Real time bend angle measuring on a press brake using lasers
Predicting material deformations is very tricky. Measuring and compensating for it in real time is even trickier.
Bit of background
Press brakes are hydraulically or electrically actuated sheet metal bending machines that are widely used in the industry. You can see one operating here in this youtube video. As you can see, these machines are extremely precise and the operators expect their sheet metal bends to come out reliably and within tolerance all the time. But the problem is even when the machine is extremely accurate the bend angles have this slight variance due to the metal composition and the crystalline structure in the material. This material property change can be observed even in the same sheet of material due to the slight variance in manufacturing processes.
People have come up with different solutions to reduce the effects of this non ideal conditions of a material. One of them is monitoring the bend angles in real time to compensate for the non-uniformity observed in each piece of material individually making the final product be withing reasonable tolerances 100% of the time.
The solution
A laser beam is shined from one end of the machine to get a shadow of the material and the tools to measure the bending angle using image processing. This is feasible since the tool and the die are uniform along the width of the machine. This gives us a clean cross section of whats going on in the machine for further analysis using clever software.
Simulation
Before going ahead and making a prototype, I did some simulation using some animations of a bending operation. The entire vision pipeline was designed using this animation prior to any real world testing. This was the first proof that I had that things are going to work out fine at least on the software side.
Real world test
There were so many challenges along the way to get this project reliably working and the times it had me scratching my head were uncountable. After months of work and countless redesigns, I finally managed to get it to a point that I'm happy to say its working. Following video shows the system working with a test material. I was working late after everyone's left work and it was a great relief to see it working for the first time ever.
Unfortunately this is all the details I can share (Believe me there's some juicy details on optical design and image processing). All the IPs belong to my employer and if you are interested in this product you can contact them through their website: cncauto.com.au