Question

Stainless Steel spoons are tested after manufacture with each test taking 10 minutes. If the plant makes 200,000 units a day and the quality Page 117-Sep-2018 assurance technologist recommends testing 1% of them to failure, is this sampling plan sensible? What would you recommend? Why?

Answer 1

A technologist can work not more than 8 hours a day. In one day he can check upto 8x60/10 = 48 samples. 1% of 200000 becomes 2000 samples. It is required more than 40 sample tester to accomplish the target of 1% .

My recommendation would be to compromise 1min of production. As at each 1 min spoins will be checked by experts simultaneously. Thus if one expert finds a fault, all products in that 10 min period will be rejected. So in Three shift duty we need 30 experts to test the samples. By this method maximum loss can be of 10 minutes 59 seconds and minimum 10 min. If we use just one tester at a time, loss would be of 19min 59sec max and min 10min. As spoon production is a continuous type production, if one machine get some problem the error will remain untill solved.

But in today's testing process are totally different. We check all the products by means of x-ray, MRI , Laser and proximity sensors. Those are fully automated and computerised. So no need of manual testing unless the testing machine is having error..

But at the end all these are required to comply with the requirements of production and the cost management and the accuracy of machines.