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Enhancing Additive Manufacturing with Reverse Engineering

Reverse engineering is a powerful tool for additive manufacturing, and the combination of both can greatly enhance product design as well as shorten the product development cycle. Whether you need to manufacture a legacy part that has no digital model or a spare part for replacement, reverse engineering has many benefits to bring to the table. A range of industries such as aerospace, automotive and medical are already leveraging the benefits of reverse engineering alongside AM, with significant time and cost savings. 

What is reverse engineering?

Typically, when designing an object from scratch, a design engineer will produce drawings detailing how the object should be constructed. In contrast, reverse engineering involves the opposite approach: the designer engineer starts from the end product, working backwards through the design process to reach the original design information. In theory, any object can be reverse engineered, whether it is a mechanical part, a consumer product or even an ancient artefact.

How does reverse engineering work?

To begin the reverse engineering process, you will typically start by measuring the object’s size and shape. This can be done manually but, particularly for industrial applications, the use of 3D scanning has increasingly become more commonplace. The data relating to the object’s design specifications is then converted into a digital CAD file. At this point, the digital model can be converted to STL, optimising it for 3D printing.  

Why use reverse engineering?

There are several reasons why reverse engineering is a useful manufacturing technique. For example, are you an automotive supplier that needs to produce spare parts, but lack the CAD data? Reverse engineering can be used to obtain the required specifications so that rare spare parts can be reproduced using 3D printing.

Additionally, reverse engineering is beneficial when you need to make improvements to an existing object, but don’t have its digital model. In this instance, reverse engineering allows you to  scan the object and make in-process design changes, resulting in significant time savings.

3D scanning: the natural companion to 3D printing

The traditional process of manually measuring an object to reverse-engineer it can be very time-consuming, as it requires various  devices such as callipers or slip gauges to both measure and draw the shape and size of a component before replicating it into a CAD program. Fortunately, we’ve seen impressive advancements in reverse engineering technology, allowing for  a faster, more accurate solution: 3D scanning.

As the digital representation of an object is the backbone of 3D printing, 3D scanning offers an efficient digital solution when there is a need to reverse engineer old parts for replacement or parts without existing CAD models. Combining 3D printing and 3D scanning methods presents significant advantages to engineering applications requiring high accuracy and shorter product development times.  

3D scanners are devices used for 3-dimensional measurement and allow capturing data of the physical object quickly and precisely to create “point clouds”, which are then rendered into digital 3D representation.

3 3D scanning techniques

The key to successful 3D scanning  is to measure your object with a sufficient degree of accuracy in order to capture the details necessary for an adequate replication. To achieve this there are a few 3D scanning options which can help to create a 3D model almost immediately ready for 3D printing.

 

1. Photogrammetry

The method of photogrammetry is based on photos, taken from different angles around an object and then “stitched” together with the help of special software to digitally replicate a physical object. However, photogrammetry requires a studio setting, since this technique involves a complex system of cameras, which can be difficult to set up and is not easily portable. Additionally, digital 3D models made with photogrammetry usually cannot compete with light-based 3D scanning in terms of accuracy and level of detail.

 

2. Light-based 3D scanning

There are two common types of 3D scanners, falling under the category of light-based 3D scanning:  structured-light and laser scanning. These scanners come in a variety of sizes with both handheld and stationary options available.

  • A structured-light 3D scanner projects the light pattern of parallel stripes onto the surface of an object. The camera on the scanner then captures this projection, which is subsequently translated into a digital replica. Structured-light 3D scanners are capable of high level of detail, although are typically used for small objects.

 

  • In contrast, laser scanning works by projecting a laser beam on the surface of an object which is reflected from the surface. The cameras on the scanner then capture the angle of reflection and translate it into coordinates of an object, which are used to generate a 3D model. This method enables free-form objects and intricate details to be scanned, making laser scanning one of the most accurate forms of 3D scanning.

BMW Group is one manufacturer currently using  blue light 3D scanners as well as photogrammetry to reverse-engineer and then additively manufacture spare parts for their customers.

 

3. CT scanning

Computed tomography (CT) scanning is another scanning method that can be applied in additive manufacturing for reverse engineering. CT scanning involves several X-ray projections through an object, creating images which are then combined to form a digital 3D model. CT scanning is particularly unique in that it provides data not only on external but also internal structures. As it is increasingly important to be able to predict and establish the structural integrity, residual stress and other parameters with 3D printed components in order to maintain their performance this capability is important to establish the structural specifications of a part. CT scanning has particularly found its niche in medical applications — for example, CT scans can be used to produce 3D-printed models of human organs, helping surgeons to prepare for complex surgeries.

Reverse Engineering and additive manufacturing: Use Cases 

Technologies like 3D scanning help to integrate reverse engineering into the additive manufacturing workflow, giving manufacturers across industries a vialbe solution for specific engineering challenges.

One example of this is in the production of 3D printed prototypes of aerospace obsolete parts. Roc-Aire, a contract manufacturer for aerospace parts, scans legacy aircraft parts before 3D printing  them for fit check and evaluation of design and function. Such a solution not only helps to speed up project development but also leads to  more effective final results.

Within the medical sector, the integration of reverse engineering and additive manufacturing is crucial for solving complex medical cases. For example, back in 2016, the Royal Hospital for Sick Children used 3D scanning and 3D printing  for ear reconstruction surgeries. With the help of a structured-light 3D scanner doctors were  to scan the unaffected ear and 3D print a polymer prototype, used  as a template for reconstruction.

Another example can be found in the automotive industry, where reverse engineering, along with  SLS technology, has been used to create a space-optimised air inlet for a racing motorbike. In this case, the use of reverse engineering and SLS has made a huge difference in reducing the time needed to realise the  project.