Tales from the quality world — Latch

Tales from the quality world — Latch

Years ago, at one of my earlier engineering positions, one of my products was a “roller skate” assembly mechanism which was installed by a Tier One into a roll-formed track and shipped to the Ford Avon Lake plant in Ohio. The skate allowed the third row seat to move fore and aft in the Ford Windstar and Nissan Quest vans (joint venture- the drawings were all Nissan drawings). Our skate had a latch shaped as below which would engage in slots in the roll-formed track to lock the seat in place. Unfortunately, we received many complaints about this latch and not fitting or functioning correctly in the track. The track sometimes did have a twist to it which resulted in the Ford assembly team having to fasten into their van in a specific sequence of bolt installation.

The latch was two “J” shaped pieces welded together with a resistance welder. The stampings were not always consistent, so that was one source of our quality problems. The other source occurred if we did not clamp the two pieces correctly when welding. The problem parts kept escaping because the gage used did not check the “J” shapes, but merely the overall width. And the two parts at the top of the gage were held on by bolts which could be loosened and allow out of spec latches to escape! The production process was to 100% gage every parts as it was released from the welder clamps before dropping the assembly into a tote.

I scrapped this poorly designed gage and had a gage made with a wire-burn process which could not be altered like the previous gage.

One morning I came in to work and the supervisor presented me with an entire pallet of latches produced the previous day which did not pass the wire-burned gage. He asked if the parts were still usable. I said they might be, but if we use them we need to do so in a controlled manner such that if there is an issue at the customer facility we can track these latch and narrow the issue down immediately. I had the pallet moved to the non-conforming cage as Until I could contact the customer about the issue. The next day, however, I came in to work to find all the latches gone. “We needed the latches to be able to ship to the customer,” explained the supervisor. UGH!

In hindsight, we needed a locked NCM cage which production had no access to. Or we could have immediately scrapped the latches. They were still making this part when I left that company and I suspect continued to have issues until the issue was resolved by re-design. The vans eliminated the rolling third row seat and instead went with stow-away seating.