Modeling and Optimization for Multi-Objective Nonidentical Parallel Machining Line Scheduling with a Jumping Process Operation Constraint

This paper investigates the nonidentical parallel production line scheduling problem derived from an axle housing machining workshop of an axle manufacturer. The characteristics of axle housing machining lines are analyzed, and a nonidentical parallel line scheduling model with a jumping process operation (NPPLS-JP), which considers mixed model production, machine eligibility constraints, and fuzzy due dates, is established so as to minimize the makespan and earliness/tardiness penalty cost. While the physical structures of the parallel lines in the NPPLS-JP model are symmetric, the production capacities and process capabilities are asymmetric for different models. Different from the general parallel line scheduling problem, NPPLS-JP allows for a job to transfer to another production line to complete the subsequent operations (i.e., jumping process operations), and the transfer is unidirectional. The significance of the NPPLS-JP model is that it meets the demands of multivariety mixed model production and makes full use of the capacities of parallel production lines. Aiming to solve the NPPLS-JP problem, we propose a hybrid algorithm named the multi-objective grey wolf optimizer based on decomposition (MOGWO/D). This new algorithm combines the GWO with the multi-objective evolutionary algorithm based on decomposition (MOEA/D) to balance the exploration and exploitation abilities of the original MOEA/D. Furthermore, coding and decoding rules are developed according to the features of the NPPLS-JP problem. To evaluate the effectiveness of the proposed MOGWO/D algorithm, a set of instances with different job scales, job types, and production scenarios is designed, and the results are compared with those of three other famous multi-objective optimization algorithms. The experimental results show that the proposed MOGWO/D algorithm exhibits superiority in most instances.

Safety and Automatization of Machining Line

Abstractthe paper deals with problematic of machining lines of machine components for the automotive industry. There is a current issue of increasing labor productivity and economic efficiency of production with full safety of production and environmental protection. Therefore, for a specific practical assignment, the replacement of existing machinery using manual workpiece handling is performed by a fully automated safety-accessible one. For this purpose, an analysis of the technical and operating parameters of the proposed NC machines has been prepared. Attention is paid to optimization of material flow and arrangement of individual workplaces of production machines including handling and transfer of material between individual workplaces. Particular attention is paid to the safety of workers and improves the environmental conditions of the production plant. Finally, the overall efficiency of the proposed solution is evaluated in detail compared to the current solution.

Design and Implementation of the Circular Saw CNC Machining of the Stone Bridge Cutting Machine

The stone bridge cutting machine is a multi-function processing machine which can saw, mill and grind. The circular saw machining is the most common processing way. This paper introduced the angle calculation method of the circular saw CNC(Computer Numerical Control) machining lines and arcs, focused on the tangential following algorithm of the circular saw, which was that the tool moved along the tangential direction of the circle or arc with the interpolated motion. Meanwhile, combining with the mechanical property of the stone bridge cutting machine, that is, the rotation angle of the C-axis was less than 360 degrees, two kinds of segmentation machining algorithms were put forward. Based on PC & motion control card, using VC++ software, the stone bridge cutting machine CNC system software was developed. By running stone bridge cutting machine CNC system and testing in the factory, the results show that the circular saw machining is stable, and can meet the requirements of the circular saw CNC cutting processing.

Restraint of Thermal Crack on Rake Face of Cermet Tool in Intermittent Cutting

Thermal cracks due to heating-cooling cycles in intermittent cutting in the machining processes of bearing production play an important role in tool life. This paper discusses restraint in the tool failure of TiC cermet used in actual machining line. The purpose of this study is to investigate two effects the appearance of the rake face and variation in the feed rate in thermal cracks on machining lines and to examine the thermal crack mechanism. As a result, we found that tools with some micro cracks were easily damaged. Removing some cracks on the rake face delays thermal crack generation time and reduces the number of cracks. Slightly decreasing the feed rate has a good effect on restraining the occurrence of cracks due to lowering of the cutting temperature.