Lean manufacturing: A closed loop system?

If you have studied the subject of control systems, you should have studied two types of systems. They are open loop systems and closed loop systems. Main difference between these two types of systems is the feedback loop. Closed loop system has a sensing mechanism which will sense the output and compare it with the desired result. If there is a variation the system will act accordingly. Open loop systems are faster and cheaper to create and operate. On the other hand closed loop systems provide the feedback of the out put and adjust the system accordingly. But they are little slower and costly to create and operate. Below is a graphical representation of open loop and closed loop systems.

If we closely study any manufacturing system, it has many smaller systems which make the bigger system. Requirement of controlling comes up when the system has a higher tolerance level and unpredictability. So the actual output can vary considerably from the desired result. So at every stage there should be a controlling mechanism which will provide some control over the result. If the actual result is considerably different to the desired result the system will stop or give some sort of a warning. Higher the risk of this happening, there is a requirement for the feedback and hence for the closed loop systems. Of cause it is very important to stop and fix any problems when they occur. This is a very important aspect of lean manufacturing as well.

But for me the lean manufacturing is a closed loop system at very lower levels of operation. The operation is closed loop at operator level. Every operator checks their product and if there is a variation with the desired result, they will stop the system and try to fix the cause of the problem. But in the bigger picture it is more of an open loop system of manufacturing. It has a defined input. And it has a well defined output. In between manufacturing system looks at meeting these outputs with the inputs. Systems are fine-tuned so that they will give the desired results most the times. For an example raw materials are source inspected and only the quality raw material is available for manufacturing. So there is a minimal chance of problems in processing. If there is a problem with desired output system will be stopped immediately and the problem will be corrected.

Lean manufacturing, although it has a feedback path and stops when there is a problem, it always looks to operate as an open loop system. This is facilitated with standard ways of working, aligning suppliers and even customers in getting the desired result, and source reduction of problem.

If you have a different view on this please leave a comment.