ABSTRACT

This chapter discusses how Paired-cell Overlapping Loops of Cards with Authorization (POLCA) deals with the situation where one or more of the supplying cells is behind schedule and those components are delayed in arriving at the assembly cell. Suppose a job that needs those components is Authorized at the assembly cell. In rare cases, if a set of loops can form a full cycle, it is possible for jobs using POLCA to get into a gridlock situation. This is similar to a traffic jam that goes all around a city block: everyone needs someone else to move first, but since no one can move anywhere, the traffic is completely halted. All manufacturing companies have to deal with real-world events such as late arrivals of parts, machine failures, urgent and necessary schedule changes. For managers to fully commit to installing any manufacturing system, they need a level of confidence that the system will be able to deal with unusual situations.