QMT Features: December 2014
Fast and flexible Inline inspection
Laser Radar from Nikon Metrology is an automated, targetless process offering speed and accuracy for automotive inline inspection


Continuously monitoring product and process quality metrics during manufacturing is vital, along with the unrelenting pressure to cut costs and increase quality. Take Body in White (BIW) assembly -- locations of holes, slots, studs, welding lines and other features need verification, not to mention flush and gap verification for door or hinge lines in the Trim and Finish section. Such critical measurements are primarily performed by either horizontal-arm CMMs offline, taking significant extra time, or on the production line, requiring dozens of sensors individually aimed at each of the features that are to be inspected.

Although CMMs provide highly accurate absolute measurements, they require laboratory conditions, only available offline. The vehicle has to be taken from the line, fixtured, aligned in the CMM, and then meticulously measured. At best, two vehicles can be inspected per shift on a CMM. This is a very small sample considering that over 1000 vehicles can be built each day in a single automotive plant.
Traditional inline systems require as many as 100 fixed sensors all individually aimed at vehicle features. These sensors are demanding to install, maintain, and do not result in ‘absolute measurements’ of a car’s coordinate system features. They can only detect presence/absence of the features in a local reference frame, meaning a complete and absolute dimensional check on the vehicle is impossible.  Additionally, most assembly lines now are ‘flexible,’ meaning they can produce more than one type of vehicle. Fixed sensors cannot be used between different vehicles styles; every vehicle requires its own custom set of sensors.
Innovating for inline inspection

The Laser Radar from Nikon Metrology provides an alternative to the shortcomings of traditional inspection methods. The Laser Radar uses a focused laser, controlled by high-precision azimuth and elevation drives. To perform a measurement, Laser Radar only needs a fraction of the laser’s signal to be returned. This gives it the ability to measure almost any surface, including highly reflective bare body panels, shiny painted surfaces, and even transparent headlights, which are very difficult to measure with typical line scanners. Such robust measurement ability means Laser Radar can be used for both BIW in production and flush and gap inspections in trim and finish. Laser Radar also has a large measurement range (up to 50m), allowing it to easily measure objects the size of cars, trucks, and other large vehicles or components.

Laser Radar is a programmable, contactless measurement system and has an accuracy <0.1mm over the volume of a car. It can be fully automated and can directly measure holes, studs, bolts, and numerous other features accurately from a large standoff, eliminating any risk of crashing into the vehicle.
Measuring up to 2,000 points per second makes Laser Radar suitable to not only measure features but also scan surfaces. The ability to program Laser Radar offline makes it ideal for inline inspections; different vehicle models on the same assembly line are simply a new inspection program.

For inline inspection, Laser Radar units are mounted to 6-axis robot arms located on each side of the production line. This type of robot, commonplace in automotive production facilities, is very robust and can easily handle the Laser Radar payload.  The robots automatically position the Laser Radar unit so it can inspect areas otherwise hidden from the line of sight of a single Laser Radar location. For example, the door frame or other body panels could be blocking line-of-sight to some features on the floor pan. Repositioning the Laser Radar unit to an alternate location will make these features visible without the need for multiple sensors.

After the robot repositions the Laser Radar, it automatically measures alignment points on the vehicle or pallet. This occurs each time the robot moves the Laser Radar, guaranteeing all measurements are collected in vehicle coordinates and ensuring measurement accuracy is independent of each robots’ positioning ability.
In each location, Laser Radar can measure dozens of vehicle features. Such measurements can be pre-programmed in the inspection software directly from the vehicle’s CAD model. After initial programming, data collection and reporting is fully automated. Unique inspection scripts can also be written for each vehicle style and model made on the production line, making the Laser Radar inspection station completely flexible. Adding vehicle styles in the future simply means re-programming the inspection plan and does not require any physical changes or new hardware.

Interaction of the Laser Radar, robot, and analysis software are fully integrated; inspections are completely automated and do not require manual intervention during runtime. This improves both speed and quality of the measurements compared to traditional methods.
www.nikonmetrology.com
  
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Rob Tremain Photographer
www.4exposure.co.uk
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