PSA: That 'good enough' finish on a prototype will come back to bite you

Three years ago at a job in Dayton, I rushed a prototype run for a client. Surface finish was a little rough, but it fit. Client signed off. Fast forward to last month, they ordered 500 units. Same program, same tool. Every single part failed their new quality check. The slight chatter marks from the prototype run were now a major defect on the production batch. Cost us a week of rework and a big chunk of the profit. The lesson wasn't about the machine. It was about setting a standard. Anyone else get burned by letting a prototype standard slide into production?

3 comments

3 Comments

pat_schmidt6028d ago

That article in Modern Machine Shop a few months back talked about exactly this kind of trap. The author called it "inheriting a flawed standard" where a fast prototype becomes the baseline for production without anyone stopping to think. What gets me is that a simple surface finish spec written down on the first order could've saved all that trouble. The shop just ran the job the same way as the prototype because nobody called out the difference between a quick proof and a real production part. That's why I tell our guys to write up a separate router for prototypes even if it feels like extra paperwork. The standard has to be intentional from the start or you end up paying for it later.

rowan7251mo ago

Ugh, that's rough. I mean, I get it, but the real mistake was the client signing off on a rough part in the first place. They basically approved the defect.

margaretm231mo ago

Nah, saying the client "approved the defect" is a cop-out. The whole point of a rough part is to check form and fit, not finish. It's on the shop to flag a surface issue that won't machine out.