6 Key Lean Manufacturing Principles

Did you know that most lean manufacturing concepts were developed from the philosophies of Benjamin Franklin?

In his 1758 essay, “The Way to Wealth,” Franklin stated the following:

You call them goods; but, if you do not take care, they will prove evils to some of you. You expect they will be sold cheap, and, perhaps, they may [be bought] for less than they cost; but, if you have no occasion for them, they must be dear to you. 

And Henry Ford cited Franklin as a major influence on his own business practices, which included Just-in-Time manufacturing.

Let’s take a look at some of the guiding principles for implementing a lean manufacturing protocol…

Waste Reduction

First and foremost is waste reduction/elimination. Historically, this is the foundation of modern-day lean manufacturing, identified by Toyota Production System in the 1990’s.

Many of the other principles revolve around this concept. There are seven basic types of waste in manufacturing:

  • Overproduction (production ahead of demand)
  • Unnecessary Motion (moving people or equipment more than is required to perform the task)
  • Excess Inventory (all components and finished product not being processed)
  • Production of Defects (leading to rework, salvage and scrap)
  • Waiting (i.e., waiting for the next production step or interruptions of production during shift change)
  • Transportation (moving products that are not actually required to perform the task)
  • Overprocessing (resulting from unnecessary work that adds no value)

Waste reduction/elimination involves reviewing all areas of your organization, determining the source of all non-value-added work, and reducing or eliminating it.

Continuous Improvement

Continuous improvement is sometimes referred to by the Japanese word “kaizen,” which literally means “change for the better.”

 

As the name implies, continuous improvement promotes constant, necessary change toward achievement of a desired state. The changes can be big or small, but they must lend themselves toward improvement.

To be effective, continuous improvement should be a mindset throughout the entire organization. Lean manufacturing experts suggest that you not get caught up in only trying to find the “big ideas,” as small ideas can often lead to big improvements.

For instance, at Toyota, the culture of continual aligned small improvements has yielded large results in overall improved productivity.

Respect for Humanity

The most valuable resource for any company is its people. Without them, the business simply will not succeed.

Staff Members

When employees do not feel respected, they tend to lose respect for their employer. This can become a major problem when a company is trying to implement lean manufacturing principles.

Most staff members want to perform well in their jobs. They’re not just earning a living; they’re also developing a sense of worth from their work.

Constant communication and praise for a job well done will go far to show people you respect them. But it’s also important to include them in upcoming changes and ideas, giving them an opportunity to provide their input. The more involved they are in decisions, the more the ideas become theirs. (And the more likely they are to accept the changes.)

The Supply Side

Implementing lean manufacturing processes requires the cooperation and participation from everyone in the company. But the respect for humanity principle goes so much deeper than the employee level.  You must also display respect for your customers and suppliers, as well as the environment.

Virtually every company is a supplier to someone else. If everyone throughout the supply chain treats their customers and suppliers with respect, working through issues becomes a whole lot easier.

Levelized Production

The basis of this principle is that the workload is the same (or level) every day. In a lean manufacturing facility, this type of standardization is very important.

The key ingredient for this lean manufacturing principle is utilization of a pull system. Components used in the manufacturing process are only replaced once they have been consumed. In this way, companies only make enough products to meet customer demand.

To achieve this, levelized production takes into consideration both forecast and history.

An Example

Your customer orders most likely fluctuate daily. Let’s say on Day 1, they want 10 black and five red parts. The next day, they want 12 red and seven black. On Day 3, they only require 13 parts.

Using levelized production:

  • On Day 1 you would set the level volume at 15 parts per day, and production would replenish the 15 parts that were ordered.
  • On the second day, the order is 19 parts (four parts higher than our levelized production volume). Production would still build 15 parts and the shipping area would take four parts from an inventory called “fluctuation stock.”
  • On the third day, the order was 13 parts, which is two less than the levelized volume. So two parts are put back into fluctuation stock.

Just-in-Time Production

The basis behind just-in-time production is to build what is required, when it is required and in the quantity required. In conjunction with levelized production, this principle works well with the pull system. It allows for movement and production of parts only when required.

The goal in lean manufacturing is to maintain finished product inventory at the lowest levels possible, while ensuring delivery does not suffer.  Of course, it is nearly impossible to carry zero inventory, particularly in facilities where short lead time is essential. So you will need to carry a store of parts to pull from when required.

Kanbans

To facilitate just-in-time production, companies typically employ a system of “kanbans.” A kanban is a hand-sized card that moves with the product or material. It signals when the product is to be built or when the material can be moved.

The kanban basically serves as a work order or pick list. But it also serves as a visual control, to identify the contents of each box. A third function of a kanban is inventory control, to determine the amount of finished product on hand.

Built-In Quality

The idea behind this principle is that quality is built into the manufacturing process. It’s built into the design of the part. It’s built into the packaging. From design to shipping, quality is a major consideration.

This means that your machines are capable of detecting abnormalities and your fixtures have mistake proofing to avoid misassembly.

Abnormality Detection

“Autonomation” pertains to a machine’s ability to judge good or bad conditions. When an abnormal condition is detected, the machine stops and triggers an alarm. A production worker then removes the parts and resets the machine. This keeps the suspect parts from continuing through the process.

Autonomation eliminates the need for a production worker to stand there and monitor each machine. It’s often referred to as “automation with a human touch.”

Mistake Proofing

The purpose of mistake proofing is to eliminate product defects by preventing, correcting, or drawing attention to human errors as they occur.

Mistake proofing can be implemented at any step of a manufacturing process where something can go wrong or an error can be made. For example, a fixture that holds components for processing might be modified to only allow those parts to be held in the correct orientation.

Presence sensors are another example. These sensors allow  only components that fit, and will trigger an alarm if the machine is cycled without all the components present.

Simulation Game

We’ve covered only six of the many lean manufacturing principles out there. If you’re thinking about employing these ideas and others, you may wish to check out the following Factory Business Game:


Sources:

Lean-manufacturing-junction.com

Lean Directions

Investopedia

Quality Digest

Lean Production