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Diagnostics

Some other Diagnostics to check when you have problems are:
M SERIES                                                      T SERIES
G138.3   External Deceleration Signal X-      G138.3 X-
G138.0   External Deceleration Signal X+     G138.0 X+
G138.4   External Deceleration Signal Y-      G138.4 Z-
G138.1   External Deceleration Signal Y+     G138.1 Z+
G138.5   External Deceleration Signal Z-
G138.2   External Deceleration Signal Z+

MAN/ABS Signal G127.2

M SERIES
X016.5    Deceleration Signal for Reference Return X
X017.5    Deceleration Signal for Reference Return Y
X018.5    Deceleration Signal for Reference Return Z
X019.5    Deceleration Signal for Reference Return 4

T SERIES
X016.5    Deceleration Signal for Reference Return X
X017.5    Deceleration Signal for Reference Return Z
X018.5    Deceleration Signal for Reference Return 3
X019.5    Deceleration Signal for Reference Return 4

F150.5    Manual Data Input Start Signal

F149.7    CNC Ready Signal

G115.0    Miscellaneous Function Completion Signal

G120.0    External Program Input Start Signal M Series

G117.0    External Program Input Start Signal T Series

F188.0    Tool Change Signal

M SERIES
G105.0    Servo Off Signal X
G105.1    Servo Off Signal Y
G105.2    Servo Off Signal Z
G105.3    Servo Off Signal 4

T SERIES
G105.0    Servo Off Signal X
G105.1    Servo Off Signal Z
G105.2    Servo Off Signal 3
G105.3    Servo Off Signal 4

F149.1    Reset Signal

G120.4    Spindle Speed Reached Signal

G120.5    Spindle Orientation Signal

G120.6    Spindle Stop Signal

F148.5    Automatic Operation Start Signal

F148.4    Automatic Operation Halt Signal

G103.7    Miscellaneous Function Lock Signal

F178.7    Feed Hold Signal

The following table is very useful:

If the Edit Protect key is on you can input characters on the buffer line
but they will not be inserted into the program.

Following is the meaning of the Diagnostics 700 - 723. 


D700       7          6           5            4            3            2              1             0
                       CSCT     CITL     COV2     CINF     CDWL     CMTN     CFIN

A 1 in the bit means the following:

CSCT
Control is waiting for the speed arrival signal of the spindle to turn on.

CITL
Interlock is turned on.

COV2
Override is 0%.

CINF
In-position check is done.

CDWL
Dwell is being executed.

CMTN
Move command is being executed in automatic operation mode.

CFIN
M,S,T functions are being executed.


D701       7          6           5             4             3             2              1           0
                       CRST                                  CTRD     CTPU

A 1 in the bit means the following:

CRST
Emergency Stop, External Reset, or Reset Button on MDI panel is turned on.

CTRD
Data is being input via Reader/Punch Interface.

CTPU
Data is being output via Reader/Punch Interface.


D712       7            6            5             4             3             2              1             0
             STP      REST     EMS                      RSTB                      CSU

A 1 in the bit means the following:

STP
Stops pulse distribution. Is set for the following reasons.
1.External reset button is turned on.
2.Emergency stop button is turned on.
3.Feed Hold button is turned on.
4.Reset button on MDI panel is turned on.
5.Manual mode (JOG,HANDLE,STEP) is selected.
6.Other alarms exist.
STP is useful for when Automatic operation won't execute.

REST
This flag is set when the External Reset, Emergency Stop, or Reset button is
turned on.

EMS
This flag is set when the Emergency Stop button is turned on.

RSTB
This flag is set when the Reset button is turned on.

CSU
This flag is set when the Emergency Stop button is turned on or a Servo
Alarm occurs. Check Diagnostics 800 - 803.

D800 - SVERRX
       SVERRX

D801 - SVERRZ
       SVERRY

D802 - ------
       SVERRZ

D803 - ------
       SVERR4

D720      7             6             5             4             3             2            1            0
            OVL         LV         OVC       HCAL     HVAL      DCAL     FBAL     OFAL

A 1 in the bit means the following:

OFAL
An overflow alarm has occurred.

