About Lean Manufacturing and Continuous Improvement
Lean principles come from the Japanese manufacturing industry. For many, Lean is the set of "tools" that assist in the identification and steady elimination of waste (muda). As waste is eliminated quality improves while production time and cost are reduced. There is a second approach to Lean Manufacturing called Toyota Production System(TPS), in which the focus is upon improving the "flow" or smoothness of work, thereby steadily eliminating mura ("unevenness") through the system and not upon 'waste reduction' per se. The difference between these two approaches is not the goal itself, but rather the prime approach to achieving it. The implementation of smooth flow exposes quality problems that already existed, and thus waste reduction naturally happens as a consequence. The advantage claimed for this approach is that it naturally takes a system-wide perspective, whereas a waste focus sometimes wrongly assumes this perspective.
Both Lean and TPS can be seen as a loosely connected set of potentially competing principles whose goal is cost reduction by the elimination of waste. These principles include: Pull Processing, Perfect First-time Quality, waste minimization, continuous improvement, flexibility, building and maintaining a long term relationship with suppliers, Autonomation (employs automatic and semi-automatic processes to reduce physical and mental load on the workers), load leveling, production flow and visual control. The disconnected nature of some of these principles perhaps springs from the fact that the TPS has grown pragmatically since 1948 as it responded to the problems it saw within its own production facilities. Thus what one sees today is the result of a 'need' driven learning to improve where each step has built on previous ideas and not something based upon a theoretical framework.
Toyota's view is that the main method of Lean is not the tools, but the reduction of three types of waste: muda ("non-value-adding work"), muri ("overburden"), and mura ("unevenness"), to expose problems systematically and to use the tools where the ideal cannot be achieved. From this perspective, the tools are workarounds adapted to different situations, which explains any apparent incoherence of the principles above.
Eliminate waste: Waste is any activity that consumes time, resources, or space but does not add any value to the product or service. There are seven types of waste: 1). Overproduction (occurs when production should have stopped)2). Waiting (periods of inactivity)3). Transport (unnecessary movement of materials)4). Extra Processing (rework and reprocessing)5). Inventory (excess inventory not directly required for current orders)6). Motion (extra steps taken by employees because of inefficient layout)7). Defects (do not conform to specifications or expectations) Reduce time: Reducing the time it takes to finish an activity from start to finish is one of the most effective ways to eliminate waste and lower costs.
Reduce total costs: To minimize cost, a company must produce only to customer demand. Overproduction increases a company’s inventory costs because of storage needs.
Steps to achieve lean systemsThe following steps should be implemented to create the ideal lean manufacturing system:
1. Design a simple manufacturing system 2. Recognize that there is always room for improvement 3. Continuously improve the lean manufacturing system design
Design a simple manufacturing systemA fundamental principle of lean manufacturing is demand-based flow manufacturing. In this type of production setting, inventory is only pulled through each production center when it is needed to meet a customer’s order. The benefits of this goal include:
• Decreased cycle time • Less inventory • Increased productivity • Increased capital equipment utilization There is always room for improvementThe core of lean is founded on the concept of continuous product and process improvement and the elimination of non-value added activities. “The value adding activities are simply only those things the customer is willing to pay for, everything else is waste, and should be eliminated, simplified, reduced, or integrated”. Improving the flow of material through new ideal system layouts at the customer's required rate would reduce waste in material movement and inventory.
Continuously improveA continuous improvement mindset is essential to reach a company's goals. The term "continuous improvement" means incremental improvement of products, processes, or services over time, with the goal of reducing waste to improve workplace functionality, customer service, or product performance.
MeasureA set of performance metrics which is considered to fit well in a Lean environment is overall equipment effectiveness, or OEE.