How Do 3D Scanners Work?

Capturing The Small Details with Structured Light Scanning

Recently, we wrote about the benefits of capturing the world around you with 3D scanners technology. Now, with the recent release of the Peel 2 CAD-S, an optimised version of the Peel 2 CAD for smaller objects, isn’t this a good opportunity to write about the other side of the 3D scanning spectrum? In other words, this post would be what you’d call its brother article, an article about the benefits of structured light 3D scanning. So, what is 3D scanning technology?

The 3D Scanners Technology

3D models are becoming one of the most versatile and useful pieces of data in this increasingly digitalised world. A 3D object offers many advantages when it comes to solutions where simulation, visualisation, analysis, manufacturing, and documentation are just some examples. On the other hand, a 3D scanner enables the user to create, from a real object, a virtual replica; in other words, a digital twin.

We can describe a 3D scanning workflow in these essential steps:

1. 3D scanners capture point data based on XYZ coordinates and colour
2. A registration software processes the data into a final point cloud  format
3. Creating mesh formats by point connection

To capture point data, there are mainly four methods                            

1. Photogrammetry: By overlapping many photographs around an object, a software application can determine coordinates via triangulation
2. Laser: 3D scanners emits a laser beam that, upon bouncing from the object’s surface, a sensor defines the collision distance. Laser scanners are powerful tools, but very expensive. However, more affordable products like the Leica BLK360, for instance, are offering optimum price-performance ratios.
3. CMM: Coordinate measuring machines use a probe that enters into contact with a part surface to create precise geometric and measurement data.
4. Structured Light: A projector emits light patterns that deform upon reflecting from the object. Then, one or more cameras recognise 3D geometries through triangulation algorithms.

Now that we have a broader idea of what 3D scanners do, let’s focus our attention on why the structured light scanner is particularly advantageous.

Structured Light 3D Scanners and the Importance of Digital Metrology

As digitalisation permeates into manufacturing and metrology processes, structured light 3D scanners technology is becoming the new standard. In fact, its unique fringe projection technology is ideal for short-range and highly accurate applications, making it optimal for feature detailing.

A wide projection area enables these 3D scanners to register over 2 million measurements per second with micrometric accuracy. As a result, outcome 3D mesh resolution allows replicating almost identical geometries from the physical object. Structured light scanning is highly dependable on the following aspects:

• Light source (White light or blue light; DLP, LCD or Laser)
• Pattern type (Stripes, grids, among others)
• Camera performance and camera distribution
• Software

All these factors enable countless iterations and a broad spectrum of possibilities for any particular set of requirements; in other words, this level of versatility leads to a vast structured light scanners catalogue in today’s market.

So, why structured light scanners are crucial in today’s market? The answer is metrology. Metrology for quality control and reverse engineering purposes in manufacturing processes have become crucial aspects of engineering standards. For these purposes, analogical precision instruments like callipers, micrometres, gauge blocks and kits, fixtures and magnifying glasses have been commonplace usage for many decades. However, traditional tools require experienced labour and lots of time, not to mention their lack of flexibility geometrically speaking.

Structured-light scanners, on the other hand, offer all these functionalities integrated into one single device while generating complex freeform digital geometries in an instant and without even touching the part. Moreover, many industries are implementing robotics as a means for closed-loop automatic scanning processes.

Key industries benefiting from structured light 3D scanners are:

• Aerospace
• Defence
• Automotive
• Medical
• Entertainment
• Archaeological documentation and studies

We’ll focus now on two main uses of metrology: Quality control and reverse engineering.

Structured Light for Quality Control

According to ISO 9000, quality control is “A part of quality management focused on fulfilling quality requirements”. It has its origins in the 1920s, a time when an increase in compliance regulations, tolerance requirements and competitivity drove manufacturers for ways to optimise verification processes and repeatability. In today’s industry, inspection processes comprise significant investments and lead times in design, implementation and execution. There are even specialised outsourcing services with top-grade equipment, just for quality inspections.

Luckily for us, measurement technologies are developing incredibly fast! As a vital part of this tendency, structured light 3D scanners can generate fast measurements with exceptional precision. But maybe the best part is its ease to integrate into digital workflows directly and in-house.

