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ALARMS





Communication Alarms

Alarm 086 means that the Data Terminal (DTR) is not ready. There is an IC on the memory board which supplies a voltage signal to this pin to indicate that the terminal is ready. Sometimes this chip will go out.

If an 086 alarm occurs when attempting to communicate with a PC, there is most likely a problem with the communication cable. Also when uploading and downloading make sure the program edit key is in the correct position. One of the most important aspects of the serial communications is the cable. It must be right or the control will not attempt to communicate. This includes the position of the jumpers. The control looks for a short between pins 6 and 20 of the connector so if you don't have a Fanuc cable a crude test of the control can be done by shorting these two pins before trying to initiate communication. If pins 6 and 20 are not shorted you will most definitely get an alarm 086. Below are the indications of a control which is functioning normally while a RS-232 tester and Fanuc cable are connected without a PC or other device connected.

IDLE STATE              TRANSMITTING                 RECEIVING

TD ------- OUT           TD ------- GREEN                TD -------- OUT
RD ------- OUT           RD ------- GREEN               RD -------- OUT
CD ------- OUT           CD ------- OUT                    CD -------- GREEN
DTR ----- RED           DTR ----- GREEN               DTR ------ GREEN
DSR ----- RED           DSR ----- GREEN               DSR ------ GREEN
CTS ----- RED           CTS ----- GREEN                CTS ------ GREEN
RTS ----- RED           RTS ----- GREEN                RTS ------ GREEN

Again, these indications are with no external device connected and will 
differ once one is.



Alarm 087 occurs when the stop bits are set incorrectly or the PC is not responding to the controls request to stop transmission. It may also occur if you mistakenly try to transmit Parameters to the Diagnostic page or Programs to the Parameter page, etc.

Alarm 085 is almost always the result of improper setting of the Baud Rate.

086 alarm means that the DR signal is not present at the port.


If you continually get Alarm 087 when you are trying to input programs thru RS-232 communication, check the Edit key position, on some machines it can cause the alarm. The Edit key address is G122.3, it should be 1 to avoid the alarm.

If alarm 087 keeps occurring when trying to send information such as programs to the control, make sure that TVON is set to 0.

If you try to do DNC operations with the I/O setting for 0, alarm 086 will be issued.

3n0 (300, 310, 320, etc.)
NTH AXIS ORIGIN RETURN
Manual reference position return is required for the nth axis.

3n1 (301,311,321,etc.)
APC ALARM: NTH AXIS COMMUNICATION
Nth axis APC communication error. Failure in data transmission. Possible causes include a faulty APC, cable or servo interface module.

3n2 (302,312,322,etc.)
APC ALARM: NTH AXIS OVERTIME
Nth axis APC overtime error. Failure in data transmission. Possible causes include a faulty APC, cable or servo interface module.

3n3 (303,313,323,etc.)
APC ALARM: NTH AXIS FRAMING
Nth axis APC framing error. Failure in data transmission. Possible causes include a faulty APC, cable or servo interface module.

3n4 (304,314,324,etc.)
APC ALARM: NTH AXIS PARITY
Nth axis APC parity error. Failure in data transmission. Possible causes include a faulty APC, cable or servo interface module.

3n5 (305,315,325,etc.)
APC ALARM: NTH AXIS PULSE ERROR
Nth axis APC pulse error alarm. APC alarm. APC or cable may be faulty.

3n6 (306,316,326,etc.)
APC ALARM: NTH AXIS BATTERY VOLTAGE 0
Nth axis APC battery voltage has decreased to a low level so that the data cannot be held. Battery or cable may be faulty.

3n7 (307,317,327,etc.)
APC ALARM: NTH AXIS BATTERY LOW 1
Nth axis APC battery voltage reaches a level where the battery must be renewed. Replace the battery.

3n8 (308,318,328,etc.)
APC ALARM: NTH AXIS BATTERY LOW 2
Nth axis APC battery voltage has reached a level where the battery must be renewed (including when the power is off).

Serial Pulse Coder (SPC) Alarms

3n9 (309,319,329,etc.)
SPC ALARM: NTH AXIS PULSE CODER
The nth axis (axis 1-8) pulse coder has a fault.


Alarm 3n9 SPC is normally the result of a loss of communications between the serial pulse coder and the control. In practice, the problem which causes this alarm is almost always a bad connection. Quite often the cause is that the military style connector has backed off of the encoder or there is coolant in this connector. However, the cause can be a bad encoder or a failed cable. The n will be replaced with a number such as 319, 329 etc., to indicate which axis has a problem and the affected axis will also be named in the alarm.

