Thursday, 30 December 2010

Leanpal - Practical Application of Kanbans

This postexplores a practical application of Kanban systems

What do we mean by Kanban?  – (Experienced readers can skip this paragraph).

Kanban is the Japanese word for ticket – the practice originates from a factory calling off the parts it needs from stores or from another downstream production cell when it needs them and not before. This is why the term Kanban is so closely associated with “Pull” production or JIT (just in Time)

Let's explain this with a real example demonstrating the difference between push and pull production, and how we helped a factory start a basic Kanban system. 

The system is not finished or perfect – it’s rather a Work-in-Progress!

The factory has 2 production departments: Cell A supplies Cell B with volume work. 

(There are other departments and satellite supply sections – for simplicity this explanation ignores them – in practice of course we had to build the Kanban System taking them into account.)

Before Kanban

The company manages the “high level” production planning very well. They have visual management showing incoming orders and their due date broken down into weekly and daily timeslots.
Incoming orders from the customer are divided into manageable portions automatically according to pre-set rules. A computer system then issues the orders direct to a printer in Cell A, where they are printed as and when they hit the printer queue.

At this stage the supervisor of cell A selects the order, matches it to a set of standard work instructions, and hands it to the team leaders responsible for the individual machines within the cell.

The team leaders/machine operators tend to pick which job to start first – in theory this should be prioritised according to the(end customer) due date, although in practice the jobs may be processed out of sequence e.g.  easier jobs are done on this shift and more difficult jobs left for the next shift.

This system “pushes” production to Cell B which may not be in the best order for the customer.

Overproduction of certain items well in advance of their required due dates physically blocks the gangways of Cell B and causes double handling of stock, as the parts required have been blocked in by parts not required at that time.  
Sometimes cell B cannot start work on a pressing customer order as it has large stocks of one component for the final build, but zero stock of the other component required to make up the assembly.  
Six of the classic seven wastes are seen in this process:- transport inventory motion waiting overproduction and defects.

Practical Application of Kanban – Phase 1

In the process described above, the company already has a “ticket” to call off production according to the end customer needs – however it is pushing this from Cell A to Cell B. The solution is to allow by cell B supervisor to prioritise the “tickets” in the order that he wants them produced to suit flow through his cell.  This was achieved by the cell B supervisor taking control of the order of the tickets at a daily morning meeting and posting these into a load levelling box according to the timeslots when he wants them produced by.  In this way cell B is now pulling the production required.

Practical Application of Kanban – Next Steps

During the next phase we need to persuade the company to produce in smaller batches, and link more closely the flow of work between individual machines in cell A and individual machines in Cell B.

Eventually we should be able to remove the intervention of the supervisor(s)  and get closer cooperation of the Cell B to Cell A machine operators themselves to drive the visual management of the “tickets”.

During most practical applications, whilst we can see what the end game (or future state) looks like, we need to proceed carefully with the people fully involved to avoid overwhelming them with too many changes at once.

Even the relatively simple change to the prioritisation of the “tickets” required three days discussions and workshops, with simulations to demonstrate how the new process would work.

Simulations using sticklebricks or lego are a great way to help people visualise the process.

If you’re interested in how we could help you and your company implement a Kanban process, or want to comment on this case study please contact us – we will also be delighted to receive any thoughts on how we could improve this implementation still further!

We'll do another post soon on a practical implementation for a more complex production system.

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