Many software analysis tools enable colour mapping comparisons. The process comprises of aligning the scanned geometries with the nominal CAD model, generating numerical and visual representations of local deviations throughout the part’s geometry. Consequently, engineers can engage in fast, efficient and highly communicable GD&T decisions via data management and visualisation.

Structured Light for Reverse Engineering

Similarly to quality inspection, structured light scanners are ideal for reverse engineering processes. In Essence, the reverse engineering process consists of acquiring design features and parameters from a finished product; in other words, inputs from outputs. So, why reverse engineering? Engineers can benefit a great deal from digitalising legacy parts, researching existing designs to implement resulting criteria into their own design processes, study part performance and failure causes, and much more. For more information on reverse engineering, check this article.

Structured Light Scanners vs Other Technologies

To better understand structured light 3D scanners performance among the whole 3D scanning spectrum, let’s make some comparisons.

Laser scanning technologies are ideal for surveying processes. Contrary to structured light scanners, laser scanners, especially time-of-flight, can register kilometric-range outdoors with tightly lit environments. Despite working at much shorter ranges, structured light scanners tend to be faster and more accurate, more affordable, and more suitable for small-to-medium object scales with intricate details.

Photogrammetry can deliver exceptionally accurate results indoors, outdoors and regardless of range. However, it strongly relies on many factors like camera resolutions, heavy post-processing power, illumination settings, textured surfaces, and, most importantly, very skilled and experienced users. If you’re looking for a more efficient, faster, consistent, real-time registration and a faster learning curve, structured light scanning is the obvious choice.

Lastly, CMM probing. It’s impossible to deny the influence that CMM has in current high-end inspection processes. These machines are incredibly accurate, automatable and clean. Nonetheless, this system works on contact, which is not suitable for soft, elastic and very small parts. CMMs are also extremely dependant on fixturing and run the risk of either damaging the probe or the part. In contrast, structured light scanners do not even touch the part.

CMMs can be very slow regarding speeds due to their point by point scanning, while structured light scanners work with entire areas per second. As a result, CMMs can’t even hope to capture point clouds as dense as structured light. Shiny, smooth, transparent and dark matte surfaces are problematic for non-contact 3D scanners in general. Perhaps the most significant advantage that contact scanners have over non-contact scanners is this. Thankfully there are ways of overcoming this issue by adding targets or applying talcum powder or primer spray.

Peel 2 CAD-S: Scanning the Smallest Features

Peel3D, a subsidiary company of Creaform, specialises in developing affordable handheld 3D scanners. Although not as potent as their Creaform counterparts, Peel3D is one of the few companies responsible for making professional quality 3D scanners more accessible. Something fascinating about this Peel3D is that it began with the Peel 1 model, which subsequently evolved into the rest of the catalogue. The Peel 2 is a more potent iteration, while the Peel 2 CAD ads extra connectivity into reverse engineering software solutions. The latest variation is the Peel 2 CAD-S, which adapts to tinier scales and finer details.

Peel 2 CAD vs Peel 2 CAD-S: Key Differences

Let’s see in what way these 3D scanners differ by comparing their main parameters.

As seen in the table, we can clearly notice that it all amounts to scale. While the Peel 2 CAD can deal with objects as big as 3 meters, the Peel 2 CAD-S is better suited for parts as small as 5cm. All in all, they complement each other very well… In fact, they come together in a bundle for a special discount price!

Software & Connectivity

These handheld scanners produce models at 550000 measurements with real-time visualisation tools. Once the model is ready, Peel3D software offers specialised editing tools for quick and efficient reverse engineering workflows. After finishing editing, a wide selection of export formats like STL, OBJ, DAE, TXT, and FBX are available, but the best part is that this software can also generate IGES, STEP and DXF. With solid part files like IGES and STEP or drawing files like DXF, working with scanned data inside CAD software like SolidWorks becomes a highly efficient process.

For more of a practical approach to understanding what comprises the Peel 2 CAD-S, watch this video covering essentials like workflows and best practices.

If you want to learn more about structured light scanners or if you’re looking to make the best choice on which 3D scanner is the most suited for you, SolidPrint3D is here to help you. For more information, please call SolidPrint3D on 01926 333 777 or email on info@solidprint3d.co.uk.