Alarm 002 TV PARITY ALARM is issued when there is an odd number of characters in a block of information which is being input via RS-232. It will only be generated if the TV CHECK parameter on the Setting page is set to 1. This parameter can also be set by changing parameter 0.0 (TVC). This is important to know because if parameter 0.0 is set to 1 in a copy of parameters you are trying to load into the control, as soon as the control reads in TVC it will generate alarm 002. In this case you would see that LSK would flash as it normally does then when the parameters start coming in the control flashes INPUT only for a second then goes into an alarm state. Often the alarm goes unnoticed because you may be loading the parameters in under an alarm state
E-Stop, etc. so alarms are already present. The fact that some parameters are read into the control and immediately take effect can cause other problems. This might cause a problem if you are loading in parameters in which the baud rate is set for something other than the rate you are communicating at.





Spindle Alarms

On most machines without a spindle speed pot pressing spindle start in JOG mode causes the spindle to run at the last speed commanded in a program or in MDI.


One alarm which is more or less common is number 4. This indicates a blown fuse at the input to the spindle drive.

The older AC SPINDLE SERVO UNITS don't have a segmented LED display. In order to indicate alarms it uses four individual LED's arranged horizontally and numbered:  8  4  2  1
Together these generate a binary number from 1 to 15. These numbers correspond to the following alarms:

AL-01   THE MOTOR OR SERVO UNIT IS OVERHEATED (THERMOSTAT)
AL-02   THE SPEED DEVIATED SUBSTANTIALLY FROM THE SPEED COMMAND DUE TO OVERLOAD,  
             FOR EXAMPLE, CAUSING EXCESSIVE SPEED ERROR.
AL-03   THE ELECTRIC DISCHARGE CIRCUIT IS ABNORMAL.
AL-04   NOT USED
AL-05   NOT USED
AL-06   THE SPEED OF THE MOTOR EXCEEDED MAXIMUM RATINGS (ANALOG DETECTION METHOD)
AL-07   THE SPEED OF THE MOTOR EXCEEDED MAXIMUM RATINGS (DIGITAL DETECTION METHOD)
AL-08   THE POWER SUPPLY VOLTAGE IS TOO HIGH.
AL-09   NOT USED
AL-10   THE VOLTAGE OF +15 SUPPLY IS ABNORMALLY LOW.
AL-11   THE DC LINK VOLTAGE IS ABNORMALLY HIGH.
AL-12   DC LINK CURRENT IS ABNORMALLY HIGH.
AL-13   NOT USED
AL-14   NOT USED
AL-15   NOT USED

Alarm AL-20 indicates a fault in the Logic Circuit of the Spindle Amp. When any alarm in the range of 16 to 23 occurs, the problem could be either a bad Spindle Amplifier or bad Parameters.

Alarm AL-12 almost always indicates a bad Transistor Module. This module is mounted on the heat sink behind the two boards. It's inputs consist of the DC Bus Voltage and the control gates B1 through B6. It's output is the motor voltage U,V, and W. The manual describes AL-12 as an abnormal current in the DC circuit. The DC circuit it refers to is the DC Bus. One of the first things you should check is the DC voltages on the board. +5, +/-15, and +24. With intermittent problems you should put a scope on the test points and look for noise.

There are two wires which come in on the top right hand corner of the amp, T1 and T2. Never remove these with power on or power up with them off. Doing so can have catastrophic consequences for the Transistor Module.

Also, if the amplifier is powered when the transistor module is defective the Logic board may be damaged.


ALARM LIST FOR SPINDLE AMPLIFIER

AL-01    Motor is Overheated (Thermostat).
AL-02    Speed Deviation is excessive. Actual speed versus Commanded speed.
AL-03    Fuse F7 at DC Link is blown.
AL-04    Fuse F1, F2, or F3 at AC input is blown.
AL-06    Motor has exceeded the Maximum Rated Speed. (Analog System Detection)
AL-07    Motor has exceeded the Maximum Rated Speed. (Digital System Detection)
AL-08    Power Supply voltage is too high.
AL-09    The Heat Sink is overheated.
AL-10    The +15 VDC is abnormally low.
AL-11    The voltage at the DC Link is abnormally high.
AL-12    The current at the DC Link is abnormally high.
AL-13    Arithmetic and Peripheral circuit parts are in an abnormal condition.
AL-14    The ROM is in an abnormal condition.
AL-16    Arithmetic and Peripheral circuit parts are in an abnormal condition.
 to
AL-23

Some of the above alarms also apply to the Power Supply Module. You can tell by the description which ones may or may not.

If a machine issues the 751 alarm when spindle orient is commanded while the spindle is running but not when commanded from a standstill, check the ATC macro to be sure M5 has not been removed. If the spindle is running at an RPM which is significantly higher than the spindle orientation speed it may not be able to make the transition from running to orientation in time to prevent the alarm.

Alarm 751 SERIAL SPINDLE ERROR AL-27 can be caused by a parameter being set wrong but before chasing this make sure that the spindle encoder is connected on the motor end as well as the amplifier side. Also, if the machine uses a separate position pulse coder, make sure it is connected on both ends.

