Technology Metrology system uses X-rays to root out hidden problems

Editor: Eric Culp

A quality control system from Nikon is said to identify all shrinkage, deformation and dimensional errors with easy-to-understand inspection reports so toolmakers can define corrective actions more easily. This cuts the time to market for new products.

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A look inside a plastic component. Tool and mould makers can take advantage of the technology to drastically reduce correction times during development, according to Nikon
A look inside a plastic component. Tool and mould makers can take advantage of the technology to drastically reduce correction times during development, according to Nikon
(Source: Nikon)

The MCT225 HA combines more than 95 years of Nikon experience in optical metrology, 50 years of LK experience in CMM metrology and 25 years of X-Tek experience in computed tomography (CT), according to the supplier. The MCT225 HA – claimed to be the most accurate in its class – is said to provide high accuracy metrology CT for a wide range of sample sizes and material densities with 3.8+ L/50 µm MPEl accuracy in accordance with the VDI/VDE 2630 guideline.

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Is this the future of dimensional inspection?

The supplier noted that all internal and external geometry is measured efficiently in a single non-destructive process. A full 3D visualization of the sample volume additionally provides valuable insights into part deformations and internal structural integrity. According to Nikon, metrology CT, which fuses metrology and X-ray computed tomography (CT), is poised to become the future of dimensional inspection.

Getting to the core with Röntgen rays

X-rays have long been used for industrial applications. With X-ray CT, a number of 2D X-ray images are taken at different angles around the sample. All of the external and internal geometry is captured as the X-rays pass through the sample. CT software constructs a 3D model of the sample using these 2D images. Dimensional characteristics such as size, position and form can be measured directly using the model as well as full part-to-CAD comparison, section reporting and GD&T analysis.

Nikon explained that for absolute accuracy for internal geometry, the MCT225 HA is set up in the factory using accuracy standards traceable to the UK's national measurement institute (NPL) and verified using VDI/VDE 2630 guidelines for computed tomography in dimensional measurement. The company noted that “absolute accuracy” guarantees measurement accuracy without time-consuming comparative scans or reference measurements; samples are simply placed on a rotary table inside the enclosure and measured.

Point the ‘cool gun’ take the shot

The key component of the system is the in-house developed 225 kV micro-focus X-ray source that is actively cooled for thermal stability. The X-ray “Cool Gun” in combination with the high resolution panel detector produces incredibly sharp images with low noise levels, enabling magnification levels up to 200x.

Another key component of the MCT225 HA is the high-precision manipulator developed in close cooperation with the Nikon development team in Japan. The manipulator guideways are equipped with high-resolution optical encoders and error corrected using the laser interferometer mapping techniques employed for CMMs.

For optimal accuracy and long term stability, Finite Element Analysis (FEA) was used during the design phase to optimize the stiffness of the manipulator. The manipulator is suspended on anti-vibration mounts to eliminate external vibration influences. To minimize thermal effects the interior of the MCT225 HA enclosure is temperature controlled, effectively creating a conditioned measurement room stable to 20C ± 0.1C.

Flexible efficiency for first article inspection MCT255 HA is an invaluable asset for manufacturers seeking to benefit from reduced lead times and inspection cycles, Nikon said. The X-ray source and large capacity manipulator combine with high magnification and detailed feature detection to create a solution suited to a variety of applications.

The advantages for tool and die makers

Plastic injection-mould and metal die-cast manufacturers can significantly reduce correction cycles during tool development and production start-up, accelerating time to market for new products. All shrinkage, deformation and dimensional errors are clearly identified in easy-to-understand inspection reports making it easier to define corrective actions, the company explained.

The system can also check mould components

Emerging production techniques like additive manufacturing now make it possible to produce small and highly complex components that cannot be inspected using touch probes or optical sensors. Here, too, the MCT225 HA makes it possible to measure and analyse these components in a single non-destructive operation, Nikon said.