Tree Journeyman 325 Help - Fault Issues/Braking Resistor Overheating

Machine details:

1987 Tree Journeyman 325
Dynapath Delta 20 Control
Fanuc A06B-6052-H002 drive (all electronics appear to be original from the factory, both control cabinets are very clean)

I purchased this mill for the purpose of learning CNC machining. I am using artificial 3 phase via a rotary phase converter. The machine is set up for 4th axis capability (4th axis included) and does have the optional jog wheel and power knee.

The previous owner had fault issues and wound up investing in a larger VMC to replace this mill. It only took me about an hour to discover that the limit switch on the X axis had bare wires visible/disconnected from the switch. During power up of the machine, the emergency stop fault would be displayed and all controls were inaccessible. After repairing the broken conncection to the X axis limit switch, I was able to clear the emergency stop fault and move forward with setting up the required axis references. Jog functions work great. Spindle runs very smooth. I decided to move on to a simple bolt circle operation. My basic process for this op was as follows:

1. Machine start up/Reference axis
2. Load material
3. Set tool length - I used the top surface of the material to calibrate my tool offset
4. Program setup - This seemed pretty simple. The control at the machine is very user friendly thus far. I used the Bolt Circle function which asks for basic information, X center of bolt circle, Y center of bolt circle, radius, number of holes, depth, etc. I also added a peck function. The first line started my spindle, the second line was the entire bolt circle function, and the third line shut the spindle off. Again, I am learning this stuff. I have so many questions about the right way to program something as simple as a bolt circle but I will save that for a later discussion.

Cycle start, off it went and in about 1 minute I had 6 holes equally spaced on a 3" bolt circle, all 5/16" diameter, .50" deep. I was happy and called it a night.

The next day was interesting. I wanted to mill a pocket inside the bolt circle. I fired up the machine, set up references for each axis and then started to write the program for the circle pocket. I ran the program first without the tool in the spindle just to watch the tool path and be sure I didn't have something completely wrong and risk breaking a tool/the machine. The program appeared to be running great. After maybe the third or fourth pass suddenly the machine stopped and a fault came up, emergency stop fault again.

I checked the wiring issue that I found on the X axis limit switch, no problem there. I went back and checked the program but I couldn't see anything that might have caused it to error out, but as mentioned earlier in this write up I am new to CNC (can you program in a way to cause a situation like this?). I went to the cabinet that houses the spindle drive and noticed intense heat radiating from the top of the cabinet. I opened the door and a small amount of smoke poured out of the cabinet/lots of heat. I immediately hit the main breaker to cut power.

I believe I have discovered what happened but I don't understand how it happened. Apparently when the Fanuc drive fails it fails with the IGBT's in the closed position and sends all DC power to the braking resistor (this is what I have read, I am not a controls expert). When this happens the braking resistor will generate an intense amount of heat and eventually lead to a fire inside the cabinet. Luckily this was not the case for me today. No visible damage to any wiring or components in the cabinet. I took a break and let the machine cool down.

I did return back to try another test run a few hours after. The machine fired up fine and seemed to be functioning normally, however, when I tried to start the spindle the machine fell back into fault mode. When this happened I quickly shut down power to the machine and decided to call it a night. I am hoping that I don't need to replace the drive, or any other major component for that matter.

I guess my first question is where do I start with a diagnosis? I got lucky with the initial problem when I found the limit switch issue. This might require a bit more digging.

I appreciate all the help in advance. This is uncharted territory for me. I am very eager/excited to get this mill dialed in and running smoothly. Pointers for this machine are greatly appreciated!

It has been awhile as my only machining center hit the scrap yard a couple years ago. I had the same issue with the braking resistors getting very hot, it was a Yasnac and those resistors were in a separate compartment vented to the outside and closed off to the rest of the components. My issue was the braking unit failed. It showed an alarm light on the outside of the unit.

If the IGBT is shorted, the resistor will start to get hot the minute the spindle drive powers up or you try to run the spindle, depending on what has failed. I have a J425 that caught fire from the same issue. It's actually pretty common. However, often there is no alarm generated.

If you push the "fault/status" button, it should provide more information on the alarms.

ewlsey said:

If the IGBT is shorted, the resistor will start to get hot the minute the spindle drive powers up or you try to run the spindle, depending on what has failed. I have a J425 that caught fire from the same issue. It's actually pretty common. However, often there is no alarm generated.