408
SPINDLE SERIAL LINK START FAULT
This alarm is generated when the spindle control unit is not ready for starting correctly when the power is turned on in the system with the serial spindle. The possible causes are:

1. Parameter set incorrectly.
2. An improperly connected optic cable or the spindle control unit's power is   off.
3. When the NC power was turned on under alarm conditions other than SU-01 or   AL-24 which are shown on
    the LED display of the spindle control unit. In   this case, turn the spindle amplifier power off and perform
    power up again.
4. Improper combination of hardware.
    This alarm does not occur after the system including the spindle control unit is activated.

409
SPINDLE ALARM DETECTION
A spindle amplifier alarm occurred in a system with a serial spindle. The alarm is indicated as "AL-XX" (where XX is a number) on the display of the spindle amplifier. Setting parameter 397.7 causes the spindle amplifier alarm number to appear on the CRT/LCD.

If an excessive spindle alarm occurs during rigid tapping, the relevant alarm for the tapping feed axis is displayed.

704
SPINDLE OVERHEAT
Spindle overheat was detected by the spindle speed fluctuation detection function (T series).


945
SERIAL SPINDLE COMMUNICATION ERROR
The hardware configuration is incorrect for the serial spindle or a communication alarm occurred. Check the hardware configuration of the spindle. Also, check that the hardware for the serial spindle is connected securely.

945
SERIAL SPINDLE COMMUNICATION ERROR
The hardware configuration is incorrect for the serial spindle or a communication alarm occurred. Check the hardware configuration of the spindle. Also, check that the hardware for the serial spindle is connected securely.

946
SECOND SERIAL SPINDLE COMMUNICATION ERROR
Communication is impossible with the second serial spindle. Check that the second serial spindle is connected securely.

If you have an alarm on an Alpha spindle amplifier, the problem may actually be the power Supply Module even though there is no alarm displayed on the PSM. This is especially true in the case of alarm 03 (AL-03) on the spindle amp. This alarm can be issued if the PSM is not outputting the DC Link voltage but also is not issuing an alarm.

Alarm 751 FIRST SPINDLE ALARM DETECTION, On a machine that uses the high resolution encoder (normally on a lathe with live tooling) check the spindle amplifier. If the alarm code on the amplifier is AL-39, this indicates the failure to detect the one rotation signal for the Cs contouring control. This alarm typically occurs when the C axis is commanded to a specific position. Most of the time this means that the two sensors of the high resolution encoder are not properly aligned, Fanuc has to make the necessary adjustment. It can also be caused by a problem, of course, with the encoders, the drum which is attached to the spindle or the cables, particularly the cable shielding. You also must consider the spindle amplifier itself. In one case the problem was found to be that the belts for the spindle motor had been made too tight causing just enough deflection between the encoders and the drum to generate the alarm every time a C axis position was commanded. In addition, the alarm would occur if the C axis was run even in manual mode above a given speed. This problem was solved by loosening the belts a little.

For Alarm 751 with AL-46, everything is the same but this alarm means that the fault was detected while in "thread cutting" operation.

In either case the problem may be with how eccentric the drum is relative to the sensors. According to Fanuc the run out of the drum must be within five microns (.0002"). Also the drum must be square with the face of the sensor to within 20 microns. The face of the sensor should be centered with the magnetic strip of the drum.


If you have alarm AL-07 on the Power Supply (PSM) and AL-11 on the Spindle Amplifier, there could be a problem with the regenerative circuit of the Spindle Amp. This situation is normally evident when the spindle is ramping down, in particular, from a high RPM. This is because when the spindle decelerates from a high rate of speed, there is a lot of CEMF to dissipate. If there is a problem with the amplifier which prevents it from being dissipated it can cause an DC Link over voltage condition on the spindle amplifier (alarm 11). When the Power Supply sees this high voltage at it's DC output it looks like a blown fuse of the DC Link (alarm 07).

On the Alpha series Spindle Amplifier, the cooling fan has a detection circuit. If the fan stops, the control will generate Alarm 409.





Power Supply Alarms


AL-01 on the Power Supply Module means that the incoming AC is adequate but the DC Link voltage is low. This normally indicates that the PSM is defective but you can disconnect the DC Link from the drives to determine if the voltage is being pulled down by one of them. When you have the AL-01 you should have AL-30 on the Spindle Amplifier since AL-30 means there is a problem with the input power circuit. If you disconnect the DC Link completely you may get AL-07 because the PSM thinks the fuse is blown. You may have to try to keep one of the drives connected.

AL-02 on the PSM (power supply module) means there is a problem with the amplifier's cooling fan.

AL-03 means the temperature of the heat sink of the power supply has risen too high.

AL-04 means the DC Link voltage has dropped.

AL-05 means the incoming AC is abnormal (open phase) or the main capacitor did not charge in the specified amount of time. The DC Link may be shorted or the recharge current limiting resistor is defective.

AL-06 means the incoming AC is defective (open phase).

