In Laser Material Deposition (LMD), the powder feed into the melt pool is of crucial importance. It has a decisive influence on powder efficiency, geometry and roughness of the layer generated and oxidation by the surrounding atmosphere. For this reason, there is a need to characterize the powder gas jet to ensure process quality. As a solution a machine integrated system was developed, that has the capability to document the particle density distribution. For standardized measurements and comparability of results the procedure is fully automated. In order to measure and capture the required parameters, the powder gas jet is illuminated by a laser line perpendicular to the powder gas stream and observed through the powder nozzle with a coaxially arranged camera. A high frame rate allows the individual powder particles to be captured in number and position. Through step-by-step movement along the powder gas stream, individual layers are recorded in order to reach the particle density distribution with corresponding algorithms. From this distribution, key figures, e.g. position and diameter of the powder focus, can be derived for certification of powder feed nozzles. This information allows the adjustment and wear state of a nozzle to be documented and the processes to be set-up reproducibly. Furthermore the system is used to study the parameters influencing the shape of the powder gas jet. This knowledge can be used for process development, nozzle development and for the production of components with high requirements upon quality.
Laser cladding processing has been used in different industries to improve the surface properties or to reconstruct damaged pieces. In order to cover areas considerably larger than the diameter of the laser beam, successive partially overlapping tracks are deposited. With no control over the process variables this conduces to an increase of the temperature, which could decrease mechanical properties of the laser cladded material. Commonly, the process is monitored and controlled by a PC using cameras, but this control suffers from a lack of speed caused by the image processing step. The aim of this work is to design and develop a FPGA-based laser cladding control system. This system is intended to modify the laser beam power according to the melt pool width, which is measured using a CMOS camera. All the control and monitoring tasks are carried out by a FPGA, taking advantage of its abundance of resources and speed of operation. The robustness of the image processing algorithm is assessed, as well as the control system performance. Laser power is decreased as substrate temperature increases, thus maintaining a constant clad width. This FPGA-based control system is integrated in an adaptive laser cladding system, which also includes an adaptive optical system that will control the laser focus distance on the fly. The whole system will constitute an efficient instrument for part repair with complex geometries and coating selective surfaces. This will be a significant step forward into the total industrial implementation of an automated industrial laser cladding process.
Shorter life time cycles of products, increasing workpiece variety and declining lot sizes demand for a closed processing chain which enables the economic production of variable products in the future. A new type of manufacturing concept for the production of the 21st century is lined out by the design of an "Autonomous Production Cell." Applied to and designed for manufacturing with laser radiation this concept shows completely new ways in comparison to former manufacturing procedures. The manufacturing processes in the Autonomous Production Cell start with a production oriented design and planning of the manufacturing procedure is including sensor controlled processing of the workpieces with integrated quality management. The quality management detects failures in the manufacturing procedure and allows back-coupling to any preceding step by means of a multistage cascaded production controller. In comparison to former concepts the user is at all times integrated into the manufacturing procedure. The user can add his own competence and creativity. At the same time he is being relieved by routine work and gets adequate help by the system in corresponding situations. The design of the components of the Autonomous Production Cell (design and planning tools, networking of sensors and actuators, user interface, etc.) has been performed as general as possible. This offers the possibility to transfer this concept with countable efforts to all the manufacturing with laser radiation such as welding, cutting, surface treatment, freeforming, rapid prototyping, etc.
The usage of a quality management, in combination with a standard certification, is nearly inevitable for today's industrial manufacturing. In laser materials processing, a periodical beam diagnosis is to be executed as a quality-maintaining measure with any change of the workpiece geometry to guarantee an unambiguous allocation of the beam quality factors. Otherwise changes in the beam quality, caused by pollution, aging or defect of the optical components, remain unidentified for a long time, leading to impairments of the treatment quality or even costly down-times. As a solution a diagnosis system is integrated into a laser system. Data sources like measuring instruments, sensors and laser control transmit the diagnosis data to a diagnosis PC. A user-friendly software, based on Fuzzy algorithms, enables the operator to retrace changes in the beam quality to failures of the laser system. All diagnosis data are getting archived in a databank. The access to the archived data through the World Wide Web allows remote diagnoses. With the help of the beam diagnosis system failures can be discovered in advance, and losses of production can be avoided. The gained transparency of the beam characteristic values facilitates the integration of the laser system in the quality management. A prototype installation has been realized and latest results will be demonstrated.
Changes in the laser beam quality caused by pollution, wasting or defects of the optical components and the laser beam source usually only can be detected by time-consumptive methods. Therefore a system is developed to automate and simplify the diagnosis of the laser beam radiation. As a solution a laser beam analyzer is permanently integrated into the laser system, an ergonomic user software is developed and the analyzer, the tooling-machine, and the laser are controlled by one computer. The user of a laser machine is enabled with this system to detect changes in the beam quality in an early state by daily measurements which are easy and fast to be carried out. Failures can be retraced to defects of the laser source, the beam guiding system, and the focussing optics by the use of image processing methods and fuzzy algorithms. Furthermore it is possible to detect stealing changes in the beam mode structure. Within the scope of quality assurance the data can be archived according to EN ISO 900x to be able to assign processing parameters to work-pieces.