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●C Axis SERVO DRIVER problems

Ans :


Reset the C axis Home position as following procedure :

Step 1 : Switch to Home Mode

Step 2: Press F6 Param set Key

Step 3: Press F7 Serial Tuning key

Step 4: Input password, then press F1 Ok

Step 5: Press F1 Normal axis

Step 6: Press F7 Set Abs Home

Step7 : Use up/down key to move yellow cursor to C position

Step:8: Press F1 set Machine Home

Step 9: Press F1 yes

Step 10: Finish C axis Home position setting

Step 11:  Use MPG to move C axis to align the C axis T slot surface parallel to x axis

Step 12 : Repeat Step 1 to step 10 to reset new C axis position as new C axis Home position.   


Video : 



For back the original C axis position, the following step is how to set the C axis position via C axis offset function:

  1. Execute C axis return (Home C)
  2. Press F6 param setting key
  3. Press F4 Home offset setting key
  4. Use up / down arrow key to move yellow cursor to C position
  5. Use MPG to turn C axis at arrow place (right position) , then see what C axis coordinate value shown on monitor
  6. input the value into C position then press enter
  7. Press F3 Run C axis offset , monitor will show to confirm offset .
  8. Press F1 Yes . Find the control will change the C axis to right arrow place position automatically
  9. Please do C axis Home again to confirm the C axis Home position is at right position.   

Video for how to set the C axis Home position via Home offset setting:


First, the error 53 is not alarm or error, it's just say the network can't find . 
CNC-300 don't use network function, it's general PC controller initial start process.  
The correct C axis Home process is 
  1. Rotary table turn CW direction until the Dog (M5 screw) find C axis sensor 
  2. C axis sensor send a signal to controller, ask C axis servo motor reverse turn (CCW) to find the encoder basic (0) point 
  3. C axis servo motor turn CW at C axis offset value (parameter 886 setting C axis Home offset) 
The C axis is not running correctly for Home problem should be caused by C axis sensor. 
How to check the C axis sensor is normal or not: 
Check it before execute C axis Home, the C axis sensor should be OFF. 
The sensor just lights ON in the period during the step of M5 screw Dog go in the sensor top area. 
Two possible reasons to cause the problem: 
  1. Any chip or dust at the locate of sensor, so chip (dust) caused the
    C axis sensor always ON and C axis turn slowly and does not stop.

    Please check it: 
    1-1. Loose 4 pcs M5 screws on cover of rotary table 
    1-2. Take off C axis cover to check the C axis sensor at right/up corner 
    1-3. After open C axis cover, please check the C axis sensor is OFF (no light) or ON (light on) first. If the C axis light ON, mean it's unnormal.
    1-4. Check if there any chip or dust between at the face of C axis sensor. 
    1-5. Clean the head of C axis sensor by air gun, and don't loose C axis sensor screws while cleaning it .

    If the C axis sensor work well (No light), then it could execute C axis Home function again .
  2.  C axis sensor normally work during 4mm space, so if any steel (iron) material at 4mm range of the sensor, the sensor will light ON.

    If C axis sensor can’t be OFF normally after clean chip /dust, maybe is the C axis sensor is too close rotary table OD surface, please losse 2pcs M3 screws to adjust the distance.


Possible reasons to cause C axis servo alarm ALE01:

  1. C axis (Rotary table) servo motor power wires is “Short-circuited”
  2. C axis servo driver is damaged:


How to check - Turn off power then turn on power again, check if the C axis alarm ALE-01 is still on C axis driver monitor or not?

If still show , then check

  1. C axis servo driver 
  2. Check U,V,W wires between C axis Servo driver and bottom connector block Uc,Vc,Wc  is short-circuited or not
  3. Take out C axis cover and disconnect U,V,W connector of servo motor , check U , V, W wires between bottom wires connector to servo motor connector side is short-circuited.


Video for electric engineer to check it to find the reason and solve the problem.



*How to check short-circuited : use electrical multimeter (Volt-Ohm-Milliameter) and turn function on Ohm to check the short-circuited While checking short-circuited , must turn off power.

