To be honest, these types of alarms can easily become more and more complicated if you only read the manual. But in practice, the problem is often not that "advanced”. The most common causes we encounter in the field are summarized below.
1. High mechanical resistance
This article really accounted for a large proportion. For example: guide rail dry, lubrication is not in place; screw resistance; long time no maintenance; a particular section of the trip card. Once the machine tool "does not go well”, the servo must desperately compensate. The result is: the actual position began to lag behind → deviation is getting bigger and bigger → report SV0475. Some machine tools performance is very typical, low-speed okay, an acceleration on the alarm. Basically, it is a resistance problem.
2. Cutting load is too heavy
This is also very common in the processing site. For example, eating too deep, feed too fast, tool wear is serious. All of these will make the axis movement "effort”. Especially some of the old machine tools, the rigidity of the general, and then increase the load, it is easy to trigger the alarm. A very practical way to determine: empty running no problem, a cutting on the alarm. Then there is no need to suspect that the basic load problem.
3. Servo motor or drive state does not work
Some of the equipment used for many years, the servo system has actually been in the "barely working”.
The common situation is that the motor torque drop, drive output is not stable, the module heating is serious. You will find that the power is fine, run for a period of time on the alarm. Nine times out of ten, this situation is related to temperature rise.
4. Encoder or feedback signal problems
This problem is a little "hidden”, but also not uncommon. For example, the encoder wire contact is not good, the plug is loose, the signal is interfered. The "position data” that the system gets is not accurate, and it will naturally determine the deviation abnormality. This situation is usually manifested in the alarm irregularity, sometimes with, sometimes without. It is easy to be misjudged.
5. Parameter setting is not reasonable (1838 / 1841)
Some machine tools do not re-optimize the parameters after the parts have been replaced. For example, the allowable error is set too small, the servo gain is not adjusted. The result is that obviously the machine can still run normally, but the system feels "unsafe”, the direct alarm. This situation is more in the retrofit machine, refurbished equipment.
6. Mechanical clearance and wear
Old equipment can not get around the problem. For example, the gap between the screw becomes large, coupling loose, gear wear. These problems will not stop the machine all at once, but they will slow down the response. Slowly build up and they can trigger SV0475.
To be honest, it's not possible to follow a "standard procedure” on site. It's more of a quick judgment based on experience. Generally, we will go through the process like this: first look at which axis is alarmed, don't just check the whole machine.
Then directly do a simple test: reduce the feed + empty run. If not alarm, prioritize the load and machinery.
Next focus on touching the mechanical: manually push the axis, listen to the sound, see if there is no jamming. If it doesn't feel smooth, you basically have a direction.
Only later will we look at the servo drive temperature, motor status, there are no other alarms. Don't ignore the encoder line, a lot of problems in the end is a line.
If the front are finished, can not find the reason, then start the "replacement method”: change the motor / change the drive. This method is simple but very effective in the field.
How to avoid SV0475?
In the end, this alarm is not "sudden”, many are accumulated slowly.
If you pay attention to these points on a daily basis, you can actually avoid a lot of trouble:
* Lubrication must be in place (really critical).
* Do not long-term overload processing
* Regularly check the screw, guide rail
* Do not drag or crush the encoder wire
* If possible, regularly look at the servo load curve
Many customers' machine tools, just because "can be used as long as it has been used”, and finally the problem burst out together.
What is the recommendation to send it for repair?
If you have done all these things: no mechanical problems, normal loads, and the wires have been checked, but the alarms are still recurring, then it's basically a case of "no problem”. However, the alarm is still recurring, then you can basically consider:
* Internal failure of the servo amplifier
* Motor performance degradation
* Encoder problem
* Or deeper control problems
It's hard to judge this situation thoroughly on site, so we suggest to go to
Fanuc test bench.
