The problem: Reading a dot matrix code on a beer can at 1200 cans per minute.
We were invited some years ago to a beer canning factory that was filling cans with Guinness. The canning company had received complaints from their Japanese customer as some of the cans did not have any batch codes printed on them. This is a big problem because:
a) It is not possible to trace batches of product if there is no batch code
b) The Japanese (allegedly) drink lots of Guinness, so the quantity of cans being shipped to Japan was enormous and therefore, so was the potential problem.
Pick up any beer can and look at the bottom of it and you will usually see a concave surface with the batch code printed onto it. So there are three main challenges for any vision system with this problem to solve:
- A concave surface means some text will be distorted
- The surface is quite reflective, so light can be reflected back towards the sensor
- The dot matrix printer does not always print all of the character and so reading this requires some element of 'forecasting' the result with the pixels that do exist
This system was developed over 10 years ago, so the tools required to create a robust system that could read every can were not as available as they are today. To add to the challenge, the customer wanted every can for which there was no read result received to be ejected from the line. So if the system did not perform, it was highly visible in the form of exploding beer cans.
The system consisted of the following components:
- Industrial firewire area scan camera with digital IO and external trigger
- Optical presence sensor for generating the trigger on the leading edge of the can
- A dome light to create diffuse lighting on the base of the can, with zero reflection
- Scorpion Vision Software running on an industrial PC with an Advantech IO Board connected directly to the ejector solenoid.
- Pattern matchers running within Scorpion Vision Software looking for a code in 16 positions.
A very fast and reliable code verification system that worked for many years and which probably saved the customer many thousands of pounds in fines and an quantifiable amount of savings in administration and of course, dramatically improved customer relationships.