Thread by @benji_york

I have a barcode debugging story.

I was working at tier-1 supplier to an auto maker. Our customer started complaining that they couldn't read some of the labels on parts we were sending them. Can you see the problem?

Our scanners could read both, but our customer's scanners couldn't. No one could find the problem.

After a while the problem came to me. I was given good and bad examples. After manually breaking down the barcodes with pen and paper I realized that one of the vertical lines was slightly thinner than it should have been.

While trying to figure out why that line was out of spec but all of the others were fine, I realized that there was a very thin white line through the whole label (borders, other text, etc.) that lined up with the edge of the slightly-thinner-than-spec line in the barcode.

It turned out that the printer in question had a dead pixel that left certain barcodes slightly out of spec when the always-white column lined up with a supposed-to-be-black part of the bar code. Our readers tolerated the variance but our customer's did not.

So, what was the fix? Repair the printer? Replace the print head? Throw the printer out?

No, I rotated the labels by 90 degrees.

Now that bad pixel drew a white line longways along the bar code instead, leaving the individual lines intact. The customer's scanner started working reliably and we had a new rule:

Don't print labels such that the lines are drawn vertically. Instead, print them horizontally so that any single stuck pixel will not corrupt the barcode.

This story was more interesting to people than I expected. If this is something I should do more of, please retweet and follow me and I'll see what I can do.

Thanks!