Finding the X-ray inspection sweet spot

High resolution and ease of integration

Balancing trade-offs in quality control

Manufacturing optimization has always been a series of trade-offs. Maximizing throughput must be balanced with employee and equipment safety. Maximizing profits must be balanced with quality raw materials. And so on.

The same is true for quality control processes. Finding the right X-ray source for specific quality control processes can be challenging, particularly when it comes to balancing the requirement for high resolution detail recognition with the need for reliable uptime, fast inspection throughput and the ease of integration into a production environment. All those parameters determine the performance, reliability, and costs of non-destructive quality inspections.

This focus topic explores the challenges and limitations of conventional X-ray tube technologies in providing cost-efficient quality control for battery inspection, for complex casts in the automotive industry, or for large and additively manufactured parts in aerospace. Also introduced is Comet X-ray’s MesoFocus technology which offers a better balance for production lines between resolution, speed and reliability in the NDT X-ray inspection process. 

X-ray inspections are an important tool for many industries, providing a non-destructive method for examining the internal structure and quality of a wide range of products. However, with today’s industrial X-ray solutions, users are facing significant trade-offs when it comes to the key requirements for a reliable and cost-optimized quality inspection.

Limits of conventional X-ray technologies

On one hand, stationary sealed X-ray solutions offer good uptime and are easy to integrate into a production setting, making them a popular choice for inline inspection systems and other applications that require stability, repeatability, and ease of care. However, sealed X-ray tubes are limited in resolution and not well suited for detail recognition below 200 micrometers, which can be a drawback for some applications that require high-resolution imaging. 

On the other hand, open microfocus X-ray modules provide excellent resolution and perform well in research laboratories, making them the preferred choice for applications that require the highest resolution possible. However, these tubes are more difficult to integrate into a volume production environment, and tend to require more maintenance and unplanned repairs, which can lead to downtime. This can be especially problematic in industries where an inspection system is integrated into a production line and that downtime can have costly consequences.

As manufacturing moves towards more advanced materials and components, such as in manufacturing of lithium batteries, complex aerospace components, and large and dense automotive parts, engineers are requiring better inspections with higher resolutions while also maintaining good uptime and improved throughput to reduce liability and maximize profits. For example, in lithium battery applications, faulty batteries can be extremely dangerous, with the potential to catch fire or even explode leading to potentially dire consequences for the public. To reduce risk without sacrificing profitability, it is critical to be able to perform fast and reliable inspection of all produced parts and components to ensure safe products for the end user without increasing the production costs of each part inspected.

The Search for a Better Balance

Is finding a suitable industrial X-ray solution that combines advanced detection of features in the 25-200 micrometer range, with stable operation, and easy integration into a production environment even possible? 

To answer this question, it is first necessary to understand the trade-offs and limitations of the X-ray modules of the past, then to examine some of the more recent advances in X-ray tube technology. 

Finding the right balance for your application

Traditional Mini Focus and Micro Focus X-ray modules

X-ray sources are classified based on the size of their focal spot (Focus). The sealed and metal ceramic isolated Mini Focus technology offers excellent uptime and is easy to integrate into a production setting, making it a popular choice for inline inspection systems and other applications that require speed, stability, repeatability, and ease of care. 

They are best suited for 24/7 operation and can reduce inspection times by up to 60% compared to standard open-microfocus modules. In terms of maintenance, sealed X-ray tubes do not require frequent maintenance and are not sensitive to dust, oily environments, or humidity. The result is less maintenance and service interventions, ensuring an improved uptime and therefore less downtime costs during quality inspection processes.

Micro and Nano Focus X-ray sources offer high and detailed resolution with feature detection down to 0.6 μm. While they may not be suitable for 100% inspection due to their slower speed and shorter service intervals, they are excellent choices for applications that require a high level of detail and accuracy. Micro and Nano Focus technologies are typically used to examine samples of electronic components, advanced semiconductor packaging or microelectromechanical systems (MEMS).

