Steffen Bonss

Precise hardening with high-power diode lasers using beam-shaping mirror optics

Heat Treatment is one of the most promising application of multi kilowatt high power diode lasers. Providing a sufficient beam quality HPDLs have the advantage of their high efficiency comparing to Nd:YAG-lasers. Application of scanning mirror optics for multi kilowatt lasers is well known at CO2- or Nd:YAG-lasers. Fraunhofer IWS has developed a special driver unit, which generates automatically an optimized scanning function to provide a stress adapted intensity profile. Know the application of this technology at multi kilowatt high power diode lasers has been implemented successfully. Using 2.5 kW diode laser power hardening tracks of 30 mm in width and a penetration of about 1 mm are possible. Applying the temperature guide laser power controller LompocPro additionally, stress adapted hardening of edges with varying cross sections became possible. Besides hardening this system allows heat treatment with a rectangular beam of 5 x 85 mm2. Some applications show the performance of this technology.

Laser heat treatment with latest system components

Laser beam heat treatment has been established during the last years as a complementary technology for local hardening treatment tasks at tool manufacturing, automotive industry and many others. Especially new high power diode lasers and a lot of process supporting systems, what have been developed in recent years, are responsible for the increase of industrial laser hardening applications. The short course starts with information about the basics of laser heat treatment. After that a review about suitable lasers and recommended systems for reliable and well adapted laser heat treatment processes is given. Examples of last ten years transfer of laser beam hardening into industry are presented and discussed.

New developments in high power diode laser welding

Welding thin sheet metal with high power diode lasers closes the feed rate gap between conventional techniques like TIG- or plasma-welding and CO2- or Nd:YAG-laser welding. Because of its size a high power diode laser can be integrated in common mobile linear welding devices. The weld seams are narrower comparing to TIG-welding, even with filler wire. Deep penetration welding with filler wire is performed with a lower heat input if a high power diode laser is used. That minimizes distortion and refinishing. Some applications for mobile use of high power diode lasers are presented. Heat treatment of conventional or laser beam welded carbon steel or TRIP-steel sheets is used to avoid cracking. High power diode lasers are well suited for that task. Surface temperature controlled post heat treatment of crack sensitive welds is presented in the paper.Welding thin sheet metal with high power diode lasers closes the feed rate gap between conventional techniques like TIG- or plasma-welding and CO2- or Nd:YAG-laser welding. Because of its size a high power diode laser can be integrated in common mobile linear welding devices. The weld seams are narrower comparing to TIG-welding, even with filler wire. Deep penetration welding with filler wire is performed with a lower heat input if a high power diode laser is used. That minimizes distortion and refinishing. Some applications for mobile use of high power diode lasers are presented. Heat treatment of conventional or laser beam welded carbon steel or TRIP-steel sheets is used to avoid cracking. High power diode lasers are well suited for that task. Surface temperature controlled post heat treatment of crack sensitive welds is presented in the paper.

Integrated heat treatment – Comparison of different machine concepts

Heat treatment of machine components or automotive parts traditionally is done at separate facilities or companies. Very effective manufacturing becomes possible if heat treatment processes can be integrated in line to avoid logistics and to save time and money. The need of qualified heat treatment experts prevents manufactures from applying heat treatment technologies so far. Laser heat treatment is very suitable for integration in production lines. And with a certain amount of hard- and software tools it becomes possible to decrease the barrier of applying heat treatment in production lines. A short overview over latest developments of these tools is given. In the framework of governmental supported and industrial projects a wide variety of solutions have been installed during the last years. A comparison gives answers which concept suites best for different conditions of for instance mass production and or single part manufacturing.Heat treatment of machine components or automotive parts traditionally is done at separate facilities or companies. Very effective manufacturing becomes possible if heat treatment processes can be integrated in line to avoid logistics and to save time and money. The need of qualified heat treatment experts prevents manufactures from applying heat treatment technologies so far. Laser heat treatment is very suitable for integration in production lines. And with a certain amount of hard- and software tools it becomes possible to decrease the barrier of applying heat treatment in production lines. A short overview over latest developments of these tools is given. In the framework of governmental supported and industrial projects a wide variety of solutions have been installed during the last years. A comparison gives answers which concept suites best for different conditions of for instance mass production and or single part manufacturing.

