Try and push a chain from one side of the room to the other, What happens? Now take that same chain and pull it from one side of the room to the other, Now what happens? You might have experienced what is shown in the picture above. When we try to push the chain it tangles, coils and eventually bunches up to where the links move rather inefficiently. But if we pull the chain from one side to the other, the links become tight and move at the pull of the chain. This analogy is very much the same as a work environment. Let's take a deeper look at each one of these systems and Find out exactly what is so great about the Pulling Concept.
The push system has been used for years in traditional manufacturing and forecasting environments, we see it fairly frequently in Make to Stock environments, although not 100% make to stock businesses are Push Systems only. The easiest way to understand what a Push system actually is, is to think of it this way.... In a push system there is no Order attached to the Product, that means that we make the product prior to any demand being created. As you may have guessed this requires very accurate forecasting techniques and often times can create a severe "bullwhip effect" as the forecasting travels up the supply chain. The other element as you can imagine that can distinguish a push system is the direction that Information flows through the Value Stream. In the Push environment information and product chases after the customer in hopes of attaching a sales order to the system in some way shape or form.
As you can probably imagine two of the most notable forms of waste associated with a push system are Overproduction and Excess Inventory although quite honestly any time product is produced before an order is maintained there is much more waste than that in the value stream. Often times in a true Push system there are absolutely no limits on the amount of Work In Progress which as you may have guessed creates a lot of unbalanced workload and unnecessary burdens on your team.
Even though the Push system tends to get a bad rap nowadays there are a few benefits to the Push system however the benefits really almost never outweigh the costs when you dig deep into it.
As you may have imagined in our Chain experiment there are many advantages to a Pull system or a "demand" driven Organization. The first that you may have been able to visualize dragging your chain around is that the chain tightens and the links stay in line, much like the chain when you pull the work down through the supply chain often times it is much easier to keep your "links" in line.
The pull system is only activated by a Customer order, which means that the large majority of WIP has an order attached to it in one way or another. One Example of a pull system might be in a Kanban system, when one bin is empty it triggers the production or replenishment of that item in "need". Essentially the Pull system is set up for items that in one way or another have a "Customer Order" attached to them. Keep in mind that although the Kanban system is an easy way to understand a pull system the goal is not Kanban the goal should always be true one piece flow.
True Pull set's limitations based on customer desires and the demand being driven, if there is no limitations in place there is a good chance that you may be looking at a push system.
To Push or Pull? that is the question, Ideally we always want to create what the customer wants and has committed to, but often times it's not either or, it is when? You see most environments are at some point in the overall system push and then transition into pull. The point at which this happens is a strategic decision that an Organization must decide on. One Key element in deciding where the transition happens is in the visibility that other partners have, that one element can help the switch from push to pull much easier. Remember too, that in a push system you are paying all the time with no guarantee of repayment so if at all possible try to pull much more than you push.
Overall the widely accepted better practice certainly is a Pull system, So why is it that so many people still push in today's day and age? Well there are quite a few reasons why, next week we will talk about a few elements of Inventory control and why some companies still operate on somewhat of a "pushy" basis.