Creo Screw Elongation

[VK_10764175]

I downloaded an iges file of a vented screw. I would like to modify it to make it longer. It is currently 8mm long, and I want it to be 50 mm long. I have tried to mirror it as a way of elongating it, but the ends don't mirror correctly. 

Is there a way to cut a section off? I could copy and paste the middle threads to get to my desired length.

[tbraxton · Accepted solution]

You can probably model that from scratch faster than you could modify the STEP model to accurately represent a longer version. 

Here is a copied and moved thread geometry to "lengthen" it. If you index the translation value, you can align the threads, so they pass a cursory view. This is a total hack for a cartoon only. If you need the actual geometry, build a model from scratch.

[BenLoosli]

I don't understand why people download such simple files that cannot be edited. So much quicker to just model it.

If you downloaded a 8mm length set screw, you should be able to find a 50mm set screw at some place like McMaster-Carr or Fastenal.

[StephenW]

Its that feeling we all get...you get something for nothing.  And then you spend hours fixing it. I'm guilty!

[Patriot_1776]

Winner winner, chicken dinner!

[kdirth]

Not the prettiest way to do it, but:

• Copy the surfaces of threads, bottom & vent
• Trim top end of copied surfaces 6 mm from bottom.
• Solidify surface
• Pattern copy by directtion - 11 members 4.2 mm (6 threads) spacing
• Pattern cut
• Pattern solidify

[Patriot_1776]

*facepalm*

No, actually, the threads DID mirror correctly, it did EXACTLY what you told it to do.

Besides, IGES files are cr@p, use STEP files if needed.  Let me guess, garbage McMaster-Cr@p model?

Don't waste time on this, remodel it the length you want with simplified threads instead of helical ones.  ASME B18.3-2012 gives you all the data you need.

You're welcome...

[KenFarley]

What none of this addresses, though, is the question of *why* have threads modeled in the first place. Screws with threads look cool and all that when you're making a small assembly, sure. But, I've encountered large assemblies where the person building it had 100s (or even 1000s) of these, and the questions are always "Why is my assembly so slow to load?" and "How come my hidden line removed views on the drawing are all messed up?". Doing this kind of thing adds 1000s more surfaces for the hidden line algorithm to deal with, results in pretty much solid filled blobs when the view scale is sufficiently small, etc.

Unless I'm going to build a 3D printed model of something (which never works the first time, does it?) and want threads on it, I don't see the use.

[Patriot_1776]

Winner winner...ahh, pizza dinner?  We're all out of chicken...  LOL

[joojaa]

I can think of 4 reasons:

1. Need to 3d print the thread, as you say (or the counterpart using boolean). Or some other nonstandard manufacturing method.
2. Need to do geometric modification away form standard shapes
3. Need for presentation graphics*
4. Need to do some sort of geometrical analysis, for say a differential thread.

* now it would be great if Creo could do simplified states that are more complex than the base model. Maybe they are complexified states? Then we wouldn't have this problem.