Creating Multi-Tiered Ruled Surface objects

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Creating Multi-Tiered Ruled Surface objects

ex7r4n1ck
I am new to the 3d printing world and just started using OpenSCAD today - be
merciful. I have dug into the manual, went through the cheatsheet, and
searched this forum and the web for similar projects and have learned a lot,
but am no where near a working model. Any pointers, help, code, projects,
models, or ideas would be greatly appreciated.

I am trying to build a splint for my wife's injured wrist and thumb(won't go
to urgent care due to high number of COVID cases in the area). First, I
designed a flat sheet that could be heated and essentially roll formed
onto/around her arm and hand. It works okish, but there are some drawbacks.
It is similar to this: https://www.thingiverse.com/thing:403001/remixes

I believe that ideally, I could create a model that built from a set of
parameters - enter OpenSCAD. This would make the design far more useful to
more people and be easier to iterate minor changes to accommodate changes in
swelling or needing more ventilation or being taken on and off, etc...

The overall form, when stood up vertically(think elbow as base, hand
straight up), would be the large arm opening, an ellipse or oval, that goes
up to another oval/ellipse opening at the wrist, then goes up to another
section(or two) for the hand and thumb.

It seems like at a minimum these parameters would need to be available:

MaterialThickness
ArmMajorVertexLength
ArmMinorVertexWidth
DistanceFromArmOpeningToWrist
WristMajorVertexLength
WristMinorVertexWidth
DistanceFromWristOpeningToHand
HandMajorVertexWidth
HandMinorVertexThickness

Currently, I don't really see how I would be able to create a shape(lets say
the arm), connect it to another shape(the wrist) to create a level within a
set distance, then stop, use that second shape(the wrist) to connect to the
third shape(the hand) to create the second level.

I have a few ideas on how to form the thumb, maybe getting the distance from
the wrist to the base of the thumb, the angles that the thumb is from the
rest of the hand, and the length and thickness of the thumb itself, but I'm
not sure what would work best or be the easiest to accomplish.

Ideally, I'd also be able to change the wall type(solid vs mesh and what
kind of mesh), maybe a couple of support locations, such as a bar(s) above
and below the wrist or on the sides of the thumb, and maybe the angles
generated - for example, only generate from 0 to 180 degrees of the model so
that the splint could be easily put on and taken off.

These three OpenSCADA projects have been my main inspiration thus far:
Excellent "mesh" customization -
https://www.thingiverse.com/thing:40703/files
Ruled Hyperboloid with link to more info -
https://www.thingiverse.com/thing:328579
Interesting box project - https://www.thingiverse.com/thing:26921

Again, I welcome any help/thoughts available and appreciate it in advance.

Thank you.



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Re: Creating Multi-Tiered Ruled Surface objects

Troberg
While it can be done, it's not easy to do in OpenSCAD. Soft, organic shapes
is not what it does best, it's more of an engineering tool.



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Re: Creating Multi-Tiered Ruled Surface objects

acwest
You likely will want to base the shape as it goes up one bezier curves. They are fairly easy to generate programmatically, and I have seen a number of implementations in OpenScad. I did one myself, even 😊

On Sun, 5 Apr 2020, 06:09 Troberg, <[hidden email]> wrote:
While it can be done, it's not easy to do in OpenSCAD. Soft, organic shapes
is not what it does best, it's more of an engineering tool.



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Re: Creating Multi-Tiered Ruled Surface objects

JordanBrown
In reply to this post by ex7r4n1ck
On 4/5/2020 1:37 AM, ex7r4n1ck wrote:
I am trying to build a splint for my wife's injured wrist and thumb(won't go
to urgent care due to high number of COVID cases in the area).

It's not a 3D printing solution, but my first thought is one of these:
https://www.amazon.com/SAM-Medical-Splint-Roll-Count/dp/B00KTKGPWI
Maybe a local drug store will have one, or something similar.  It's bendable but holds its shape.  You can cut it if need be.  Combined with some kind of first aid tape you should be able to come up with something.

Unfortunately, with Amazon deliveries running slow, ordering it from them isn't a very timely solution.

I would worry a bit about texture - 3D printed stuff tends to be a bit rough - and about issues with keeping skin in contact with plastic for a long time.  Anything you do should probably involve layers of fabric or other padding.

I believe that ideally, I could create a model that built from a set of
parameters - enter OpenSCAD. This would make the design far more useful to
more people and be easier to iterate minor changes to accommodate changes in
swelling or needing more ventilation or being taken on and off, etc...

Remember that 3D printing large objects is very slow.  Even if your design is totally parameterized, it could easily be several hours from when you decide that you need a new shape until you actually have it in hand.

Currently, I don't really see how I would be able to create a shape(lets say
the arm), connect it to another shape(the wrist) to create a level within a
set distance, then stop, use that second shape(the wrist) to connect to the
third shape(the hand) to create the second level.

The simplistic answer is to specify all of the locations and angles explicitly:
translate(...) rotate(...) cylinder(d=120,h=2);
translate(...) rotate(...) cube(...);
...
The next-most-simplistic answer is to define the various things in a nested fashion, e.g.
module arm() {
    ... stuff to create arm part ...
    // position wrist relative to arm
    translate(...) rotate(...) wrist();
}

module wrist() {
    ... stuff to create wrist part ...
    // position hand relative to wrist
    translate(...) rotate(...) hand();
}

module hand() {
    ... stuff to create hand part ...
    // position thumb relative to hand
    translate(...) rotate(...) thumb();
}

module thumb() {
    ... stuff to create thumb part ...
}

The most general answer is to use a library that understands connecting one object to another.  I've never worked with one, but there's one at https://github.com/davidson16807/relativity.scad/wiki .

As others have said, organic curvy shapes are possible but not easy.



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Re: Creating Multi-Tiered Ruled Surface objects

ex7r4n1ck
Thank you all for the replies. Much food for thought. I will take some time
to digest the information and put in some more work. I'll follow up with
where I land. It does look like using that relativity library will prove
useful.

And to be clear, I already have a working splint for my wife. It will just
require printing another and reforming it to her wrist when the swelling
goes down(took about 4 hours to print on a mostly homebrew printer). She can
remove it easily to shower and whatnot. Seeing that there weren't any
parameterized options available, I picked up another project. lol.





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Re: Creating Multi-Tiered Ruled Surface objects

adrianv
ex7r4n1ck wrote
> Thank you all for the replies. Much food for thought. I will take some
> time
> to digest the information and put in some more work. I'll follow up with
> where I land. It does look like using that relativity library will prove
> useful.

The BOSL2 library also has relative attachment features, as well as support
for beziers and sweep, path_sweep, skin and other operations that might be
useful for your project.  Note, however, that it's still under development
so things are still changing.  

https://github.com/revarbat/BOSL2/wiki




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