Gerber Sabre 408 Error Z Encoder/Motor

[Mikexx]

I'm a newbie to this machine and had it working for a short while.

Recently, when turning on the machine I got the above error. I also have an illuminated Red LED for AMP FAULT.
All the green LEDs are lit apart from SPIN #2

My background is in embedded systems (mix of electronics and software) so hope to delve deeper into this in a meaningful way.

I can confirm the Z-Limit switch is functioning as expected.

Any help would be appreciated. Also any pointers to the Service Manual would also be appreciated.

 

[Mikexx]

I've downloaded various manuals from:
https://www.service-manual.net/?download=57239-gerber-sabre-404-408-series-service-manual
for $13.

Unfortunately it doesn't have any of the PCB circuit diagrams for the boards in the Electrical Tower. So don't feel much further forward :-(

 

[David A]

Not sure it's referred by the error code, but take the top cover off the spindle carrier and look to be sure the circular clamp that holds the motor drive to the z-axis worm gear isn't broken - try to move it by hand - it's not always easy to see if there's a crack. A broken clamp might be the cause of the z-axis error.

 

[Mikexx]

Not sure it's referred by the error code, but take the top cover off the spindle carrier and look to be sure the circular clamp that holds the motor drive to the z-axis worm gear isn't broken - try to move it by hand - it's not always easy to see if there's a crack. A broken clamp might be the cause of the z-axis error.

Many thanks for the idea.

I have the cover off and I can rotate the work and can confirm the motor is connected. All looks and behaves in a mechanically sound way. Before I get the long 'beep' the motor and screw does 'inch' down a small motor step. I have also checked the limit switch which operates as expected. s/c when z-axis is down and o/c when the limit switch is operated.

The service manual gives possible causes and solutions for the “Error: Z Encoder / Motor” message. Namely:

1) Swap Z Motor & Encoder Cables (#'s 163 & 164)
with X Motor & Encoder Cables (#'s 154 & 155) at
Tower and retry. If error now reports as X
Encoder/Motor, Problem is "on the table"
(Remember to replace the Cables to their proper
Tower Connections).

2) Remove Z Motor from top of Carriage and attach
directly to Tower in place of the Z Motor & Encoder
Cables (#'s 163 & 164). Retry. If no error, one of the
Cables is bad. Repair/replace as required. If Error
still reports, see next step below.

3) Remove side of Electrical Tower. Swap the Z
Servo-Amp Board Assembly with the X Servo-Amp
Board Assembly. Retry. If error now reports as X
Motor/Encoder, replace the Servo-Amp Board
Assembly. If error still reports as Z Motor/Encoder,
replace the Servo-Motor.

I did (1) where the error was still “Z Encoder / Motor”
I also did (3) without swapping the cables back to try and eliminate the Z Servo-Amp PCB but the error still comes up as “Z Encoder / Motor”.

By doing all this I feel I have eliminated any problem with the Z Servo-Motor, Z limit switch and the Z Servo-Amp PCB.

 

[packratsigns]

Many thanks for the idea.

I have the cover off and I can rotate the work and can confirm the motor is connected. All looks and behaves in a mechanically sound way. Before I get the long 'beep' the motor and screw does 'inch' down a small motor step. I have also checked the limit switch which operates as expected. s/c when z-axis is down and o/c when the limit switch is operated.

The service manual gives possible causes and solutions for the “Error: Z Encoder / Motor” message. Namely:

1) Swap Z Motor & Encoder Cables (#'s 163 & 164)
with X Motor & Encoder Cables (#'s 154 & 155) at
Tower and retry. If error now reports as X
Encoder/Motor, Problem is "on the table"
(Remember to replace the Cables to their proper
Tower Connections).

2) Remove Z Motor from top of Carriage and attach
directly to Tower in place of the Z Motor & Encoder
Cables (#'s 163 & 164). Retry. If no error, one of the
Cables is bad. Repair/replace as required. If Error
still reports, see next step below.

