Masanori Miyagi

Adaptive shape control of laser-deposited metal structures by adjusting weld pool size

LMD (Laser Metal Deposition) is a technique used to repair damaged components and directly form three dimensional structures. From the aspect of productivity, improvement of the shape accuracy of the deposit is required to reduce machining process after LMD. Objective of this work is to control the build-up shape by adjusting the weld pool size. Configurations of deposits made with various LMD process conditions were measured in cross section. In addition, the signal intensity of heat radiation, plume emissions and laser reflections from the weld pool was monitored by photodiodes intergrated in laser processing head during LMD process. The results showed a strong correlation between weld pool size and signal intensity of heat radiation. Adaptive shape control system, which consists of in process monitoring system and PID (Proportional-Integral-Derivative) controller using that correlation, was developed to control build-up shape. Due to the liner relationship with weld pool size, laser power was selected ...

Effect of alloy element on weld pool dynamics in laser welding of aluminum alloys

In this manuscript, weld pool dynamics in laser welding of various series of aluminum alloys were investigated by the in situ X-ray phase contrast imaging system. The experimental results showed that metal irradiated by laser was evaporated immediately, which generated the keyhole. Then metal surrounding the keyhole was melted gradually with the heat from keyhole. The growth rate of keyhole depth had a positive linear correlation with the total content of low boiling temperature elements (TCE), so did the keyhole depth and diameter at the stable stage. Longitudinal view area of the molten pool had a negative linear correlation with the thermal conductivity of aluminum alloy. The measured laser absorption rate had the same variation trend with the ratio of keyhole depth to diameter, and the highest absorption rate of 58% appeared in laser welding of aluminum alloy with TCE equal to 2.1%. Violent fluctuation in keyhole shape was avoided in aluminum alloy with TCE lower than 2.1%, where the surface tension and recoil pressure of metal vapor were balanced. To sum up, the effect of alloy element on weld pool dynamics in laser welding of aluminum alloys was firstly quantified in this manuscript.

Development of spatter suppression technology for copper by high speed laser scanner welding

Copper is frequently used as the current-carrying component in such products as batteries, power modules, and industrial motors due to its high electric conductivity. A highly efficient and stable welding method has long been sought for copper because of its low weldability due to its high heat conductivity and high reflectivity of 1-μm wavelength laser light. The objective of this research is to investigate the laser welding phenomena of pure copper and to improve the copper welding quality. A synchronized high speed camera and X-ray observation system was used to observe the weld pool in order to better understand it and the keyhole behavior during welding. It was confirmed that the melt pool ejection involved large spatter due to the enhancement of the inside pressure of the keyhole and a surface void was formed after the melt pool ejection. The large spatter and surface void in copper welding was confirmed to be suppressed by using high speed welding. High speed scanning welding was conducted to improve the welding geometry. The scanning track was circular, and the diameter of the circle and the rotation frequency were changed to investigate the effect of the scanning parameters on the spatter and welding geometry. It was confirmed that the large spatter and surface void was suppressed at a scanning speed of over 500 mm/s. In addition, it was found that the welding geometry can be controlled by adjusting the scanning parameters. The details are discussed in this paper.Copper is frequently used as the current-carrying component in such products as batteries, power modules, and industrial motors due to its high electric conductivity. A highly efficient and stable welding method has long been sought for copper because of its low weldability due to its high heat conductivity and high reflectivity of 1-μm wavelength laser light. The objective of this research is to investigate the laser welding phenomena of pure copper and to improve the copper welding quality. A synchronized high speed camera and X-ray observation system was used to observe the weld pool in order to better understand it and the keyhole behavior during welding. It was confirmed that the melt pool ejection involved large spatter due to the enhancement of the inside pressure of the keyhole and a surface void was formed after the melt pool ejection. The large spatter and surface void in copper welding was confirmed to be suppressed by using high speed welding. High speed scanning welding was conducted to impro...

Adaptive shape control of laser metal deposition by adjusting weld pool size

Laser Metal Deposition (LMD) has been developed for repair of damaged components and for the direct forming of three-dimensional structures. From the aspect of productivity, shape accuracy of the deposit must be improved to shorten the machining process after LMD. The objective of this work is to control build-up shape by adjusting weld pool size. Configurations of deposits made with various LMD process conditions were measured by cross sectional observation. In addition, signal intensity of heat radiation, plume emission and laser reflection from weld pool were monitored by photodiodes integrated in a laser processing head during the LMD process. The results showed strong correlation between weld pool size and signal intensity of heat radiation. An adaptive shape control system, which consists of an in-process monitoring system and Proportional-Integral-Derivative (PID) controller using that correlation, was developed for controlling build-up shape. Due to the linear relationship with weld pool size, laser power was selected as a PID output parameter adjusted by heat radiation signal. Since the target value of heat radiation signal can be changed flexibly during LMD process in our PID control system, deposit shape is successfully controlled as required with sufficient profile accuracy of build-up layers.Laser Metal Deposition (LMD) has been developed for repair of damaged components and for the direct forming of three-dimensional structures. From the aspect of productivity, shape accuracy of the deposit must be improved to shorten the machining process after LMD. The objective of this work is to control build-up shape by adjusting weld pool size. Configurations of deposits made with various LMD process conditions were measured by cross sectional observation. In addition, signal intensity of heat radiation, plume emission and laser reflection from weld pool were monitored by photodiodes integrated in a laser processing head during the LMD process. The results showed strong correlation between weld pool size and signal intensity of heat radiation. An adaptive shape control system, which consists of an in-process monitoring system and Proportional-Integral-Derivative (PID) controller using that correlation, was developed for controlling build-up shape. Due to the linear relationship with weld pool size, las...