Ans .

ALE-11 alarm means encoder unnormal.

The Servo motor alarm trouble shooting as attached for reference. 


Please check following items to find the reason:

  1. Check the C axis encoder connector CN2 is connected well or not ? 
  2. Loose 4 pcs M5 screws on the rotary table top cover, take out the cover to find the C axis servo motor at right –front direction of rotary table, check the encoder connector of C axis servo motor is connected well or not ?
  3. Check the CN2 cable between C axis motor end to C axis servo driver end is any damaged or broken?
  4. )Causing by C axis motor encoder damaged, please check it.
  5. Also possible cause by C axis servo driver damaged sometimes.


How to check if the C axis servo driver is OK:

Due to the Y axis and C axis CN2 encoder cable is same but power is different, it can only check it without movement status. Don’t move and note to connect Y axis CN2 back Y axis servo driver, C axis CN2 cable at C axis servo driver.


  1. Turn off power and open electric box:

a-1. Connect C axis CN2 connector to Y axis servo driver CN2 position

a-2. Connect Y axis CN2 connector at C axis servo driver CN2 position

a-3. Turn on power only to check servo driver monitor display

             *Remind: Don’t move machine, only check.


  1. Since the Y axis servo motor and servo driver is OK. 

b-1. If C axis servo motor encoder damaged : Connect C axis CN2 cable to Y axis servo driver, Y axis servo driver should happen ALE-11 .

b-2. Y axis servo motor is OK, so connect Y axis CN2 cable to C axis servo driver, C axis servo driver ALE-11 alarm will go away

b-3.If C axis servo driver damaged, it will see C axis servo driver still issue ALE-11alarm, and Y axis servo driver is OK.


MOT 023 C axis fatal following error exceed & MOT 008 C axis loss pulse could be as one alarm message, it means there is any obstacle stop the C axis smoothly running.


Please find the reason, check by manually:

  1. Check the keyless locking bush of C axis servo motor is tightened completely?  
  2. The servo motor shaft need to connect the timing belt pulley .
  3. If the worm shaft side happen loose or slip problem?
  4. Check the both side shaft was absolute tighten by keyless bush?

    After done the check for item 1~4 but problem not solved:
  5. Please turn off power to release the servo motor torque.
  6. Rotate the worm shaft pulley manually to drive the Rotary table, check the worm and worm gear drive by hand manually is OK? 

    If not, mean there is any obstacle cause motor can’t drive by it smoothly, please check and solve it until you can use hand to rotate rotary table well. 
    *If customer tried to rotate the table by hands but it is hard. Probably it is required to adjust the engagement of the worm with the gear. Please find solution on Q7.
  7. use MPG to turn C axis and check the C axis run smoothly or not?  



***When customer tried to rotate the table by hands but it is hard. Probably it is required to adjust the engagement of the worm with the gear.

Since if rotate the table manually will be difficult have force to rotate it , need to assembly timing belt , then pressed emergency stop to release the C axis servo motor torque power (Let C axis motor free no torque) , and rotate two pulley as video shown :

  1. Without adjusting the engagement: Please do it first.
    If the backlash between worm and worm gear is still tight , then just following second video to adjust the engagement of worm and worm gear.
  2. How to adjust the engagement of warm and worm gear


Due to remove timing belt, so need to rotate the rotary table to suitable position , then add the value to parameter 886 by MPG ( C axis Home offset value to adjust the C axis T slot direction).

How to take the value of parameter 886:

  1. Press F6 parameter key ,
  2. Press F5 Goto parameter
  3. input 886 + password
  4. Do C axis zero return , then witch MPG mode,
  5. Turn C axis to the position in need  
  6. Add the value to 886 parameter value .


For example: Turn to + 12.500 degree , it can add the 12515 into the original position as new position .

Please change 886 value to new value, then do C Home to check the C axis zero point is at new position.

Usually there are 4 possible reasons caused it :

1.The C axis servo motor or servo driver problem:

1-1.Take off C axis timing belt , turn off and turn on power again to check it.

