Fanuc servo / encoder problem

[Andy Fritz]

Hi all!

I just bought an old Hitachi Seiki VA35, VMC from 1981 and the z axis servo might have been rolling around in the container. After powering up the mill and Fanuc 6MB control there are no warnings, but the Z shows 0.000 on the crt, even though the Z axis is way down as the spindle is locked to the table for transport. Jogging it does not work, but X and Y jogs fine.
It is not out of travel as the limit switch is not tripped.
I meassured the voltage coming out from the pulse coder multiport on the Z servo and it is barely noticable. Then I did the same on the X and it was a lot higher. So, this would suggest the pulse coder is broken, or am I jumping to conclusions too fast? Could there be something feeding the pulse coder from the NC or electrical enclosures broken?

Would it be a good or bad idea to simply swap the drivers to see if the control can move the Z using the driver from the X or Y? Would that mess something up?

On the DC servo there are 4 plastic screws with coin slots behind rubber caps. Are they the encoders attachement point to the servo?

Is there an easy way to remove the encoder and do some tests to see if it is broken?

Are there any glass fuses inside the encoder / DC servo motor housing?
I tried to find any fuses in the electronic enclosure but found nothing, (or don't know what they would look like!).

Thing is: I live on a tropical island and there are no service techs around. If I can find out that the encoder is in fact dead, I could just order another and get on with chip making.

The Fanuc DC servo is a 20M, model number AO6B-0652-B,(last digits ilegible but it reads (25POM) in the end). The serial is M130825.

Any help or suggestions would be great!

Andy

[HillBilly]

The coin slots behind the rubber caps are the motor brushes. It would be best to look at the drives and see if Z is showing a fault.

Another thing to check is the spindle chiller. If I remember correctly it is interlocked to the Z axis on these machines.

Darek

[Andy Fritz]

Thanks for the info!

I checked all driver boards and they are fine. I did a diagnose check on the Micon 8 aux control and it all shows no warnings. I tried swapping Z and X encoders and X is travelling fine using the Z encoder. Z axis is still not moving. All interlock are supposed to be bypassed if pressing spindle stop button in the same time as jogging. Also this does not work.

The ATC is not responsive to manual operations other than magazine commands, like rotate, tool select etc.

I have searched the manuals for spindle chiller but found nothing.

The mill is supposed to get shop air, but I have none and it looks like it was never used before either. The ATC is using the air, but I am not sure how.

Could the lack of air be causing the problem?

Andy

Originally Posted by HillBilly The coin slots behind the rubber caps are the motor brushes. It would be best to look at the drives and see if Z is showing a fault. Another thing to check is the spindle chiller. If I remember correctly it is interlocked to the Z axis on these machines. Darek

[Al_The_Man]

It may be possible that the air may be used for Z axis counter balance, but usually is Hydraulic, if you have it.
If you are getting no faults or alarms then it would seem that encoders or drives are OK.
Do you have documentation, including the Ladder diagram?
Al.

[Andy Fritz]

Hi Al,

Thanks for the input.
The only thing about the air mentioned in the manuals is that it is used to blow through the spindle between tool changes. As the PT 1/4" air fitting was completely filled with dirt, it would appear it was never used though.

The unit has a hydraulic system and it is working. The Z motor also have a brake and it is engaged, but should likely get diengaged automatically on traverse.

I have full documentation for the unit, but not the Fanuc 6MB control.

Also complete wiring diagram, but I don't have enough tech knowledge to make much out of it.

The Micon 8 auxillary control have a means to check what signals are active and there is one parameter that indicate that Z axis is interlocked. With what it is interlocked with I don't know. I would suspect the ATC as it needs to coordinate with the spindle and Z axis for tool changing.

Another strange thing is that I can not move the double tool arm manually.
The tool magazine works as I can manually rotate it, though.

The Fanuc have a lot of parameters, but as I don't have any parameter sheet I can't risk changing stuff around.

If there is any member of this forum who have the parameter sheet for a Fanuc 6MB I would be eternally greatful for a copy per email.

I will look for a ladder diagram.

Andy

Originally Posted by Al_The_Man It may be possible that the air may be used for Z axis counter balance, but usually is Hydraulic, if you have it. If you are getting no faults or alarms then it would seem that encoders or drives are OK. Do you have documentation, including the Ladder diagram? Al.

[Al_The_Man]

I would not start changing any parameters, but I would make sure you have a copy, if not download them.
You may also want to try the cnczone.com CNC forum, also there is MMSonline and I believe there was an Hitachi-Seiki forum started a few months ago.
(Sorry it was a Mori-Seiki site)
Al.

[HillBilly]

These are some notes i made for a VA65 with Fanuc 6M control.

1. Air interlock keeps machine from coming out of E-stop.
2. Micon must display "H" or Z will be interlocked
3. Spindle chiller must be on and no alarm or Z will be interlocked.

The spindle chiller is usually right behind the machine. It circulates the spindle oil and cools it if needed.

Darek

[Andy Fritz]

Darek,

Thanks for your input.
The Micon can not show the H on Mode 45 as the Z need to be homed first. As I can not move the Z it can not be homed. There is no spindle chiller on this machine. According to some Hitachi Seiki tech, the air is only for blowing dust and chips out of the spindle on tool change does not play a critical role in the function of the machine.

I noticed the hydraulic oil level was very low. Still the pressure is 35kg/cm2, where it should be and tool clamp/unclamp works. Maybe it is not enough for keeping the Z out of E-stop?

I have ordered the hydraulic oil, but it will not arrive until a week from now.

If it is not the oil level, I would guess some parameters in the Fanuc could be the answer. Just need to get a copy of the parameter sheet!

Andy

Andy

[Hitachi_man]

Reboot the machine holding down cancel and p until you hit stand by this should bring z back to life

[Andy Fritz]

Thanks. I tried it and it did not work.

Strange that this is not mentioned in the maintenance manual.
I can force the three bottom solenoid righ side coils on with FF mode, but after botting u again they are not on.

I found a Fanuc 6M parameter check sheet that at least covers up to #166. These settings are very different from what I have in the control, but I am not sure if I chould change them as several parameters from the check sheet only shows 4 bata bits, where I have 8.

Andy
Do you know what it does? Will any Micon parameter have to be reset after?

Originally Posted by Hitachi_man Reboot the machine holding down cancel and p until you hit stand by this should bring z back to life

[Hitachi_man]

the 4 digits are bits 0-3, or starting on the right and moving left. if you decide to change them make sure you write down what is in your control!! If you can email me the machine model, serial number I will look and see if I have the data sheets for you. I should have the generic settings for it that should help.

[Andy Fritz]

Hi,

Thanks! The machine is a Hitachi Seiki VA35, serial VA3053. The control is Fanuc 6MB. I wonder if there is some type of master reset that bring back ALL default settings for both Micon 8 and the Fanuc. Is quite strange that many of the Fanuc parameters are different from the check sheet. The machine was running fine until taken out and shipped to me. At lest the seller claims so! Why would the parmeters have changed?

I suppose I could write down all settings and try to change them. But anyway the check sheet I have only cover up to N166 and there are many more than that. I will pm my email.

Andy

Originally Posted by Hitachi_man the 4 digits are bits 0-3, or starting on the right and moving left. if you decide to change them make sure you write down what is in your control!! If you can email me the machine model, serial number I will look and see if I have the data sheets for you. I should have the generic settings for it that should help.