Not a week goes by without multiple calls from clients asking about F228 faults on their Rexroth Servo Drives.
The manual has a very dense explanation for a very simple error, which often times leads clients down the wrong path. F228 means that the motor can’t keep up with where it is supposed to be. Its official name is “excessive deviation.” That sounds more exciting than it is.
It means that the machine calculates where it thinks it should be and compares that information with where it actually ends up. If there’s a difference between the two (that’s the deviance), then obviously you’ve got a problem.
What causes the deviation?
In a system that has been running for years, this usually means that something mechanical has gone awry. There are plenty of things that can go awry:
- You’re asking your machine to accelerate faster than it can.
- The axis is locked.
- The bearings are dry.
- Something else needs lubrication.
- You are running material that is heavier/thicker/somethingelser than it should be.
When F228 springs out at you, find out about any recent changes made to the product, and check the mechanics and lubrication. At least 90% of the problems that F228 point to are mechanical in nature.
What about that other 10%?
The other 10% are, for the most part, hard to diagnose. About 5% of the time, the problem is that you have dropped an incoming phase because of a fuse blow at some point in the system. Rexroth drives are designed to run on 2 phases, but you have to derate the drive substantially when this is done. So the drive will not throw an error saying it has lost a phase, but it will only be running at about 50% capacity.
If you check the incoming phase voltages, and they are all present, that leaves you with a failure in the drive or motor. You will have to swap drives or motors in order to try to make the problem move. HOWEVER, don’t do that before checking the mechanicals. We typically have 10 to 12 service calls a year that cost clients thousands for us to point out that they need to grease a chain or bearing, or need to replace a gearbox.
We would much rather save that for real Rexroth problems. Contact us for immediate assistance.