Monitoring of high power diode laser sheet metal welding

Welding thin sheet metal in the 1 mm range with high power diode lasers closes the feed rate gap between conventional techniques like TIG- or plasma-welding and CO2- or Nd:YAG-laser welding. This was presented by Fraunhofer IWS at former ICALEO events. Applying sheet metal welding with high power diode lasers for industrial manufacturing raises the question of monitoring full penetration. Two sensor principles have been investigated concerning their suitability at welding nickel base alloy sheets in a controlled shield gas atmosphere. A special shield gas chamber for high power diode laser applications has been applied to avoid any oxidation of the weld. Optical emission spectroscopy and an infrared sensitive camera delivered promising results each. Both sensor principles are an approach for future optimized welding sensors.Welding thin sheet metal in the 1 mm range with high power diode lasers closes the feed rate gap between conventional techniques like TIG- or plasma-welding and CO2- or Nd:YAG-laser welding. This was presented by Fraunhofer IWS at former ICALEO events. Applying sheet metal welding with high power diode lasers for industrial manufacturing raises the question of monitoring full penetration. Two sensor principles have been investigated concerning their suitability at welding nickel base alloy sheets in a controlled shield gas atmosphere. A special shield gas chamber for high power diode laser applications has been applied to avoid any oxidation of the weld. Optical emission spectroscopy and an infrared sensitive camera delivered promising results each. Both sensor principles are an approach for future optimized welding sensors.

Fast and innovative determination of parameters for steel hardening with high-power diode lasers

Laser Beam Hardening with High Power Diode Lasers is presented as an excellent method for local heat treatment and minimum distortion. An overview is given about several strategies for local heat treatment and different industrial applications. Precise measuring and controlling of the surface temperature makes the process very reliable and is an essential tool for industrial users. To keep a constant penetration of the hardening zone at constant surface temperatures the feed rate can be adapted to local heat flow conditions. A former postprocessor of Fraunhofer IWS generates a CNC-program for the treatment and changes the feed rate in dependence of the surface shape. The new processor additionally considers local heat flow variations of a part caused by boreholes, grooves and changing local thickness. The processing is very fast and can be applied for solving daily problems of laser beam hardening. Some examples show the performance of the new postprocessor.

Computational process parameter optimization for laser beam transformation hardening

Laser beam transformation hardening is rapidly growing in popularity as a method to achieve high quality surface hardened zones. At the same time, the complexity of the parts and the requirements are increasing. Currently a direct calculation of the hardening parameters is only possible on very basic geometries, therefore an experimental approach is almost always used instead. But cost and time considerations, as well as rising demands on quality and process stability, make it unavoidable to explore new ways to determine the process parameters.This paper presents a new approach to find the parameters semi-automatically. The approach, a self-optimizing finite differences method (FDM) simulation, was pinpointed as the most promising method in a former investigation. To prove its applicability, a new software package was developed to calculate the feed rates for laser hardening on two-dimensional shaped parts. Several differently-shaped work pieces with complex geometries (complexity as seen from a hardening-process point of view) were used for testing. The results from the simulation were applied on real parts to evaluate the quality of the parameter prediction. The tests showed not only a good agreement of the simulation with reality, but also that the automatic parameter calculation was able to find suitable process parameters as required.Laser beam transformation hardening is rapidly growing in popularity as a method to achieve high quality surface hardened zones. At the same time, the complexity of the parts and the requirements are increasing. Currently a direct calculation of the hardening parameters is only possible on very basic geometries, therefore an experimental approach is almost always used instead. But cost and time considerations, as well as rising demands on quality and process stability, make it unavoidable to explore new ways to determine the process parameters.This paper presents a new approach to find the parameters semi-automatically. The approach, a self-optimizing finite differences method (FDM) simulation, was pinpointed as the most promising method in a former investigation. To prove its applicability, a new software package was developed to calculate the feed rates for laser hardening on two-dimensional shaped parts. Several differently-shaped work pieces with complex geometries (complexity as seen from a hardening...