Looking at the characteristics of Mini, Micro, and Nano Focus solutions, it is obvious that there are significant trade-offs to be made when making a choice or high costs involved when integrating both technologies into a single inspection system.

New MesoFocus Technology

MesoFocus technology combines the best characteristics of sealed and open Micro Focus X-ray tubes, bringing lab performance to the production floor with a resolution down to 25 μm allowing high throughput and low downtime which reduces quality control costs in manufacturing.

Achieve better detectability without sacrificing throughput

Resolution capabilities for reliable failure detection in combination with the applicable power (W) that delivers the speed and throughput capacities are the key requirement in many inspection applications. With no doubt, the exact performance of an inspection system is determined by many parameters covering the entire image chain (detector type and resolution, magnification, imaging software, etc.). Nevertheless, standardized focal spot and resolution measurements allow a comparison (Fig. 4) of different systems in terms of the capabilities of X-ray sources.

With its multiple focal spot design (Fig. 2), MesoFocus technology enables the user to define the most efficient balance between detectability of features (double wire resolution) and throughput performance (W), making the technology a versatile and highly efficient solution for many steps in quality controls whether it is fast recognition of high-level patterns or specific details in high resolution.

The focal spot measurements according to ASTM 1165-12 and ASTM E 2002 illustrate the trade-off between resolution and power nicely. The power performance correlates linear with the focal spot size, except for the for focal spots below 100 in the 450 kV X-ray module.

Comparing resolutions

Looking at hands-on application examples, the resolution capabilities and differences can be easily grasped. The example of an electro-mechanical part shows the resolution of a copper coil in a relay (Fig. 3). Thanks to the symmetrical focal spot, MesoFocus delivers identical resolution in all directions.

Resolution performance comparison Meso- vs Open Micro Focus at 225 kV 

The comparison with the pinhole method allows visualization of the resolution capabilities of different X-ray sources (Fig. 4). 
Comparing an open Micro Focus source with MesoFocus technology, it shows little difference below 100µm at the same power ranges. Above 100µm, the resolution capabilities are significantly higher. 

Resolution comparison Meso- vs Mini Focus technology at 450 kV 

Now that the trade-offs between the different systems are understood, a look at a real world application can provide further insight. For years, many industries such as aerospace and additive manufacturing, have been demanding a high-resolution and robust 450 kV solution for DR and CT applications. In addition to high resolution and detail recognizability, there are always other requirements such as quick readiness, high voltage stability, maintenance-free, ease of use, and use without special tube know-how. This is where the benefits of the balance found in MesoFocus technology really shine.

Fit for the future of non-destructive testing

There are several trends in various industries that are driving the need for advanced inspection technologies like MesoFocus

One is the increasing use of automation and artificial intelligence to perform tasks that are faster, more accurate, and/or more reliable than humans. This trend towards automation is leading to the use of advanced inspection equipment in manufacturing processes. For example, in the manufacturing industry, automation and advanced inspection equipment can be used to reduce the number of defects and prevent costly product recalls. In the aerospace industry, advanced inspection equipment is used to ensure the safety and reliability of aircraft components. In the automotive industry, it can be used to identify defects in car part manufacturing and improve the overall reliability and safety of vehicles.

There is also a growing demand for electric vehicles and even electrified air transportation which is creating a large need for batteries in all forms of shapes and sizes. The production of these batteries requires accurate and efficient inspection systems to ensure a safe and reliable operation. MesoFocus technology enables fast and reliable detection of typical defects such as anode overhang, misaligned electrodes, and assembly flaws at the resolution necessary to help ensure public safety.

MesoFocus is a new X-ray technology helping many industries and NDT application experts choose a solution with a better fit for their inspection jobs to be done. It offers an optimized performance package enabling reliable, stable and cost-efficient quality control to provide safe products for users without major trade-offs.