If you push the "fault/status" button, it should provide more information on the alarms.

Click to expand...

I suspect you may be the individual who posted the video on Youtube with the awesome price tag on your 425?!

I will see if I can get a fault code today and report back.

Down in the shop looking into this today. Machine powered up just fine, ran through all axes references. Option 3 program, N0, M03, S500, cycle start...spindle did not turn on. Heard a clunk from the cabinet, emergency stop fault on the monitor. No signs of heat at this point. Shut off power to the machine.

Decided to try again with the spindle in CCW. Went to option 3 program, N0, M04, S500, cycle start and the spindle turned on. I monitored the drive and braking resistor for bad signs. After about 2 minutes with the spindle running I used M05 to shut the spindle off. No problem there. I went to the back of the machine to check for heat and could tell that the braking resistor was showing signs of getting hot again but not much. I imagine some heat is normal, but you shouldn't be able to fry eggs on top of the cabinet.

About 1 minute after using M05 to stop the spindle I heard a clunk from the back of the machine, almost like a contactor opening or closing and sure enough went to check the control display, emergency stop fault was on the monitor. No code. Went to the drive in the cabinet to check for any red LED's...only 1 green. No red. At this point I cut power as I could feel the heat coming from the braking resistor.

Discovered this, wiring for the braking resistor was baked to the resistor housing.

Braking resistor measures 15.6 ohms, according to the Fanuc technician this is right in spec.

Measured each phase coming into the machine, incoming voltages are as follows: 245v 250v 235v

As mentioned earlier, I am running this machine from my rotary phase converter. The machine was previously wired in a commercial building on 220v 3 phase. Perhaps this move to a rotary phase converter with higher voltages is causing some issues? I know this machine has several transformers all over it. I need to research this.

Per the Tree manual, there is a procedure to set up the machine for different incoming voltages. I double checked and it is set for 240v. The other 2 options are 230v and 220v.

Something interesting worth mentioning, the spindle drive has 5 small LEDs on the board used to show alarm codes. The first is green and is illuminated when the machine is powered up/no faults. The remaing 4 have numerical values above them, 8, 4, 2, and 1. I noticed that 2 of the 4 ligt up briefly when I shut power down to the machine. I am seeing a consistent alarm code 10 (8 & 2 both illumiate) each time. Should the alarm be dispalyed continuously, or is it intended to flash the LEDs when the main breaker is switched off? This seems strange.

I have a General Numeric manual that actually references my Fanuc spindle drive in it (actually lists the exact model #) and has an alarm code chart. Alarm 10 comes back as abnormally low AC power (15% or less).

Definitely getting to know this machine. More to come.

I would check the power supply. It puts out a few different voltages, It's a major source of problems. Also what voltages is your phase converter putting out when running alone versus when machine is running. I would suggest keeping it under 230v.

sam_stlouis said:

I would check the power supply. It puts out a few different voltages, It's a major source of problems. Also what voltages is your phase converter putting out when running alone versus when machine is running. I would suggest keeping it under 230v.

Click to expand...

I will get voltages from the phase converter by itself. I think I had the mill power on when I took those voltages that i posted earlier.

As far as the power supply, are you reffering to the power supply on the side of the Dynapath controller?

Thank you for the help!

OK. The sound you are hearing is the e-stop contactor. When the machine goes into e-stop, that main contactor drops out and you lose whatever is on that circuit. I can't remember how it is set up of the top of my head.

When the machine goes to e-stop, do you have to reset the spindle drive, or just the control? If you are not getting an alarm on the spindle drive, I'd say that's not the source of the issue.

When you have the issue, check the LEDs on the actual control boards in the control chassis and tell us what you see. A bad power supply will often give a WDT alarm LED. That's a watch dog timer that monitors voltage.

The brake resistor should not be getting hot at idle and really is only used during braking. I would check the DC buss voltage on the spindle drive. I would think it should error for over voltage but maybe not. What I suspect is possibly the voltage is too high and the drive is enabling the brake transistor to bleed off excess voltage to the resistor. This should not happen unless under braking.

Be careful or you might be rebuilding a drive. If its getting hot, there is an issue. It is normal when doing lots of stopping to see temp rise but not idle.

Depending on where you got your converter, many are built with ridiculous voltage balance so A-C, and B-C might stand 20V higher than A-B. This will cause the DC buss voltage to stand higher than nominal. What is the recommended input voltage? You may need an autotransformer, if one is not in the cabinet, to reduce voltage.