FBAL
A wire disconnection alarm has occurred.

DCAL
An alarm of regenerative discharge circuit has occurred.

HVAL
An over voltage alarm has occurred.

OVC
An excessive current alarm has occurred.

LV
An under voltage alarm has occurred.
OVL
An overload alarm has occurred. (Alarm 400 - 402 ) Power transistor heat sink or Discharge unit overheat or motor overload.

400,402 = Overload Alarm OVL OH or thermostat of AC servo motor functions.

Corresponding LEDs.

ALARM         LED
DCAL            DC
HVAL            HV
HCAL            HC
LV                 LV
OVL              OH

Diagnostic 720 is for the X Axis, 721 Y Axis, 722 Z Axis, 723 4th Axis.

D27       7             6             5             4               3               2               1               0
(T)                                                    PCS                                         ZRNM       ZRNL
(M)                                                   PCS        ZRN4       ZRNN       ZRNM       ZRNL

A 1 in the bit means the following:

ZRNL
One rotation signal of pulse coder for L axis is on.

ZRNM
One rotation signal of pulse coder for M axis is on.

ZRNN
One rotation signal of pulse coder for N axis is on.

ZRN4
One rotation signal of pulse coder for 4th axis is on.

PCS
One rotation signal of pulse coder for spindle is on.

This table is helpful for self diagnostics:

DGN No.         DISPLAY DATA

000-022         Input signals from machine tool.
                      (Output signal from receiver. No. 016-022 are effective without PMC.)

027                One revolution signal from pulse coder and position coder.

048-053         Output signals to machine tool.

080-086         Output signals to machine tool. Output signals to driver.
                      (These numbers cannot be used without PMC)

100-147         Input signals from machine tool (PMC). 
                      (No. 116-122 are effective without PMC)

148-199         Output signals to machine tool (PMC)
                      (no. 148-153 are effective without PMC)

200-249         Window data from PMC to CNC.

250-299         Window data from CNC to PMC.

700,701         Status of the CNC when it appears not to be working in automatic operation.

712                Automatic operation stop and pause conditions.

720-723         Alarm contents of servo system.

800                Position Deviation amount of X axis.

801                       "            "              "      "   Y  (M)   Z (T)

802                       "            "              "      "   Z  (M)

803                       "            "              "      "   4th axis.

820                X axis machine tool position from the reference point.

821                Y (M)  Z (T)  axis machine tool position from the reference point.

822                Z (M) axis machine tool position from the reference point.

823                4th axis machine tool position from the reference point.


Diagnostic 720 is for the first (usually X) axis, 721 is the second (Y for a mill, Z for a lathe) etc.

720 Bit  6 = LV  (Low Voltage at the Servo Amplifier)
             5 = OVC (Over current in the Servo Motor)
             4 = HC  (Abnormal Current in the Servo Amplifier)
             3 = HV  (Over Voltage at the Servo Amplifier)
             2 = DC  (Regenerative Discharge at the Servo Amplifier)



Also check the Servo Amp for and LED indication of the alarm.

If you have one of these bits turned on but there is no LED indication on the amplifier, check the amps operating voltages.

+20V     +20V  +/- 2V
+24V     +24V  +/- 2V
-15V      -15V  +/- .75V
+15V     +15V  +/- .75V
+5V       +5V   +/- .25V

If any of the voltages are abnormal check the 220VAC supply.

Another useful diagnostic:

D820 Distance from Reference Point X axis (Detection Units)
D821 Distance from Reference Point Z axis

The Diagnostic or Keep Relay lists of some machines will show certain bits as UNUSED or NOT USED. Quite often this will indicate that those bits are Fanuc defined. They may have significance to the operation of the control as it relates to the operation of the machine. This becomes important if you load the PMC into the control and the bits get reset. 


