- Kanban gets a lot of its ideas from lean manufacturing.
The famous engineer Taiichi Ohno created Kanban
as a way to improve the Toyota production system.
The system uses Kanban cards as a way to signal
when you needed to pull more products into the pipeline.
That's why Kanban is called a pull system.
This means that you pull more products
based on when there's increased demand.
Think about how this might actually work in practice.
Let's imagine using a Kanban system
with a small sandwich shop.
Most sandwich shops use a push system.
That means at the beginning of the day
the restaurant owner tries to guess how many people
will want different menu items.
Then, they try to make sure that they have
all the ingredients for these items.
In a push system,
when someone orders a grilled cheese sandwich,
the kitchen staff will quickly work
to manufacture the sandwich.
Then, they push the order out to the customer.
Let's imagine a pull system.
Here, at the beginning of the day,
the kitchen staff starts to prepare
most of the popular sandwiches.
Just before lunch,
the kitchen will start making top menu items
even before any customers enter the restaurant.
By the time the shop opens, the kitchen will have
stacks of grilled cheese sandwiches, French fries,
and popular side dishes.
They put these items just outside the kitchen
for the waitstaff to deliver to the customer.
When there's only one sandwich left,
the waitstaff puts a red card on top of the last item,
to signal the kitchen.
Then the kitchen will start to make
another stack of grilled cheese sandwiches.
When the system is working well
the customer doesn't have to wait for their order.
The waitstaff just pulls their sandwich and French fries,
and then delivers it to the customer.
When the sandwiches are getting low,
the kitchen staff delivers a new batch just in time
for the next orders.
If you're a fan of fast food,
then you probably recognize this Kanban sandwich shop.
This is exactly the type of system
that most popular fast food restaurants use to create meals.
A large chain like McDonald's may make
stacks of cheese burgers
ready to be delivered to their customers.
When there are only a few cheese burgers left,
the kitchen works hard to add more sandwiches to the stack.
If you look closely, you'll see that McDonald's
actually line their sandwiches up in little batches.
These are like little horizontal stacks.
They're waiting in line,
ready to be eaten by the next customer.
When the batch gets too short,
the kitchen throws a new batch of cheese burgers in line,
so they won't have to wait for their order.
The key thing to remember
is that the kitchen will work hard
to create the right sized batches.
If there's too many sandwiches, then they'll get cold,
and won't be purchased by customers.
If there are too few sandwiches,
then there'll be unhappy customers waiting for their meal.
They want to deliver the exact number of sandwiches
that will be consistently pulled through the system
at a predictable pace.
The same thing will be true with any Kanban system.
You want to make sure that you have
consistently sized batches,
so that your customers don't have to wait.
That's why you hear a lot about queue sizes.
This is the optimum amount of work
that you want in the queue
for your customer to pull out of the system.