AL-07 means the DC Link is too high. There could be excessive power being regenerated or the impedance of the AC supply is too high, an incoming AC variation of more than 7% can cause this or a defective regeneration unit. 


System Alarms

The 950 PMC SYSTEM ALARM can be caused by a problem with the I/O, particularly if an external voltage is applied to the I/O system.


The 911 RAM PARITY ERROR alarm may mean that the Memory board has failed but it may also mean simply that the parameters have been lost due to a bad battery. The only way to find out is to do a memory clear. Turn the NC off, hold the RESET and the DELETE button, turn the NC back on while holding both buttons. If the alarm goes away and is replaced with servo alarms, etc. then the Memory board is probably ok. At this point you must follow the procedures for bringing back a brain dead control. If the CRT is flashing BAT, go ahead and install new batteries before you start.


910
MAIN RAM PARITY
The RAM parity is related to low order bytes. Replace the memory PC board.

911
MAIN RAM PARITY
This RAM parity error is related to high order bytes. Replace the memory PC board.

912
SHARED RAM PARITY
This parity error is related to low order bytes of RAM shared with the digital servo circuit. Replace the axis control PC board.

913
SHARED RAM PARITY
This parity error is related to high order bytes of RAM shared with the digital servo circuit. Replace the axis control PC board.

914
SERVO RAM PARITY
This is a local RAM parity error in the digital servo circuit. Replace the axis control PC board.

915
LADDER EDITING CASSETTE RAM PARITY
This RAM parity error is related to low order bytes of the ladder editing cassette. Replace the cassette.

916
LADDER EDITING CASSETTE RAM PARITY
This RAM parity error is related to high order bytes of the ladder editing cassette. Replace the ladder editing cassette.

920
WATCHDOG ALARM
This is a watchdog timer alarm or a servo system alarm for axes 1-4. Replace the axis or master control PCB.

921
SUB CPU WATCHDOG ALARM
This a watchdog timer alarm related to the sub CPU board or a servo system alarm for axis 5 or 6. Replace the sub CPU board or the axis 5/6 control PCB.

922
7/8 AXIS SERVO SYSTEM ALARM
This is a servo system alarm related to axis 7 or 8. Replace the axis 7/8 control PCB.

930
CPU ERROR
This is a CPU error. Replace the master PCB.

940
PC BOARD INSTALLATION ERROR
PC board installation is incorrect. Check the specification of the PC board.

941
MEMORY PCB CONNECTION ERROR
The memory PCB is not connected correctly. Check that the PCB is connected securely.

945
SERIAL SPINDLE COMMUNICATION ERROR
The hardware configuration is incorrect for the serial spindle or a communication alarm occurred. Check the hardware configuration of the spindle. Also, check that the hardware for the serial spindle is connected securely.

946
SECOND SERIAL SPINDLE COMMUNICATION ERROR
Communication is impossible with the second serial spindle. Check that the second serial spindle is connected securely.

950
FUSE BLOWN ALARM
a fuse has blown. Replace the fuse (+24E F14).

960
SUB CPU ERROR
This is a sub CPU error. Replace the CPU PCB.

998
ROM PARITY
This is a ROM parity error. Replace the ROM board in which the error occurred.

Generally speaking, anytime you have Parity alarms or most any 900 series alarm the first step required is normally to clear out the memory by holding the RESET and DELETE buttons while turning on the NC power. This will delete all parameters and programs.


Alarms 910 to 914 (RAM PARITY ERROR) will occur if the RAM chips are removed and replaced even with the power off because of the battery back-up.

Alarm 950 FUSE BREAK (+24E:FX14) means that F14 the 5.0 amp fuse is blown. This is the bottom fuse on the front of the Power Unit. It's labeled +24E.




1000
EXTERNAL ALARM
This alarm was detected by the PMC ladder program. Refer to the relevant manual from the machine builder for details.



Servo Alarms


Placing the Control in E-Stop will remove the servo alarms allowing you to enter the parameters by hand, but remember that if you are in E-Stop you can not communicate via RS232.



If a machining center keeps issuing the 430 alarm while performing a peck drill cycle, check that the drill is sharp. This is especially true for softer materials such as aluminum and plastic. If the drill is dull, the rotation of the spindle can pull the head into the work making it difficult for the Z axis motor to stop within its In-position width setting. This causes the 430 alarm.

Sometimes you might see an alarm that says SOFT THERMAL (i.e., 436 X AXIS SOFT THERMAL). This alarm is normally seen during referencing (zero return). It basically means that the axis is loading up while traversing slowly. A common cause of this is for chips to build up between the table and the motor or the bearing housing. When this happens, in most cases, the motor is able to compact the chips enough to make it almost home but the current required is very high causing the alarm.

Alarm 436 can be generated for any axis, the control will specify on screen which axis is at fault. if for some reason an axis is not specified, check the LED display on the amplifiers.


