PLC not following program set

[John Lee]

Hi hopefully this helps

 

[drforsythe]

Do you have an electrical schematic of the system? I assume this is a three phase powered system. Check that you have the proper voltage level on all three phases at the drives. We still don't know what kind of motors / drives are in the system, but a missing phase will cause lower power, slowing the motors. Normally, this would generate a bus fault, but that could have been disabled depending on the drive manufacturer.
Is it one drive per motor, or multiple motors per drive? Need more info to go further.

 

[robertmee]

More than likely, the two 5HD01 modules, which are 4 channel analog output modules, are your speed setpoints to your 8 spindle drives. It's unlikely both modules and 8 channels have failed. Which means either the scaling in the program was changed, or the scaling at the 8 drives were changed. Those modules support both voltage and current (0 to 10v, 4-20ma), so you'd have to do some investigating as to what the signal should be, but you could measure them. However, again, if all 8 drives are running slow, it's likely that they are being told to from the scaling in the PLC. There could be a remote possibility that those modules are set for 0-10v, and the supply voltage has failed and drooped, so instead of send 8V for X RPM, the module is only managing 6V. The supply voltage for those modules should be 24VDC on connector pins 1 and 20 (L+ and M), so I'd start there if you're 100% certain noone could have changed a scaling factor in the PLC. Also to consider, these modules are programmed for their voltage output type. They could be 0 to 10V, 1 to 5V and +-10V. Default is +-10V, so if they were operating at 0 to 10V, and someone set them to 1 to 5V, you'd get apx half the voltage.

Alot of speculation. You really need someone to get online with the PLC and drives to see the scaling relationship between the two. If you're not capable of that, check the supply voltage on those two analog modules to see if you have much less than 24V. Barring that, not sure what else to tell you.

If you're certain the control system scaling hasn't been altered, then I would go back to my original thought and what others have suggested. Look at the supply voltage to the drives and measure for lost phase or droop.

 

[robertmee]

@John Lee seems to be saying that the rotation speed (RPMs) displayed in the HMI is correct, but that the spindle is actually moving at a slower rotation speed.

We don't know where the rotation speed (RPM) displayed in the HMI is coming from, but it is probably a measured value (e.g. encoder, etc.). But we do know that the actual spindle rotation speed (RPM) is slower than that HMI-displayed value. So I think the problem is somewhere between the measurement system and the HMI display. Unless someone changed some scaling parameters in the PLC and/or HMI, the problem is unlikely to be downstream of the RPM input on the PLC. So I would start at the sensor and transducer and whatever else is between the sensor and the PLC. That is why I suggested looking for a physical disconnect between the spindle and the encoder (or whatever) device.

There is no rotational feedback from the pictures. It's a dumb system. All discrete IO and Two 4 channel analog output modules that are likely sending speed to the 8 drives. The RPM is therefore a setpoint, not feedback. A blind system so to speak.

Edit: That's assuming they're not talking across Profibus to some drives.

 

[John Lee]

Thank you I appreciate your knowledge

I can run the machine but when it comes to this it’s beyond me and we don’t have anyone that can help that’s why I joined trying fix this situation

 

[John Lee]

Where I check the voltage ?

 

[robertmee]

Thank you I appreciate your knowledge

I can run the machine but when it comes to this it’s beyond me and we don’t have anyone that can help that’s why I joined trying fix this situation

Unfortunately it's going to take some electrical and mechanical diagnostics to solve. If you're not comfortable doing it or have someone there that can, best to hire a local PLC integrator to assist. It appears to be a fairly simple machine, so shouldn't take long to diagnose. If noone there is capable of going online with the PLC or HMI, and so no chance of anyone fat fingering a setting, most likely a failure:

Supply voltage of those analog cards
Supply voltage or loss of phase to drives/motors
Mechanical binding or slippage in the drive system.

The PLC itself would be a useful tool to help diagnose, but almost certainly not the root cause, software wise. Unless there is a settings menu (often OEMs include) on the HMI where the scaling of the RPM setpoint is adjusted, and someone accidently changed a value.

 

[John Lee]

Do you have an electrical schematic of the system? I assume this is a three phase powered system. Check that you have the proper voltage level on all three phases at the drives. We still don't know what kind of motors / drives are in the system, but a missing phase will cause lower power, slowing the motors. Normally, this would generate a bus fault, but that could have been disabled depending on the drive manufacturer.
Is it one drive per motor, or multiple motors per drive? Need more info to go further.

Where would I see if it’s 1 drive or multiple? Please

 

[robertmee]

Where I check the voltage ?

For the two 5HD01 modules, on the pins I said in my post. Meter on DC.

For the drives/motors, would depend on the drive and motor. And if youre not knowledgeable on doing so, not something to experiment with. Those voltages are likely AC and have the potential to hurt you when poking around.

 

[robertmee]

Where would I see if it’s 1 drive or multiple? Please

Is there one of those per spindle, or does that drive all the spindles?

 

[John Lee]

Is there one of those per spindle, or does that drive all the spindles?

Per spindle

 

[robertmee]

I'm guessing the Rothy 806X7 is possibly the drive...its an AC to DC converter. If you trace the motor leads from your spindle motor back to the cabinet, where do they terminate?

I haven't found a manual in English on that drive, so maybe someone else has some experience with it. Possible that this unit has failed as well.

 

[John Lee]

Unfortunately it's going to take some electrical and mechanical diagnostics to solve. If you're not comfortable doing it or have someone there that can, best to hire a local PLC integrator to assist. It appears to be a fairly simple machine, so shouldn't take long to diagnose. If noone there is capable of going online with the PLC or HMI, and so no chance of anyone fat fingering a setting, most likely a failure:

Supply voltage of those analog cards
Supply voltage or loss of phase to drives/motors
Mechanical binding or slippage in the drive system.

The PLC itself would be a useful tool to help diagnose, but almost certainly not the root cause, software wise. Unless there is a settings menu (often OEMs include) on the HMI where the scaling of the RPM setpoint is adjusted, and someone accidently changed a value.

I do have a settings menu for adjusting the RPM on the HMI

I can check the set point


Just the spindles 3 of the motors are set to the program and one of them turns off “randomly” and after the machine rotates it wakes up again but still not running the proper RPM from plc

 

[Steve Bailey]

Here's a link to a German language manual for the 806x7 drive. http://rossmanith.de/wp-content/uploads/2012/04/1S4111BA.pdf

It appears to be a permanent magnet DC motor. I can't read the armature voltage from the picture provided, but if you measure the voltage across terminals X3.13 and X3.14 you should measure the nameplate voltage at full speed of 1680 RPM. At half nameplate voltage you should see half anmeplate motor speed.
You can measure the speed command at terminal X2.5. There should be a direct relation between the voltage at X2.5 and the voltage across X3.13 - X3.14. At 10 volts on X2.5 you should see nameplate voltage on X3.13, X3.14. At 5 volts on X2.5 you should see half the nameplate voltage on X3.13, X3.14

Be extremely careful making your measurements. If you're not sure of what you're doing, hire someone who knows how.

 

[John Lee]

I'm guessing the Rothy 806X7 is possibly the drive...its an AC to DC converter. If you trace the motor leads from your spindle motor back to the cabinet, where do they terminate?

I haven't found a manual in English on that drive, so maybe someone else has some experience with it. Possible that this unit has failed as well.

Yes I see the rothy boxes are the amount of spindles that spinning


I am in South Jersey how I can find someone to look at it ?