1-2.Press MPG mode , switch MPG at 4 to use MPG rotate the C axis servo motor under no loading status .

1-3. If C axis motor pulley can run smoothly under without connecting timing belt status , or the controller don’t show C axis servo driver alarm message →C axis servo motor and servo driver is no problem.


After confirmed C axis servo motor and servo driver no problem, then focus the problem caused by C axis Mechanism:

2.Check motor side pulley :

There have two keyless bush in pulley to tighten motor shaft with pulley.

If keyless bush don’t tighten well (loose) , it will cause servo motor happen unstable load and let the timing belt driving not smoothly ,then cause C axis servo motor happen overload suddenly , so that controller issue C axis fatal following error exceed and C axis servo driver alarm .

Vdeos for Keyless bush checking:  



3. Use hand to rotate rotary table side pulley (Worm shaft side pulley) to let rotary table rotate. Please rotate worm shaft pulley to test one complete circle and confirm there is not any obstacle during rotation in 360 degree.

Also check the pulley was completely fixed with worm shaft well.

Video for How to check worm shaft /worm gear mechanism: 


4. The timing belt too tight.

Please use hand finger press timing belt center position by 1.3kgs , the timing belt should be able push down about 2.1mm depth.

If the timing belt too tight, It will let motor side happen abnormal force or let drive not smoothly then happen motor over load problem, please adjust timing belt at suitable status.

Ans :

The C axis servo driver will show 7 then 1 then 0 when C axis happen overload alarm 710H and 910H .

The possible reason is from mechanism of C axis rotary table or C axis servo driver /C axis servo motor damaged.


  1. Please turn off power then turn on power again, don't run C axis and check the C axis driver display show about.
    If after turning on power, then C axis alarm message still showing like O,7 …. Etc. → C axis driver or C axis motor damaged.
    Normal C axis driver will just show dot like :

    If it’s normal and CNC controller screen no issue alarm
    → C axis servo driver and C axis motor no problem , then the problem comes from C axis mechanism ( see item 2.)
  2. Check the C axis mechanism:
    A.If there have any obstacle stop the C axis smoothly rotating:
    1. Take out the C axis rotary table cover to check
    2. Use MPG mode, press monitor to C axis loading rate for check C axis loading : 
    3. Turn C axis by MPG slowly to find where to cause the C axis can’t turn smoothly. 
    4. After find the position, press emergency stop button to servo off C axis motor.
    5. Turn worm side timing-belt pulley manually by hand, it needs to can manually turn by hand.  If not, please trouble shoot it. 

    B. keyless bush maybe loosens:
    1. Please double check and tighten the keyless bush well. 
    2. After confirmed C axis rotary table can turn by manually and smoothly, turn off power and turn on power again to check the C axis running loading is normal or not.

       Video for instruction: 



MOT 36 is “C axis can't leave home dog “, PLC 068 is “C not yet back Home”.

Normally, C axis sensor should be under OFF.

The sensor just works while the home dog moving into the working area of sensor within 4mm distance.


C axis sensor just light ON during C axis dog at C axis sensor, and work at period of C axis Home process, at the other time C axis sensor light ON is unnormal.


Two possible reasons to cause error MOT36 and PLC068:

1.Sensor touch to the bottom plate of C axis cover :

  • 1-1. Please loosen 4 pcs M5 screws to take out C axis cover
  • 1-2. Find the C axis sensor at right -45-degree position.
  • Take out the C axis cover .
  • 1-3. If the C axis sensor is OFF, please execute C axis Home again. After that, if it's normal, please install C axis cover again then execute C axis Home.
  • 1-4. If it happen C axis can't leave Home dog, possible reason is C axis sensor active area the bottom surface of C cover, please adjust the C axis sensor angle downward avoiding sensor look the C axis cover bottom surface.
  • 1-5. After adjusting the C axis sensor position well, test C axis process again. 


2.If the C axis sensor light still ON, possible reason is proximity switch (sensor) too close the OD of rotary table.