You have to be very careful about changing Keep Relays and Diagnostics because of how machine builders use them throughout the ladder. Setting these wrong can cause some bizarre behavior. In the case of an Ecoca SJ-20 this can mean the turret will index fine at home (G28 U0 W0) but will hang up any where else. In this case, the hang up is not as simple as the turret not starting the index or a turret alarm being issued, it may cause the turret to overshoot in one direction or the other or both or undershoot in one direction or both or to undershoot on one tool but overshoot another, etc.

Bit 7 of Diagnostic 760-767 does not indicate and alarm when a serial pulse coder is used it should be 1.

Sometimes a machine with a Fanuc control will use data bits in the ladder to function as diagnostic bits or keep relays. These will be denoted with D (i.e. D0009.6). This is a G.DATA bit and works like a keep relay, in that, making its value equal 1 will normally have the effect of enabling something in the ladder, but just as with keep relays this is determined by the instruction which is associated with the data bit. An important point is that the G.DATA values are displayed as decimal numbers and normally you will be changing only one bit as previously mentioned D0009.6 so you will have to convert the bit that needs to be changed to a decimal number and enter it, if the current value of the address (D0009) is 0 or add the new value to the current value if it is something other than 0. For example, if you are trying to enable some function in the ladder (parts catcher, bar feeder, etc.) and the instruction that has the function disabled is D0009.6 and this instruction is an Examine On instruction (this is explained later) then you will need to change the value of D0009.6 from 0 to 1. The first thing you need to know is how to convert the bit information to decimal. When you look at the G.DATA table you will see:

G.DATA

NO.       ADDRESS        DATA
0000      D0000              16
0001      D0001              0
0002      D0002              64

etc... these are merely examples.

Scroll down to the data address you need to change. A data value of 16 is equivalent to a binary value of 00010000. The bits are assigned decimal values based on their position in the eight bit binary number. The least significant bit (first from the right) is assigned a value of 1, the next bit from the right is assigned a value of 2, the third bit is assigned a value of 4 and so on until the most significant bit (first from the left) is assigned a value of 128.

Decimal    128     64     32     16     8     4     2     1 
Binary           0       0       0       0     0     0     0     0

So, using our example of D0009.6, if the current value of D0009 is equal to 0 you would change bit 6 to 1, bit six has been assigned a value of 64 so you would enter 64 as the value for D0009. If, however, the current value of D0009 was something other than 0, let’s say, 32 which tells us that D0009.5 equals 1 you would have to add to the two values together to avoid setting bit 5 to 0. So just add the 64 to the 32 and enter a decimal value of 96. The control interprets this and sets bits 5 and 6 to 1. Changing a bit from 1 to 0 is the same, just using subtraction instead of addition.

Most of the Keep Relays used on a control are used by the machine builder but
there are a few which are defined and used by Fanuc, they are K16, K17(K900),
K18(K901) and K19(K902). These are reserved for use by the PMC control soft-
ware and cannot be used for any other purpose.


                    7                  6                 5                 4                 3                 2                 1                 0
K16        MWRTF2    MWRTF1


Servos


If you have an axis problem you can insert a dummy plug into the Servo Amp axis plug to loop back the signals to differentiate between a true axis problem and an amplifier problem.


For excessive axis noise and vibration adjust the Servo Tuning Parameters. The Proportional Gain parameter is the most effective but normally requires a large change in value to produce a noticeable result. Adjusting the Filter Parameter can help sometimes. Adjusting either too far will cause the Excessive Servo Error alarm.

To access the Servo Tuning parameters:
1. SYSTEM
2. DGNOS
3. Right Chapter button.....


If the displayed position does not match the actual movement, check the Servo Parameter Page. In particular check the Feed gear and Ref. Counter values.

If the Feed gear number is set too low, the machine will display a position greater than the actual movement. If the number is too high, the machine will display a position less than the actual movement.

