by Rajan Suri and Ananth Krishnamurthy
In today’s marketplace, there is increasing demand for customized products, either through customers choosing from a large menu of options, or even through companies custom-engineering products for individual orders. Manufacturers that have to supply such high-variety or custom-engineered products are struggling to implement effective material-control strategies on the shop floor.
These companies are finding that lean manufacturing concepts such as flow, takt time and pull/kanban systems are not meeting their needs. POLCA (Paired-cell Overlapping Loops of Cards with Authorization) is a material-control system designed with these situations in mind. It is a hybrid push-pull system that combines the best features of card-based pull (kanban) systems and push (MRP) systems. At the same time, POLCA gets around the limitations of pull systems in high-variety or custom-product environments as well as the drawbacks of standard MRP, which often results in long lead times and high WIP.
POLCA was developed as part of the overall strategy of Quick Response Manufacturing (QRM), which focuses on lead time reduction throughout the enterprise. In partnership with its member companies, the Center for Quick Response Manufacturing has implemented POLCA at several factories in the United States and Canada. In this paper, we first give an overview of the POLCA system, explain how it works, and provide qualitative comparisons with pull/kanban systems.
Then we present a step-by-step procedure for implementing POLCA in a factory. Using examples from the implementation of POLCA at several plants, we address practical issues such as computing the number of POLCA cards needed, determining the quantum of work a POLCA card represents, and addressing part shortages. We also discuss the manifold performance improvements that have resulted from these implementations, including reduction in lead time and