Arrow 2 1250C X-Axis Gain Issue

[JordanMach]

Hi Everyone. I have searched and havent found what I was looking for. We recently acquired this machine a few months ago and it has been quite a learning curve for me. Upon receiving the machine, I greases all bearings, cleaned up all the chips in the nooks and crannys and also adjusted the balance and gain of X,Y, and Z axis. All of them were fairly close in the voltage for the gain adjustment. Ill just say they were all within 1 of 319 Rev/Volt for the Gain. Well last week we found out we needed to replace the X axis bearings on the ball screw as they were pretty bad and I started having issues with X axis alarms. We had our mechanic change out the bearings and this is where I am now.

When we move the X axis slowly it moves fine. Once I start moving a little bit quicker(maybe 15in/min) The X axis motor starts humming and will not stop till I E STOP the machine. Mechanic said to look at the X axis Gain as it will be different since the motor doesnt have to try as hard to spin the ball screw. I checked my gain and in order to get it up to where it is supposed to be I need to drop the 319REV/VOLT down to about 300REV/VOLT. This is all based on mathematical calculation as I dropped it 2REV/VOLT and got a gaine adjustment of .03. And I need to adjust my gain .14. I honestly dont know what these numbers mean. I just know the Tech Support guy from Cincinnati said to get the Gain adjustment as close to 2.0000 as possible. I am not sure if that far of a change is okay or not or if we need to adjust our ball screw and bearing tightness to make it tighter or looser to get the gain adjusted closer. I hope this makes sense as reading this after writing it makes no sense at all.

Thank you all for your help.

ADDED: This is an A2100 Control with Siemans Drives and motors.

Jordan

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[meckardt55]

What year is the machine?? Do you have scales for the positional feedback of the axis or is it from the motor?? What is most important is the gain and not the REV/VOLT. The REV/VOLT is what you adjust to get the gain to 2.000. You need to look at the gain while you are moving the axis and adjust the REV/VOLT to get the gain to 2.000 ( upper left on the screen). The REV/VOLT can vary depending on how the axis drive is set up. It sounds like you need the machine tuned up and some training on the control. We can also align the machine and laser calibrate the 3 axis. Where are you located??

Mike CNC Machine Services INC | Cincinnati Milacron MachinesCNC Machine Services

[JordanMach]

I understand that I am trying to adjust the gain to 2.000. I'm just curious if it was normal to drop that rev/volt by 10 volts or not? My Z and Y axis are both around 319 and to make the X as close to 2.000 I have to drop to 310. Where as before the repair it was too 319. Just curiosity on my end as it bugs my OCD that before all 3 were similar and now after the one I repaired does not match.

I did end up trying to adjust the gain and got it as close to 2.000 as I could but it's very spuratic as that humming sound starts. I took the cover off of the Spider coupler and saw that when the humming starts the motor starts over correcting itself for location. It constantly jittering back and forth to keep the table still but only does so once the table moves faster than 10ish in/min. I am not sure what causes this, but I know we did NOT have this issue before. Hoping I can fix this myself as our mechanic is busy till the end of october. He said we may need to loosen or tighten the ball screw? I did the repair with him so I know how to do it, I just don't know what to do to fix this issue. Don't want to tighten ballscrew when I need to loosen it.

This is an 01 with scales for positioning and I'm in Rochester NY. I would love to have it lasered but at the moment we cannot afford it as we have just dropped the money in buying this then fixing it and would like to run it a bit before we can justify droping more money into it. In the future maybe. Also want to add 4th axis in the future but need to make some money with it first.

Thank you for the quick reply.

[meckardt55]

The problem is that the axis has to much backlash and the control/servo is trying to fine tune the axis position but it can't because of the excessive backlash or excessively tight thrust bearings . You may need to tighten the thrust bearings. If you push on the slide very hard in both directions (one at a time) the noise should go away. This is because you have taken up the backlash and the control is happy. If you have 0.005" to 0.010" backlash or more it can cause this problem. Don't worry about the REV/VOLT as long as the gain is 2.000. This is a common problem with scales and excessive backlash.

