Full Version: Modeling a thread with tapered end

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Hi Michael,

Thank you! If I've performed a Boolean operation (union) with success, so that my thread and cylinder becomes a "solid object".. Does the "barely skimming" thread, before the boolean, still cause problem when I want to add the Fillet later?

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Hi Frederick,

re:
> Does the "barely skimming" thread, before the boolean, still cause problem when I want to add the Fillet later?

Yes it can, in your case here there is kind of a little shelf where you want to fillet:







- Michael

Image Attachments:
frederick_skimming3.jpg  frederick_skimming4.jpg  frederick_skimming5.jpg 

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Hi Frederick, here's a filleted version. I used FlowExtendSrf (http://moi3d.com/forum/index.php?webtag=MOI&msg=9747.7) to extend the thread surfaces so they pushed through the cylinder with a little margin and then boolean union and filleted with radius = 0.35mm .

- Michael

Attachments:
Thread-Fillet-02-problem2_2.3dm

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Thanks again Michael, much appreciated!

Did you need to re-model the thread from scratch for this to work, or can I somehow use FlowExtend on my existing thread? I downloaded FlowExtend now, but I don't understand what it does.. It added a lot of flat planes to my model when I tried to use it on my edges (see screenshot)?
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BTW, is there a way to add a shortcut for "Reset Current view"? I only found a script to "ResetAll views".

Image Attachments:
Taco_Thread_FlowExtend.jpg 

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Hi Frederick,

re:
> Did you need to re-model the thread from scratch for this to work, or can I somehow use FlowExtend on my existing thread?

I used it on your existing thread but basically resetting it using Edit > Separate to break it into individual surfaces, then selecting all edges and hitting Delete to do an "untrim" and recover the full underlying surfaces.

Then I used FlowExtendSrf on each individual thread surface.


> I downloaded FlowExtend now, but I don't understand what it does.. It added a lot of flat planes to my
> model when I tried to use it on my edges (see screenshot)?

You're getting a bunch of pieces extended there including the cylinders and cylinder end caps which don't need it. If you break it into surfaces using Edit > Separate you can be more selective for which pieces to extend.


> BTW, is there a way to add a shortcut for "Reset Current view"? I only found a script to "ResetAll views".

Try this one:

script: /* Reset current view */ var vp = moi.ui.getActiveViewport(); if ( vp ) { vp.reset(); }


- Michael

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I'm not sure what I'm not understanding...
I'm a "polygon modeler", so I'm not used to all the difficulties with Fillets and Chamfers, and the "broken edges" that I experience when learning modeling in MoI. There must be something fundamental that I'm missing because I really struggle so often when trying to add Chamfers or Fillets to my objects.

In the attached examples (3DM file included), I start with the thin joined surfaces. They look clean to me… I offset this using the "Shell" command, and now this is a "solid". When I select the highlighted edges, I can perform a partial Fillet on the edge (but it's limited to only half the thickness of the shell). And the Chamfer doesn't work at all?

What is it that I'm missing? Also, is there some kind of "optimize" command that cleans my model from corrupt edges and welds edges within a certain distance?

Attachments:
Thread-Chamfer_object-03.3dm

Image Attachments:
Taco_Thread_chamfer1.jpg  Taco_Thread_chamfer2.jpg  Taco_Thread_chamfer3.jpg 

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I wouldn't shell the separate parts. If you look at the profile of the curved interior area the shell pushes that portion out. I would revolve the whole top part, shell that then cut the curve interior away. that guarantees a clean profile. At that point you can chamfer/fillet the edge.
On a side note, shell has a similar effect in poly modelers as well.

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Hi Frederick, sorry you're having difficulty.

Yes, CAD modeling tends to be more finicky than poly modeling. That's generally because CAD modeling is trying to generate geometry that accurately represents shapes and not just making a "looks like it" approximation.

There are some tips here for people coming from a poly modeling background:
https://moi3d.com/forum/index.php?webtag=MOI&msg=4865.2

The main concept is in CAD modeling you want to build a simplified extended shape and then cut that up using booleans.

For your case here that means the initial target that you want to get to is this:



You can use Shell to get this:



Then the largest fillets:



Boolean difference with a cutting line to cut it in half:



2nd largest fillets:





So note that once you have formed the initial solid it's good to try and keep working on it as a solid if possible because you can then use booleans to cut pieces.

- Michael

Image Attachments:
frederick_extended1.jpg  frederick_extended2.jpg  frederick_extended3.jpg  frederick_extended4.jpg  frederick_extended5.jpg  frederick_extended6.jpg 

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