In the case of Servo Alarms always confirm that MCC is energized. For an 18 control this normally requires that the 24vdc on CX4 is routed through the machine and back to ESP. On most machines this is accomplished by connecting the normally open contacts of a relay to CX4. This relay is energized by the E-Stop circuit. MCC is normally energized by passing the 220vac through CX3 to the coil of MCC and back out to another phase of 220. In turn MCC supplies 220vac to power the PSU.

If you get AL-12 on an amplifier, try powering up with the motor leads off of the amp. If you still get AL-12 the amplifier is almost certainly bad.

If you have trouble with alarm 329:SPC and you check the cable and it rings good, keep in mind that the maximum allowable resistance for the 5 volt signal on each conductor is only .5 ohms.

Remember that when dealing with these Serial alarms as well as some other Servo Alarms, after you enter the correct Parameters, the alarm will not go away until you have cycled not just the NC power but the power to the amplifiers as well so you must turn the machine completely off.

About 90% of the time alarm 4n0 indicates a bad motor, but in some cases it may be an axis board, drive, or cable problem. If you suspect a drive, it is usually easier and better to physically swap with another axis than to swap cables. If you do swap cables, be sure to swap both motor cables and encoder cables. The encoder cables can be swapped at the Axes PCB. 

If alarm 4n1 will not go away after completely cycling power, check the 24 VDC which is "daisy chained" to the Spindle and Servo amps. As a last resort, try removing and replacing the connector under power.


In the case of alarm 414 with an indication of 8. on the servo amplifier, check the motor power cable for that amplifier. A conductor (U,V,W) that is going to ground can cause this condition. Sometimes you may see this situation on a machining center with a multiple axis amplifier and you might suspect that the amp is bad because the X axis will issue the 414 alarm when the Y axis moves. What may be, in fact, happening is that as the Y axis moves it drags the X axis motor power cable into a position where it grounds out, since on an X over Y machine the X axis motor cables run through a flexible wireway that moves with the Y axis. If alarm 414 occurs, check Diagnostic 200 and Diagnostic 204.
Two bits of Diagnostic 204 apply to alarm 414, they are bit 5 and 6. Bit 5 is
MCC, Bit 6 is OFS.

Seven bits of Diagnostic 200 apply to alarm 414, they are bit 0(OFA), 1(FBA), 2(DCA), 3(HVA, 4(HCA), 5(OVC), 6(LV).

OFA = Overflow alarm.
FBA = Disconnection alarm.
DCA = Discharge alarm. LED 4 or 5 lights.
HVA = Over current alarm. LED 1 lights.
HCA = Abnormal current alarm. LED 8 lights.
OVC = Over current alarm.
LV  = Low voltage alarm.

All of the bits above should be 0. A 1 indicates a fault of that bit.

Diagnostic 200 applies to 16, 18 and 0 controls.

The OFA bit can be set if certain parameters in the 1800 series are set wrong. (16/18 control)

A problem with one of the drives will almost certainly generate alarm 401.

Quite often when you have the 401 VRDY OFF alarm it means that the servo has not had power supplied to it by the energizing of MCC. A common cause for this is an E-Stop condition which prevents the power supply from sending power to the servo unit. In this case there will be no alarms displayed on the amplifier. If you watch the drives during the NC power on sequence, you can see it power is sent to the drive then MCC drops back out which may indicate a problem with the amplifier which the amp cannot detect or a problem with either the CPU or the communication between the amp and CPU. IF the MCC contactor never energizes, look for a machine side problem such as the E-Stop


Alarm 411, 421, 431 means that there was an excessive deviation between the commanded position and the actual position during axis movement. The amount of deviation which generates the alarm is defined by parameter. There are two things to look at first when the alarm occurs, does the motor actually move when commanded or not. If the motor does move a little then the alarm is issued, check the mechanical portion of the axis for tightness. If the axis is too tight the motor can usually turn just a bit before everything binds up then the alarm is issued because the motor is not able to reach the commanded position. You have to go by the actual motion of the motor since the position display will typically change with the commanded movement before actual motor movement takes place. If the motor never moves at all check the output of the servo amplifier. If the motor winding is open or the cable is broken, etc. the motor will, of course, not move at all then the alarm will issue. In this case the position display will change with the commanded movement then after the alarm is issued, the display will return to the position displayed before the movement was commanded. Again the amount the axis will move before the alarm is issued is defined by parameter but a typical distance is .050".


400
SERVO ALARM: 1, 2th AXIS OVERLOAD
1-axis, 2-axis overload signal is on. Refer to diagnostics 720 or 721 for details.

401
SERVO ALARM: 1, 2th AXIS VRDY OFF
1-axis, 2-axis servo amplifier READY signal (DRDY) went off.

402
SERVO ALARM: 3, 4th AXIS OVERLOAD
3-axis, 4-axis overload signal is on. Refer to diagnostics 722 or 723 for details.

403
SERVO ALARM: 3, 4th AXIS VRDY OFF
3-axis, 4-axis servo amplifier READY signal (DRDY) went off.

404
SERVO ALARM: NTH AXIS VRDY ON
Even though the nth axis (axis 1-8) READY signal (MCON) went off, the servo amplifier READY signal (DRDY) is still on. Or, when the power was turned on DRDY went on even though MCON was off. Check that the axis card and servo amplifier are connected.