Check terminals of dual servo amplifier are:
0V       0 volts
5V       Control Power +5V (+5 +/- 0.25)
IRL      R Phase motor current of L axis
ISL      S Phase motor current of L axis
IRM     R Phase motor current of M axis
ISM     S Phase motor current of M axis

When tuning a servo, increase the gains one at a time. Increase until the motor starts to vibrate while at rest then decrease the value by 20%.

When working with an older Servo Amplifier(Velocity Control Unit), there are three adjustments to be aware of. These are potentiometers RV1, RV2 and RV3. In the event of an amplifier which drives more than one motor these will be arranged RV1-RV3 from top to bottom and X to Z from left to right. Adjustment of these is almost always necessary after replacing an amplifier with a new one or even when putting a repaired one back in to service. In this case, also be aware of the jumpers or shorting pins on the drive which may be different as well. It’s a good idea to record these settings before sending the unit to Fanuc. RV1 is the Gain adjustment. The most obvious symptom of a need for adjustment of this one is rough or jerky movement of the motor. RV2 adjusts the position deviation amount while the axis is at rest. Ideally, this should be zero and is easily attainable with this adjustment. The exception is for a gravity axis such as the X axis on a turning center. The deviation will normally move between 1 and 2 due to the effects of gravity. The deviation amount can be monitored by diagnostic function. In the case of a zero control on a lathe this is Diagnostic 800 for the X axis and 801 for the Z axis. Once this is adjusted for zero or very close to it, the deviation amount in each direction will be the same value. This adjustment is critical to operation of the machine because if the position deviation amount is too great, the machine will not operate as it should. Programs will not execute in MDI or AUTO. The spindle will not run, etc. The determining factor in this is the value set it Parameter 500 for X, 501 for Z. This parameter is the In Position Width. The control compares the value of this parameter to the value in Diagnostic 800, 801, etc. If the value in the diagnostic exceeds the value set in the parameter bit 3 of Diagnostic 700 is set to 1. Diagnostic 700.3 is the IN-POSITION CHECK (CINP). If this bit is set to 1, automatic operation will not execute. Another thing you will find is that commands whether given in Auto or MDI will not be performed. For example, if you command M3 in MDI mode, press Cycle Start, the Cycle Start lamp will turn on, BUF will be displayed on the CRT showing that the command was read into the memory buffer but will not be acted upon. The same is true for a tool (T) command or speed (S) command. In addition, the spindle will not start. A more or less typical value for the In-Position Width is 20. This is in Detection Units. RV3 adjusts the deviation amount while the axis is in motion. The difference between actual position and commanded position while in motion is known as LAG and is relative to feedrate. As the feedrate increases so too does the lag. Sometimes the lag can become excessive and cause servo problem. To adjust the lag, move the axis while watching Diagnostic 800, 801, etc. Rotate RV3 clockwise to decrease the amount of deviation.

Newer Fanuc motors always come with a pulse coder but there was a time when they could be bought without one. Typically this is true for controls Series 6 and older. The number on the nameplate indicates if a pulse coder is supplied or not. The part of the number that determines this is the last two digits. If the last two are either 05 or 25, no pulse coder is supplied. There may be other numbers which fit this description but motors with these two numbers never have pulse coders. It is hard to determine by physical appearance if a pulse coder is supplied because the motors use the same end cap and cable connector for the tacho-generator so a motor with a tach will look the same from the outside as one with a pulse coder.

If you replace the motor or pulse coder on a Fanuc servo motor you must perform a grid shift for the axis unless you can put the pulse coder back in the same location radially relative to the axis position. This is very hard to do in some cases because of the coupling device not being keyed, etc. This is normally a problem only when the entire motor is replaced. Generally speaking, the pulse coders have a slot across the face of the shaft which matches a slot in the shaft of the motor by way of a driver that goes between them. In this case, as long as the the motor's position is not change between the time that the pulse coder is removed and replaced then there are only two possibilities. Either the axis position will be correct or the pulse coder will be out by 180 degrees which will result in an error of half a revolution of the ball screw. Sometimes the error can go unnoticed if the machine operator goes ahead and re-touches the tools on that axis without checking actual position first and if they are not using all of the travel on the axis.

