Manouk Nijhof POLCA is a shop floor material control strategy. It is a variant of Kanban, especially useful for organizations dealing in a high mix, low volume environment. POLCA stands for Paired-cell Overlapping Loops of Cards with Authorization. Paired-Cell Overlapping Loops of Cards with Authorization - POLCA

How to control the material flow on the shop floor in a context of low volume or customized products?

Lean Manufacturing is about the elimination of waste, such as inventory. Therefore, a lot of organizations invest in streamlining the production process. By making use of Kanban, they try to control the flow of orders/products. A Kanban card is a material signal. When the inventory of this product needs to be refilled, a signal is sent to the department which is responsible for its supply. This strategy works fine when you have a relative low amount of product variants. However, when your organization makes high variety of products in different volumes, a material signal does not work.

To control material flow on the shop floor, we need a system that works well in the context of low-volume or customized products. Additionally, it should work in the context of a cellular structure.

POLCA is designed to meet these needs specifically. In comparison to Kanban cards, POLCA cards are capacity signals. These signals does not indicate the need of a specific product or material, but it indicates the availability of capacity to work on any type of product or material.

First, you should identify the POLCA loops. 

1.      Reduce variability in products

2.      Create an overview of the inter-cell traffic

3.      Create a From-To-Table

4.      Design the actual loops

Then, you should calculate the number of POLCA cards needed. Therefore you use the following formula: (The number of POLCA cards) equals (the sum of the lead time of cell A and the lead time of cell B) times (the number of jobs exchanged from cell A to cell B during the planning period) divided by (the planning period D). See figure below.

Third, when necessary, you could add a POLCA safety card. A POLCA safety card can be used in case of disruptions in supply by external suppliers or non POLCA cells. Safety cards are temporary solution for unplanned events. Safety cards are typically authorized and circulated by one individual on the shop floor (production manager, scheduler, etc). If the disruption is gone, this individual takes the card out of the system again.