Bolt Thread Interferences

[MrSnap]

Hi Pro-E experts,





I have a caught a bit of a snag in pro engineer in making bolt and nut
threads and assembling them. I'm using wildfire 5.0 for Vista 64 bit
version. I'll try to be brief:





1) For example If you make a base sketch of your bolt on the front
plane, extrude it and thread it using helical sweep cut, and you draw
your nut profile on the right plane, extrude it and thread it using
helical sweep protrusion it will give you global interference error,
despite the fact that I used exactly the same trapezium dimensions
(i.e. thread profile) for both sweeps. If you sketch both the nut and
the bolt on same plane, and repeat the process you will not get the
global interference problem. Why is it like that ?





2) I'm making a bottom bracket for a bicycle frame. I've done the frame,
made screw caps, threaded everything on the same planes. When I'm trying
to assemble the bottom bracket it gives me a global interference error
between the frame and the cap. And in the interference volume it gives
me a question mark. I've tried doing the bottom bracket shaft
separately and then merging with the frame - didn't work. What I am
doing wrong ? Is there a different way to do this ?

 

[SRINIVASANIYER1]

Modeling Threads is a waste of time. Use Cosmetic Threads
from Insert --> Cosmetic...
As for the problem, if you insist on modelling the thread,
define a point on the pitch line on both Bolt and Nut. This
way the assembly would not give you interference.
Threads are modelled only where you wish to go for RPT.
Else, cosmetic threads should suffice, giving you all the
engineering data required.

 

[MrSnap]

I'll have a go at the cosmetic thread, but just in case I need to make a real thread, how do you define a point on the thread ? Do you mean, that when assembling nut and bolt,you have to select the outer surface of the bolt thread, and the inner surface of the nut thread ? If that is the case - thats what I've been doing all along. Could You give me link or a simple walkthrough ?

Note - you cant make a cosmetic left thread if you need them - and I need a number of different sizes and shapes.




Edited by: MrSnap

 

[SRINIVASANIYER1]

Look upon a screw and nut connection as a point on curve, connection. Things would then become clear. The mechanism would then be a "Point on Curve". The point can be on the crest of the screw thread and the Curve on the Valley of the Female thread.

 

[MrSnap]

I've tried an assembly method point on a line. Selected the crest of the
bolt, and the inner thread surface of the nut, the bolt would orientate
itself, so that the the threads are perpendicular, and the whole thing
looks nothing like a nut and bolt assembly. I assume that I understood
You incorrectly.