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SENSOR APPLICATIONS IN ADVANCING ADDITIVE MANUFACTURING

18-08-2019
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Controlling the distance of the print head

Additive manufacturing, generally referred to as 3D printing, has become prominent in the manufacturing industry as it is a cost-effective and flexible manufacturing technique in comparison with traditional manufacturing processes. The technological advancement in additive manufacturing has revolutionised the manufacturing industry with its design-driven approach and rapid prototyping capabilities.

The technology has proved to be beneficial to a wide range of industry sectors by offering distinguishing benefits such as reducing material usage and manufacturing automation. These allow for the manufacturing of highly complex structures at a higher production rate and improved production efficiency. The technology is highly utilised in series productions and by OEM suppliers to create distinctive profiles based on new and custom geometries, faster development cycles and the ability to meet sustainability goals.

The medical industry has become the pioneer of this technology by adapting bioprinting for creating 3D printed organs from human cells. These organs will be utilised in medical research for the development of accurate, targeted and more personalised treatment solutions to treat patient-specific illnesses. It is also theoretically possible to create viable and fully-functioning organs from 3D printing; however, there is still a long way to go to achieve that breakthrough.

In the transport and building industries, 3D printing offers an opportunity for cheaper and more efficient manufacturing methods compared with traditional manufacturing. 3D printing has been widely used in rapid prototyping applications as it is a cost-effective solution in product testing. Recent developments in 3D printing have observed a need to expand into creating functional structures and components that are more specific and objective-driven, in order to drive more value to the business.

Considering the rapid advances in additive manufacturing, it is undeniable that sensors should be implemented as part of the system to improve the customised products in terms of functionality, preciseness and quality.

Specialising in sensors and instrumentation, Bestech Australia offers a wide selection of precise and high-performing displacement sensors from Micro-Epsilon for applications in additive manufacturing, such as laser sensors, laser profile scanners, inductive eddy-current displacement sensors and capacitive measurement systems. These non-contact sensors are well-suited for a wide range of industrial measurement applications due to their ability to provide accurate and reliable results on different components or surfaces. They can also be easily integrated with existing industrial interfaces.

Surface contour/edge detection in laser cladding

Laser cladding or laser metal deposition is a manufacturing technique of applying powder substances to modify and enhance the surfaces of an object. The powder is sprayed into the protective gas stream and melted with the help of a laser. This technique has been widely used in surface coating and the development of innovative alloy materials in advanced laboratories.

Sensors are used to control the trajectory of the deposition tracks to ensure that the products are manufactured with the highest precision.

Laser profile scanners can detect the contour, profile and edges of an object with high accuracy. They can be used to determine the welding path by taking the profile before the deposition. The resulting profile is used to determine the guidance of the weld head.

They can also be used to monitor the thickness of the coating during the deposition process. As the laser is used to metallurgically bond the coating material with the base material, certain imperfections may occur. Laser profile scanners typically have a high scanning resolution to reliably detect these anomalies during the deposition.

Quality monitoring and inspection

Success in the manufacturing industry is all about quality and efficiency. A reliable monitoring system is needed to check the quality of printed products to ensure that they meet the reuqired standards. Blue laser scanner technology can be used for this monitoring application. The generated 3D images are compared with the CAD data in the computer, and a logic control can be used to accept or reject the products based on the comparison.

Blue laser profile scanners have an operating wavelength near that of the ultraviolet range. Due to the short operating wavelength, the laser projected from the sensor does not penetrate the object deeply. Therefore, blue laser scanners offer higher resolution and better accuracy with conventional laser profile scanners. Examples of applications include the monitoring of small components, surface etching or embossment depth.

Distance control of the print head

Adjusting the distance of the print head is crucial in ensuring the quality of the final product in additive manufacturing. In 3D printing applications, the print head has to be positioned at an exact height for a flawless process. It is necessary to ensure that the print head is always positioned at the same height at all times. A non-contact laser triangulation sensor offers high precision and a high-speed measurement for this type of application. More importantly, laser sensors are typically small and compact, which makes them easy to be integrated with machinery. The sensors can also compensate for surface reflection and against different materials.

As an example, the exact height of the print head is crucial in the assembly of printed circuit boards, to enable smooth progress during printing, soldering and parts assembly. In addition, the laser sensor can also reliably detect the thickness of the glue bead, which is generally applied on the soldered circuit to protect it from damage. The head positioning also directly affects the final quality of the printed products. Laser triangulation sensors typically offer fast distance measurement up to 4kHz. This enables the system to readjust the process when errors are detected.

High-precision position monitoring

In selective laser sintering, a laser is used as a power source to solidify the powdered material into a compact form. During the process, the building platform is lowered with every melt cycle by a defined value which corresponds to the required print resolution. An inductive eddy current measurement system can be used to monitor the building platform to ensure that the print head is aligned in parallel.

Unlike laser-based displacement sensors, an eddy current sensor is more suitable for this type of application due to the environment. Eddy current sensors are robust and resistant to oil, dirt, dust and extreme environments such as high pressure or high temperature. They are also miniature in size, which makes them ideal to be integrated with industrial plants and machinery. Eddy current sensors are one of the most advanced non-contact technologies in the market for measuring displacement and position in an industrial environment due to their robustness, high precision and excellent frequency response.

In another application, sensors are also needed to monitor the position of a squeegee blade, which is commonly used in a 3D printing system to ensure repeatable and consistent printing quality. The blade moves over the powder bed and applies the next powder layer to the component design on the assembly space. It needs to be tilted at a precise angle in order to spread the material evenly on the building platform.

Two synchronised, high-resolution sensors at each end of the blade are needed to measure its exact tilt angle. Capacitive displacement sensors are recommended for monitoring the position of the blade as they can measure accurately with sub-nanometer resolutions. The sensors are connected to a multi-channel controller, making it ideal for synchronous detection of multiple sensors for measuring at multiple locations. It also has a high-frequency response for dynamic and high-speed measurement, which is ideal for this type of measurement. This system is ideal to be used for long-term measurement in a clean environment.

Summary

Although there is a wide range of precision sensors available in the market, there is no sensor that can be used in all measurement applications. Selection of a suitable sensor depends largely on the operating environment and the type of surface material to be measured. When applied correctly, the industry will reap the benefits of additive manufacturing, which will further accelerate growth in the field.

Bestech Australia
03 9540 5100
www.bestech.com.au

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