I'll start this story off with some questions and I want each of you electrical engineering guys and gals to take a moment to think about these questions and how they relate to your past experiences.
How well do you work with mechanical engineers? Do you ever battle it out regarding design changes? Do other departments and managers seem to favor mechanical engineers' opinions over yours? Does anyone at your company understand your views or why you need to do things a certain way? Here's an example to explain what I mean. Has this happened to you?
The project is halfway through the schedule and it's a whirlwind in every department because tooling release is coming up. Mechanical engineers and drafters are putting final touches on their designs and tweaking the 3D CAD models and drawings. Tooling is being quoted. As for the electrical team, first PC boards have already arrived for initial testing. You had to get layouts and boards done to stay a step ahead of the project because there are some long lead times on several critical components and you needed to give your layouts, schematics, and board samples to UL.
It looks like everything is running fairly smoothly, until the lead mechanical project engineer walks up to your desk. After checking 3D CAD assemblies and SLS prototypes, it seems that one of the plastic ribs in the enclosure is interfering with one of your tall electrolytic capacitors by about 1mm. The request is for you to move the capacitor over. In turn, your request is to move the rib or shorten it. The duel begins, back and forth, managers get involved, panic mode sets in After all, tooling fabrication has started. Who will give in and change their design?
Now let me take you through a chain of events from both sides and you decide who should make the change. The mechanical team runs to their management and to the VP and convinces them why they can't change their enclosure. Besides, if they do, it will delay the tooling, which may delay the project. They just want you to move a cap. As things work out, they convinced the entire management team.
As an aside, here is what would have happened if the mechanical team had not convinced management. A drafter would take an extra hour to shorten the rib and change the drawing. The drafter would have created a work order and sent it to the tooling department. The tooling department would have quoted the change (which is quite simple) and reported a cost of about $500 and one day lead time. Not surprisingly, no one wants to pay and possibly delay the schedule a few days.
Now, here's the other side — what happens if the electrical engineer moves that capacitor over enough to clear the rib. Move it 5mm — if you are going to make a change, it's best to add a little margin so you don't have to do it again. How hard could this process be? You move the capacitor, which changes the board trace patterns. That causes interference with several other components. You now need to move those around, which causes more traces to change.
Before you know it, you are relaying out the entire PC board. Because of that, you need to modify the board tooling, which will cost several hundred dollars. Because the traces were changed substantially, you will need to have all new board samples assembled and sent to you from your assembly house. That will take two to three weeks. On top of that, you need to tell UL to stop their preliminary review because the board layouts and silk screens they have don't match the new board layout.
You will have to redo some of your testing because of the trace changes. You will need to recheck signal integrity. You are hoping your assembly house has enough components on hand from the first build and won't have to reorder anything. Yikes — what a nightmare just to move that capacitor a few millimeters.
Now, who should make the change? I know there are a lot of variables in this scenario. Perhaps you have gone through changes comparable to this. Have you had a similar situation where you were forced to be the one to make a change? Did you know that at the end, it would probably cost more and be riskier to the production schedule? Have you had to do battle with the mechanical group?