[ajh88]

Have a friend with a Tree mill running PC-2100 controller. I'm new to CNC but very computer savvy and I'm trying to get some online help before he drops another couple grand on repair parts.

History:
A couple of years ago the machine started throwing errors and stopping. Not sure of the errors. He just started trying to resurrect it.
Has replaced the X-Axis Encoder, Servo Motor, and shielded cable in an attempt to fix the problem. It worked for a while, now he's getting an X-axis encoder error and he has to power cycle the machine.
Initally the machine would start and run after the error came up (not sure of that error number), but now it requires a power cycle and it errors out almost immediately after completing all 12 startup tests.
The error he consistently gets now is 44-52 - X Axis Encoder Error - see attached screenshot.

If anyone has seen this before or has any advice for a newb such as myself, I would be very appreciative. If you need more info, please let me know and I'll try to get it for you.

Thanks!

[trelos_zoi]

curious if you ever figured this issue out? I too have an older tree vmc750, rebuilt motor and encoder it went away then came back today!

[meckardt55]

I am not sure about how TREE locates the X axis encoder cables but most of the time the cable runs along the Y axis in a cat track. The cat track bends 360 degrees in about a 6" dia and causes the cables to brake and short out or open up, we see this often. If you put the X and Y axis in the middle of the travel and turn off the machine, you can switch the X and Y plugs on the DV5 board at the control. If both axis are wired the same, the problem should switch to the Y axis for the alarm. This tells you that the problem is not in the control. If the alarm doesn't switch to the Y axis then the problem is in the control. What drives do you have on this machine???

Mike cncmachineservices ( dot ) com

[trelos_zoi]

Hi meckard55,

Thanks for quick response.. always amazed at how quickly folks jump in here when needed. Last time underthetire helped me a bunch with a simple fix.

I swapped cables on mine and error swapped to "X" axis, when it fired up originally it was on "Y". I was suprised when I rebuilt motor and encoder that problem went away but in less than 6 mos is back.... You thinking it could be cable related? I suppose it is either that or the encoder is bad again.

Are there any other "external" electrical issues that could cause the same encoder to go bad? I guess I'd be suprised that lightening or ground issue would cause the exact same problem though.

Thanks!

[meckardt55]

trelos_zoi

Do you have the Tree machine or a Cinci Arrow or Sabre machine. What axis drives do you have??? This test tells you that the problem is not in the control. Generally the Y axis motor and cables do not move and are not the problem. Are you using a phase converter and have you checked the machine grounds??

Mike cncmachineservices (dot) com

[trelos_zoi]

meckardt55

Tree vmc 750, the MAS one not ZPS. yaskawa SGMG-13A2ab. Yes, using american rotary phase converter. not using seperate ground rod on machine, running back to 3 phase breaker box after rotary phase converter, which runs to main panel. All right behind the machine. haven't tested grounds. you referring to simple continuity check or something more in depth?

Ted

[meckardt55]

The biggest problem we see with phase converters is proper grounding. We have good luck using a ground rod made of 5/8 steel, copper coated ONLY, 10 to 12 foot long. It must be the only ground the machine has, no metal water or air pipes. You must use a MEGGER to insure that the resistance is less then 5 ohms between the ground rod and the main electrical ground of the building.

Mike cncmachineservices.com

[slowlearner]

Mike,
Thank you for this information. I am getting ready to install an Arrow 1000 in my barn.
I have often wondered if there were any specifics on these vmc's powered by rpc's.

[meckardt55]

I hope this corrects your problem. Let me know.

Mike CNC Machine Services INC | Cincinnati Milacron MachinesCNC Machine Services

[trelos_zoi]

Mike,
Thanks for info and feedback. So to clarify:
1. you typically drive ground rod (5/8" 10' long steel/copper plated) next to machine and ground to machine base.
2. Use megger to measure ohms between that rod and exterior bldg ground rod. must be less than 5 ohms..

I notice you are in the business of doing equipment repairs so I appreciate your professional advice... I have read all kinds of info related to using rod at machine or not but most discussions do not include the use of RPC, which creates another dynamic I think.

thanks again.

[trelos_zoi]

Mike,

Although related to the below topic, another question more in the general "electrical" arena... I have 2 service panels, 200amp each, 1 panel runs office/living area, and the other panel is dedicated to shop equipment. Outside they each have their own ground rod, not tied together... Since this is essentially the same bldg shouldn't those be tied together? They are currently about 4' apart. Had a local guy that works in industrial shop run the main lines and hang panels so I assumed he knew what he was doing....

Just curious what your opinion is on that configuration as it could relate to my problem as well.

Thanks again,
Ted

[meckardt55]

Ted,

You got the ground rod correct but it must be the only source of ground and you must connect it to the main ground terminal ( usually a common copper ground bar where all the grounds are connected) inside the mag panel. Do not have the ground wire connected to the machine when you use the megger. We are looking for the quality of the ground and to eliminate any ground loops or voltage spikes that effect feedback signals. Many people use the incorrect ground rod that corrodes and in a few months the machine does not have a ground or develops a ground loop within the shop. I have seen black pipe, galvanized rod, steel rod and others used for a ground rod and all have oxidized, rusted or corroded and caused many intermittent problems related to ground. You need a separate ground rod for each machine, you can't over ground a machine. To answer your other question, your electrician is correct, you want ground isolation between the shop and the office so that any voltage or ground spikes do not go through the office equipment.

Mike http://cncmachineservices.com

[trelos_zoi]

Mike,

Think your onto something with the ground. Although I measured from cnc cabinet incoming ground back to breaker and got low numbers, seemed to flucuate a bit on my cheapo multimeter under 1 ohms. I decided to remove a ground from the machine base to inside the cabinet that was connected to the main ground bar inside cabinet. Encoder fault didn't show up initially but then would intermittently pop up at times.

So when I install ground rod at machine I will remove the ground wire coming from the breaker box..this is in reference to your comment of ground rod being the only ground..? I used metal flex conduit coming into machine from breaker as well, isn't this another form of ground as well, would I need to swap out to a "non-metallic" conduit then as well?

Greatly appreciate your patience with all my questions..

Ted

[trelos_zoi]

Update... Installed 10' ground rod and non-metallic flex conduit from breaker to cnc machine. Disconnected ground from panel and machine. Connected ground from rod to main ground connection inside cabinet. Initial power up and test had no issues with encoder error popping up!!

Now I'm waiting for someone to come do ground-earth test between new ground rod and existing building ground for confirmation.

@Mike thanks for direction here, so far looking good!

On another note the more I read on this topic the more confused I became as there are a lot of different theories surrounding grounding these machines and I guess there isn't a 1 setup suits all machines, buildings, environments kinda deal here...

Thanks again.

[meckardt55]

Ted,

I am glad I could help. Run it for a few weeks and let me know how it is working.

Mike CNC Machine Services INC | Cincinnati Milacron MachinesCNC Machine Services

[slowlearner]

trelos,
Did the ground rod eliminate your problem permanently?

[trelos_zoi]

Since doing the local ground rod at machine base I have not encountered any more encoder errors. All other grounds through panel were removed going to machine. I even removed metal flex conduit going to machine and replaced it with non-metallic flex conduit.

Let me know if you need any other details.

[trelos_zoi]

Just thought I'd add a little info to this as follow up. Prior to finding ground problem I had an issue with the "Mag Load" button on pendant not working. This presents selected tool to load new tools manually. I had just worked around this using MDI commands and figured this was the way it was gonna be short of buying a new pendant (not on my top 10 list, LOL) but interestingly enough this now works too since I fixed the grounding issue. Very interesting and strange grounding problems are....