Cutting a helical thread

Hello,

I'm trying to model a cut helical thread. I'm getting the resolve
error and "Could not intersect part with feature."

I tried everything to correct the problem without any luck.

I modeled many threads in the same manner without this error.

Does anyone have any clues how to correct this?

Thank you

 

Hello,

I'm trying to model a cut helical thread. I'm getting the resolve
error and "Could not intersect part with feature."

I tried everything to correct the problem without any luck.

I modeled many threads in the same manner without this error.

Does anyone have any clues how to correct this?

Thank you


This is still very backward, Menu Manager functionality that hasn't been touched for 10 years. So, it's probably something old, like you made the pitch 1mm and the cut sketch exactly 1mm and the accuracy value was set too low and it choked on some imaginary value out at the 12th decimal place. Or the CL wasn't constrained properly to the center of the part. Or some other such foolishness. When I've had trouble with a helical sweep (years ago when I was brave and foolish enough to use one), it generally fixed this error to make the sketched section .98mm on a 1mm pitch. And to start the profile past the end of the part, so that it took a turn of cutting before it 'entered' the part. And to jack up the accuracy value to .000001 or some such. (And, PLEASE, can't Pro/e, such a smart, expensive program, TELL ME WHERE THE PROFILE OF A CYLINDER IS!?!?! and put a chamfer on the end!!! ~ you break fewer cutters that way, PTC). {rant over, sigh, somebody got me started on helical swamps}

David Janes

 

May I suggest enabling absolute accuracy in your config.pro file, and
setting the absolute accuracy of the part to 0.01 (for metric parts) -
It's pretty much the industry norm for automotive models & works
pretty well.

 

May I suggest enabling absolute accuracy in your config.pro file, and
setting the absolute accuracy of the part to 0.01 (for metric parts) -
It's pretty much the industry norm for automotive models & works
pretty well.

Really, is Absolute Accuracy available on part? I thought is for comparing parts in an assembly! Would be nice to get this straightened out.

David Janes

 

Since rev 17. By default, it's not available, as PTC don't like having
their customers tell them how they want to use their software. You
need to enable it in your config (enable_absolute_accuracy set to yes)
(possible whilst setting use_intent_manager to no and trail_delay to
300) and then it will appear in setup-accuracy.

I'd suggest putting a standard default accuracy in your start part,
then all your merges & shrinkwraps will miraculously work.

 

Since rev 17. By default, it's not available, as PTC don't like having
their customers tell them how they want to use their software. You
need to enable it in your config (enable_absolute_accuracy set to yes)
(possible whilst setting use_intent_manager to no and trail_delay to
300) and then it will appear in setup-accuracy.

Oh, sure, I have it enabled. And it makes a big difference in the success rate of, as you say, merges/cutouts, shrinkwraps (especially applied to assemblies). I just never saw it make a difference in the parts themselves. The parts we're talking about would regnerate just fine, as parts, and then fail whwen they got into a new situation as the cutout part in an assembly. Then, suddenly the cutout operation would fail. Not the part, but an operation using the part in the context of the assembly, where, apparently, part accuracy could not be "translated" in the context of the assembly's enlarged envelope.



I'd suggest putting a standard default accuracy in your start part,
then all your merges & shrinkwraps will miraculously work.


Good point. Yes, do enable_absolute_accuracy (nothing else required), set a low enough default_abs_accuracy, something lower than the largest/smallest part envelope ratio that you think you'd ever encounter (including fasteners and by a decimal place to the left {when in doubt}) and use 'Edit>Setup>Accuracy' to, by default, 'turn on' Absolute Accuracy (I'm not 100% sure, but this may be accomplished by simply setting a default_abs_accuracy value). Do this in both your start part and start assembly parts. Again, I'm not convinced this makes a difference in part regeneration, per se, (lowest possible part accuracy may be suffient), but it definitely makes a world of difference in any function involving assemblies.

David Janes

 

Hi David,

 

Hi David,
PTC claim absolute accuracy slows regeneration and increases model
size, which is why they don't recommend it as default. With a setting
of 0.01, models with a bounding box size smaller than about 60mm are
smaller with absolute accuracy, and larger if the bounding box is
larger. However, the effect is trivial, with a V18 cylinder block,
about 2m long, only taking about 10% longer to regenerate with
absolute rather than relative accuracy. - I found with these very big
parts, sections are much more reliable with absolute accuracy.

 

Re the helical sweep, maybe the OP could do it as a protrusion
instead, reducing the underlying diameter to the bottom of the thread
profile. Or it could be done as a surface and solidified afterwards.

 

Re the helical sweep, maybe the OP could do it as a protrusion
instead, reducing the underlying diameter to the bottom of the thread
profile. Or it could be done as a surface and solidified afterwards.

What you're saying makes sense. Adding material doesn't balk at 'self-intersection' and doesn't leave 'slivers' of material the way cuts may ~ two fewer farts facilitating feature failure. Compounded by accuracy issues.

David Janes

 

Hi David,
Setting a 'default' absolute accuracy doesn't seem to do anything,
apart from set the default value offered when you switch to absolute.
You still need to set it in your start part.

 

Hi David,
Setting a 'default' absolute accuracy doesn't seem to do anything,
apart from set the default value offered when you switch to absolute.
You still need to set it in your start part.


Hmm, yeah, thanks, didn't realize I could set absolute accuracy in the start part. I guess I must have assumed you needed some real geometry to be set to that accuracy. Turns out that if you set absolute accuracy in the start part, all subsequent features will be generated that way. And, naturally, if you plan to do a lot of them for an assembly, they'll all have the same accuracy, so no problems with them communicating their accuacy with each other. Good practice if you model a lot for accuracy sensitive assembly operations like merge or cutout or shrinkwraps.

David Janes