Optimizing your processes must be done hand in hand with quality control.  Sure, you can identify some low hanging fruit to fix obvious problems with your processes, but unless you take into consideration your quality gaps and evaluate the processes around those, you may not be addressing your first pass yield failures and will have slower cycle time due to fire fighting. 

Any time there is a first pass yield failure or quality issue, the first thing to ask is “Why did this happen?”  Keep asking why questions (thus the 5 why's principle) until you find the root cause and then determine what needs to be done to close the gap. 

 
Finding the root cause may show gaps in your processes that, once resolved, will result in greater first pass yield and cycle time results.