Helical sweep - unattached cut!

[PRO_E_H8TR]

Alright, so I am trying to model threads (16 pitch) on a 15" dia surface, and keep getting "unattached cut, could not intersect part with feature". Now before you picky veterans get all over my case about why don't I just insert a cosmetic thread... I need to eventually provide detailed drawings for marketing literature (cross section view), so I would like to model this correctly. Now I also could just fudge a thread in there to make it look pretty, but c'mon, there's no reason why I can't do this the right way.


So anyway, like I said, I have a 15" dia ring, 0.38"h, and I want to cut a 16 pitch thread along the entire surface. I have read posts in the past that detail to sketch the section below the profile, and have the profile extend 1/2 thread past the last surface... that doesn't work.


I keep getting the unattached cut error no matter what I try and do. The profile is constrained to the outer surface, and the section is completely inside the feature and still it doesn't work.


WTF is going on??!! This error is bogus!

 

[kdem]

Can you post a picture of the cut profile? Sometimes having sharp corners can cause this problem.

 

[nofalloff]

go here: http://e-cognition.net/Video/Helicals.html

 

[kdem]

Another thing you may want to try is to model the thread as a surface then use the solidify feature to remove material to create the threads in the solid.

 

[gafatwork]

Could it be Model Accuracy


Edit>set up>accuracy


Sounds like a fairly large model with possibly a small thread


-gafatwork

 

[PRO_E_H8TR]

Can you post a picture of the cut profile? Sometimes having sharp corners can cause this problem.

Here's a sweep that worked


Overview:





Profile:





Section:








Here's the other piece, same I.D. helical sweep, same section, just a slightly different profile (does not work). The only way I can have it work is if I increase the pitch to 0.1" instead of 0.0625"... which doesn't make sense.








Profile:








Section:








What I want to do is start the helical sweep above the surface so I get a "true" cut, like the cutting tool entering the part, so I don't have a stupid step leftover. It works just fine in the 0.1" pitch where I start it above and end below the surface, but not the smaller pitch. The section height is less than the pitch if anyone's wondering... it's straight out ot the Machinery's Handbook.

 

[design-engine]

for problem solving these issues try converting your solid cut to a surface. Often this can help you figure out whats wrong.

 

[PRO_E_H8TR]

Could it be Model Accuracy


Edit>set up>accuracy


Sounds like a fairly large model with possibly a small thread


-gafatwork

THAT WAS IT!! NICE WORK!!


My relative geometry was set at 0.0012 and I changed it to 0.0005, and that took care of it. Now I can cut before and past the surface without any problems. What you said made sense too, because one of the other engineers here made the same profile, section, and pitch, but only on a 1" dia... and his worked... but mine didn't.





Thanks again!!

 

[kdem]

I have had this happen before and the problem seemed to be the sharp corners (corners were the 60 angle dimension is in last section picture) over lapping as the section is swept around. Try changing the pitch in the dialog box so that it is a little larger than pitch dimension in your sketch. Another thing that may becausing the problem is that the start point for your trajectory is on the geometry. Try redefining the trajectory so the start point is off the geometry.

 

[gafatwork]

Glad it worked out for you.....


-gafatwork