New Dimensions in Metrology

Nikon Metrology takes non-contact multi-sensor 3D metrology to the next level, realizing faster investigation and serial inspection by capturing full-part geometry with a single system.

0
642

As components get smaller and more complex, and the demand for high precision rises, manufacturing companies are challenged to produce high-quality products in a shorter time. Relying solely on tactile inspection requires excess overhead in terms of measurement preparation and execution, and it covers only a small portion of the entire part surface. This makes it necessary to use other metrology systems to gather additional geometry information; not exactly the ideal recipe for error-free data consolidation and fast, automated inspection. To overcome this obstacle Nikon Metrology incorporated several of its leading non-contact 3D technologies into one brand-new HN-6060 system.

Instead of getting partial inspection results from different metrology systems, Nikon Metrology combines multiple non-contact 3D technologies in a single inspection system. Equipped with a newly developed high-precision laser scanner measurement head, the HN-6060 system digitizes components at a rate of 120,000 points per second. To access the complex geometry of a spiral bevel gear or any other sophisticated part, the five-axis Coordinate Measuring Machine (CMM) can position the head and tilt and turn the specimen exactly as desired. Furthermore, the multi-sensor head incorporates proven optical image processing with built-in LED illumination, Shape From Focus (SFF), laser autofocus and zoom, and tactile probing. The HN-6060 is designed to acquire and process the full point cloud data of the diverse surface colors and textures of complex automotive molded and machined components, toothed wheels, gears, and medical devices, etc. Figure 1

Higher Accuracy
To ensure its laser scanner met the highest-precision standards required by advanced part manufacturers, Nikon further enhanced its non-contact sensor optics. It achieved unprecedented measuring accuracy by the use of a new cylindrical lens for the laser emitter, and an image-side telecentric optical system which, with high precision, directs the object image to a detector. The hardware mechanism is designed to suppress magnification variations resulting from temperature changes. The hinged optical system allows surface data to be acquired by the CCD with a constant focus. The enhanced CCD, in tandem with the bright optical system, allows glossy as well as low-reflectivity part surfaces to be captured without spraying or other manual preparation. Figure 2

Nikon engineers designed HN-6060 laser scanning optics and motion control with highest precision as the prime objective. Every second the laser scanner captures up to 120,000 points, each at 4 micron accuracy and with a line pitch of 20 micron, to accurately describe the waviness of freeform surfaces and the shape of geometric features. Capturing a multitude of scanned inspection points provides more valuable data than touch-probing a handful of points.

Powerful Video Measuring
To complement 3D laser scanning, the Nikon Metrology HN-6060 features the proven high numerical aperture zoom optical system from the Nikon NEXIV VMR series CNC video measuring systems. This enabling vision technology now exclusively uses LED illumination as well as image processing developed in-house by Nikon. Advanced edge detection by image processing increases measuring speed and confidence. Figure 3

In addition, the system is equipped with the very latest Shape From Focus (SFF) inspection sensor. Using an active texture pattern projection mechanism, the system can perform high-precision shape acquisition for surfaces that are devoid of texture, such as the surface of a mirror, while TTL laser AF enables level difference and profile measurement. To catch the finest details, Nikon optics provide crystal-clear and pinpoint-sharp 15x image magnification.

Managing Measurements
Regardless of the technology used to collect the data, the Nikon HN Metrology software manages the acquisition of point clouds through laser scanning and the SFF sensor. It also integrates a whole range of image-processing and touch-probe-related measurement tasks. HN Metrology software is an evolution in multi-sensor metrology software, based on the dimensional inspection software used on the NEXIV VMR. The software’s intuitive graphics support straightforward setup, macro-based teach-in, quick shape and distance measurement, and insightful 3D part-to-CAD comparison. The optional Focus Inspection software offers the edge in point cloud processing, providing the most detailed analysis and reporting capabilities.

After setting up an inspection routine that involves sampling complex shapes, the HN Metrology software offers a practical way to simulate system operation prior to taking actual measurements. The operation function simulator reads in the CAD model data, and completes the taught measuring process within the software. It is a unique feature that shows how geometry data capturing will proceed, predicts potential collisions, and checks whether full surface coverage will be obtained. The simulator may be run either in on-line mode or off-line mode. Figure 4

Since the HN Metrology software deals with 3D point cloud data, the data can also be used for reverse engineering purposes. This technology is typically utilized to create CAD from handmade clay models, to generate CAD data from existing parts when the original CAD data is missing, to update designs from part surface data produced by high-yield dies and molds, or to serve as input for rapid prototyping of freeform parts and products.

Synchronized Motion Control
The HN-6060 reaches the full potential of non-contact 3D inspection by having a two-axis rotary stage present the part for inspection. The high precision and rigid unit can dynamically apply the optimum rotation and tilt angles to scan around ribs and flanges, and to fully capture pockets, slots and notches. Important in this regard is the concurrent movement of the measuring head, which is optimized by a newly developed high-precision orthogonal drive system. A system console provides easy control over full five-axis synchronized head and specimen motion. It features a straightforward configuration that includes switches for changing between sensors and buttons for carrying out simple inspection. Figure 5

The adoption of five-axis synchronized hardware control is particularly useful for spur, helical, spiral, and other gears. By continuously adapting the orientation of a gear, the HN-6060 is able to fully digitize the faces and flanks of all gear teeth as well as the geometry in between them. Figure 6 As it successfully deals with the most complex gears, the system can accurately and fully digitize any intricate component. This makes the HN-6060 the preferred inspection system for machined (toothed) rotating parts, composites and smaller stamped or cut sheet metal components. It is equally suitable for plastic and metal devices made using (injection) molding or additive technologies, which covers an extensive number of parts used in automotive, aerospace, medical, and manufacturing industries.