Adaptive-feedrate interpolation for parametric curves with a confined chord error

Recently, modern manufacturing systems have been designed which can machine arbitrary parametric curves while greatly reducing data communication between CAD/CAM and CNC systems. However, a constant feedrate and chord accuracy between two interpolated points along parametric curves are generally difficult to achieve due to the non-uniform map between curves and parameters. A speed-controlled interpolation algorithm with an adaptive feedrate is proposed in this paper. Since the chord error in interpolation depends on the curve speed and the radius of curvature, the feedrate in the proposed algorithm is automatically adjusted so that a specified limit on the chord error is met. Both simulation and experimental results for non-uniform rational B-spline (NURBS) examples are provided to verify the feasibility and precision of the proposed interpolation algorithm.     

Comparing and combining off-line feedrate rescheduling strategies in free-form surface machining with feedrate acceleration and deceleration

Off-line rescheduling feedrates based on changing surface geometry in free-form surface machining could reduce machining time, increase tool life, and improve surface finish quality. Various feedrate rescheduling strategies have different feedrate rescheduling control parameters. These parameters could be chip thickness, metal removal rate (MRR), or resultant forces. The paper compares these feedrate rescheduling strategies in machining time and feedrate changes. Machining time could be reduced significantly if appropriate values are set for those control parameters. Further, various strategies are combined for better results in two ways: the minimum and the maximum feedrate combination. Machining time could be reduced with both feedrate combinations. The minimum feedrate combination could protect machining against excessive chip thickness, MRR, resultant force, or other conditions that may occur using only one of these rescheduling strategies. The maximum feedrate combination could further reduce machining time with a loose control on those conditions. The paper also points out that advantages of feedrate rescheduling may not been in real if distances between neighboring cutting locations are too small for the machine to arrive at rescheduled feedrates in sharply changing cutting directions and feedrates. The method to calculate real feedrates and machining time is provided in consideration with feedrate ac/deceleration.     

A model for integrating process planning and production planning and control in machining processes

The goal of process planning is to propose the routing of a previously designed part and results in a sequence of operations and their parameters. It concerns and requires detailed information about the process. The goal of production planning, on the other hand, is to schedule, sequence and launch the orders introduced on the routing sheet into the job-shop according to the enterprise's strategic goal and the actual conditions of the production plant. The goals, information and decisions taken in process planning and production planning and control are often very different and, because of that, it is very difficult to integrate them.

The objective of this work is to develop a model that can be applied in the future to the development of an integrated process planning and scheduling tool using an integrated definition (IDEF) methodology to design an activity model, which integrates process and production planning in metal removal processes. An activity model will be used to develop a system that allows the user to plan the process and the production at the same time in collaborative engineering work. To design the activity model, a wide range of parts were evaluated and processed in an actual job-shop factory. Several activities were developed in detail to be tested in real cases, and an example of one of them is introduced in this article.