Self-optimizing Assembly of Laser Systems

  Laser Systems Copyright: Cluster of Excellence Integrated Production Technology for High-Wage Countries

Photonic technologies play an important role in industrial production with increasing relevance. Short product life cycles require improved and novel solutions for the production of laser systems which are capable of meeting the demands regarding mass customization.

 

Practical Issues

Laser Systems Copyright: Cluster of Excellence Integrated Production Technology for High-Wage Countries

Customer-specific requirements and relatively low production volumes between one and a thousand units per year are characteristic of the production of micro-optical laser systems today. Versatility leads to a high degree of manual processes for assembly and thus leads to rising product costs. Therefore manual processes claim up to 80 % of the added value of such a laser. In a few cases automated solutions have been installed. Rigid automation concepts can only be economic for high-volume production. Rigid automation is based on the dominating imperative programming paradigm which requires the manual planning and storing of all decision points that can possibly occur during assembly and respective process steps of handling, alignment and bonding. Product variance – and even scaling the production – usually leads to massive re-programming efforts for the stored complex decision points and can also leads to a modification of the used hardware. The demonstrator for self-optimizing assembly of laser systems validates methods which intend to increase flexibility of assembly systems and to allow economic production of low-volume production.

 

Approach

Laser Systems Copyright: Cluster of Excellence Integrated Production Technology for High-Wage Countries

For decreasing assembly costs, manual assembly shall be replaced by flexibly automated processes. The efforts for planning and commissioning of processes on the assembly platform need to be reduced. An increase of the degree of autonomy reduces the need of implementing decision points in an imperative manner. Self-optimization is applied in order to achieve the goals. A self-optimizing production system is characterized by the ability of detecting tolerance chains, finding optimization patterns and compensation strategies which allow an automatic reaction to changes in external influences and adapt own behaviour to new situations. Adaptation capabilities include the change of behavior (structure or logic of internal state machine). Due to this flexible use of the production system a reduction of setup times occurring to the change from one product to another increase the production flexibility.

 

Technical Challenges

Laser Systems Copyright: Fraunhofer IPT

High flexibility is only possible if production tools provide standardized interfaces with regard to hardware and software interfaces which allow fast re-configuration and easy change of the control program. The task is to provide interfaces which serve as a common standard, while not limiting future applications, and at the same time are easy to implement. Flexible production processes need to be specified in a flexible manner so that optimization
potential can be realized. Especially the demanding field of laser assembly requires the use of simulation models during production in order to optimize the optical function of the system. Simulation-based approaches need to be capable of compensating for work piece tolerances and limited machine accuracy. A core challenge is the mapping of measured data into simulation models. Robots with large work space as well as ultra-precise micromanipulators need to be integrated in the control architecture. Calibration plays an important role in order to link the real world with the world of simulation models. Tolerances can be exploited in order to compensate for abberations by dynamically changing the order of assembly and applying tolerance matching techniques. This requires the characterization of individual parts and their influence on the optical quality. The process of engineering self-optimizing control requires novel methodologies in order to minimize costs for software development.

The demonstrator will realize industrial assembly processes by applying new approaches. One focus is the assembly of collimation optics for diode laser systems, which are used to parallelize diverging laser beams, as they occur in diode laser systems. Such elements require the highest precision to six degrees of freedom covered by a micromanipulator developed in the first phase of the project. The complexity of tasks requires the use of model-based and self-optimizing control. The integration of sensor technology and intelligent evaluation algorithms are able to map reality to models during assembly and to compensate for possible deviations dynamically. Active alignment is carried out operating the laser source based on online sensor data. Novel concepts regarding the analysis of measurement data used for beam shape characterization are applied. The demonstrator consists of an assembly cell at Fraunhofer IPT, as well as a robot cell for measurement development at the Chair for Technology of Optical Systems, which are continually enhanced by new concepts. Through the distributed nature of the demonstrator, the transferability of software architecture is demonstrated.