themselves if it is the control curve that matters?

you select the sketch with control curve and insert the name of the variable which should be driven by the feature inside of the sketch of cross section. so the only thing what the feature does - it vary the value of corresponding variable by the given graphic law. whatever dimensions in the sketch are driven by this variable would be regenerated with the new values extracted from the graph dependency ordinates. so for your case you need to define circle diameter to depend from variable of length type (#d for example). if you want to drive any other sketch cross section degrees of freedom (like rotation) you need explicitly make them to depend from some dimensions which include variables of length type.

So is it scaled to the length of whatever control curve I draw in the direction of X. Or do I need to calculate the sweep path length and match this length in X?

yes, the length of the control curve along X scales to the full length of the path

Again, the goal is a simple taper, if any of the above is beyond the scope of this goal, feel free to ignor them in your response. All I need is control over the start and end diameter and the path itself.

 here is the example for your particular case https://cad.onshape.com/documents/2d81c59d7fc5df36ecbaecf3/w/a2de18e932e02a4bd51d3af3/e/c0ad31bea8b3a1e375349e39

Lansteys

Great! I just managed to get it working before I saw your comment. The variable being in that profile sketch is what I missed first try...

So I understand it as well as I need to for my application now I think. (If I ever need to rotate things I’ll be back)

Thanks heaps for taking the time to explain everything. It has been very helpful!