This paper proposes a new rotary welding torch with a ball-jointed mechanical seal structure that simultaneously realizes the enclosure of CO₂ gas, the energization of welding current, and the insulation for system protection. In order to effectively compare the operation mechanism of the proposed device with the conventional rotary welding torch, a schematic technique is introduced to clearly visualize the operation and connection structure of the model. The kinematic state and constraint degrees of freedom of the tool are clearly shown, and it is easy to distinguish between the two designs that use different component parts and connection structures but result in the same final motion. In addition, the four dynamic characteristics of a rotary torch operating at 20 Hz (driving torque, vibration reaction force, natural frequency, and inertial mismatch) were analyzed to demonstrate superior performance to conventional products. The welding test showed that the tool normally operated even in a harsh welding environment, verifying its applicability in the field.

This paper presents a search methodology for the optimal operational path of robots using a genetic algorithm. The work scheduled to be performed using a robot was characterized. Collision avoidance between the robot including the working tool and the target object was considered. In this study, we followed the general steps of data mining. We compared the time taken by the robot moving along the path created by our proposed methodology with the time taken for the robot along the path created by real humans. The results show that the path generated by this study was more efficient than that of humans.

This paper presents a scheduling problem for a high-density robotic workcell using multi-objective genetic algorithm. We propose a new algorithm based on NSGA-II(Non-dominated Sorting Algorithm-II) which is the most popular algorithm to solve multi-objective optimization problems. To solve the problem efficiently, the proposed algorithm divides the problem into two processes: clustering and scheduling. In clustering process, we focus on multi-robot positions because they are fixed in manufacturing system and have a great effect on task distribution. We test the algorithm by changing multi-robot positions and compare it to previous work. Test results shows that the proposed algorithm is effective under various conditions.

Inconel 718 super alloy was aging heat treated at the temperature range from 675°C to 785°C for 5~40 hours after solution annealing at 1025°C for 1 hour. The aging treated specimens were investigated microstructure, mechanical properties and thermal expansion/contraction. Precipitates appeared for a long time aging treatment were niobium carbide and also γ’ phase. For the aging treatment time of 10 hours, the changes in strength and hardness with increasing aging treatment temperature showed the maximum value at the temperature of 725°C. This maximum value is to be related with the precipitation of γ’ and γ’’ phases. The decrease in strength, elongation and hardness during long time aging at 725°C were thought to be induced from the coarsening of the grain size and the transformation of γ’’ phase to γ’ phase. For the specimens treated for 10 hours, impact energy showed constant value of ~105 J with increasing the aging temperature, however this value continuously decreased with elapsing time at the aging temperature of 725°C. It was found that the decrease in impact value was induced from the coarsening of grain size and the carbide coarsening. The coefficient of thermal expansion of aging treated Inconel 718 alloy increased with raising test temperature, and the coefficient was appeared 11.57~12.09 ㎛/m?°C and 14.28~14.39 ㎛/m?°C, respectively, after heating to 150°C and 450°C.