Most people will recognise Kanban as the material management system from Lean Manufacturing. Kanban can be a good help for the realisation of pull production. The disadvantage of kanban is however that it is actually only suitable for repeating products. Taking into account that the 21st century market is characterised by low volumes and many variants, the chance of a product being repetitive is smaller and smaller. When we are dealing with constantly varying products, we cannot manage any more on product level, because we simply don’t have any products any more. In this situation Kanban has its limitations.
Within QRM a similar material management system has been developed and it’s called POLCA.
How does POLCA work?
POLCA is a material management system that is based on released capacity in the next work cell. Work cells are connected with one or more work cells downstream and together form a loop. In this loop a number of POLCA cards circulate. When the receiver finishes his work, he sends the released POLCA card which accompanied this work back to the supplier as a sign that he can send a new order. In fact he gives a signal that he has capacity to start working on a new product, regardless of the kind of product. An ERP system then authorises which orders can be released or, in other words, on which product we can start working. The number of cards in a loop represents a quantity of work in process.
POLCA stands for Paired-cell Overlapping Loop of Cards with Authorisation, and it is a combination of pull (cards) and push (ERP).
- An ERP system releases orders and generates lists with dates on which an operation
can start (authorisation list)
- POLCA cards are used to communicate and to accompany material movements between cell pairs in a loop
- POLCA is a capacity replenishment signal
- POLCA cards aren’t linked to products
- Kanban on the contrary is a stock replenishment signal
- A kanban card is linked to a product
- A POLCA card stays with the order within the loop and returns to the first cell
of the loop when the operation in the second cell has been finished
POLCA has other advantages next to those of Kanban, for example the lower level of work in process. POLCA is applicable in engineer to order environment and in an environment with a lot of customer specific demands.
Just like kanban POLCA also has some conditions:
- You need to have work cells and mechanisms for flexibility
- The ERP system must correspond with the structure of the organisation
- A high-level capacity and leadtime planning must be present
- A release list needs to be created: organised on authorisation date with the next cell included
- Manco’s need to be under control
POLCA is net als Kanban een materiaal controlesysteem. Dit houdt in dat het geen planningsysteem is. De planningtools dienen aanwezig te zijn en vormen de basis om POLCA toe te kunnen passen.
POLCA is a material management system just like Kanban. This means that it is not planning system. Planning tools need to be present and form the basis to apply POLCA. With POLCA you are able to prevent congestion with very little work in process, so you can maintain the flow in the chain. A QRM implementation can never start with the introduction of POLCA. You first have to form work cells or Q-ROC’s. Also the necessary measures have to be taken to reduce the lead times and the people must have the discipline not to start working on orders too soon, even when the pressure is high.
|Lean and Kanban||QRM and POLCA|
|“Send one, make one” means that there is already one product in stock to be sold/sent.||Goal of QRM is not to start working before there
is an order.
|Best suitable for products with known options on base items.||Works best in a market with a high variation and
engineer to order products.
|Demands constant demand and a replacement market.||Is used to enter new markets with a character of unpredictable demand and customer specific questions.|