65 lines
3.4 KiB
Markdown
65 lines
3.4 KiB
Markdown
## Intro to Reverse-Engineering
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Q. What is reverse-engineering?
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A. Stepping backwards from a finished design, analyzing how it can be re-created, usually for the purpose of modification, enhancement, or re-production.
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Q. Why would we want to reverse-engineer?
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Reverse-engineering is used for far more than simply re-creating commercial products (making a "knock off"). Throughout history, many of mankind's best scientific advances have been the result of reverse-engineering designs from nature.
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In modern times, reverse-engineering has become ever more important. Today many products are intentionally made to break or to become obsolete. For such objects to continue to be useful instead of heading for a land-fill, reverse-engineering plays a vital role, allowing makers to extend the life of their tools and every-day items.
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Reverse-engineering is also an outstanding outlet for creativity and personal expression, allowing creative people to customize and personalize the items we carry with us every day.
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In this third lesson of Practical Printing we will walk through a reverse-engineering exercise based on a common device - a tablet.
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### Reference Images
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Reference images are vital for reverse engineering and can be obtained any number of ways. We will focus on two methods - a 2D scanner, and a camera.
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#### 2D Scanner
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The big advantage of using a scanner is that items scanned will be preserved at accurate scale when we attempt to use them in a CAD software.
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Of course the down-side of a 2D scanner is that many objects will not fit properly in the scanner so it's use may be limited.
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#### Camera
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Using a camera allows us to take a wide variety of reference images. But there are a significant number of disadvantages as well:
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* Lens distortion - ALL photographic images suffer from lens distortion, and the smaller the lens the more they tend to distort. This can play havoc with the accuracy of reverse-engineering.
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* Orientation - it is difficult to orient objects relative to a camera in a way that provides good reference surfaces.
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* Shadows, tricks of light, etc. - These can all make it difficult to cleanly re-create designs.
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### Exercise 1: Reference Images
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We will use a combination of techniques involving both the scanner and a camera.
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* Scan the two faces of the ipad
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* Using a level, set up a shoot for the other surfaces of the ipad including the bottom, top, and sides
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### Exercise 2: Photographic Editing
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We will prep our images before bringing them into modelling software. This is important, as it is virtually certain that the images will have a certain amount of rotation in them, along with the lens distortion. Use Inkscape to remove rotation in the scanned images, and clip them.
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The images taken by camera will not know their scale, and so they will need to be fixed in scale along with rotation. (They should not have a perspective problem, provided the images were taken at perfect level)
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### Exercise 3: Reference Images in CAD
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Learn to bring images into FreeCAD and orient them on their correct planes. In Inkscape, a common graphic/vector editing software we will learn to:
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* Rotate Images
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* Create a clipping mask
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* Scale a clipped image
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* Export a corrected image
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### Exercise 4: Modelling
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Learn to model using the photographic reference material. Topics covered include:
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* Multi-body modelling
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* Use of the "additive pipe" (also known as a sweep)
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* Using boolean operations (for cutting out ports)
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* Cloning bodies
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* Slicing bodies as prep for printing |