Problem- Nakamura Slant Jr. - Fanuc 10T spindle alarm

[nlh]

The machine is an early to mid 80's Nakamura Slant Jr. It has a 10T fanuc control. Machine was installed a few weeks ago and everything was verified to be in working order.

A couple days ago the machine was powered up to do a job, and both the Spindle and Machine alarm LED's were activated on the control panel.

The CRT only shows that there is an E-Stop condition but doesn't show any other alarms or messages. The spindle drive itself doesn't have any of the alarm LED's activated. Green PIL light is on. I have checked voltages and found most everything as it should be. The correct power is going into the spindle drive.

The only thing that I have found so far that struck me as a little funny was the power input to the servo drive/s (this machine has some sort of shared servo drive between x and z axis). There are 3 black lines, R S and T. Voltage measured in reference to ground is 177v on both R and T, on S it measures 20v AC. Is this right? It sure doesn't sound it. I tried tracing it back but there are only 2 transformers and all the taps are putting out the correct voltage.

This one has me really stumped. I have no formal training in electronic or machine repair but I've been able to pick up enough knowledge along the way to do my own repairs.

Any ideas what could be going on here? I don't have alot of experience with Fanuc controls, mostly Yasnac and Mitsubishi(Mazak) experience. I really appreciate any advice I can come across to get this machine going again.

Thanks,
Nate

[GPena]

Well, if you read that voltages between R,S,T and groung then there is something bad, and the problem is that. If I am not wrong your drives must be 220 Volts between phases (R,S,T). Check your input voltages and follow the line to the drive, it is possible that the drive is energized through a mangentic contactor and maybe that MC is bad, try to follow the R,S,T line and see what is going on there.

Good luck.

GP.

[nlh]

Thanks for the input GP,

I'll see what I can find.

[nlh]

GP,

I was finally able to find the time to work on the machine today. I traced the R,S,T wires back to a large transformer (Fanuc #A80L-0001-0426-01). These lines connect to taps labeled 185V. There are no contactors involved in this area. There are also another set of taps directly below these on the same connector bar that are labeled 175V. Checking voltages at these locations gave the same results as the ones at the drive. The transformer appears to have a bad winding.

Now, I have an idea, but before I try it I want to see what others think. Incoming voltage is 208. On the input side of the transformer there are many different taps for voltages up to 460. Since I am using 208, would there be enough margin for error by wiring directly from the 208 side to the inputs on the servo drive? 208 vs 185? At least for the time being until a proper replacement can be sourced.

What do you think?

Thanks
Nate

[cnc2149]

If your CNC is in ESTOP with no other fault messages, it is normal that the spindle servo amplifiers will not be energized (the MCC will be dropped out). You should try to determine why the CNC is in an ESTOP condition.

There are 2 input signals that must be satisfied in order to relesase ESTOP:

1. X008.4 is a hardware input (24VDC) that must be present. It could be used with an I/O Card, I/O Base Unit or Connection Unit 1 board, depending on what this machine builder uses for his I/O connections.

2. There is also a G-coil in the ladder that must be a logic 1 in order to release ESTOP.

G000.4 if using BMI interface

G010.4 is using FS3 or FS6 interface

You can examine the status of the bits by going to the PCDGN page. Press NC/PC to go to the PMC side. Then go to PCDGN page and observe the bits listed above.

Report back with the settings in CNC parameter 2001 if you are not sure which interface this control uses.

[nlh]

cnc2149,

Thank you for the input on this problem. The machine is unfortunately at another location and I won't be able to get back to it until possibly tomorrow but more than likely next week. Very interested to check these items you posted against my machine.

I will say however that there isn't any MC between the transformer output and the power input to the drive. I have confirmed this both physically by tracing wires and also with the electrical manual (which is the only manual I have). The weird voltages I found present were measured not only at the drive, but also directly at the output taps from the transformer.

When I know more, I'll let you know.

Thanks,
Nate

[cnc2149]

If you have FANUC Spindle and Axis Servo drives, their is an internal MCC contactor in each of them. An ESTOP input condition will drop them out. If the drives themselves were unhappy with the AC input voltage levels, they each have monitor circuits that would post such faults as HV (High Voltage), LV (low voltage) or DC (discharge Alarm). Good luck with tracking the ESTOP - they usually are not technically too difficult to correct.

[nlh]

Thanks again! I Will let you know what I find.

[nlh]

GPena,

It took me awhile but yesterday I was finally able to get back to the machine and check the things you mentioned.

Here is what I found,

G000.4 in the PCDGN page was all 0's.

I could not find address G010.4 anywhere.

Onto CNC parameter 2001 it read 00100000.

Does this give any insight on what's going on?

Please post back with your thoughts.

Thanks again,
Nate

[cnc2149]

Since you have par 2001 bit 5 = 1, this machine uses the FS3 interface.

The Estop bits are as follows:

X008.4 Estop (Hardware input) if you have built-in DI/DO card

G010.4 Estop (PMC G-bit coil)


In order to see the G010, you should go to the PCDGN display and then press the Page Down key. You can also eventually page down to the X008 to record the hardware X input. In order for the Estop condition to be released, both of the bits must be logic 1. Usually, the ladder is written so that the X bit will be in the network that controls the G bit, so the problem usually requires you to chase the X bit in the machine wiring. X008.4 comes in at connector M1 (19) on the built-in DI/DO board. It must have 24VDC present to release the Estop condition. Make sure that the Estop pushbutton is released, door guards all closed, air pressure up, etc.

[nlh]

I have some further information to add here. Today I had the opportunity to look at the machine again. Unfortunately it was not a planned event and as such did not have the ladder/wiring diagrams nor a printout of this thread. Instead I decided to pull and reseat the I/O card. When I pulled the card (A16B-1210-0322/03A), I found a small 3.2A fuse that was blown. I had a spare so I swapped it out, reinstalled the board, and found that upon power up, it blew again.

What does this fuse protect? Does it protect the board from the incoming voltage, does it protect an Input from a faulty circuit from somewhere in the machine, or could it possible protect a circuit in the machine from a faulty Output from the card, or something else? I have a feeling if I can solve the fuse issue, probably everything else will follow.

Thanks again!

[cnc2149]

The blown fuse on the Built In I/O Card explains why you are missing the 24VDC at the Estop Input. There is a short in the machine wiring or a device (e.g. switch) that is blowing the fuse. To confirm, replace the fuse and power up with all of the I/O Card Honda plugs disconnected. The fuse will most likely NOT blow in this situation.

To isolate where the external short is, you'd have to look at the 24V commons on each of the Honda cables to see if you can find the short.

FANUC outputs 24VDC on the following I/O Card connection points:

M1 pins -29, -30, -31, -32
M18 pins -30, -31, -32
M20 pins -30, -31, -32

With the machine turned off and the Honda plugs disconnected, I'd put an ohmmeter to each of the above pins with respect to 0V. You are looking into the cable side (not the I/O Card side) of the connection.

Nakamure may not have used all of the contact pins so they may measure open. If you measure a short, then you have found the 24VDC common where the short circuit exists. You may find it on more than one connector so it may not be so easy to trace within the machine wiring. If you don't feel comfortable tracking down the short at this point, you can bring in any machine service man and he should be able to chase it.