Conics in varible sectional sweeps

[shankar_me]

Hi everyone,


Can conics be used in sections for variable sectional sweep and swept blend?


Regards,
Shankar

 

[jeff4136]

Conics are ideally suited for VSS sections.


Not sure how it would apply to Swept Blend?


Whatcha trying to put together?

 

[jeff4136]

Ok. Does the section vary or is it constant?
I think I'd probably try to do that with a single
traj curve and control the section with equation,
but ...
Can you post your traj curves? (I'm WF2, IGES is ok)

 

[shankar_me]

Hi Jeff,


The section is a constant section. I was able to achieve the same using a simple helical sweep. But still I want to know why my part is failing in this case. I cannot post my part. I created the helixes using equations. The equations are defined using default cartisian coordinate system.


The equations are given bellow:


x=15*cos(t*360*4)
y=15*sin(t*360*4)
z=60*t



x=20*cos(t*360*4)
y=20*sin(t*360*4)
z=60*t



x=17.5*cos(t*360*4)
y=17.5*sin(t*360*4)
z=1+60*t



x=17.5*cos(t*360*4)
y=17.5*sin(t*360*4)
z=60*t-1



I am using WF3.0. When using single trajectory, the section would twist as shown in the figure bellow.





Regards,
Shankar

 

[jeff4136]

2008-01-23_081912_vss-helix-ellip_sec--wf2--.prt.zip


I suspect there was just aproblem with the way the section
was related (dims, constraints) to the traj ref pts,
H/V axes, etc. I'm not sure how the interesting twist
and taper was achieved. ... I don't really pretend to
understand some of the things I do see come from VSS.
It is sometimes interesting to select the Constant Section
Option and see what happens (if a constant section is
acceptable) when things go 'wrong'.

 

[shankar_me]

Hi Jeff,


Thank you for the reply. I am able to do VSS by using normal to x-trajectory option. But still I am not able to control the orientation of the section when using single trajectory.





Regards,
Shankar

 

[jeff4136]

Hmmm... I'm not sure what might be happening.
For the single traj example I picked the trajectory and went to Sketcher
without trying to define any other references / options. There I created
and dimensioned x and y line segments anchored on origin reference point,
H and V constrained. Then created the ellipse center on origin and
coincident to the x and y line segment ends.


If you can't get it working, post a sample. I can't look at it but surely
someone with WF3 can take a look and help.


- - - -
I'm sorta wondering if you didn't try to define a specific x,y orientation
reference. I ('m really stretching on this and might be incorrect) believe
that should default to the traj curvature / normal vector. The curvature
vectors for a constant radius constant pitch curve should be uniformly
perpendicular to the helix axis. Any other choice would not remain valid
as the curve rotates about the axis(?) and might cause what you're seeing.)
- - - -

 

[shankar_me]

Hi Jeff,


Thank you for your reply. I did sketch the section in the same way as you specified and did in the model you posted. The result is what I have shown in my previous post. I will upload a sample shortly as you said.


Regards,
Shankar