In the field to deal with F31100, I have developed the habit of not first dismantle the encoder, but first follow the cable all the way through. Especially those cables that follow the drag chain back and forth every day, they look fine on the outside, but when you peel off the outer skin, they may be broken on the inside. The most prone to problems in those places: the motor tail root of the bend, the drag chain repeated bending of the zone, and long-term oil soaked joint position, as well as vibration is particularly large places. The most annoying thing is that this cable broken core is often not a one-time dead through, but "sometimes good and sometimes bad”. May be reported today alarm, tomorrow and run quite happy; low-speed go no problem, a high-speed alarm. This kind of intermittent failure can wear people to no temper, because the signal is not completely disappeared, just occasionally flash off. Ordinary power lines may be fine with an occasional flash, but the encoder signal is a high-speed, low-voltage feedback signal that is particularly delicate. Especially with the DRIVE-CLiQ port of the system, the communication stability requirements are very demanding, the signal waveform a little bit of burr, will trigger the F31100.
Speaking of this, we must mention the "interference” of this invisible pit. Encoder feedback line is a weak signal, the most afraid and strong wires stirred together. Some workshops play a bad ground, or when the wiring to save trouble, the encoder line and power line bundled in a slot, or even wear a drag chain together, the short-term machine may not be a problem, but for a long time, a variety of strange and bizarre encoder alarms came, what F31100, F31101, F31110 rounds out. I have encountered an old gantry milling, as long as the spindle all chip cutting, Z-axis reported F31100, and finally take an oscilloscope to see, the encoder signal stacked on a string of interference burrs. The root cause is the spindle inverter output cable and Z-axis encoder line in the same drag chain pipe side by side for seven or eight meters. Move that encoder cable out separately, add a metal hose and then grounded, the problem immediately quiet. So a lot of old workshops, equipment change east and west, the line is a mess, this time out of F31100, nine times out of ten to electromagnetic compatibility on the investigation.
Loose connectors is also a common disease. Especially vibration equipment, such as stamping automatic line, heavy-duty handling axis, large
servo drive, day after day, the plug will inevitably be a little loose. Sometimes just the contacts oxidized, or into a tiny bit of cutting fluid oil mist, the pin blackened, will lead to contact resistance suddenly big and small. To the system, this poor contact is reflected in the electrical characteristics and looks the same as a faulty zero mark signal. I've personally seen a plug that locks up tight on the outside, pull it out and see that one of the pins on the inside has retracted halfway, and before that it was actually barely getting a signal through, giving you an alarm now and then. Anything can really happen in the field.
Then why change the encoder will still alarm? Because the most fundamental reason may not be in the encoder at all. This is a particularly big misunderstanding in the field repair: a see "encoder alarm” four words, think it is the encoder body hangs. In fact, in my experience, cables and connectors are much more suspicious than the encoder itself. Especially for Siemens system, DRIVE-CLiQ communication is very sensitive, shield grounding is not good, a core wire resistance value becomes large, the plug slightly back pin, may let the drive misjudged as encoder failure. So the really old maintenance engineers, go up the first step is often touch the wire, change the plug, clean contacts, redo the grounding, these do not spend money or spend a small amount of money to check the place, and finally go to move that encoder.
In addition to wires and interference, parameters are a corner that cannot be ignored. A lot of times the F31100 comes up after the motor has been changed, the drive has been changed, or the parameters have been re-potted. the Siemens encoder type, the reference point configuration, and the feedback parameters, all three of these have to match up perfectly with the actual hardware that is being installed. If the parameter is set to incremental encoder with zero mark, and you replace it with a non-original product without zero mark or with a different zero mark distance, the system will immediately think that the zero mark distance is incorrect when powering up the self-test and report F31100 on the spot. this is especially easy to step on the pitfalls when the equipment is modified or non-original encoders are replaced. Check the encoder data such as P0404, can often save a lot of time.
