Precision + Clean Topology Possible?

S

Shotster

0
Precision + Clean Topology Possible?

Ok, so I need to create a simple "T" intersection of pipes. This is to be 3D printed, so I need accuracy.

The simplest, most intuitive way to go about it is to create a couple of parametric tube objects with the required inner and outer diameters and arrange them perpendicular to each other. Perfect!

Well, not quite - for two reasons...

1) I don't want a sharp angle at the joint. It must be a gradual transition - more like a clean weld. I can't figure out how to do that with C3D.

2) It has to be a single mesh, so if I "union" the parametric tubes using booleans, I get a butt-ugly triangulated mess.

Then I decided to just box model it (not my strong suit). It's far more time consuming and not very intuitive when I'm thinking in terms of pipes and tubes. Anyway, when I box model it, I can't figure out how to get the dimensions precisely at the values I need. When I apply a subdivision modifier, the diameter of the inner or outer dimension changes because the surface is computed between the verts.

So I guess my question is, short of buying an actual CAD program like Solid Works (which I presume would make this kind of stuff easier), what's the best (fastest method yielding high accuracy) way to go about this seemingly simple task?

I hope I'm overlooking some simple approach. Thanks for any help!

-Steve
 
frank beckmann said:
Is the cross section angled and how does exactly the "T" looks like?
Click to expand...

No, not angled. It's a simple right angle "T".

tube-t.png

I must be overlooking something obvious. This seems like it should be ultra simple.

-Steve
 
This is closer to what I'm after, although it was much more time consuming and less intuitive to create. It was box modeled with a subd modifier.

tube-t-welded.png

My question is, how do I accurately determine the inner and outer dimensions?

-Steve
 
Last edited:
What Frank is going to say is you should model it and then subdivide. And, in this case.

1) Create a six-sided cylinder (create a cylinder and reduce its sections to 6).
2) Make it editable (double-click on it in the object browser), and delete the top and bottom caps.
3) Select the remaining polygons and scale them vertically as desired.
4) Now go back to object mode, copy and paste this object, and move it into position to be the shaft of the T (scale as appropriate).
5) In the object browser, drag it to be a "child" of the other part of the pipe. Make sure there's a gap between the two pieces.
6) Select "Import Children" to pull the shaft into the original object.
7) Delete the shaft (or double-click on the main object).
8) Back in polygon mode, make two ring cuts on the cross-piece either side of where you want the join.
9) Ideally you want to remove two quads
10) ... and Bridge the hole left behind to the cross-piece.
11) Now select Coordinate System and Burn Transform
12) Finally add (in this order) a subdivision modifier followed by a shell modifier (set the shell thickness to taste).
 

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podperson said:
What Frank is going to say is you should model it and then subdivide.
Click to expand...

Thanks, podperson. That's close to what I'm after except that the tubes are different diameters. However, my biggest question is, how do I accurately set the inner diameter of each tube? When the subd modifier is applied, the diameter "shrinks".

-Steve
 
Subdivision is going to provide somewhat inaccurate results (so is using a cylinder, but you have more obvious control). Essentially I'd build a scaffold object with correct(ish) dimensions and eyeball it.

Note that you can subdiv earlier in the process (since it's a modifier) and get the dimensions right before you bridge, etc.

BTW I think we started writing our responses at the same time, but mine (for some reason ;-) ) took a bit longer to finish.

Edit: attached the file.
 

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Study these wires. Hope it helps!
 

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Last edited:
T-pipes with cylinders of same diameter is kids' stuff. :p
With different diameter plus subdivision and avoiding dents+bumps is more tricky.
@ Shotster. The easiest and painless solution is a CAD software when you have to be absolute precisely.
T-Pipes.jpeg

Cheers
Frank
 
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frank beckmann said:
T-pipes with cylinders of same diameter is kids' stuff. :p
With different diameter plus subdivision and avoiding dents+bumps is more tricky.
Click to expand...

Yeah, tell me about it. :confused:

frank beckmann said:
The easiest and painless solution is a CAD software when you have to be absolute precisely.
Click to expand...

That's what I suspected. Even SketchUp turned out to be problematic. Creating the "weld" (smooth transition) is a PITA. (...although there might be a plugin to simplify the task)

So which CAD program did you use?

-Steve
 
MoI for me is the most intuitive CAD type modeler I have tried but I am very new to this approach to modeling. Also the mesh it creates is very clean, which is important.
 
Yeah I think MoI would probably produce a lighter mesh than C3D with subdiv would for this kind of thing. Lovely program — wish it ran on the Mac (or iPad).
 
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