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New Modular Production System Architecture to Combine Flexibility a nd Productivity

Exploitable results

The aim of the project is to define a new architecture for a manufacturing system that is able to provide a better answer to the dichotomy of productivity versus flexibility. In particular the project addresses itself to the hardware and software solution to manage the flow of tools, parts and information inside the manufacturing facility while seeing all this as a system. It proposed new hardware modules for the pallet exchange and transport, the tool exchange and transport, and software modules for the implementation of non-linear process plans and for the subdivision of machining operations between the workstations of the system. The main technical objectives of project were: - A detailed definition of the system reference architecture; - The test bed to evaluate its performance; - Detailed specifications of requirements, conceptual designs and implementation of prototypes for innovative tool and pallet transport devices; - Investigation of non-linear process plans for machining operations; - The development of a suite of software tools to simulate and to evaluate the performance, to configure and to manage the proposed architecture. Globally, the project reached its expected results, even if we experienced some problems to achieve the required performances for the pallet transport system. MFP is a modular system comprising general purpose NC machine tools and innovative automated handling devices to manage pallets and tools to produce a large number of different part types in large volumes; in this system parts are processed by a subgroup of NC machine tools. The main features of the new architecture are: - MCs have at least three numerically controlled axes; - Only one part is mounted on the fixture; - Fixtures have small dimensions, depending only on the part dimensions; -MCs are identical machines; -Each MC can have a buffer of one or more positions (Active Pallet Stand) in which pallets wait for the availability of the MC; -The Tool Room is the central tool storage. Each MC has a tool storage, named local magazine, containing from 15 to 40 tools. The Tool Carrier can bring tools from the Tool Room to local magazine, and vice versa, and from a local magazine to another one. A part can be processed by a single MC or by more MCs. In the first case the part flow is similar to that of FMS's; in the last case MC's represent the stations of a mini-line in the system : parts move from a MC to another one as in a transfer line. The number of MC's of the mini-line depends on various factors such as : volumes, number of operations, contact time for each operation, number of tools, availability of the MC's, availability of the tools, etc. The Carrier must guarantee high speed and acceleration; it is a module that can be used to transport parts or tools. In the proposed architecture there are two carriers, a part carrier and a tool carrier. Active Pallet Stand is a module that can exchange the part from other adjacent APS's in short time. Part programmes are not managed as rigid sequences but they are decomposed into many single operations, connected by precedence relations due to various technological constraints; this increases a lot the flexibility of the system.