House of lean is a diagram that provides a visual representation of the sequence in which lean methods should be implemented. A “house” is used for the analogy because it illustrates the required foundation before the house can be built. The walls must be built before the roof can be put on and so forth. A solid foundation sets up a successful implementation of lean, resulting in improved quality, delivery, and customer satisfaction.
Let's take a look at the structure of this house, starting with the foundation.
House of Lean – Stability
Basic Stability – Having essential capability, availability, and flexibility in the 4Ms—manpower, machines, materials, and methods. A lack of basic stability in a process prevents improvements from either occurring or being sustained.
A stable process or system is one that operates reliably and predictably, with consistent availability in the four M's:
It is impossible to sustain improvements resulting from lean methods without a stable process. You'll never know if an improvement, change, or problem resulted from instability or from the application of lean. An improvement might unknowingly be offset by the instability of the system. New or old processes our expected outcomes could just keep going wrong without an immediate apparent cause.
Tools such as a control chart and value stream mapping can be used to measure the stability of a process and better understand how that system functions.
What are the causes of instability? Machine breakdown, machine production speeds not being synchronized, raw materials are not available or not to specification, or employees who are not properly trained or who are not familiar with the work. Addressing problems in these areas are the foundation to lean success. Don’t get stuck focusing all of your attention on basic stability. Continue moving forward in other areas of lean once the basics are met. You can visually follow the House of Lean diagram as a map for implementation. Refer back to it, if you feel overwhelmed or need to check that.
House of Lean Pillars: Standardization & Kaizen, 5S and TPM
Standardized work is not just a format for documentation of work. It is a basic Toyota Production System (TPS) philosophy that is intertwined with that of Kaizen, which creates a continuous improvement environment by providing a constant 'pull' to make things better, though in very small increments. With this relationship, it becomes quite obvious that standardized work is not permanent, even if the current process seems optimum. There must be a constant drive for improvement, but to minimize risks, the improvements should be in very small steps so that they can be quickly evaluated so that the gains can be established as the next norm or the changes abandoned with the least disruption.
Without standards you don't know where you've been. Without standards there is no baseline from which future improvements can be measured. Without standards maintaining improvements will be difficult, poor habits develop, and work practices tend to drift away from the ideal. Without standards, successful improvements are difficult to share and implement in other locations. Standards are crucial.
The Kaizen process involves continuous improvement, usually accomplished in small steps, and then making the resulting improvements into standards.
Creating a standard means writing down (documenting) the new procedures or process. The objective is to establish a written record describing how the task is accomplished, or the process is run, in the best possible manner, and how this can be measured.
5S involves getting a facility cleaned up and organized. It results in the disposal of unused materials, and the simple, visual organization of the materials and tools that are needed.
Total Productive Maintenance (TPM) is another lean method that helps to build the foundation of your House of Lean. TPM places the responsibility for routine and preventive maintenance in the hands of those responsible for running the equipment.
The next step is to optimize both production and quality.
The Toyota Production System is often modeled as having two pillars, with one of the pillars being JIT, and the other Jidoka.
Optimize Production (JIT)
Optimizing production does not mean finding ways to push people and machines harder in an effort to get more out of them, using less time and fewer resources. Optimization means to use resources more effectively by eliminating waste. Let's take a look at three lean methods used to optimize production, and free employees to contribute more to ongoing process improvements.
The Takt Time is the amount of time that can be used to make a product such that production exactly meets customer demand. For example, if the factory operates ten hours per day, and customers purchase 100 units of a product per day, then one unit of the product must be produced every six minutes. That is the Takt Time.
The amount of time required to actually produce one unit of a product does not necessarily equal the Takt time. The actual production time is called the cycle time.
Takt Time is typically calculated for the entire production process, and also for each step within the process. This helps reveal and eliminate waste at each step. Any non-value adding task is considered waste, and eliminating that waste reduces the cycle time.
Knowing the Takt Time for each step in a process also makes it easier to spot new bottlenecks and problems, and get those resolved before they impact overall production.
Finally, when Takt Time becomes less than the cycle time, it is immediately obvious that the production process is stressed and changes need to be made. More product is needed than can be made. This results in pushing men and machines beyond their limits, typically causing quality to drop and the number of unplanned outages increase.
Knowing Takt Time is important for understanding what a system is required to produce. It eliminates guesswork in planning, and helps to identify areas where waste can be eliminated,
Kanban is a system in which customer demand pulls products through the manufacturing process. Products are only made when there are orders from customers, and raw materials only are purchased when needed to produce products customers have ordered.
Kanban sounds good, but in the real world orders do not come in at a steady rate. Some days are busy and some days are slow. How do we deal with the real world orders that do not come in at a steady rate? The answer is Heijunka.
Heijunka involves doing things such that a level rate of production is achieved, typically by smoothing out demand. Without Heijunka the Kanban process will not be effective.
JIT (Just In Time)
All of the above support the principle of “Just In Time” delivery. The concept of JIT is not complex. The goal is to minimize inventory so that only the absolutely necessary levels of inventory are maintained. This frees up assets that were used to store inventory. The result is that JIT reduces costs and promotes flexibility in production.
Optimize Quality (Jidoka)
What is quality? Quality is a product or service that meets a customer's expectations. This includes performing as expected; not having defects; lasting as long as expected (durability); being delivered when expected; and being produced in safe manner.
Some of the lean methods that can be used to improve product quality include:
This is a method of designing processes so they are mistake-proof. Producing a defect becomes impossible.
Kaikaku (Five Whys)
The Five Whys is a process used to get to the root cause of a problem. It involves asking “why” at least five times.
An “andon” is a visual signal, usually a light that indicates there is a problem in a process. The andon does not immediately stop the process, so production can continue while people resolve the problem. The objective is to ensure that defective product is not being produced, and if there is a problem that might result in defects, that problem is fixed before additional product is produced.
Jidoka can be described as automation with a human touch. Without Jidoka, JIT does not work. That's why it takes two pillars to hold up the roof of the House of Lean.
Customer Satisfaction in the House of Lean
These six simple principles of lean consumption provide a new definition of value for today's consumer, which we'll express in the voice of the customer:
Solve my problem completely.
Don't waste my time (minimize my total cost of consumption, which is the price I pay plus my time and hassle.)
Provide exactly what I want.
Deliver value where I want it.
Supply value when I want it.
Reduce the number of decisions I must make to solve my problems.
The above is from: Lean Solutions: How Companies and Customers Can Create Value and Wealth Together, by James P. Womack and Daniel T. Jones
The objective of lean is to achieve customer satisfaction. Your customers are the ones who provide the money for your paycheck, as well as paying all of the other bills. But, customers are not willing to pay for things that do not deliver value to them. The objective of the foundation and walls of the house of lean is to deliver value to the customer. Everything else is waste to be eliminated or minimized. That's why the focus of lean is on eliminating waste.
The House of Lean visually shows the importance of lean methods being built upon each other. Trying to use JIT or Jidoka, without building the ground work will result in failure. However unlike a house, building the House of Lean is never finished. Lean is an on-going process of continually improving, from basic stability, up through JIT and Jidoka. The House of Lean is never finished, it just keeps getting better.