Day to day, you would use complex and precise testing equipment to inspect, measure, take samples, or one of a number of other processes to make sure each part or product is up to snuff. You might also test raw “ingredients” and materials to verify that what you’re sourcing from other manufacturers meets the specifications they promise. Most of the time, if all goes well, you’ll report back that everything is a-okay, but it will be your responsibility to take action and stop production when a defect or imperfection is found.