One of the key differences in lean production is to use pull system rather than push system. While pretty much everyone knows (at least in theory) how to implement it using kanban, the underlying fundamental differences are a bit fuzzier. But what exactly is the difference between push and pull? Also, what makes pull systems so superior to push systems?
Let us dive in push vs. pull systems.
In a push system, the previous process stages push production forward to the next process. It is the common way to organize production and is widely extended throughout organizations
Its main disadvantage is that it keeps a massive production regardless of the next process needs or capacity, which leads to overproduction, the deadliest of all the wastes of Lean.
This misconception of massive production based on numbers derives from numerous factors like company sales or goals, or even a previous year’s data instead of actual.
It leads to tons of products housed until these products find a buyer. The problem is that this storage increases cost and the probability of defects exponentially.
And what about a housed product that cannot be sold? In this case, monetary loss and inventory waste appear.
It is hard for push system companies to find a way to eliminate all these expenses. But, as soon as they reduce inventory, they will find several improvement opportunities to overcome all this waste.
The truth is that keeping inventory is like an ocean that hides the most significant part of the iceberg. It makes it very hard to realize how inefficient the methods are until inventory is reduced.
Batching and queuing parts between processes should be avoided if possible. Having WIP (work in progress) waiting between process stages add inventory and cost. The extra resources needed to manage this in-between inventory work may damage the product itself as it is waiting for a buyer.
How to reduce inventory waste from Push Systems
Diving in headfirst can be a bad idea, especially if you are new to lean.
A good idea may be reducing inventory by 10% and dealing with the inefficiency that will appear. Then, reduce the inventory by another 10% and repeat the same process.
This way, it is possible to make the switch without abruptly stopping operations.
There is no doubt, one of the hardest principles of Lean to implement as a manufacturer is the pull system.
In a Pull System, also known as Make to Order, the production matches the customer demand or Takt time.
Pull Systems work on the demand side, such as Just-In-Time (JIT) or Continuous Replenishment Program (CRP), and keep inventory to a minimum, where products can be supplied with short lead times and at high speed.
One of the best examples of a pull system is a supermarket. Every time a customer buys an item, there is a signal that goes to the supermarket’s inventory control center detailing which items the customer is purchasing and in which quantity. Then, the exact items that were sold are replenished.
Move to Pull System with ISC
DGL, the advanced and professional line balancing software from ISC, guarantees an efficient real-time analysis of the WIPs in your process.
With DGL you will move to a pull system to prevent excess inventory. Just draw the current process layout and navigate to the Simulations module to check the behavior of your entire process. Balance your line and run simulations on the improved one, saving an incredible amount of time in analysis while optimizing your line’s capacity and productivity.
The main difference between push and pull systems is the WIP limit in your production line.
In the case of an explicit limit on WIP, the process has a pull system and hence has access to all its benefits. If there is no explicit limit on WIP, then it is a push system.
If interested in moving from a push system to a pull system, you must set first an explicit limit on your WIP. At this point, ISC is the right adviser that guides you through the entire process and performs a thorough analysis of all possible scenarios.
Ready to go? Start limiting your WIP and organize your industry with ISC!