405
SERVO ALARM: ZERO POINT RETURN FAULT
Position control system fault. Due to an NC or servo system fault in the reference position return, there is the possibility that reference return position return could not be executed correctly. Try again from the manual reference position return.

406
SERVO ALARM: 7, 8TH AXIS OVERLOAD  7, 8TH AXIS VRDY OFF
7-axis, 8-axis overload signal is on. Refer to diagnostics 726 or 727 for details. 7-axis, 8-axis servo amplifier READY signal (DRDY) went off.

4n0
SERVO ALARM: NTH AXIS EXCESS ERROR
The position deviation value when the nth axis stops is larger than the set value. This value must be set in parameter for each axis.

4n1
SERVO ALARM: NTH AXIS EXCESS ERROR
The position deviation value when the nth axis moves is larger than the set value. This value must be set in parameter for each axis.

4n3
SERVO ALARM: NTH AXIS LSI OVERFLOW
The contents of the error register for the nth axis exceeded +/- 2 to the 31st power. This error usually occurs as the result of an improperly set parameter.

4n4
SERVO ALARM: NTH AXIS DETECTION RELATED ERROR
Nth axis digital servo system fault. Refer to diagnostic 720-727 for details. For the 4n4 alarm, there is a troubleshooting flow chart in the Fanuc Maintenance Manual. When the alarm occurs you need to check Diagnostics 720 to 724 to determine if the problem is low voltage, high voltage, etc.


4n5
SERVO ALARM: NTH AXIS EXCESS SHIFT
A speed higher than 4000000 units was attempted to be set in the nth axis. This error occurs as a result of improperly set CMR.

4n6
SERVO ALARM: NTH AXIS DISCONNECTION
Position detection system fault in the nth axis pulse coder (disconnection).

4n7
SERVO ALARM: NTH AXIS PARAMETER INCORRECT
This alarm occurs when the nth axis is in one of the following conditions (digital servo system alarm).

1. The value set in parameter 8n20 (motor form) is out of the specified limit. 

2.A proper value (111 or -111) is not set in parameter 8n22 (motor revolution direction).

3. Illegal data (a value below 0, etc.) was set in parameter 8n23 (number of   speed feedback pulses per motor  
    revolution).

4. Illegal data (a value below 0, etc.) was set in parameter 8n24 (number of   feedback pulses per motor  
    revolution).

5. Parameters 8n84 and 8n85 (flexible feed gear ratio) have not been set.

6. An axis selection parameter (from 269-274) is incorrect.

7. An overflow occurred during parameter computation.

490
SERVO ALARM: 5TH AXIS OVERLOAD
5-axis, 6-axis overload signal is on. Refer to diagnostics 724 or 725 for details.

491
SERVO ALARM: 5TH, 6TH AXIS VRDY OFF
5-axis, 6-axis servo amplifier READY signal (DRDY) went off.

494
SERVO ALARM: 5TH, 6TH AXIS VRDY ON
The axis card ready signal (MCON) for axes 5 and 6 is off but the servo amplifier ready signal (DRDY) is not. Alternatively, when the power is applied the DRDY is on but the MCON is not. Make sure the axis card and amplifier are connected.

495
SERVO ALARM: 5TH, 6TH AXIS ZERO POINT RETURN
This is a position control circuit error. It is likely that a return to the reference position failed because of an error in the NC or the servo system. Retry a return to the reference position.


When working on newer controls, 16, 18 etc., be aware that the alarm numbers do not work the same as they did on the 0 controls. Using the 400 series alarms as an example, alarms 400 through 405 mean the same thing on both controls after that the two controls diverge. Alarm 410 on the 16/18 is the same as alarm 4n0 on the 0. The difference is that in the case of the 16/18 the failed axis will be displayed on the screen with the 410. In the case of the 0 control the n will be replaced with the number that identifies the failed axis. It's important to be aware of this but you need to look very closely at the alarm section of the manual.


Alarm 401 indicates that the VRDY signal is off. In other words, a servo amplifier is not ready to run. You have to determine if the amplifier is off because there is something wrong with it or if there is an external cause. The most likely external cause is a problem with the 100 VAC supplied to the amplifier. If this is missing the amplifier will not power up. The problem is that this can quickly become a chicken or the egg problem. An easy way to find the culprit is to have someone turn the NC on while you watch the amplifier. If the DRDY (Green LED) comes on then goes back off, there is something wrong with the amplifier. If it never comes on at all, the trouble is external to the amp. In the case of an Alpha drive, the alarm number displayed on the amplifier will normally get you going in the right Anytime you have Alarm 419, check the Servo Motor cables, especially the motor lead cable. This alarm is often a bad connection.

