What Is Lean Manufacturing?

Lean manufacturing is the practice of improving efficiency by eliminating waste from a production process. For machine shops, reducing waste can lower costs, shorten lead times, improve quality, and help deliver better results to customers. Because every process can be improved, lean manufacturing is an ongoing effort rather than a one-time project.

Eight common forms of waste are summarized by the acronym DOWNTIME: defective production, overproduction, waiting, non-used employee talent, transportation, inventory, motion, and excessive processing.

Defective Production

Defective parts consume additional material, machine time, tooling, and labor. A shop may have to rework the parts or manufacture replacements, potentially making them much more expensive than planned. Mistakes cannot always be eliminated, but shops should continually work to reduce their defect rate.

Overproduction

Producing more parts than a customer requires ties up machine capacity and creates storage costs. Excess parts can become a complete loss if the customer discontinues the product or chooses another supplier.

Waiting

Waste occurs when either parts or employees are waiting. Stock may sit before cutting, work may wait between machining operations, and completed parts may wait for shipping. Reducing these delays frees space, shortens delivery time, and allows the shop to begin other orders sooner.

Non-Used Employee Talent

A shop wastes valuable talent when skilled employees are assigned work far below their capabilities. For example, a machinist experienced in multi-axis machining or programming may be more valuable on complex jobs than on routine grinding or simple mill work. Additional training can help employees move into roles that make better use of their abilities.

Transportation

Transportation waste consists of unnecessary movement of parts and materials. Machine-shop layouts should minimize the distance that work travels between receiving, storage, machining, inspection, and shipping whenever practical.

Inventory

Excess inventory occupies space and represents time and money invested before the parts are needed. Producing more than an order requires can therefore create waste even when the additional parts meet specifications.

Motion

Motion waste is unnecessary movement by workers. During setup, tools and materials should be prepared and placed near the machine. Organizing items used for loading, unloading, inspection, and deburring within easy reach can save substantial time over repeated production cycles.

Excessive Processing

Extra work that does not add customer value is also waste. A machinist should not spend unnecessary setup or cycle time trying to hold every feature at its nominal dimension when the drawing permits a wider tolerance. Parts that meet the specified tolerances should be acceptable unless their fit or function indicates that the drawing itself needs correction.

How Machinists Benefit

Machinists can apply lean principles by organizing their work, preventing defects, reducing unnecessary movement, preparing tools efficiently, and identifying delays. Demonstrating these habits can strengthen a machinist’s reputation and may support advancement. Employees can also contribute by respectfully suggesting process improvements to supervisors, even when they do not directly control the affected process.