Production synchronization for fixed-position assembly islands under graduation intelligent manufacturing system

Abstract

The layout of fixed-position assembly islands (FPAI) is widely used in the heavy equipment industry. It is normally adopted when products are too bulky or fragile, i.e., ships, aircraft, locomotives, big milling machines, and heavy-duty laser equipment. In such configuration, workers move from one workstation (island) to another, while the product normally remains at one workstation for its entire manufacturing (assembly) period with required materials and equipment/tools are moved to the workstation. The layout of FPA is not only suitable for producing bulky or fragile products, but also offers considerable flexibility and operational efficiency for production with medium/small variety and volume. With the unique production operations as well as the increasing customized demands, manufacturing practitioners are plagued by long production lead time, too frequent setups, delay of shipping deadlines, and high work-in-process (WIP)/finished product inventory levels in FPAI. The dilemmas impel manufacturing practitioners to re-evaluate their current production and operations management strategies in FPAI. This thesis presents a concept of production synchronization as a new production and operations management strategy in the era of Industry 4.0, and explores how to achieve synchronized operations to overcome the above dilemmas with four related scenarios in FPAI. The first scenario presents an overview of Graduation Intelligent Manufacturing System (GiMS) for FPAI with reduced complexity and uncertainty. Inspired by graduation ceremony, a novel manufacturing mode Graduation Manufacturing System (GMS) with three kinds of distinct functional tickets is designed to organize and manage production operations in FPAI. Industrial Internet of Things (IIoT) and digital twin technologies are deployed for transforming GMS to GiMS with real-time visibility and information-sharing. The key characteristics of GiMS are discussed and a prototype of GiMS for FPAI is developed in the lab. The second scenario investigates the synchronization of production and delivery with time windows in FPAI under GiMS. The IIoT-enabled GiMS is developed for achieving real-time operational visibility in FPAI. Under GiMS, consider customer requirements and production constraints, a coordinated decision-making model of production and delivery with time windows for FPAI is developed. An industrial case from a laser equipment manufacturing company is carried out to validate the effectiveness of the proposed approach. The third scenario studies the synchronization-oriented reconfiguration of FPAI under GiMS. This work extends GMS with ticket-based reconfigurable structures for the reconfiguration of FPAI. Under the IIoT and digital twin-enabled GiMS, a synchronization-oriented reconfiguration mechanism is proposed to achieve synchronous interactions among changing customer demand, island configuration, and production activities allocation rapidly and cost-effectively. An industrial case from a laser equipment manufacturing company is carried out to validate the effectiveness of the proposed approach. The fourth scenario studies the synchronization of shop-floor logistics and manufacturing in FPAI under GiMS. Four pillars include synchronization-oriented GMS, digital twin-driven synchronized information-sharing reference model, real-time ticket pool for synchronized decision-making and synchronized operations with cloud-based ticket services, are proposed for achieving shop-floor logistics and manufacturing synchronization in FPAI. An industrial case from a cutting tool manufacturing company is carried out to validate the effectiveness of the proposed approach.