If the machine is in E-Stop mode, the 100 VAC will not be present. The electrical drawings for the machine should show this circuit as well as how it ties in with MCC etc.

The above condition does not apply to Alpha drives.

Anytime a machine displays Alarms 400, 408, 418 and 424 (maybe more if the machine has more axes), check the LED displays on the amplifiers. If they are all blank, the AC Link is probably missing. This comes in on CX1A of the power supply and goes out on CX1B to CX1A of the spindle amplifier. For most applications, this is where the 220 vac stops. This AC voltage is typically 220 and is normally fed directly to the power supply through two fuses. This is determined by the machine builder and it is rare for the voltage to go through anything but a fuse. This voltage is converted to 24 VDC which is fed from connector CX2B of the power supply to CX2A of the spindle amplifier from CX2B of the spindle amplifier to CX2A of the first servo amplifier and so on. This 24 VDC is what supplies the power to all of the other drives to power the
LEDs, control circuits, etc.


PMC Alarms

600
PMC ALARM: INVALID INSTRUCTION
An invalid instruction interrupt occurred in the PMC.

601
PMC ALARM: RAM PARITY
A PMC RAM parity error occurred.

602
PMC ALARM: SERIAL TRANSFER
A PMC serial transfer error occurred.

603
PMC ALARM: WATCHDOG
A PMC watchdog timer alarm occurred.

604
PMC ALARM: ROM PARITY
A PMC ROM parity error occurred.

605
PMC ALARM: OVER STEP
The maximum allowable number of PMC ladder program steps was exceeded.

606
PMC ALARM: I/O MODULE ASSIGNMENT
The assignment of I/O module signals is incorrect.

607
PMC ALARM: I/O LINK
An I/O link error occurred. The details are listed below.

607 010
* Communication error (SLC master internal register error)

607 020
* An SLC RAM bit error occurred (verification error).

607 030
* An SLC RAM bit error occurred (verification error).

607 040
No I/O unit has been connected.

607 050
32 or more I/O units are connected.

607 060
* Data transmission error (no response from slave).

607 070
* Communication error (no response from the slave).

607 080
* Communication error (no response from the slave).

607 090
An NMI (for other than alarm codes 110 to 160) occurred.

607 130
* An SLC (master) RAM parity error occurred (detected by hardware).

607 140
* An SLC (slave) RAM parity error occurred (detected by hardware).

607 160
* SLC (slave) communication error.
  * AL0 : Watchdog timer
   DO clear signal received

  * IR1 : CRC or framing error
          Watchdog timer alarm
          Parity error

* indicates a hardware error.



Overtravel Alarms


An OVERTRAVEL ALARM as well as some other problems can occasionally be cured by resetting the Grid. The procedure for resetting the Grid is as follows:

1. Turn the control off
2. Press the P key and the Can key simultaneously while turning the   control back on
3. Hold both keys until the final screen is displayed
4. Turn the control off again
5. Turn the control back on normally

This is especially useful for over travel alarms since this procedure causes the control to ignore stored stroke limits. An important point to remember is that after performing this procedure, the control must be turned off and back on normally. The reason is that after resetting the grid the stroke limits will be ignored for as long as the power remains on no matter how long that may be. This will prevent the machine from stopping when a stroke limit has been reached, a potentially dangerous condition. Cycling power normally causes the control to once again check stored stroke limits. Also, performing a Zero Return will put the stroke limits back into effect. Make sure this zero return is done at a low feed rate (i.e. 25%) just in case the axis misses the ZRN switch. If the axis misses the switch and the stroke limits are turned off, the axis will crash.



5n0
OVERTRAVEL: +N
Exceeded the nth axis + side stored stroke limit 1, 2.
The 5n0 alarm is generated due to an over travel of either the first or second stroke limit.


5n1
OVERTRAVEL: -N
Exceeded the nth axis - side stored stroke limit 1, 2.

5n2
OVERTRAVEL: +N
Exceeded the nth axis + side stored stroke limit 3.

5n3
OVERTRAVEL: -N
Exceeded the nth axis - side stored stroke limit 3.

5n4
OVERTRAVEL: +N
Exceeded the nth axis + side hardware OT. (M series)

5n5
OVERTRAVEL: -N
Exceeded the nth axis - side hardware OT. (M series)

5n4
OVERTRAVEL AT +N AXIS
The tool moved beyond stored stroke limit 4 in the positive direction of the nth axis. (T series)

5n5
OVERTRAVEL AT -N AXIS
The tool moved beyond stored stroke limit 4 in the negative direction of the nth axis. (T series)

520
OVERTRAVEL AT -Z AXIS
The tool moved beyond the hardware over travel position in the positive direction of the Z axis.

590
TOOL POST INTERFERENCE ALARM AT +X AXIS
A tool post interference alarm was issued while the tool was moving in the positive direction along the X axis.

