What is the easiest way to modify/resize an object inside a STL file?



I have this GoPro mount for a quadcopter as STL file. It looks as follows.

enter image description here

How do I modify it so that it is wider and longer by a few millimeters but the screw holes stay the exact same size? Additionally the angle of the upper surface must stay the same. Please suggest the easiest solution for someone like me who as no idea about CAD software.

The perfect solution for me would be to just import it in Tinkercad and then modify it however I have no idea what the steps are.

Tony Stark

Posted 2016-06-13T18:08:39.310

Reputation: 183

If you only need a few millimeters, you can probably just stretch/scale the entire model by the required amount in all directions (to maintain angles/proportions) and the screw holes will still be close enough to the correct size to work fine. You can do that kind of scaling in your slicer slicer without even changing the model file. – Ryan Carlyle – 2016-06-13T20:39:41.723

I have no idea which answer is the best. I ended up diving into Tinkercad, measuring everything and designing something similar (see http://www.thingiverse.com/thing:1624957).

– Tony Stark – 2016-06-16T21:52:01.467



Many resources are available for modification using 3D CAD (including learning a tool such as sketchup, which is VERY beginner friendly). The easiest and fastest solution to your particular problem may be the reddit community "3D Print My Thing" which was created for EXACTLY this type of situation (help with modelling parts which will be 3D printed.) Another potential useful reddit community is "3D Modelling" which will have many people who are able to help you with this quadcopter/Go-Pro attachment 3D model.

Third solution: Thingiverse has a customize option for 3D models (including this one). have you explored using this interface to edit the model? This is most likely the easiest DIY solution.

J. Roibal - BlockchainEng

Posted 2016-06-13T18:08:39.310

Reputation: 423


Unfortunately, there is no simple method for modifying specific features of an STL. You are pretty much limited to the following actions:

  • Scaling (The entire model along three independent axis)
  • Breaking the model into parts/chunks
  • Mirroring or Rotating the object
  • Skewing an object (twisting)

Even the last action requires a 3D CAD program. I would suggest you develop your own model. OpenSCAD is a free 3D CAD program that works well. If you are comfortable with TinkerCAD, you should be able to easily develop your own version of this mount.

Good luck!

Jason King

Posted 2016-06-13T18:08:39.310

Reputation: 71


I think what you are trying to do is somewhat non-trivial so whatever tool you choose there will be some learning curve.

OpenSCAD, as mentioned above, is pretty well established as an open source tool for modifying STLs; however you have to be comfortable writing programmatic CAD instead of using GUI tools. Personally, I think programmatic CAD is MUCH easier but I realize not everyone feels that way. FWIW, I would probably break this into three STLs using a DIFFERENCE method, stretch the outer ones using a SCALE method, then use a UNION to put them back together.

The one problem that I've had with OpenSCAD is that it will frequently crash unexpectedly or run incredibly slowly when dealing with an STL with a large number of triangles.

AtomicCompiler.com is very similar to OpenSCAD but runs as a web service and seems to do a bit better when dealing with large STLs. I might try that first, as it doesn't require a download or even a login.


Posted 2016-06-13T18:08:39.310

Reputation: 11


Well. I would cut it into two STLs, using netfabb slice / split tool.

in 123d I would fill in the hole with the merge union (with a cylinder object), scale it, and either keep it unfilled and drill it, or do a subtraction union on where you want the holes. (again with a cylinder)

Scaling otherwise you need the original model and solidworks..

Split in 2, scale the piece you want and re-add the other half is probably the best way.


Posted 2016-06-13T18:08:39.310

Reputation: 2 913


By far the easiest program to use is Tinkercad and it's free.

Michael Parks

Posted 2016-06-13T18:08:39.310

Reputation: 1

2Hi welcome to 3DPrinting.SE! Thanks for your answer but we are looking for comprehensive answers that provide some explanation and context. Very short answers cannot do this, so please [edit] your answer to explain how you would do that in the referenced tool. Additionally, we prefer answers to be self contained where possible. If you add more context and detail, it is more likely that people will find your answer useful. – 0scar – 2021-01-07T22:53:46.850

This *really* doesn't answer the question. How does it explain resizing/modifying an object? Explain how to modify/resize in TInkercad, if that is your preferred application. Otherwise, this answer should be considered just SPAM and deleted. – Greenonline – 2021-02-12T12:03:52.323


I would suggest using Blender for this purpose. It has excellent selection tools, you can undo/redo selection and obviously you can resize any portion without affecting the others. However, you may need to learn Blender to an intermediate level to be able to effectively do that.

Cem Kalyoncu

Posted 2016-06-13T18:08:39.310

Reputation: 179