【转帖】help on building helical surface with sweep

yang686526

help on building helical surface with sweep
hello all,
if someone could help with this situation...
i am trying to create a surface sweep by using 2 helices. this is the step-by-step of what i tried:
1) create large helix: draw circle diameter = 2m in front plane; define pitch = 1m, revolutions = 5, start angle = 135.0deg,
clockwise, taper helix = 50.0deg outward
2) create small helix: draw circle diameter = 1m in front plane; define pitch = 1m, revolutions = 5, start angle = 135.0deg,
clockwise, taper helix = 5.0deg outward
3) using tools/mesure, record the start/end coordinates (precision: 8 digits after decimal point) of both curves.
4) using these coordinates, build 3d lines as shown in image:
     - connect start points of the two spirals with a straight line
     - connect end points of the two spirals with a straight line
5) go to insert/surface/sweep
   - choose one of the straight 3-d lines as profile
   - choose small (internal) spiral as path
   - choose large (outward) spiral as guide curve
sweep fails with the message: "sweep operation failed to complete".
i tried various combinations of choices, selecting spirals as path or guide curve but nothing helps.
i am doing something wrong, but what is it?
thanks for any suggestions you may have.

you're method can be somewhat simplified by skipping steps 3 and 4.
  

here's an even simpler method ...

hi
thanks for your answer. could you explain (if possible, step-by-step) of what you did to make it work? most of all, if you could comment on where is my mistake, because i could never complete the sweep. i must be missing a key requirement somewhere and want to avoid my mistake in the future.
regards

1) create large helix;
draw circle diameter = 2m in front plane
pitch = 1m
revolutions = 5
start angle = 135.0deg
clockwise
taper helix = 50.0deg outward.
2) create new sketch;
draw construction line from centre of helix halfway toward helix start point
draw co-linear line from end of construction line to near the helix start point
add a pierce constraint between the end point of the line and the helix
dimension length of line.
3) insert > surface > sweep
select line as profile and helix as path
orientation/twist type = follow path
path alignment type = none
click the tick.

sorry, forgot to mention ... the above is for the "even simpler" model. also, ignore the z axis and sketch1. they were a hangover from something else i was playing with.

i'm not sure where you were going wrong, but my guess would be at the co-ordinates step. even though you were using 8 places, it may not have been accurate enough. i seem to re  
if he wasn't using the pierce constraint, that could have tripped him up, too.
dan
couldn't make it work. tried to increase the taper of the inner helix. still, the sweep fails. tweaking the options follow path/etc. give surfaces, but they are not the right ones.
i guess the piercing constraint is not the solution here.
i will simply try replacing the inner helix with the z-axis.
when the inner helix shrinks to be the z-axis, the sweep should work. i have managed to do it before (with some help).
many thanks for your input!
unless i'm missing something, you are making this more complicated than necessary. from the original description and image you posted, you don't need a z-axis or an inner helix.
were you able to open and review the 'even simpler' model from my second post?