Servo parameter settings are determined by the Motor I.D. number. This is a two digit number which is defined by parameter. In the case of a 0 control, it is set in parameter 8120 for the X axis, 8220 for Y, 8320 for Z, etc. To determine the correct setting for a motor, look at the table in the Maintenance Manual.

The Motor ID number for the A06B-145-B077 is 10, A06B-146-B077 is 27 and A06B-147-B077 is 20.

The pins of the motor connector for the Alpha series are:

A - U
B - V
C - W
D - Ground

When looking at the connector (motor) face on, the pin to the right of the notch is pin A, below it is pin B, to it's left is pin C, above it is pin D.

The resistance from any of the windings of a Fanuc motor to it's frame should be 100 megohms or higher. A reading of 10 to 100 megohms indicates that the winding has begun to deteriorate but operation should be, for the most part, normal. A reading of 1 to 10 megohms indicates considerable deterioration but the motor will still run although likely abnormally. A reading of less than 1 megohm cannot be tolerated, the motor must be replaced.

An important thing to know about Fanuc servo motors is that unlike a normal AC motor, they use permanent magnets. This gives them exceptional positioning ability and controllability but they do have a down side, in that, the magnets can become demagnetized or the poles may become scrambled. When this happens the motor will exhibit one or more of the following symptoms:

1. Cogging (when the motor is rotated by hand you feel notches similar to the   way a DC motor feels).
2. Motor pulls high current even under little or no load.
3. Motor has no torque (in extreme cases it can be stalled by holding the shaft with your hand.
4. Motor rotation feels rough or jerky.

A common cause for this condition is if the motor gets too hot. Also, a servo amplifier can fail in such a way as to cause this problem. In either case, magnets can be re-magnetized by a either Fanuc or a company in Chicago called Endeavour Technologies.

Another thing to know about these motors is that they are like a DC motor in that if one of the windings is shorted internally or if two of the output phases of the amplifier are shorted together the cogging effect will be present. In this case the motor will normally be harder to turn than it is when the poles are demagnetized or are scrambled.

The following pin outs are typically of a Fanuc Alpha I64 pulse coder:

Honda Connector       Cannon Plug
(M185, M188, etc.)

1 --------------------------------- N
2 --------------------------------- T
4 --------------------------------- J
5 --------------------------------- K
6 --------------------------------- H
14 ------------------------------- F
15 ------------------------------- G
16 ------------------------------- A
17 ------------------------------- D
20 ------------------------------- H

You will notice that both pin 6 and pin 20 of the Honda connector are connected to pin H of the Cannon (military style) plug. Typically what you will find is that pin H has no connection to the pulse coder. Pin H is used as a tie point for the two wires. This is preferable to connecting a jumper between the two pins at the Honda connector.

The magnets used in Fanuc Alpha series motors are Neodymium Ferrite.

When trying to determine the compatibility of motors:

A06B-XXXX-XXXX

A06B identifies it as an Alpha motor.

The next two numbers identify the range of models.
03 -  a1/3000
        a2/2000
        a2/3000
        a65/2000
        a100/2000
        a150/2000
01 -  a3/3000
        a6/2000
        a6/3000
        a12/2000
        a12/3000
        a22/1500
        a22/2000
        a22/3000
        a30/2000
        a30/3000
        a40/2000
        a40/2000 (with fan)
013  a300/2000
        a400/2000

Of these the most common found on YCI, Takumi, etc. is the a22.

The next two numbers define the specific model.
71 - a1/3000
72 - a2/2000
73 - a2/3000
23 - a3/3000
27 - a6/2000
28 - a6/3000
42 - a12/2000
43 - a12/3000
46 - a22/1500
47 - a22/2000
48 - a22/3000
51 - a30/1200
52 - a30/2000
53 - a30/3000
57 - a40/2000
58 - a40/2000 (with fan)
31 - a65/2000
32 - a100/2000
33 - a150/2000
7  -  a300/2000
8 -   a400/2000

The first number after the B indicates the type of output shaft.
0 - Taper Shaft
1 - Taper Shaft with brake
5 - Straight Shaft
6 - Straight Shaft with brake

The taper shaft is considered the standard configuration.