3) Remove side of Electrical Tower. Swap the Z
Servo-Amp Board Assembly with the X Servo-Amp
Board Assembly. Retry. If error now reports as X
Motor/Encoder, replace the Servo-Amp Board
Assembly. If error still reports as Z Motor/Encoder,
replace the Servo-Motor.

I did (1) where the error was still “Z Encoder / Motor”
I also did (3) without swapping the cables back to try and eliminate the Z Servo-Amp PCB but the error still comes up as “Z Encoder / Motor”.

By doing all this I feel I have eliminated any problem with the Z Servo-Motor, Z limit switch and the Z Servo-Amp PCB.

Z limit also can be a ground issue, two sets of z limit switches run from the machine to the controller. Could also be a static thing. Turn the machine off, push the head down manually. Start machine backup and use the keyboard to clear it if it happens again and then hit enter a couple of times. Repeat this until it clears and it should be fine. It usually holds this in its memory and needs to be cleared. If it doesn't go away then you may have a broken wire and you can check continuity of the wires on the switch back to the wire end that plugs into the controller. If the wire is bad you can switch the wires on both ends to use the two spare ones that were from the original build of the machine.

 

[Mikexx]

Z limit also can be a ground issue, two sets of z limit switches run from the machine to the controller. Could also be a static thing. Turn the machine off, push the head down manually. Start machine backup and use the keyboard to clear it if it happens again and then hit enter a couple of times. Repeat this until it clears and it should be fine. It usually holds this in its memory and needs to be cleared. If it doesn't go away then you may have a broken wire and you can check continuity of the wires on the switch back to the wire end that plugs into the controller. If the wire is bad you can switch the wires on both ends to use the two spare ones that were from the original build of the machine.

Thanks for the reply. Any suggestion is very welcome.

The Z-Axis has a single limit switch, with the second hardwired to be a s/c.

The X, Y and Z axis limit switches and motor/encoders are identical. In theory it is possible to mix and match these to the Electrical Tower and the machine would operate similarly, albeit with the directions being transposed.

I have swapped the X and Z axis connectors as specified by the Service Manual and confirm the error is still in the Z-Axis. This should eliminate the possibility it's a limit switch or a servo motor/encoder issue.

The red fault LED comes on immediately after switch-on, so currently think it may be a PCB or other internal connection fault.

I'm currently stuck with a non-working machine. A set of circuit diagrams for the control Electrical Tower would allow me to home in on the fault.

 

[JBurton]

2) Remove Z Motor from top of Carriage and attach
directly to Tower in place of the Z Motor & Encoder
Cables (#'s 163 & 164). Retry. If no error, one of the
Cables is bad. Repair/replace as required. If Error
still reports, see next step below.

Try this. You could have a pinched wire going to you z axis motor. According to what you've done so far, it's a bad motor, but if you do this step you can eliminate a bad cable/connection to the motor, which is much cheaper to repair.

 

[Mikexx]

Thanks for the suggestion.

I have already swapped the connectors for X and Z motor encoders and get the same error. I therefore beleive I had eliminated both the Z motor/encoder and the Z wiring from causing the error/fault.

 

[JBurton]

You can't eliminate the z wiring until you pull the motor and put it next to the cabinet and wire it direct. Currently it sounds like the z motor, but hopefully you find the cables have a bad spot.

 

[Mikexx]

You can't eliminate the z wiring until you pull the motor and put it next to the cabinet and wire it direct. Currently it sounds like the z motor, but hopefully you find the cables have a bad spot.

Many thanks for your reply.

Yes, that may be another compounded problem, but this was working before the fault and when the X-Motor/Encoder plugged into the Z-Motor/Encoder socket and visa-versa I still get the error for the Z-axis.

As a result, I feel I can discount both the Z motor/encoder and the Z wiring from causing the error/fault.

 

[JBurton]

X-Motor/Encoder plugged into the Z-Motor/Encoder socket and visa-versa I still get the error for the Z-axis.

