Virtual Shop Clusters – A New Layout Concept for a Ship Repair and Maintenance Facility

Brian Mayer, Shahrukh Irani, Hosni Adra

Abstract

Organic ship maintenance facilities and depots of the Navy are mostly organized as trade-specific shops rather than by product (or process) families. For example, welders are in the weld shop, machinists are in the machine shop, pipe-fitters are in the pipe shop, etc. There is a belief that this guild-type organizational structure is what enables a repair facility to do almost anything, albeit at the cost of moving product all over the “factory.” This skill-based organizational structure is identical to the functional (or department) layout that is preferred by most jobshops in the commercial manufacturing sectors. But, any company that has successfully implemented Lean Thinking has almost always replaced a Functional (or Process Village) Layout by a Cellular Layout. At the Navy's Southeast Regional Maintenance Center (SERMC), a typical repair job must visit multiple shops that pass work back and forth between them. For example, a pipe job may be sent by the pipe shop to the machine shop for re-threading, then routed to the weld shop where it is welded to a frame, after which the welded sub-assembly returns to the pipe shop for inspection and final assembly. Thereby, significant delays and operational wastes occur because people have to walk between the shops, discuss matters at daily production meetings, and e-mail/phone each other to make sure that their schedules match. If activities are not completed as per schedule, the jobs get further delayed because they queue at the shops, waiting to be served. This lack of detailed (and accurate) planning and scheduling, combined with poor schedule visibility and shop floor control, is the curse of the Functional Layout that currently exists at SERMC. This paper will describe a pilot project to assess the feasibility of cellular manufacturing at SERMC. The fundamental hypothesis that was tested is that even in a repair and maintenance facility there could exist several families of repair jobs where jobs grouped into a family require similar combinations of processes, equipment, materials, etc. that can be provided by a small group of shops. In fact, several potential families of repair jobs, and the appropriate cluster of shops for each family of repair jobs, were identified using the Production Flow Analysis and Simplification Toolkit (PFAST) software. Based on these results, it was decided to implement a shop cluster (or focused factory, or repair cell) to complete any repair jobs done by the dive shop. It was recommended that the dive shop be merged with a few other shops, and be provided the necessary tools, cross-trained personnel, equipment, and other support systems to become an autonomous multi-function shop. Simulation using the SimCAD software from CreateAsoft Inc. (http://www.createasof.com) was used to verify the results expected from making the proposed changes. The primary analysis was intended to evaluate the benefits of implementing a focused factory in the dive shop. The secondary analysis was intended to evaluate the advantages of implementing a virtual shop cluster (or focused factory, or repair cell) in any ship repair facility like SERMC. The simulation results showed that implementing either physical cells or virtual cells based on the different families of repair jobs identified by PFAST could improve job turnaround times at any Navy ship repair facility like SERMC. Both the types of delays as well as the time values of these delays differed significantly across the existing and alternative shop configurations that were proposed.