MIKE CNC Machine Services INC | Cincinnati Milacron MachinesCNC Machine Services

[JordanMach]

I will try that tomorrow when I get to work with pushing the table back and forth to stop it.

I do find it hard and so does my mechanic that it is a backlash issue as before the work was done we did not have this issue and did not have backlash like you describe.

Is there a way to adjust servo loop gain? I just spoke with my mechanic and he said that is what needs to be adjusted. It is going too fast into position and is over shooting where it needs to go. He doesn't know this control very well but said on some Fanuc machines they auto adjust the loop back gain so as bearings get worse they slowly adjust to comensate. Then when you go and change bearings you get this same issue and you need to go into the parameters and either turn it off or reset it. Is that possible on this machine?

[JordanMach]

Okay. So we have gone over everything again in the X axis and all looks to be good. Seeing as this is a new to us machine, and we do not know the history to it. We think the previous owners had the servos tuned. Problem is they tuned it to bad bearings in the X axis. We have no backlash and thrust bearings are good. The servos are now over compensating movement so its constantly over shooting its position due to the new bearings being a lot smoother then the old bad ones. Can any one help me with adjusting the parameters inside the Servo Unit? I am hoping this is a fairly easy fix like it is in our Fanuc 0T Lathe.

[JordanMach]

So upon some research of the SIMODRIVE Manual I found the parameters I think I need to change. Or at the very least I want to compare my X axis parameters to my Y and Z axis Parameters to see of they are drastically different from the previous owner. My issue is I cannot seem to view parameters below 511. Is there a reason, I have unlocked ALL parameters for reading and writing and for some reason will not go below parameter 599.

Also does anybody have the SIMOCOM U Software that you use to connect a computer up to the drive instead of doing everything through the 3 button keypad and small LCD display?

[JordanMach]

UPDATE:

I was able to find and download SIMOCOM U which is the software that allows you to communicate with the Servo Drives via RS232. I also received the Parameters that were installed into my machine when it was built. This allows me to compare the parameters inside the machine to the correct set to see if anything has been changed from factory settings. All 4 Drive parameters matched the parameters I received that were originally installed in the machine upon building it. I still question some of the parameters as looking through the manual there are many parameters below 599(that 511 in my last post was a typo) that would cause the issues I am having. I am still unable to read or write any parameters from 0-599 either threw the Drive LCD itself or even through the SIMOCOM U software. Am I missing something? Some of the parameters I have found, but not through the drive. i found them on the on screen menus on the machine control itself, an example is parameter 201 Backlash Compensation. Why does the control have access to this parameter while the drive or SIMOCOM U does not? And why does the Control have access to that parameter and not 200:8 Kv factor (position loop gain)? There are a few parameters that I can see causing the issue I am having and want to view them and compare them to the Y axis(which is a good, smooth, working axis) and see if there are any that are DRASTICALLY different that the previous owner adjusted to compensate for the drag of the X axis with the bad bearings.

[JordanMach]

UPDATE:

I have found that using SIMCOM U I am able to compare 100% of the back up parameter file with the parameters in the drive. I edited a parameter in the back up that was below my 599 that would not show in SIMOCOM U and when comparing it came back showing that my edited parameter did not match what was in the drive. So all parameters are the same as when the machine was built. I was then leaning towards 1 of 3 things. A bad motor, cabling, or power supply.

Going with that information I have. I have removed the X axis motor from the ball screw but kept it attached to the cabling. I was able to control the motor via SIMOCOM U and found that around 40RPM is when the hunting began. Using SIMOCOM U it ignores the Scale reading so it cant see the backlash nor is the motor seeing any misalignment in the axis IF there was any as its not even attached to the ballscrew and is free spinning. This leads me to believe the motor. I decided to switch the Z axis Motor with the X axis motor to see if the issue followed the motor or not. It did NOT follow the motor and remained the same issue on the Z motor connected to the X axis. The X axis motor attached to the Z cabling and Z drive ran perfect. I was able to run the x axis motor to 120RPM, stop reverse, and stop again with zero issues at all. I am now looking into my cabling, and if that looks to be good I will be looking into the power supply and see if any transistors or capacitors are bad. I will update when I find more information.

