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I'm relatively new in the field of 3D printing and design. By now I've created and printed some technical objects with TinkerCAD, but now I've a task, which I don't know how to solve.

I have the following model as STL-file: enter image description here

Now I want to "adjust" the arms of the model, as shown in the picture. I want the arms to hang besides the body.

I know that I could cut and rotate the arms and then merge them again with TinkerCAD but the outcome dosn't look good and the workflow feels wrong.

So what is the right tool/way to get this task done?

*Disclaimer: I'm not Denis Almaral, but he released this model unter CC license. So I kept his name on the image to credit him, as requested via CC.

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Basically there's no good easy way to do this.

At this point you only have the mesh - a list of triangles - the 3D model you have does not contain the concept of joints or moving parts so it can't regenerate the shoulder after the rotation.

The original author may or may not have the ability to do this, depending on his workflow and software.

If all you have is the STL your only choice is to rotate the arm and then rebuild the shoulder from scratch and manually fix anything that doesn't look good

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  • $\begingroup$ Hi @Nir - thanks for your answer. That's what I initially tried - and failed. But then I'll try again. I thought that something like joints/moving parts is included - but if you say it isn't - I understand, why it isn't possible to do it in an easier manner. $\endgroup$ – netblognet Jan 11 '18 at 8:30
  • $\begingroup$ @netblognet - I did start by saying it isn't easy :-) you said you tried doing it in ThinkerCAD, I think it will be easier in a program that let you draw/edit the mesh directly like Blender, it's not a simple software package but there are a lot of online tutorials $\endgroup$ – Nir Jan 11 '18 at 9:01
  • $\begingroup$ Ok - you and @mac brought me onto the right path. I read more on different file formats and realized that the author of the model also delivered a fbx-file. This contained a rig (did I use the word in the right context?) which allowed me to "form" the body and arms with threejs.org/editor $\endgroup$ – netblognet Jan 11 '18 at 13:05
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The correct/good method to achieve this is called "rigging", but it is not an easy feat (as pointed out by others), as it requires plenty of knowledge about the software being used to edit the model, and a good understanding of the theory behind it.

Skeletal animation requires the designer to set up a skeleton (also called "rig", hence the slang term "rigging") for the mesh and define the variables controlling the motion range of the joints and and the geometry and deformation of the mesh.

It's quite some job to perform, so - unless this assignment is the first in a series of assignments having to do mesh movement for this model, or you have a keen interest in the topic - I would suggest you to take a shortcut and edit the mesh directly in a "one off" not reusable fashion.

(Rigging would conversely allow you to create a "rag doll" or at least a "rag arm" to freely and intuitively move around as you please).

The tool I would use for either task is blender. If you want to take the shortcut, maybe a less complex software like meshmixer could also do the job (I don't have direct experience with it, though, so I'm not 100% sure).

The blender foundation have a nice series of videos on the topic, called "humane rigging".

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