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Running out of a thread when modeling a thread in Pro/E

F

Freecat

Member
Hello,



When machining an internal or external thread on a CNC lathe (with a single-point tool), it is common for the threading tool to be pulled away from the stock during the last couple of revolutions of the thread cut. In Pro/E I know how to do a helical sweep to accurately model a thread, but my question is how can you model this pull-out that takes place? (I am refering to threads that are cut without a threading relief). Any methods or even a CAD model would be most appreciated!



Sincerely,

Rich
 
Rich,

When you are in the sketch mode for the sweep profile, instead of sketching a straight line, sketch two lines. One that starts clear of the part and one that begins the lead out from the thread. Everthing else after that should be the same. To check this feature, exagerate the lead out. Start it about half way down the thread with a large angle.

Hope this helps!



Christopher
 
Ouch! Why model the thread at all? The CNC programmer knows perfectly well how to achieve one where required (and prefers that you NOT furnish him with a file including the thread with all the detail). Why not keep it simple?



For external threads, simply model a cylindrical protrusion with diameter=major diameter and cover it with a cosmetic thread over the length to be threaded.



Use a similar practice for blind internal thread except create a hole (or cut) with or without a 118 degree drill angle (for english standard drills) at the bottom. Make the internal thd diameter=major diameter and again create a cosmetic thread over the required length. Depending on how critical the tap depth is, often you can do without the drill angle in your model.



A word or advice: keep it simple. Modeling threads, while probably fun, will only tend to make your files big (thus increasing regen and startup times) and increase your modeling time. Also, the CNC programmer will ignore your thread features anyway and do it the way that he usually does it.



Tunalover
 
Ouch! Why model the thread at all? The CNC programmer knows perfectly well how to achieve one where required (and prefers that you NOT furnish him with a file including the thread with all the detail). Why not keep it simple?



For external threads, simply model a cylindrical protrusion with diameter=major diameter and cover it with a cosmetic thread over the length to be threaded.



Use a similar practice for blind internal thread except create a hole (or cut) with or without a 118 degree drill angle (for english standard drills) at the bottom. Make the internal thd diameter=major diameter and again create a cosmetic thread over the required length. Depending on how critical the tap depth is, often you can do without the drill angle in your model.



A word or advice: keep it simple. Modeling threads, while probably fun, will only tend to make your files big (thus increasing regen and startup times) and increase your modeling time. Also, the CNC programmer will ignore your thread features anyway and do it the way that he usually does it.



Tunalover
 
Thanks for the replies! I didn't think about doing the helical sweep in two trajectories (two lines). I will try it.



As luck would have it I am a CNC programmer, I currently program 5 axis lathes. I agree with simplicity and that Cosmetic threads should be used. But I need to keep my supervisor on his toes! When I hand him a beautiful print brimming with nice threads his eyes just lite up! Or maybe it's silent rage that I'm witnessing? :)



But seriously I know that Cosmetic threads should be used, but occasionally I come accros a part that benefits in appearance, and computers are now getting much more powerful, so it really is possible to do a thread or two when they are needed without major problems.





Thanks again for the explanations, now it's on to my next question, showing simplified representations of threads using the Cosmetic thread function. I will post the question in the main area for others to read.



Sincerely

Rich
 
Thanks for explaining your situation. Did you describe to your supervisor how much time you spend on modeling the threads? If he understands the investment of your time vs. the added benefit and if he's the one who writes your appraisals, then by golly he should get what he wants.



Tunalover
 
hello,

how to do cosmetic thread. i had to make an internal thread, but i couldnot give cosmetic so i gave hellical thread . no pitch was coming. the hellical thread was circular.

how to make a metric thread in cosmetic. plese tell steps. thanks for help.

hartej gill.
 
The reason to model threads in a part is that is it they are being molded, cosmetic threads won't product a moldable feature
 
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