adding or subtracting screw thread often "cannot be computed"

[Funkart]

Have others come up with this issue? I often need to create a solid with internal or external screw threads. Having created the thread, when it comes to adding or subtracting sometimes it works, other times (and more often that!) I get the "You're creating an object that can't be computed" message. After a fair bit of messing about I can usually work around, but today the frustration got a bit more. Perhaps others have had this and have an answer? (VW 21)

thanks 

Arthur

[VIRTUALENVIRONS]

can you post the file

 

[Funkart]

Thanks. What format do you want? STP?

6.15 Vector.stl

[Pat Stanford]

Please post the VW file.

 

Did you create the threads in VW? Or in some other program and then imported?

[Funkart]

Thanks. All VW. I then find stop won't upload, hence sty. Any other preferred?

 

[Funkart]

Stupid auto correct: The components were all created in the same VW file. I then find that STP is not a accepted format, hence STL.

 

 

Thanks.

[Pat Stanford]

For us to help you we want you to upload the VWX file so we can see what is happening.  Export to STL and then reimport results in an entirely different object. We want to see the original object.

[Funkart]

Ah, capiche! (apolgies)

Thread Issue.vwx

[Funkart]

(I sent that reply previously, yet discovered this morning it was not there...Hey ho)

[VIRTUALENVIRONS]

Hi Funkart,

Your problem appears to be intersecting geometry on the thread.  I just change the pitch slightly and it worked.

 

Try adjusting it.

[Funkart]

Now I'm both impressed as well as puzzled. Intersecting, how? I've set it up following standard thread pitch values, unless the issue is one of those ".0001" changes and everything works. You've alerted me, I'll play away.

Many thanks. 

[VIRTUALENVIRONS]

I don't know the answer to that.  I could speculate a half dozen theories, but still not have it.

 

BTW, does it work for you now.

[Pat Stanford]

I think Virtual Environs is correct that it is intersecting geometry.  I think somewhere in the sweep, the "back" corner of the profile polygons are overlapping.

 

I slightly "sloped" the back edges "down" to make the back edge slightly smaller and then the sweep and the shaft were able to be Added.

 

 Original

 Modified

 

Vectorworks really does not like having overlapping geometry in the same object.

[VIRTUALENVIRONS]

Another way around this besides Pat's explanation is to simply remove the redundant part of the thread geometry.  Just sweep the angular thread only  slightly inside the bolt shaft.  That would preclude any intersecting geometry at the centre of the rotation.

 

[jmcewen]

Late to the party, but is this something that could be solved using the tapped hole tool from the Detailing toolset?  It is a tool I never use because accurate thread geometry is rarely important to me in my modeling, but it seems that Vectorworks may be more amenable to geometry that was created in Vectorworks.

[Funkart]

You've given me plenty to play with and see but not had a chance to try it yet - small business and I'm chief cook and bottle washer. I have noticed that on occasion VW says it doesn't like something that you believe to be correct. i.e. the infinitesimal alteration and VW is now happy. But have taken on board all the suggestions and probably have a go later today. fighting the resulting 3D prints at the mo. I'm wondering if it might be internal rounding errors, hence my previous thought.

 

[Funkart]

Got it!

Thanks to everyone. Now can you help me with my battle with UPS...?

Didn't think so. then again, it's only been going on for 17 months, so perhaps I'm being a tad impatient?

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