On models a1 and a2 the brake is 2 Nm.
On models a3 and a6 the brake is 8 Nm.
On models a12, a22, a30 and a40 the brake is 35 Nm.
On models a65, a100 and a150 the brake is 100 Nm.

The next two numbers indicate the type of pulse coder supplied with the motor

75 - Pulse Coder aA64
77 - Pulse Coder aI64
88 - Pulse coder aA1000


If a Fanuc servo amplifier has S1 and S2 (shorting pins), normally S1 will be empty and S2 will be shorted. If S2 is not shorted the result may be that when the axes attempt to move, the position display will count but the servo motors will not move. In the case of a gravity axis, it may oscillate once the brake releases. 

If you are working on a motor or encoder problem and you need the machine on with a cable disconnected, you can power the control up with the E-stop engaged to avoid the generation of servo alarms. This is very useful for looking at and changing parameters and diagnostics which cannot be when a servo alarm is active.

When the Alpha drives power up they will flash the software version on the LED display. For example, it will flash a 10 for 9010 or 20 for 9020, etc.

If an axis jumps and jerks for several seconds after the axis command is removed, check the Motor ID parameter. If it gets changed, the axis can behave this way.

Some motor horsepowers:

a22/1500  4 HP
a22/2000  5 HP
a22/3000  5.9 HP

a30/1200  4.4 HP
a30/2000  6.7 HP
a30/3000  7.1 HP

All of Fanuc's motor data can be found in the Servo Descriptions manual, part number B65142E.


On an Alpha series servo amplifier that controls three axes the motor terminal configuration is:

1st axis (X)         2nd axis (Y)          3rd axis (Z)

U   V              |         U   V           |       U   V
                      |                            |
W   G             |        W   G           |      W   G

G = Ground


Fanuc Beta series motors are not as smooth as Alpha series. On a machine that uses Beta series for axis control, you may notice roughness. In most cases, this is normal.

With Beta series drives the parameters are stored in the drive so if you
replace the drive the parameters will go with it.

To save and restore Power Mate CNC Manager parameters to Beta Servo Drives:

This is required when replacing a Beta drive and applies to the following
controls.

16iA,18iA,21iA,16iB,18iB,21iB,20i,16,18,21,0i,Powermate-iD and Powermate-iH.

1.  Make NC PRM 960.3 (PMN) = 0 (Enables PMM function).
2.  Select where parameters are to be saved (to save to memory card on i  series controls make PRM 960.2
     (MD2) = 0 and PRM 960.1 (MD1) = 1, to save as a part program make PRM 960.1 = 0).
3.  Set parameter 8760 to the program number you want the parameters to be stored as. Note 1.
4.  Press the SYSTEM button then the RIGHT CHAPTER button until the Power Motion Manager screen is
     displayed.
5.  Press the SYSTEM soft key.
6.  Press the PARAM soft key.
7.  Press the OPRT soft key.
8.  Press the RIGHT CHAPTER button. READ and PUNCH soft keys will be displayed.
9.  Select EDIT mode.
10.To save parameters from Beta drive to CNC press the READ soft key, press the ALL soft key then the EXEC
     soft key.
11.To restore the parameters from the CNC to the Beta drive press the PUNCH soft key, press the ALL soft key
     then the EXEC soft key.

Parameter 960.0 (SLV) determines how many slaves are displayed on the screen when the Power Motion Manager is selected.

0 = One slave.
1 = Up to four slaves with the screen divided into four.

Parameters 960.1 (MD1) and 960.2 (MD2) set the slave parameter input/output destination.
MD1 = 0, MD2 = 0, destination is the part program storage.
MD1 = 1, MD2 = 0, destination is the memory card.