591
TOOL POST INTERFERENCE ALARM AT -X AXIS
A tool post interference alarm was issued while the tool was moving in the negative direction along the X axis.

592
TOOL POST INTERFERENCE ALARM AT +Z AXIS
A tool post interference alarm was issued while the tool was moving in the positive direction along the Z axis.

593
TOOL POST INTERFERENCE ALARM AT -Z AXIS
A tool post interference alarm was issued while the tool was moving in the negative direction along the Z axis.

If an axis will zero return okay, but issues a soft limit over travel alarm when you try to execute G28, check the value of the second stored stroke limit. It should normally be 0. 


If an axis continually over travel, while trying to perform reference return there a few things you can work with. Of course, the easiest thing to try is making the soft limits ineffective by holding P and CANCEL while powering up the NC. This works in the majority of the cases. Sometimes you come across a machine which needs this procedure performed every time the machine is turned on. Normally this can be corrected by moving the decel dog in toward the center of travel just a very small amount, as little as .020 is often far enough. From time to time you may have a situation where this does not work or a case where using P + CAN causes the machine to hit the hard limit switch. For these machines, it may be necessary to adjust the Grid Shift Parameter. When an axis is reference returned, it moves toward the decel dog, the dog is contacted, the axis goes into decel until the switch drops off of the other side of the dog, the NC issues the one revolution signal which causes the motor to make one full revolution, the axis then moves a specified distance, then looks for the encoder marker pulse and stops at this point, it is now at home. The specified distance is determined by the Grid Shift Parameter. Parameter 508 in the case of the X axis of a 0 controlled machine. If this value is set too high, the axis will over travel when trying to reference return because the soft limit value defines a distance from a point in this travel prior to the execution of grid shift. In other words, the soft limit is how far the axis can travel from the reference return point not including the distance traveled due to execution of grid shift. The Grid Shift Parameter allows you to set the reference point as close to the soft travel limit of the axis without having to spend forever doing trial and error moving the decel dog. If you set the Grid Shift Parameter to 0, the axis will stop moving immediately after the motor executes the one revolution and finds the marker. As far as adjustment, you should determine the physical limit of the axis, set the hard limit switch such that the axis can come to a complete stop from maximum feed rate before reaching this physical limit. Set the soft limit parameter so that the axis can come to a complete stop from maximum feed rate before contacting the hard limit switch. Finally set the Grid Shift Parameter such that the Reference Point is as close as possible to the soft limit. Keep in mind that the position of the decel dog will shift everything in the chain except the hard and physical limits. 


Other Alarms

When alarm 401 occurs without any obvious cause and the drives simply display -- (Not Ready), the PSM (Power Supply Module) may be at fault. This may have to do with the fact that the serial cable which is used for communication with the servo amplifiers, spindle amplifiers, etc. connects to the power supply.

In the event of an Alarm 90 (Abnormal Reference Position Return) which keeps occurring, one of the following parameters could be set incorrectly:

518-521
559-562
517
533
3.4
534
1.5

If you have a problem with a machine that issues 011 NO FEEDRATE COMMANDED, at times when no feed movement is being commanded, particularly during a tool change, make sure that G1 is not modal. A good practice is to program a G0 in a program before the tool change either as a preparatory command, in the block with the tool index or yet another way is to make parameter 3402.0(G0) = 0 so the control will power up in G0 mode.

Also, when parameters are lost, Parameter 517 (Loop Gain) will become 1. In this case, Alarm 410 or 420 or 430 will be generated but this parameter will not cause all three at once. The typical value for this parameter is 3000.

700
OVERHEAT: CONTROL UNIT
Control unit overheat. Check that the fan motor operates normally, check the air filter.


M-Net Alarm

899
M-NET INTERFACE ALARM
This alarm is related to a serial interface for an external PMC. The details are listed below.

899 0001
Abnormal character (character other than transmission codes) received.

899 0002
"EXT" code error.

899 0003
Connection time monitor error (parameter 464).

899 0004
Polling time monitor error (parameter 465).

899 0005
Vertical parity or framing error detected.

899 0257
Transmission timeout error (parameter 466).

899 0258
ROM parity error

899 0259
Overrun error detected.

Others 
CPU interrupt detected.

On a Fanuc control a Not Ready indication without the presence of an alarm usually means that the E-Stop circuit is open. On most machines, the hard limit switches are tied in series with the E- Stop circuit.

Under some conditions alarm 128 ILLEGAL MACRO SEQUENCE NUMBER may be issued while trying to do DNC operations. In this case, it has nothing to do with a macro but rather it's caused by a baud rate mismatch.

In the Ladder, alarms have the address designation A.

On most controls, turning the NC power off while uploading/downloading programs will cause Alarm 101. In this case the program memory will have to be cleared.



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The information on this and subsequent pages is intended to supplement and reinforce the knowledge of competent machinists and technicians. The authors of this website are in no way lialble for damage or injury resulting from the improper use of the instructions contained herein.