http://www.deltamotion.com/pet...ools/FlyingShear.zip
The zip file includes a video and program for a flying shear. I send this file to customers that want to do flying shears and don't know where to start.

I have customers that want to cut sheet material. There are two basic ways you can do this. You can move the material by the cut length stop the material and cut or you can keep the material moving and synchronize the shear with the material and cut the material every cut length. Sometimes it is much harder to start and stop the material because it is coming from a big roll of steel and there is too much inertia to start and stop.


This a a pretty demanding problem hydraulically. Most mount the cylinder so that the cylinder extends down stream. The rod is then attached to the shear that moves. This is the obvious way. The problem is that the shear must retract quickly to get ready for the next cut and it must do this while retracting and everybody knows that servo cylinders do not retract as fast as they extend. What makes matters worse is that the rod side of the piston must do the braking while extending and the acceleration while retracting. If one is not careful the pressure on the rod side will intensify above the system pressure. The system becomes uncontrollable unless there is a pressure drop across the servo valve from the supply to the actuator. This has happened at least once and I documented this case well.

Back to the video. I don't have a flying shear in my warehouse but I can simulate the hydraulics and all the motion. This allows me to determine how fast the system can go a whether a particular design will meet the customers design goals. The hydraulic designer can see how fast the actuator must go and what accelerations rates that must be achieved. I don't use the natural frequency method because it will fail. The programmer can sit at his desk at write the code before the machine is built. Actually you can see that basics are already done and well documented.

The reason I have done this is to reduce design time and mistakes. I have seen plenty of mistakes. The faster the customers get the machines running the faster they have money and time to upgrade the next machine.

I have tried to tune a flying shear over the internet. I failed but the the conclusion I came to from looking at the graphs is that there must have been something wrong with the valve. The customer replaced the valve and restored the original gains and the system worked like new. Being able to diagnose system over the internet saved 2 days of travel ( 2000 mi away ) plus a day on site and about 1.5 days of production. That is big savings. The controller paid for itself that day.