High Wip To Make Production Control Easier ?

Early in the morning the ramp up manager tell me the project that I hand over giving him a lot of problems. The machine stoppage and yield loss is high. He as me why and ask me to walk into the production floor to have an investigation for him.

I quickly pull the process engineer and walk into the line. We inspect the machine hardware and software set up, no abnormality observed. So, we load in a fresh lot to let the machine run so that we can monitor the performance. The machine runs without giving any error message. I waiting at the machine for 2hr, I didn’t observe any problem. Therefore I go back to the office and tell the ramp up manager – No Problem.

He look at me with a big eye and say,
“of course you don’t see problem because you load in a fresh lot right from the N2 chamber. Try to run the lot that already exposed to the production environment for more than 1day. See you still can get the machine run without giving problem or not”

I ask him, why we have lot that exposed in the production environment for more than 1 day? Why can’t he control the peoples working in the production floor only draw a lot from N2 chamber when they really need?

He reply, it is a production Standard Operating Procedure to keep one “Standby Lot” beside the machine to ensure continue supply of raw material.

I don't agree his point because with a process cycle time of 50 second and lot size of 1400 units. Machine time required to complete one lot take 19.44 hour provided the machine running non stop. This mean, the standby lot at the machine will be exposed to the production environment for nearly 24 hour before being process. No wonder the machine giving lot of problem when processing such material.

Do we really need a Standby lot in this case? We knew that material surface will be contaminated when exposed to the ambient. That is the reason why we keep it in the N2 chamber. Another question, since we knew the material need to keep it in the N2 chamber and N2 chamber is very expensive to maintain, why we produce so much from the upstream process and keep? Why can’t we produce just enough to cover the need of the downstream process?

Answer given to me was: it makes the production control easier.

I want to faint when I get the answer like this.