Zulfa Wahida DMAIC and DMADV methods will help not only to reduce the product defects but also to reduce the reoccurrence of those defects, Let me explain how;
In any manufacturing system, a product is manufactured by means of some processes and equipment. We set the limit as per customer requirements and fix the equipment according to that. A defect in the product means the thing which we don't expect or does not add any value from a customer point of view.
Before starting any analysis, we shall have to be particular about what analysis we are going to study and which are our focused areas to reduce the defects. This stage is called the DEFINE stage. People ignore it to jump directly into visual observations but this is the important stage and in this, we need to look for the root of the company.
Now a defect can occur due to malfunctioning of equipment, process or human. If we know the problem from where defects came from then our half problem been solved. This process is nothing just a "ROOT CAUSE ANALYSIS" in DMAIC methodology.
After getting the root causes of defects, we will sort the actual causes by using some metrics and we will proceed for the next step which is ANALYSIS. In this stage, we will thoroughly study our equipment, workers' behavior, processes, TAKT time, lead time and process efficiency. Here we will get some chance to reduce the defects. We will do some required changes which will change the output, "obviously a good output".
We will observe new things for a while and will get some results. If these results will show some improvement then we will try to keep maintain this, else we will try to begin from step 1. (CONTROL phase)
These are the steps for the product which we already have. But DMADV is used for new product development. This is nothing just a pre-planned study so there will be minimum defects.
I hope this will clear your doubts at some extends. Let me know on [email protected] if you need any detailed things.
Its like a mat equation: your defect and time becomes a Y, anf the root causes become the x´s, so you have Y f(X), now use six sigma to findout the few vitals x´s
(of course u have to apply some statisticall tools)