Lean Applications in Different Manufacturing Processes

Process manufacturing is fundamentally different from discrete manufacturing in the way material flows. Material flows in a continuous stream in process manufacturing, while parts move in discrete batches in discrete.

 

Since there has been so much work done in developing these methodologies in discrete manufacturing and very little in process, it might seem logical to apply them “as-is” to process-manufacturing industries.

 

However, this approach is like trying to fit square pegs into round holes. The better approach is to adapt these techniques within a process improvement framework that identifies the various forms of waste in the process-manufacturing value stream, and manages the wastes with the appropriate concepts and tools.

 

Lean manufacturing defines seven types of waste that make a production system inefficient and costly. These are:

1. Over-production: Producing too much, too soon.
2. Inventory: Extra production required to buffer process variability.
3. Transportation: Movement of materials without adding value.
4. Waiting: Increasing production cycle time without adding value.
5. Movement: Movement of operators without adding value.
6. Defects: Product that does not conform to customer specifications.
7. Over-processing: Processing a material more than is necessary to meet customer specifications.

 

The first three types of wastes above relate to a lack of material flow. By the very nature of process manufacturing, material flows in a continuous stream from one process to the next, without periods of stopping and waiting in between (the possible exceptions being some batch processing in the chemical and steel industries). Therefore, the lean ideal of flow occurs by default. As a result, over-production, inventory and transport are either non-issues or only minor issues in process manufacturing.

 

Movement waste is also less relevant to process manufacturing because operators typically monitor automated equipment. Their movement usually does not have an adverse impact on the ability of the equipment to continue processing the material.

 

However the three types of waste – waiting, defects and over-processing – do exist in process manufacturing and are fertile ground for the application of lean and Six Sigma methodologies. For instance, product changeovers, which in process manufacturing can sometimes take 18 hours or more, are an example of waiting waste. Defects are the result of production of material that does not meet the specifications of the downstream internal/external customer.

 

Over-processing occurs when the material is processed to a greater extent than is required by the downstream customer. All of these add to costs and can be reduced and/or eliminated through the use of these methodologies.