Reverse Engineering for Dummies

More and more often in the world around us, we can encounter the term "Reverse engineering" (abbreviation RE) - that is, reverse engineering in Czech. If you don't know what it is about, or you have an inkling but would like to gain a deeper understanding, then this article is just for you.

What is reverse engineering?

This is a process where we need to build a data model back from an already existing object, which completely describes the given object for future re-production. This term can be found in many industries. For example, even in medicine - a new type of virus will begin to spread among people - in order to create the right antibody, it is necessary to completely map what the virus consists of and how it behaves. Subsequently, an effective defense substance can be created.

In our case, however, it is a conversion of an already existing part back into computer form. We carry out reverse engineering even if we measure the part with classic gauges (with calipers, tape measure, angles...) and build the part again in the CAD system based on these values. 3D scanning finds its application here if the part to be measured is more complex in shape or contains many elements that must be measured. The time saving is then noticeable and the accuracy higher. After the scan, we also have the data stored on the PC and can return to it regardless of whether we still have the physical part.

How does reverse engineering with 3D scanning work?

We scan the part that we need to recreate for subsequent production or archiving using a 3D scanner. In this way, we get its 1:1 form in digital form - on a computer. However, the scanned part is created using a triangular polygon mesh. The recording format is most often STL. Changing this triangular network directly is very difficult, often almost impossible. Therefore, the scanned part must be re-modeled using parametric elements that can be modified and easily changed.

Subsequently, using a suitable program, we remodel the part into parametric elements using sketching and functions such as extension, lofting, dragging, etc. A so-called CAD model is created, which we can further modify and work with. Once the model is built in the computer, we can change its size and individual dimensions.
The time required to re-create a CAD model that can be further worked with and, for example, remanufactured, depends on the shape complexity of the given part. Size doesn't matter. It can often take 5x longer to create a model for a 5cm part than for a 3m part.

What is the precision in reverse engineering?

This question is always very difficult to answer. The resulting model is formed by the sum of several deviations, and this then forms the resulting inaccuracy. Although these deviations differ from the real part, they also form a model that is suitable for new production. The total deviation is therefore composed of:

• 3D scanner accuracy: No 3D scanner captures a real shape exactly. There will always be a small but countable deviation.
• Part Remodeling: The biggest deviations are loaded here. We need to convert the scan to parametric elements. For example, if we scan a flat surface, it is never flat on the scan. We make it straight during modeling and proceed further. The walls will be perpendicular to this area, etc. Here, it depends a lot on how much the given part is worn and how much we have to repair it to its ideal condition. The second example is openings. The part has a drilled hole with a diameter of 10. Already during the production itself there is a deviation and the hole is made with a diameter of 10,04 mm. It also wears over time and we will scan it and it will be 10,08mm in diameter. In the new model, however, we will want to correct the hole and make the diameter equal to 10 mm. This is a deviation from the scanned shape, but an approach to the correct state. Many arise during the modeling of these situations.

Finally

Reverse engineering is a huge help. It helps to remanufacture parts that no one makes anymore or that are in short supply. Very often these are parts from damaged machines, spare parts for veterans or re-production of discontinued products for which the documentation has been lost. Of course, it can also be used in combination with 3D printing for smaller projects at home (e.g. a broken cap).
The more complex the shape of the part, the longer the time required to process the data in the computer itself. For example, only statues can be scanned and directly 3D printed. Tenths don't matter here.