Reverse Engineering Article

Beginners guide to the reverse engineering process for product design.

Reverse Engineering is the process of taking a real world item or product back to its base design intent. When we say design intent we mean the original nominal design level, ready to manufacture.

Reverse engineering is becoming more and more common with the advent of new technologies and techniques.

In reality, the reversed engineering process has been used for a long time. It is just the techniques used that have changed. Prior the to the digital revolution in the design process a product will have been measured using a number of different common tools and then those measurement were used to create a 2D paper drawing which would of included all the manufacturing and package constraints.

However, this methodology had a number of serious flaws which modern technology can overcome and give the designers and engineers a lot more flexibility and control. The main issues / flaws with the traditional method are accuracy and freeform shape capture. Modern reverse engineering techniques are able to capture items, both very small to very large at very high levels of accuracy, but the major drawback was the inability to capture uncontrolled freeform shapes in full detail.

The modern reverse engineering process includes a number of technologies to overcome these flaws. It is common now for most if not all products that are to be manufactured to be designed on a computer aided design system (cad). The reason for this 3D approach is to allow a number of follow on or allied processes to use the same data, such as CFD, FEA, CNC milling etc. There is a plethora of design software available to the user. All are useful to one level or another. As with most things the general rule of thumb is that the more you pay for the software the better and wider the capability range. There are many cad software packages which allow you to competently design geometric shapes extremely well but there are still only a very few which really allow you to explore full freeform shape control to any level allowing you to supply the highest quality results.
The other facet of reversed engineering is 3D scanning, this is probably the most recent a crucial part of the reverse engineering process. 3D scanning technology allows us to capture the full 3D form of any shape and this is particularly crucial in the area of uncontrolled freeform shapes. In the product design arena of reverse engineering the two types of 3D scanning technologies that are used are structured light and laser scanners. As with the design software there are a range of scanners on the market. It is important to choose the correct scanner for the desired outcome.

The typical reverse engineering process consists of

1-    Assessing the part to be scanned and preparing it to get the best results. This may include, depending on the scanner used, the application of target markers and the treatment of any see through or reflective finishes.
2-    3D Scanning the part to be scanned including a period of post processing. As most scanners are fully portable this can be done almost anywhere.
3-    3D cad modeling. The scan data is imported into our design software and is used as reference allowing us to recreate all the design intent of the freeform shapes. We can also impose / incorporate any manufacturing conditions such as angle of draw and draft angles as well as accommodate any package conditions / constraints.

The process above allows us to deliver a shape / design representative 3D digital model in a file format ready for any amount of onward engineering possibilities, particularly manufacture.

The reasons for reverse engineering a product are many fold. Examples of two applications are.

1.    A part has been made for a number years using a mould tool. The tool is wearing badly and there is no drawing available, either 2D or 3D cad model. We can both scan the tool or the component and thereon follow the reverse engineering process above.
2.    A part has been developed (changed) in the tool or in its assembly / package condition. The 3D cad model or 2D drawings have not kept up with these changes and they cannot be quantified. Again we can scan the tool, component or both and again thereon follow the reverse engineering process above.

File formats.

3D scan data is not the friendliest to use and many types of software are still not comfortable with using it. And when all said and done the scan data is only a reflection of the part scanned. This is not necessarily the design intent.
The sort of information released from a 3d scanning process is called a polygon mesh model. A typical file type would be a .STL file.
When we follow the full reverse engineering process and reproduce a full 3D cad model the resultant cad models will either be a full surface model constructed of either Bezier or nurb surfaces and typically released as an iges or step file. There is also the possibility of providing a solid model which provides a fully editable parametric model.

Keep an eye on this blog for details of projects completed.

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