Local laser heat treatment of stainless steel at very high speed

Laser beam heat treatment has been established during the last years as a complementary technology for local hardening treatment tasks at tool manufacturing and automotive industry. Especially new high power diode lasers and a lot of process supporting systems, what have been developed in recent years, are responsible for the increase of industrial laser hardening applications. But heat treatment is more than hardening. Even local softening in some cases is necessary to improve formability at a specific area of a part while the mechanical properties of the remaining part are kept untouched. The presentation gives examples where local softening of stainless steel components for medical and electrical applications is done at very high speed. A specific measuring and control system has been developed for such processes what is indispensable for reliable industrial processes.Laser beam heat treatment has been established during the last years as a complementary technology for local hardening treatment tasks at tool manufacturing and automotive industry. Especially new high power diode lasers and a lot of process supporting systems, what have been developed in recent years, are responsible for the increase of industrial laser hardening applications. But heat treatment is more than hardening. Even local softening in some cases is necessary to improve formability at a specific area of a part while the mechanical properties of the remaining part are kept untouched. The presentation gives examples where local softening of stainless steel components for medical and electrical applications is done at very high speed. A specific measuring and control system has been developed for such processes what is indispensable for reliable industrial processes.

Laser beam hardening – Energy efficient heat treatment?

Laser beam hardening has been established during the last years as a complementary technology for local heat treatment tasks at tool manufacturing and automotive industry. Especially new high power diode lasers and a lot of process supporting systems, what have been developed in recent years, are responsible for the increase of industrial laser hardening applications.In the context of energy saving and green house gases the question about consumption of electrical energy at manufacturing of any product is asked more frequently. Application of any kind of heat treatment process will be evaluated according its energy consumption increasingly. Premise, of course, is a comparable qualification of the considered part concerning the behavior in application. After a fundamental comparison of laser heat treatment and more conventional heat treatment processes several examples will give concrete data for a comparison. These examples are industrial applications where laser heat treatment and conventional heat treatment have been or are still used for hardening of identical parts. The very high efficiency of modern high power diode lasers and the comparable low heat input are pros for low energy consumption of such processes if laser hardening can fulfill or beat the demands of the application.Laser beam hardening has been established during the last years as a complementary technology for local heat treatment tasks at tool manufacturing and automotive industry. Especially new high power diode lasers and a lot of process supporting systems, what have been developed in recent years, are responsible for the increase of industrial laser hardening applications.In the context of energy saving and green house gases the question about consumption of electrical energy at manufacturing of any product is asked more frequently. Application of any kind of heat treatment process will be evaluated according its energy consumption increasingly. Premise, of course, is a comparable qualification of the considered part concerning the behavior in application. After a fundamental comparison of laser heat treatment and more conventional heat treatment processes several examples will give concrete data for a comparison. These examples are industrial applications where laser heat treatment and conventional heat treat...

Camera based system for laser beam online monitoring

Surface hardening with high power diode lasers has been developed to an industrial accepted process in the last years. The multiple adoption of this complex process in the industrial environment makes great demands on process control, safety und simplification. To meet these demands a special camera based monitoring system has been developed. This system is able to monitor many laser beam characteristics during the hardening process online, which creates new options regarding the process quality control. Furthermore typical commercial high power diode lasers emit two different wavelengths superposed to one beam. For a proper verification of the beam characteristics the system can measure each wavelength separately in real time. It is possible to acquire and control laser beam shapes, which are generated, e.g., by a scanning system. As sensor a low cost camera is used. All parameters like accuracy, resolution and the measured spectrum are adaptable to the specific requirements. The system can be integrated very easily in existing hardening systems and is controlled by software. The state of the development of this system is demonstrated on typical applications.Surface hardening with high power diode lasers has been developed to an industrial accepted process in the last years. The multiple adoption of this complex process in the industrial environment makes great demands on process control, safety und simplification. To meet these demands a special camera based monitoring system has been developed. This system is able to monitor many laser beam characteristics during the hardening process online, which creates new options regarding the process quality control. Furthermore typical commercial high power diode lasers emit two different wavelengths superposed to one beam. For a proper verification of the beam characteristics the system can measure each wavelength separately in real time. It is possible to acquire and control laser beam shapes, which are generated, e.g., by a scanning system. As sensor a low cost camera is used. All parameters like accuracy, resolution and the measured spectrum are adaptable to the specific requirements. The system can be integrated...