[JordanMach]

UPDATE:

I was about to pull the power supply out yesterday when I thought of switching the X and Y motors/cabling to the others controller card. I switched everything around in the cabinet so that the X motor/cabling ran off the Y drive and the Y motor/cabling ran off the X drive. Using SIMOCOM U I started with the X drive/Y Motor/cabling and it ran smooth as could be. Ran it to about 150rpm CW and CCW with no issues at all. I then switched to the Y drive/X motor/cabling and it ran terrible as usual. So this leads me to the cabling for the X axis. I ohmed out the encoder cable with all but 2 wires measuring .2-.3 ohms each. The 2 possible trouble wires measured .6 and 1 ohm each. One wire is for the B signal while the other is for the D signal. Not sure what the D signal is but I do know that the B signal is important and can cause issues I am having. I also checked out the power cable. U, V, W, and G wires all measured .2-.3 ohms each. Next I checked between all the wire. The encoder cable checked out good. On the other hand my power cable did not. I measured 28Mohms between V and G with .042uF. I am leaning toward my power cable being the cause of all this and not the encoder which I at first thought with those slightly higher resistances. I priced out both cables from Cincinnati. The encoder cable isnt too badly priced at $268.00 while the power cable is priced at a wopping $1,504.00.

My question is. Does anyone know of a good place to order some 4 stranded wire suitable for the power cabling? The end coupler that attaches to the motor I should be able to re-solder to the new wire and the drive end just uses 3 spade connectors with set screws to hold them in place. Why in the world is this wire so much while it runs right along side the encoder cable so they are the same length?? I am confused but also dont want to drop that much money on over priced wire.

[ifixcnc]

IGUS = the only word you need to know for high quality wire. No minimum order, cut to order and shipped same day.

[JordanMach]

I assume you are a sales rep for them?? haha

Dont have a problem with that, just ask because I am curious if you carry the connectors I need as well that connect to the motor? They are 6 pin siemens connectors. Dont have a part number. But I can get a picture of it tomorrow when I get back to work if you need one to verify.

[ifixcnc]

I sell nothing but repairs, but in doing so I have to source lots of pieces parts. LOL

[JordanMach]

UPDATE:

After a LONG struggle with this machine, I finally threw the towel in on it. I decided to have a Professional tech from either Cincinnati, Siemens or Mike come in to do the repair. After failed attempts to set up on site repair with two of the options, my last option was with Siemens. I had a Siemens tech come out yesterday and he checked all my parameters in the machine and the drives and all looked good. He hooked up his laptop with SimocomU to the X axis drive and started running some tests. After a few tests and some tuning he saw that there was harmonics in my mechanicals and that was the noise I was hearing. He said it was more than likely due to the ball screw either being bent, not centered, or weak and that is why I was having trouble with this machine. He was able to tune my X axis and Z axis to mask this noise. He said it bought me time (5 years would be nice), but that I may see this noise come back due to the machine wear. At that point I will probably dive in knowing what my issue is and maybe have the ball screws repaired in the Z and X axis and I will then be able to go back to stock tunes from Cincinnati.

In the end, Im finding that Siemens over does things. Why is the drive so sensitive that its seeing the slightest vibration or harmonics in the ball screw and amplify it? Why cant it just ignore those harmonics and turn the ball screw x.xxxx turns? I dont know, it seems to be too sensitive for its own good. If someone has an answer for me please tell me, but i think its a little ridiculous. My ball screw is only out of center or bent .001" at the center of it. I have seen worse in older machines and they run flawlessly.

For anyone that has this humming sound coming from an axis. It is more than likely the ball screw. Hope this helps to anyone in the future. If I had known this from the begining I would have not dumped any money on cables, motor repair, or drive repair, or troubleshooting my own time, I would have just had the ball screws and bearings replaced/repaired.