It goes
Board---------->Encoder----------->Motor
So swapping the encoder is only meant to tell you if the encoder is the problem. Swapping z encoder to x, and seeing the error change to the x axis, indicates it's the z encoder. No change in the error means its either in the wiring between the z encoder and motor, or it's the motor itself. Since getting a new motor in for troubleshooting is not feasible, pluck that bad boy off the machine and run it straight into the encoder.
Your problem is one of three things at this point (In order of least expensive to most expensive): cable, motor, board.

 

[Mikexx]

It goes
Board---------->Encoder----------->Motor
So swapping the encoder is only meant to tell you if the encoder is the problem. Swapping z encoder to x, and seeing the error change to the x axis, indicates it's the z encoder. No change in the error means its either in the wiring between the z encoder and motor, or it's the motor itself. Since getting a new motor in for troubleshooting is not feasible, pluck that bad boy off the machine and run it straight into the encoder.
Your problem is one of three things at this point (In order of least expensive to most expensive): cable, motor, board.

Sorry, but where am I going wrong?

If I plug the X-Motor/Encode and X-Limits plugs into the Z-Motor/Encode and Z-Limit sockets on the electrical tower and get the same fault, why haven't I eliminated issues or faults with the Z-Axis motor and encode and Z limit switches?

 

[JBurton]

I think I see where I was confused

I have already swapped the connectors for X and Z motor encoders and get the same error

I thought you meant you swapped the encoders themselves, not the connections running to the table.

I also did (3) without swapping the cables back to try and eliminate the Z Servo-Amp PCB but the error still comes up as “Z Encoder / Motor”.

So here's the other issue, I think. Redo step 3, with the cables as they should be installed, and see what you get. If you get it to say X axis error, it may be the motor itself. The way you tested step 3 previously had the z encoder talking to the z motor. If the Z motor is buggered, it won't communicate back to the encoder properly. If you swap the cables to their default location, the X encoder will try to communicate with the Z motor, which will test whether the Z encoder or the Z motor is bad.
My head hurts after typing this, basically redo step 3, exactly like they say to, see what error that gives.

 

[Mikexx]

I think I see where I was confused

I thought you meant you swapped the encoders themselves, not the connections running to the table.

So here's the other issue, I think. Redo step 3, with the cables as they should be installed, and see what you get. If you get it to say X axis error, it may be the motor itself. The way you tested step 3 previously had the z encoder talking to the z motor. If the Z motor is buggered, it won't communicate back to the encoder properly. If you swap the cables to their default location, the X encoder will try to communicate with the Z motor, which will test whether the Z encoder or the Z motor is bad.
My head hurts after typing this, basically redo step 3, exactly like they say to, see what error that gives.

Many thanks. I redid step 3 exactly as per instructions and I still get the error on the Z-Axis. It seems any permutation of limit switches / Motor/Encoder / Driver PCB I get an error on the Z-Axis.

As I have said, I appreciate any ideas.

 

[fdarling]

Many thanks. I redid step 3 exactly as per instructions and I still get the error on the Z-Axis. It seems any permutation of limit switches / Motor/Encoder / Driver PCB I get an error on the Z-Axis.

As I have said, I appreciate any ideas.

If you swap all 3 cables related to the Z axis (motor, encoder, and limits) with another axis such as X, and it doesn't move the axis error, then it's one of three things:

1) the emergency stop cable going to P123 on the motherboard is unplugged, or the cable is damaged (not completing a circuit properly)
2) the motherboard *thinks* the emergency stop cable is unplugged/damaged, due to fried circuitry.
3) the Z axis related circuitry on the motherboard is damaged, so it doesn't matter what is happening externally

A lot of people don't realize that the E-stop circuit can raise this Z axis error message. (Gerber acknowledges that the error message is misleading).

Either way, the issue can be tracked down by using a USB logic analyzer and monitoring various points on the motherboard to see how signals are propagating to the CPU board. You can see my reply here where I talk about this:

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