1,305 research outputs found
Good Production Cycles for Circular Robotic Cells
In this paper, we study cyclic production for throughput optimization in robotic flow-shops. We are focusing on simple production cycles. Robotic cells can have a linear or a circular layout: most classical results on linear cells cannot be extended to circular cells, making it difficult to quantify the potential gain brought by the latter configuration. Moreover, though the problem of finding the best one part production cycle is polynomial for linear cells, it is NP-hard for circular cells. We consider the special case of circular balanced cells. We first consider three basic production cycles, and focus on one which is specific to circular cells, for which we establish the expression of the cycle time. Then, we provide a counterexample to a classical conjecture still open in this configuration. Finally, based on computational experiments, we make a conjecture on the dominance of a family of cycle, which could lead to a polynomial algorithm for finding the best 1-cycle for circular balanced cells
An analysis of cyclic scheduling problems in robot centered cells
Cataloged from PDF version of article.The focus of this study is a robot centered cell consisting of m computer numerical control (CNC)
machines producing identical parts. Two pure cycles are singled out and further investigated as
prominent cycles in minimizing the cycle time. It has been shown that these two cycles jointly
dominate the rest of the pure cycles for a wide range of processing time values. For the remaining
region, the worst case performances of these pure cycles are established. The special case of 3-machines
is studied extensively in order to provide further insight for the more general case. The situation where
the processing times are controllable is analyzed. The proposed pure cycles also dominate the rest when
the cycle time and total manufacturing cost objectives are considered simultaneously from a bicriteria
optimization point of view. Moreover, they also dominate all of the pure cycles in in-line robotic cells.
Finally, the efficient frontier of the 3-machine case with controllable processing times is depicted as an
example
Scheduling in a three-machine robotic flexible manufacturing cell
Cataloged from PDF version of article.In this study, we consider a flexible manufacturing cell (FMC) processing identical parts on which the loading and unloading
of machines are made by a robot. The machines used in FMCs are predominantly CNC machines and these machines are flexible
enough for performing several operations provided that the required tools are stored in their tool magazines. Traditional research
in this area considers a flowshop type system. The current study relaxes this flowshop assumption which unnecessarily limits the
number of alternatives. In traditional robotic cell scheduling literature, the processing time of each part on each machine is a known
parameter. However, in this study the processing times of the parts on the machines are decision variables. Therefore, we investigated
the productivity gain attained by the additional flexibility introduced by the FMCs. We propose new lower bounds for the 1-unit
and 2-unit robot move cycles (for which we present a completely new procedure to derive the activity sequences of 2-unit cycles
in a three-machine robotic cell) under the new problem domain for the flowshop type robot move cycles. We also propose a new
robot move cycle which is a direct consequence of process and operational flexibility of CNC machines.We prove that this proposed
cycle dominates all 2-unit robot move cycles and present the regions where the proposed cycle dominates all 1-unit cycles.We also
present a worst case performance bound of using this proposed cycle.
2005 Elsevier Ltd. All rights reserved
Cyclic production in regular robotic cells: A counterexample to the 1-cycle conjecture
Robotic cells consist in a flow-shop where transportation of the parts between machines is handled by a robot. We consider cyclic production of identical parts and optimization of the cell's throughput. Production cycle of 1 part are easier to describe implement and there is a conjecture about their dominance. This conjecture has been studied for linear layout cells, for which the 1-cycles are well known, but not for cells with circular layout, where the input and output buffers are at the same position. We provide a counterexample to the conjecture for this case
An analysis of pure robotic cycles
Ankara : The Department of Industrial Engineering and the Institute of Engineering and Sciences of Bilkent University, 2008.Thesis (Master's) -- Bilkent University, 20068Includes bibliographical references leaves 84-87.This thesis is focused on scheduling problems in robotic cells consisting of a
number of CNC machines producing identical parts. We consider two different
cell layouts which are in-line robotic cells and robot centered cells. The problem
is to find the robot move sequence and processing times on machines minimizing
the total manufacturing cost and cycle time simultaneously. The automation in
manufacturing industry increased the flexibility, however it is not widely studied
in the literature. The flexibility of machines enables us to process all the required
operations for a part on the same machine. Furthermore, the processing times on
CNC machines can be increased or decreased by changing the feed rate and cutting
speed. Hence, we assume that a part is processed on one of the machines and
the processing times are assumed to be controllable. The flexibility of machines
results in a new class of cycles named pure cycles. We determined efficient pure
cycles and corresponding processing times dominating the rest of pure cycles in
the specified cycle time regions. In addition, for in-line robotic cells, the optimum
number of machines is determined for given parameters.Yıldız, SerdarM.S
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