**First, the fiber-optic cable is the most likely to have problems.
The optical fiber thing looks like a thin wire, with two plugs plugged in at both ends. But in actual maintenance, because of it, there are especially many 408 alarms. For example:
- The plug doesn't stick all the way in, it's loose;
- Optical fibers were bent too hard, causing internal damage ;
- Dust or oil stains on the connector ;
- A wire was accidentally pulled when the case was disassembled.
Once we went to a client's site. Their machine table was in a molding workshop. The environment wasn't very good, and there was a thick layer of dust on the fiber optic plug. After cleaning it up and unplugging it again, the alarm went away. Another time, the fiber was pressed down by the wiring slot. Over time, it became a bit deformed, so we just had to replace it.
So when you encounter a 408 alarm, don't rush to suspect that the main axle is broken. Look at the optical fiber first.
**Second, the main axis amplifier is completely out of power.
A few times we helped clients with remote troubleshooting, asking them if the light on the main axle amplifier was on, and they said they didn't know where the amplifier was. In fact, the amplifier was in the computer cabinet, with an indicator light on it. If the light wasn't on, it meant it hadn't started at all.
What causes a power outage?
- The fuse in the cabinet burned out;
- Control power deficiency;
- The contacts don't fit;
- Or the power supply line is loose somewhere.
In this situation, the CNC has been waiting for the
amplifier to respond, and when the amplifier doesn't turn on at all, it must be calling 408. So looking at the amplifier's power indicator light, this habit is very important.
**Third, the amplifier itself has already reported incorrectly.
There is also a situation where the amplifier is powered, but it is also in an alarm state. For example, an internal failure, parameter error, or overflow protection. The amplifier itself is not normal, so it cannot communicate normally with the CNC.
At this time, if you only look at the CNC screen and just stare at 408, you won't find the reason. You have to go to the magnifying panel to see if there are other alarm codes. Many times, that small screen on the magnifying device has already given you the answer, just that you didn't look.
We once repaired a LGA, also a 408 alarm, and checked the fiber optics and power supply for problems. Finally, we discovered that the amplifier showed overflow. Later, when we dismantled it, we discovered that the module was broken. This example illustrates that the alarm of the amplifier itself cannot be ignored.
**Fourth, although there are few problems with the system and hardware, they are not nonexistent.
For example, the communication interface on the motherboard is broken, the communication board inside the amplifier is broken, or the parameters are set incorrectly, or the system version and amplifier model don't match, these situations we have also encountered. But such problems require some specialized tools and experience to be judged.
Typically, at this point, the previous optical fiber, power source, and amplifier status have all been checked. If they haven't been resolved, then they have to consider whether it's a hardware problem.
