Journal of Mechanical Working Technology最新文献

The trend toward factories of the future, indicates that world class manufacturing systems will have no more than 20 highly productive machines with an automated material handling system. These factories will operate in Just-In-Time mode under computer control. The machines, in general, will be more versatile. It is also expected that by the year 2000, cutting speed will be up to 10 times faster than today's standards.

Reduced lot sizes will dramatically increase the demand on material handling; cooperative workstations will have to be close to each other.

The numerical control code will not be generated until the specific routing for a certain order is known. A typical factory order will require only a few units up to less than a hundred. Every order will be produced in exact quantity Just-In-Time for shipping, hence with no inventory.

We strongly believe that the virtual cell concept, extensively documented by McLean, etc., and others, will meet the requirement for the factory of the future. This concept has the potential for making flexible manufacturing systems (FMS) even more efficient, because of its inherent capability for sharing resources. Contrary to the group technology cell configuration, a virtual cell is not identifiable as a fixed physical grouping of workstations, but as data files and processes in a controller. Upon selection of a job order, a virtual cell controller is created. The controller takes over the control of a set of workstations capable of processing the job for which they have been selected. This temporary grouping of workstations is called a virtual cell. Once all resources have been requested and awarded, processing can begin. Parts are moved from workstation to workstation similar to a flow line sequence.

We have extended the virtual cell concept proposed by McLean and we have developed a scheduling algorithm that permits the creation of virtual cells and schedule them under workstations and tools availability constraints. Equally important, the algorithm is characterized by its polynomial time complexity. The size of the model grows quickly, but linearly, and remains reasonable for a typical size factory. It is efficient enough to be executed in real time for scheduling any virtual cell based system within hundred of seconds with current computer technology.

The scheduling model has many advantages that makes it suitable for scheduling factories of the future. Firstly, it permits consideration of critical tools. Secondly, it provides a quick reaction to unexpected events. Finally, it enables a coherent planning of resource utilization, potentially reducing possibilities of delays and deadlock, which are very common in fast pace manufacturing systems.

The behaviour of certain tool material and work material combinations with respect to penetration rate and tool wear under the influence of different parameters in ultrasonic drilling are discussed in this paper. The observations include penetration rate, tool wear, geometrical inaccuracy of the drilled hole, surface finish and influence of working conditions on the drilling forces.

The advent of CAD/CAM system, robotics simulator and off-line programming tools has provided a significance contribution to advanced manufacturing technology. A natural progression would be to integrate these computer aided tools with a robotics workcell within a flexible manufacturing system, FMS. Such an integrated approach is currently developed within GINTIC for the assembly of modular fixtures in its intelligent flexible manufacturing system, IFMS for the machining of complex shape components. This paper describes the configuration and development of this system. The functions associated with each modules within the integrated robotics off-line programming system will be also elaborated.

A systematic approach of designing Cellular Manufacturing Systems (CMSs) in three steps is presented in this paper. The first step is the implementation of group technology techniques which provides tools to group similar parts into a family and corresponding machines into a manufacturing cell. The second step is the scheduling of each family parts which generates an efficient method of arranging the facilities of each cell. The next step is developing a flexible system and integrating the production planning and control processes. This can be achieved by using KANBAN and decoupler between manufacturing processes.

The efficiency of empirical studies aimed at establishing the cause-and-effect relationships between the manipulable parameters of a manufacturing process and the resultant measurable process behavior can be greatly enhanced by the appropriate application of experimental design methodologies. Some techniques of selecting suitable experimental parameter settings in the face of certain special process characteristics and operational constraints are discussed in this paper with particular reference to fractional factorial designs.

This paper describes the analysis and design of a robot platform with two drive wheels, each with an independent steering mechanism resulting in three independent degrees of motion. The kinematic and inverse kinematic analyses are derived in detail. An adaptive controller is designed to compensate for large inertial variations and to satisfy the velocity (nonholonomic) constraints.