To get the best out of 3D printing, it helps if you can design your own parts. In this tutorial series, we will learn to use a free 3D CAD program to do just that. In this episode, we look at situations where a model has already been designed that we want to modify, but the author has not made source CAD available, so all we have is an STL. Onshape has improved its functionality and it’s now possible to add and subtract geometry from STLs and other meshes. We also briefly look at working with a 3D scanned mesh. 0:00 Introduction 3D design for 3D printing Onshape playlist:    • 3D design for 3D printing tutorials   Direct link to create a free account: https://www.onshape.com/en/products/free Source CAD for tutorials: https://cad.onshape.com/documents/b5475ccd1f83733e348c59b0/w/f0f78c61f2ac76b0b03c0692/e/2693d666ff5f1d3749f8b85d?renderMode=0&uiState=62fb0fbda209767dfe1e6bf0 0:46 What we are designing/modifying Ender 3 electronics case video: https://www.youtube.com/watch?v=k83M5H796U8 Ender 3 electronics case on Printables: https://www.printables.com/model/180138-ender-3-all-in-one-universal-rear-electronics-case 1:46 Taking measurements Digital calipers on Amazon : https://amzn.to/3Bu6yjN 2:01 Importing STLs into Onshape 3:24 Taking measurements from the STL 4:23 Sketching on the STL snapping to vertices 6:24 Removing portions from the STL 7:10 Adding parts to the STL 8:18 Limitations and workarounds 9:57 Slicing, and test print 10:38 Modifying a more difficult shape - electronics case Mesh friendly boolean FeatureScript by mbartlett21: https://cad.onshape.com/documents/84d939daceef6a928b8abcba/v/cc61d2dc258bf444bbef75a5/e/7c5dcdb503f7e2f6ddba9d30 12:36 Working with a 3D scanned mesh Thanks to Andy for providing the 3D scan. Buy quality and affordable filament from X3D. Buy 3, get 1 free and a free sample pack with every order: www.x3d.com.au Get Quality Resins from 3D Printers Online. 5% off storewide for Teaching Tech subscribers [Code: tech5] https://3dprintersonline.com.au/ Take a look around and if you like what you see, please subscribe. Support me on Patreon: http://www.patreon.com/teachingtech