High-precision distance sensing

The manufacturing industry has a steady need to improve production yields and product quality. Non-destructive on-line monitoring systems have therefore become a prerequisite for many companies to keep a competitive edge.

High end clamping systems of System 3R International have an impressive precision of 0.5µm in their mechanical clamping mechanism.

The project aims at developing a low cost and industrially relevant solution to very accurately determine the position of a workpiece in a robotic manufacturing line. By integrating an optical fiber into the steel chuck and using non-contact optical techniques, the clamping system is enhanced by measuring the absolute position of the work piece within tens of nanometers. The machining process can then be adjusted accordingly to garantee higher manufacturing accuracy.

Generic sensor solution

The fiber optic sensor consists of a broad-band light source, a spectrometer and an optical fiber probe. The solution is generic and is an interferometric sensor that measures the distance to a surface from a fiber end. Three parallel channels can be read with a single interrogating unit.

In this project, the fiber is embedded into the chuck, measuring the absolute position of the work-piece in the machine chuck. 

Several unique features

Compared to other techniques, our concept enables a set of the unique features, including:

  • high-speed: real-time measurements by using a CCD-based spectrometer – no need for scanning interferometers, a measurement spectrum is acquired in one shot and delivers a distance measurement within a few hundreds of milliseconds.
  • in-situ, flexible: optical fiber probes can be embedded in different parts of manufacturing equipments that can otherwise be very difficult to access by other techniques, and can easily be scanned over a sample/manufactured product
  • low-cost: CCD-based spectrometers and low-cost broadband light source make possible production costs in the range of a few tens of kSEK.
  • high-accuracy: despite the use of low-cost components, high resolution (at nanometer level) is achieved thanks to original (patented) signal processing algorithms
  • absolute measurements: the concept provides an absolute value of the distance without any need for external reference surfaces.

The low-cost fiber optic sensing enables efficient production of high precision components, such as high quality optical components, MEMS and micro machined parts for the demanding and fast-changing mobile phone market.

The system enables lower production costs, better quality, and a higher degree of automation.

About the project

Project objective: To develop a system that gives nanometer-precision positioning information in an industrial environment.

Project leader: Acreo Swedish ICT

Project members: Acreo Swedish ICT, System 3R International.

Other: Project is carried out within Acreo Fiber Optic Center.

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