Parameter 960.3 (PMN) sets the status of the power motion manager function.
0 = Enabled
1 = Disabled (Communication with slaves is not performed).

Note 1: The program under which the parameters will be stored is derived by multiplying the number of the Beta drive I/O link group by 10 and adding the result to the value in parameter 8760. So if the group number is 2 and the value of parameter 8760 is 9000, then 9000 + (2 x 10) = 9020, the parameters will be stored in program O9020.


On the older servo amplifiers, the TGLS indicator (red LED) is for tacho generator loss of signal. It normally comes on when either the motor or tach is disconnected from the amplifier. Some machines will have a contactor which disconnects the motor from the drive when the NC is off or the machine is in E-Stop, etc which will cause the LED to be on.  The motor output on these drives is at terminals 5,6,7 and 8. Terminals 5 and 6 will be tied together at the drive and 7 and 8 will be tied together.

For a machine with Alpha drives if MCC does not energize and there is not an E-Stop condition, check that connector K9 (JX1B) for the SPM or SVM has been attached at the end of the connection chain. There may be a problem with the cable that connects JX1A on the Spindle or Servo Module and JX1B on the Power Supply Module. Also check pins 1 and 3 of CX3. These pins correspond to the normally open contact of the MCC driving relay which energizes MCC.




Axes


Fanuc controls do not have an Axis Release parameter like a Mitsubishi control but an axis can be designated as unused by the control. Fanuc calls this clamping and it is accomplished by placing a jumper between the DRDY and the MCON signal of the axis not being used. The number of the connector will vary depending on which control and/or axis card is used. As an example, to clamp the X axis on a zero control you would short pins 7 and 12 of M34 or M184. When this is done the axis in question still has to have it's parameters to prevent generation of an alarm.


One way to perform grid shift is to:

1. Set the Grid Shift Parameter to 0.
2. Zero return the axis.
3. Measure the distance from where the axis referenced to where the  actual physical home is supposed to be.
4. Remove the decimal point and enter this value into the Grid Shift Parameter.

This only works if you know where the home is supposed to be. Some machines will have marks for this purpose, normally two arrows on the axis which line up with one another.


When working with problems regarding G28, axes at home, etc., be aware of the signals ZPX (F94.0) and ZPZ (F94.1) for the X and Z axes in the case of a lathe. These signals turn on when the reference position has been established. These signals are typically used by the builder to turn on the axis home lamps. Also be aware of the signals F120.0 and F120.1.

When working with parameters whose setting unit is specified as detection units it helps to know what a detection unit is. A detection unit is the smallest increment of movement that can be expressed (Least Command Increment). To find out what this unit is, you must observe the position of the machine in metric mode. In most cases you can go to the position page and observe the MACHINE position which is almost always in metric. Otherwise you will have to go to the SETTING page and change the machine to metric mode. The LCI is determined by how many places there are to the right of the decimal point. If there are three places to the right the Least Command Increment is 1/1000th of a millimeter. In this case when you enter a value into a parameter that is specified in detection units, if you enter a value of 1000, you have actually entered a value of one millimeter, etc.

Position Deviation while the axis is at rest is known as OFFSET and when it is excessive, can cause a number of problems.

If a machine will not execute axis motion in controlled feed (G01), try to run in Dry Run mode. In this mode the control does not care about the spindle in executing G01.

Even though an axis may appear to be in position according to the position display, it may not be in position as far as the control is concerned. The control's in-position window is very, very narrow. This window is specified by parameter and can be changed but shouldn't be. If an axis pulls high current while at rest, it may not be in position. To check this, go to the Servo Tuning page. If you can't get any axis to move on a control, check the Machine Lock (MLK) signal. Normally this signal must be high to allow for axis motion. In some cases you may have a switch supplied by the machine builder for Machine Lock.
If a wire is broken at the switch, etc nothing will move but the spindle will run, M functions will execute, etc.


For information concerning Grid Shift refer to GE Fanuc document ST940819 GRIDSHFT.DOC


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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.