Many people call Tsurube as system, however, from my point of view and based on my
experience in Japanese companies, is a Method
into the Pull System (JIT). Tsurube combines FIFO (First In First Out) with Kanban,
promoting, sequencing and the correct leveling of inventories at the same time.
Tsurube is the Japanese word for “well bucket”.
As I have commented, it is a method of the pull system, a material replenishment
method used when there is the middle process step is physically separated from
the upstream and downstream processes by lead-time due to distance and/or batch
processing. A “bucket” (container of unprocessed material) is sent down the
“well” (the remote process) and at the same time a full “bucket” (processed
parts) is returned up from the well.
Tsurube is not easy to implement because it requires a
very good quality in processes and a good up time of the machine, since any
interruption or variation breaks the FIFO sequencing.
However many companies require this method or in
other words must implement immediately, hence the importance of having someone
with extensive experience in the implementation.
This
Tsurube method, is used to maintain
a continuous flow when there are interruptions such as process off-line or
off-site and must have a batch system.
Used when the product leaves the production cell
lines or because the process, can not, be in the cell (Kilns, painting, heat
treatments, anodizing, plating, ect) and operates as follows.
A supermarket finished products located at the
end of the line, which has predetermined quantity of material, usually a PITCH,
in this example it will be 30 minutes.
Once the amount is removed; then a kanban signal
its send to the process A, which can be the pacemaker; which prompts you to
start producing parts (quantity = pitch) is sent.
Usually the FIFO system is used to move the
product to process B. Process B also, have and process the same quantity and
this is passed to the process that we have offline. (Process C)
And this last process the same amount to the
process C is passed to end the cycle Process D and then to SMKT Finish Goods;
ant his process is repeated as often as needed.
It is very important to consider the SWIP (Standard Work In Process) the usual way to
calculate is the following.
SWIP = [Total Lead Time =(Transportation Lead
Time + Manufacturing Lean Time)] / Takt Time.
The SWIP (two buckets) maintains continuous flow
through a batch or outside process. Transportation of materials is never empty
in either direction and the arrival of the bucket to the well process is a
signal to produce. It is in effect an instance of a non-card type production
instruction kanban ; it is a FIFO process sequencing.
There are three golden rules for this Tsurube
method:
1.- Respect the FIFO sequence
2.- Quantity shipped must equal amount received
3.- Do not send more parts if those sent were
not received.
Zero Defects and TPM must be implemented before
or at same time (in parallel).
I hope this information will be helpful in your
next kaizen event.
