Just-in-time and Kan Ban are two important elements in the lean system.
JIT stands for Just-in-time.
The idea is that you get supplies and materials just when you need them,
not before, and in the quantities you need, not more.
Probably the biggest misconception about JIT is that you
can implement JIT without implementing a Lean system.
One purpose of JIT is to drive improvement.
Some organizations have attempted to impose a system of
JIT on their suppliers without any process improvement.
The hope seems to be that the purchasing organization can reduce its inventory.
Ultimately, when this is attempted,
inventory is not reduced – the burden of inventory is simply shifted to the supplier.
This new burden can threaten the viability of supplier organizations,
and this could ultimately disrupt the supply chain.
JIT is properly part of a Lean system.
JIT facilitates both flow and pull.
By itself, it's just an idea.
It primarily serves to reduce lead times and eliminate the waste of overproduction.
Inventory reduction does occur,
but it's a benefit,
not necessarily the goal.
The goal, as it is for the Lean system,
is to shorten cycle times and eliminate errors in order to better serve customers.
SMED (or Single Minute Exchange of Dies) and
TPM (Total Productive Maintenance) are the elements that make JIT work.
SMED is sometimes just referred to as quick changeover.
The faster you can changeover a process,
the shorter cycle time will be and
the more responsive an organization will be to its customers.
Total Productive Maintenance is a careful system of
preventative maintenance so that processes are more predictable and reliable.
Kan Ban and Point of
Use Storage are other elements that are almost always part of an effective JIT system.
Kan Ban is a visual production signaling system which we will discuss next.
Point of Use Storage is just what it sounds like.
If through this system you can reduce work and process inventory adequately,
you can store all of your work-in-process right where it will be used.
This eliminates the waste of transporting it to the warehouse and back.
So what is Kan Ban?
It's not a system for controlling inventory,
although it does have elements of material control through the information on the cards.
Kan Ban is a visual scheduling system.
Because it is visual,
you can determine the status of the system at a glance.
It will tell you what to produce,
when to produce it,
and how much to produce.
None of these tools works well alone,
Kan Ban needs to be part of the Lean system.
When it is, it can help eliminate the waste of overproduction.
You'll produce just what is needed and no more.
Additional benefits including increased flexibility for your customers.
It is also possible to greatly simplify
procurement processes and tie your production to the customer.
Additional benefits from this Lean system will
include reduction in work-in-process inventory,
which will cause a reduction in
cycle time and an improvement in service to your customers.
Internal benefits are improved quality and
additional floor space available for production purposes.
We've referred here to a Lean system,
and the word system is critical.
All of these tools have to work together.
Some of these we've already discussed,
others we will discuss in the future.
But the key is they're all required to make this work.
In order for Kan Ban to work,
we must be able to change quickly and reliably from one product to another.
SMED and TPM both make this possible.
The reliability and predictability that comes from
SMED and JIT also improves first-time quality.
JIT and Point of Use Storage help to
reduce work-in-process level so that Kan Ban is manageable.
Kan Ban is one part of a larger Visual Management System that
allows you to determine the status of production with just a glance.
5S is a workplace organization tool that's also a part of the Visual Management System.
And finally, Kan Ban is designed for use in a Pull system.
There are three elements in the Kan Ban Signaling System: the KanBans themselves,
dedicated space for storage,
and a scheduling board.
A Kanban is simply a card with
the necessary information on it for a fixed unit of production.
You can design these cards to meet your needs.
But it does not have to be a card –
a visual signal can be an empty tote or other standardized container.
If cards are used,
they're generally collected in a scheduling board.
When a predetermined number of cards are collected,
it's a signal to start production.
When those cards are used up,
it's a signal to stop production.
This is a set of rules for managing a Kan Ban System.
We'll go over them one at a time.
Downstream processes withdraw items from upstream processes.
That is, the internal customer draws from the internal supplier.
In practice, sometimes the upstream process might deliver,
but the supplier never delivers before it's asked for.
The production signals are strictly adhered
to – never produce more than you have Kan Bans for.
This is a significant shift in mindset from more traditional manufacturing models.
Remember our principle of pursuing perfection?
The supplier is responsible for quality.
Only 100% defect-free products are delivered to the next process.
When a quality problem arises,
production stops until it's resolved.
In order for this system to work smoothly,
it helps to level production.
It's necessary to work with your customers to level their orders.
Many companies do exactly the opposite when they offer volume discounts.
If your customer is ordering a large quantity,
it's unlikely they will use them all at once.
Often customers order large quantities because they do not trust
us to be able to meet their requirements – they're establishing a buffer.
It may take time,
but it's possible to earn their trust and get them to
order smaller quantities more frequently.
Whether the KanBan is a card or a tote,
it stays with the parts until they're used,
and then it's returned upstream.
Remember, this is the signal for replenishment.
One way to reduce work-in-process inventory is to actively manage KanBan levels.
When the system is first designed,
there's probably some cushion in it.
By observing the levels of work-in-process – remember this is
a visual system – it's possible to reduce the number of KanBans over time.