  • 2-1. Please loose the 2 xM3 screws to move the sensor out a little
  • 2-2. Use MPG to move M5 C axis Home dog into sensor working area and test it , it should be M5 screw (C dog) in sensor area , it light ON and sensor must off while M5 screw move out sensor working area .


Note: Sensor also can't too move outside too much, it will cause sensor can’t work while M5 C axis dog move in sensor working area.

Please adjust the sensor at suitable position, then test C axis Home process again to confirm the C axis sensor position is correct, then fix it well. 


  1. Please checked C axis mechanism no problem first.
  2. Double checked C axis can rotate +360 degree and - 360 degree smoothly to confirm the C axis rotary table mechanism 100% no problem.
  3. After checked the C axis mechanism is no problem, the possible reason is possibly caused by AC servo motor.
  4. According to the servo motor alarm message, ALE-04 is servo motor problem. Servo motor supplier suggested to buy a new servo motor to replace or send back motor for inspection. *Please discuss with EASTAR for this issue.

Ans .                                            

The problem is possibly caused by:

1. C axis (Rotary table) can't turn smoothly:Check any obstacle at C axis to cause C axis can't run smoothly (overload).

1-1. Turn off power first , then turn on .

1-2. Go to MPG mode and use MPG to turn C axis forward and backward to check the C axis can run smoothly.

1-3. If C axis can run smoothly, then do C Home again.

1-4. If C axis can’t run smoothly, then need to check where to cause it can't run smoothly, then try C home again.                                         


2. If it still can’t do C Home after MPG test

2-1. Take out C axis guard

2-1. Please use hand to turn the pulley and check it can turn smoothly by hand

2-2. If not, then check worm and worm gear matching clearance is too tight or not ? 

2-3. Adjust C axis mechanism run smoothly, then MOT 23 problem can be go away.


The problem is caused by C axis overload problem. And it is possibly caused from the mechanical trouble:

1.Worm drive worm gear mechanism:

Take out the belt and use hand to rotate worm side timing belt pulley, to check worm can drive the worm gear smoothly without obstacle.  

2. After that, check the servo motor side pulley :

Please confirm the inside keyless bush was tighten completely and locked well, the overload could be cause by the inner keyless bush don’t holding /tighten the shaft , so caused the ALE-09 overload problem.

Please check the above two items carefully, video for reference:

  1. keyless bush checking


  1. how to check worm shaft /worm gear mechanism: 




Those C axis alarm was caused by :

  1. C axis mechanism (worm/worm gear)
  2. Motor pulley which Inside keyless bush do not tightens well. 
  3. Timing belt too tight.

How to solve:

  1. Please take off timing belt, let C axis servo motor under no load status
  2. Turn off power then turn on power again.
  3. If the controller only shown X not yet back Home, Y not yet back Home , C axis not yet back Home → means that C axis servo motor and driver is normal.
  4. Then using the MPG mode, switch to 4 (C axis) , use MPG to rotate the C axis servo motor, if it can rotate smoothly, it means the C axis servo motor is no problem.

***Then focus the problem caused by following possible reasons:

1.Motor pulley side which inside keyless bush don't assembly well: 

Not completely tighten, when connect timing belt to worm shaft side pulley, the motor shaft pulley tilting , caused have abnormal loading force , then controller issue the above alarm.


2.Worm shaft side pulley can't drive the Inside worm gear smoothly:

Maybe there is any position face obstacle etc .

While C axis servo motor would like to rotate it via timing belt, the load too big, so controller issues the above alarm.

Please use hand to rotate by hand to check it can rotate one circle no problem, confirm there is without obstacle during one complete circle rotating.


After confirm item 1 . motor shaft side pulley and item 2. worm shaft side pulley is OK.

3.Connect timing belt :

Please notice the timing belt cannot too tight , otherwise it will have abnormal load to C axis servo motor shaft side , servo motor will also issue alarm .

When install the C axis timing belt , please use hand finger to press the middle of timing belt , the push force is about 1.3kgs  , the push down distance is about 2.1mm .