How one Lego reseller built an artificial intelligence to sort bricks

Jacques Mattheij hoped to make some cash buying cheap boxes of used, unsorted Lego that he'd organize into more valuable assortments for resale. After acquiring two metric tons of bricks, he was motivated to build a technological solution for sorting. He outfitted a conveyor belt with a cheap magnifying USB camera and employed air nozzles to blow the bricks into various bins. The bigger challenge though was how to get the PC to identify the bricks. From IEEE Spectrum:

After a few other failed approaches, and six months in, I decided to try out a neural network. I settled on using TensorFlow, an immense library produced by the Google Brain Team. TensorFlow can run on a CPU, but for a huge speed increase I tapped the parallel computing power of the graphics processing unit in my US $700 GTX1080 Ti Nvidia video card….

…I managed to label a starter set of about 500 assorted scanned pieces. Using those parts to train the net, the next day the machine sorted 2,000 more parts. About half of those were wrongly labeled, which I corrected. The resulting 2,500 parts were the basis for the next round of training. Another 4,000 parts went through the machine, 90 percent of which were labeled correctly! So, I had to correct only some 400 parts. By the end of two weeks I had a training data set of 20,000 correctly labeled images…

Once the software is able to reliably classify across the entire range of parts in my garage, I'll be pushing through the remainder of those two tons of bricks. And then I can finally start selling off the results!

"How I Built an AI to Sort 2 Tons of Lego Pieces" (IEEE Spectrum)