New thread modeling method

[dantheguitargod]

A co-worker has shown me his method of modeling stub acme threads. He makes a single revolved cut of the thread form,and then patterns it with no angle.In a sectioned view the thread appears to have a normal form. In a full view however, there is no angle to the thread.


I prefer to use the helical cut to make the thread as acurate as possible. I only use real threads for the "pretty pictures" for sales guys, and use cosmetic threads on drawings.


He prefers to show the thread in the drawing, only it turns to a black blob when printed.


Two Questions:


1) Does copying a single revolved cut x 60 create more entities/memory thanone helical sweep?


2) If you are going to model the thread, why not make it accurate? One process is not any harder than the other.


Looking forward to your thoughts on this.


Best Regards


Dan

 

[dr_gallup]

I don't do any solid features for 99.5% of screw threads, I just use the cosmetic features which do just fine at creating drawings that meet standards.

Occasionally, when I need a pretty picture or I need a non-standard thread, I will model it with a helical sweep. I don't see any point in doing a revolve & patterning it. Not only do you have a lot of overhead, it's not even correct geometry.

In answering your question 1, I expect the helical sweep consumes more memory & CPU cycles than the patterned revolve because there geometry is more complex. It depends too on how detailed you get with things like the thread root radius, etc.

 

[zpaolo]

I don't know which technique is more demanding in terms of regenerating time, memory ecc, but I know for sure that if I'm asked to actually model something, I tend to model it correctly. In drawings I usually have no need for "modeled" threads, as for pretty pictures, I can tell when the thread is modeled right or not, so I'd stick with cosmetics for the drawing, sweep for the model.

I mean, you don't want to see this: http://zpaolo.deviantart.com/gallery/#/d1rzree with a fake uncorrect thread ;D

Paolo


Edited by: zpaolo

 

[dantheguitargod]

I didn't find the target that the link points to, but I was very impressed with your otherartwork.


Nice job ! Pretty Pictures !!


Dan

 

[zpaolo]

I didn't find the target that the link points to, but I was very impressed with your otherartwork.


Nice job ! Pretty Pictures !!

Hmmm maybe deviantart has some glitch with the new team... this is the picture directly, I tried posting it as link to the jpeg but did not work :/ Thank you for the good comments

And I thought from your nick you would appreciate

 

[dantheguitargod]

WOW. That looks great ! Better than a real photo of an actual part.


I have that bridge on one of my guitars. My favorite bridge. Love the fine tuners. (Just don't break a string or your done.)

Can I see the build? What do you use to render it? Interested in how you did the knurls.


Sorry for getting off subject. I get distracted easily.


Regarding the part that started this thread: I recently got the chance to re-model it. It's now 100% accurate. I feel better now.

 

[zpaolo]

Well I rendered it in Hypershot, actually I think it is a snapshot of the realtime preview after some minutes of refinement.
Modeling is nothing special: the bridge itself is mainly built through cuts and rounds.
For the knurl I did like this: i wanted to apply the knurl _after_ the chamfering and rounding of the top part, so I created a cylindrical surface, then sketched a slanted line on the front plane

View attachment 4599

the line was projected on the surface and used as a trajectory for a VSS cut

View attachment 4600

The cut was then radially patterned, and the pattern mirrored:

View attachment 4601

The VSS has a variable section but its sketch plane is always normal to the top of the screw. The section is tweaked so the outer diameter is not reduced too much.

This is probably not the best method: I should've made a wrap of the trajectory, or create a proper helical trajectory with the VSS trick, and then drive the VSS through that normal to surface... but hey this is just for looks and I think it looks good enough

Paolo


Edited by: zpaolo