Thursday, September 1, 2011

An annoying application story

I’ve just read a run-of-the-mill vision application story in Assembly magazine that really made me quite cross. Now usually I’m a fan of their vision articles, but “Vision System Enables Manufacturer to Achieve 100 Percent Quality Inspection” (July 28th, 2011,) was disappointing.

It wasn’t that not a word was said about the lighting that enabled this Cognex InSight system to detect cracks in ceramic parts, though that would have been interesting. Rather, it was the statement that, “The vision system also eliminated the problem of good parts being detected as faulty.”

Don’t misunderstand me, reducing false rejects is good, eliminating them would be wonderful, if that was indeed what the integrator had done, but it wasn’t. The problem was that some parts were “discolored due to dripping oil.” So does that mean the vision lighting and algorithm were smart enough to handle such contamination? Well here’s how they did it: “Now, the assembly machine stops automatically once three faulty parts pass through the test system in succession.”

Excuse me but that hasn’t eliminated the problem of good parts being rejected at all. All it’s done is reduce the up-time or OEE of the equipment. I was hoping to learn about some clever new technique, perhaps involving a Pat tool from Cognex, that made the oil drips invisible, but no such luck.

I know everyone is short of time and it’s tempting to reproduce the press release without spending a lot of time on analysis, but please, let’s not repeat claims without thinking them through first.

No comments: