[barchdesigns]

Hi, My Mitsui Seiki VR3A with Fanuc 6M control system has been running good for years. I turned it on this morning and the spindle just keeps spinning when it tries to orient for a tool change. It worked fine last night when I shut it off, and now won't spindle orient today.

It has a magnetic sensor setup. When I watch the Fanuc Spindle Drive Board in the back of the machine after issuing an M19 command, I can see the ORIENTATION LED come on, and the IN-POSITION LED light up every time the magnet goes by the sensor. However the spindle never locks in place and just keeps going around and around until it times out.

Any ideas what I should look for to fix the problem? I can take pictures/Video if needed.

[nsdjole]

Atempt by the FANUC procedure

[barchdesigns]

I've been looking for those instructions everywhere, thanks! It all looks pretty straight forward in the documentation, however when I press SW1 while in test mode, the spindle doesn't turn as it should.

I started down the instructions and got to the section on page 469 about adjusting the variable resistors. I put on the test jumper and measured pins 15 & 16 and adjusted RV1 until it was exactly 0 mV.

Then the next step says to press SW1 repeatedly while turning RV2 until LED3 begins to light. Well pressing SW1 does nothing. Any ideas of what this may indicate?

Thanks,
Ben

[nsdjole]

Ok, check first connectors at Fanuc magnetic sensor Amplifier ( sometimes water and oil leakage, electrolysis can "EAT" pin ) - black box between sensor and orientation board.
I like Fanuc 6

[barchdesigns]

The connectors look to be in good shape. I disconnected and inspected them and they look to be clean and dry inside. Is there a way to test the sensor and amplifier to see if they are working electronically? I've attached a picture of the spindle and mag sensor.

Ben

[nsdjole]

I think.. if you check with oscilloscope, signal from amplifier, you can see how signal jump from -several V to +several V, when magnet on spindle pass over sensor. After that slowly go to 0.
Now I'm sorry I do not know which pin is output on connector from amplifier.

[barchdesigns]

Does anyone know the wiring diagram for the magnetic sensor, amplifier, or orientation board? I don't have a oscilloscope available to me. Is there another way to test these parts to see where the problem is?

I have found some limited info for the magnetic sensor amplifier (attached to this post) however, I am not sure which pins the Fanuc 6M Orientation board uses. I do measure 15 Volts DC on the wire going to the amplifier from the machine side, but 0 volts on the side of the amplifier where the mag sensor connects. I assume that is normal though as the 15V power shouldn't be needed to the mag sensor itself, but only needed to the amplifier.

It looks like the CNA connector is the one that has the wires I need to be measuring I believe. Has anyone every retrofitted these machines with a new mag sensor setup, or use a different type of sensor? Seems like the sensor setup should be less than $50 to replace, but an original Fanuc magnetic sensor kit is well over $1,000.

Ben

[barchdesigns]

I tracked down an Oscilloscope and measured the MSA and LSA pins coming from the amplifier to the orientation board via pins 1,2, and 16 conveniently located right on the orientation board. From what I can tell by asking the Fanuc Rep what his interpretation of the readings were, is the amplifier has gone bad on the LSA line. I was only reading about 2V Peak Voltage and he said he remembers it needing to be near the 10V peak like MSA. Otherwise the shape generally looked good.

He thought the amplifier just wasn't amplifying enough for the orientation board to be picking it up. This would explain why I can see the LED's of the Orientation board light up every time the magnet goes by the sensor and why the spindle never locks in position.

The next step is to tear apart the amplifier and fix it because I can't justify spending the $675 for a used one or $1,400 for a new sensor and amplifier kit. I've started to tear into it and this is where I am at. They fill the whole thing with a rubber substance that makes cleaning it all out a pain. After a couple hours I got it cleaned up and now need to check part numbers and see if I can figure out the circuit, and what to actually replace....if not all of it.

Barch Designs
877-201-9771

[nsdjole]

Good luck, rooting for you

[barchdesigns]

Things went bad. I got the replacement transistors, capacitors, zener diodes, and resistors. I started by replacing the 2 transistors and then measuring with the oscilloscope. The waveforms looked better, I had a proper peak voltage on LSA now. The spindle still didn't lock on the orientation though....just kept spinning as before.

Because of the better LSA voltage, I thought I was on the right track and started replacing the caps and anything else that looked like it may have went bad. I tested a few more times and somewhere in the process things seemed to have gone awry. Instead of the apx 10V on MSA it was now down to about 5V. I also noticed that when I measure in DC vs AC mode that the Voltage offset was somewhere around -8 volts. It should be less than 0.5. So I started testing more and replacing more, and then a wire came loose on the amplifier circuit board and caused smoke to come out of the 39 ohm resistor. I reattached the wire and replaced the resistor and tried again....and it blew it up again. For some reason I am getting too much current pull through the circuit.

At this point it is beyond my circuitry knowledge. I found someone with a working "used" fanuc amplifier willing to part with it for a measly $500.....ouch! I broke down and purchased it and it should be here Monday. I hope that fixes the problem. If I knew just a little bit more about small circuits I know I could replace everything on that board for under $50. Yesterday I bought everything on it except for the induction coil and what looks to be two small transformers. (No numbers that I could see to match up for replacement) for $16.82 + $50 overnight shipping.

I thought I would have had this fixed for under $100 after seeing the simplicity of the circuit. Maybe I should have taken more electronics classes growing up.

Hoping the new "used" amplifier works on Monday.

[barchdesigns]

At this point I'm stuck. Hopefully someone will have an idea of what direction to go from here.

I've replaced the pre-amplifier yesterday and no change.

This morning I've replaced the Orientation board and still no change.

I am wondering if it is the magnetic sensor itself or the Spindle Drive Main PCB

Attached are two pictures of the wave forms I am getting on MSA and LSA. These readings are the same no matter which Orientation Board I am using. You can see how reading in DC mode that the LSA offset voltage is way down around -10V. The basic shape is there, but the offset voltage is way low. *edit - I've just talked to a Fanuc tech and they believe it has to be the sensor head itself at this point from these readings. Hopefully I will have a replacement in hand either tomorrow or the day after.

[barchdesigns]

We're now back up and running. After replacing the magnetic sensor itself (part# A57L-0001-0037) the machine started operating correctly. I found a used one for around $500 and Fanuc wanted about $1,350 for a new one direct from them.

I checked the waveforms coming from MSA and LSA and they looked picture perfect. At the very least I guess I have a couple spare boards at this point from it all.

I wonder why it went bad. I would have thought it was just a passive component and it wasn't physically damaged before it stopped working.