I vote with Huelo. Drive smells fishy. Maybe check your line V as it goes into the drive. The 350J only has two line wires feeding the drive. If the 325J is the same make sure your not using the generated leg.

With the little while I've been registered on this forum, it looks like Tree Journeyman's have been becoming popular. Wondering if we can get our own dedicated subforum to collect all of these topics?

ewlsey said:

OK. The sound you are hearing is the e-stop contactor. When the machine goes into e-stop, that main contactor drops out and you lose whatever is on that circuit. I can't remember how it is set up of the top of my head.

When the machine goes to e-stop, do you have to reset the spindle drive, or just the control? If you are not getting an alarm on the spindle drive, I'd say that's not the source of the issue.

When you have the issue, check the LEDs on the actual control boards in the control chassis and tell us what you see. A bad power supply will often give a WDT alarm LED. That's a watch dog timer that monitors voltage.

Click to expand...

10-4 on the E-Stop contactor. This makes sense.

As for the fault error...it is always the control. I haven't had any red LED alarms on the spindle drive. Just the green LED. I have made sure to inspect those LEDs immediately after the machine goes into E-Stop.

I havent checked any LEDs on the control boards yet. I will do some homework on this. I am a bit hesitant to fire the machine up and run it, as many have cautioned me to be careful with the situation. The drive still operates, the controls still function, but the machine is going to E-Stop after a few minutes of spindle run time. The machine can sit powered up and I have control on all axes, johs no problem. But when I start the spindle it brings the heat!

Thank you for your help!

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You can run the spindle with the braking resistor unhooked. You will likely get an alarm on deceleration, but it should run fine. So if you are worried about it, just pull the wires.

huleo said:

The brake resistor should not be getting hot at idle and really is only used during braking. I would check the DC buss voltage on the spindle drive. I would think it should error for over voltage but maybe not. What I suspect is possibly the voltage is too high and the drive is enabling the brake transistor to bleed off excess voltage to the resistor. This should not happen unless under braking.

Be careful or you might be rebuilding a drive. If its getting hot, there is an issue. It is normal when doing lots of stopping to see temp rise but not idle.

Depending on where you got your converter, many are built with ridiculous voltage balance so A-C, and B-C might stand 20V higher than A-B. This will cause the DC buss voltage to stand higher than nominal. What is the recommended input voltage? You may need an autotransformer, if one is not in the cabinet, to reduce voltage.

Click to expand...

Understood! The last thing I want is to damage something as expensive as a spindle drive. Quotes for reworking one of these drives are over $3K. I want to stay out of that rabbit hole.

The braking resistor doesnt seem to be heating at all during idle. I can power up and mess with axis controls/write programs all day long with zero issues. The problem seems to begin when the spindle starts.

I can run the spindle for a few minutes and then expect the E-Stop error and the machine stops. From that point forward is where the heat really begins to come off the braking resistor.



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Aejgx6 said:

I vote with Huelo. Drive smells fishy. Maybe check your line V as it goes into the drive. The 350J only has two line wires feeding the drive. If the 325J is the same make sure your not using the generated leg.

Click to expand...

I will check into this. I believe you are correct, 2 phases to the drive. As mentioned earlier the artificial phase from the rotary converter is at 250v and could very well be feeding that drive.

Thanks!

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ewlsey said:

You can run the spindle with the braking resistor unhooked. You will likely get an alarm on deceleration, but it should run fine. So if you are worried about it, just pull the wires.

Click to expand...

Will this have any other effect on components inside? If the system is trying to dump excess voltage and I remove the resistor what is the outcome?

I ask because I just don't know. I appreciate the help!

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Anything that dumps voltage also monitors voltage. If it gets too high it will alarm out.

Not the same machine but my AHC converted Omniturn's braking resistor over heats when the line voltage gets over 248. Went through this 6 or 7 years ago and again last week. this time I called the electric co-op and they said they thought 249/251 was ideal and did not want to change it. I ordered a couple of buck/boost transformers that day. The next day the voltage was back to 244/246 and the machine ran fine.
The Mitsubishi Freqrol dumps excess into the resister when the voltage gets too high.

Swapped the location of the artificial leg for the incoming 3 phase power on the breaker today. As soon as I turned power on I had a clear alarm on the spindle drive, #8 LED, which my book indicates too much AC voltage.

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