Axis Movement Issue - Fanuc 10M Control on Mori MV-45
Hello there and thanks for any help that can be offered - This one has me chasing my tail!
Problem in General Terms:
Y axis movement is inaccurate. A move of a known distance, as measured with indicator, is displayed on the controller as something different. The error is much worse when traveling in one direction (Y+) than travel in the other direction (Y-).
Specific Problem Data:
Test-1: With a 2" travel indicator mounted on the table indicating on the spindle, an actual Y axis move of 2.0000" in the negative direction had the controller showing a move of 2.0024". When moving back in the positive direction you would expect to see the same error; however, this was not the case. With the same setup; an actual Y axis positive move of 2.0000" was shown on the controller as 2.0122" This same exercise was repeated 8 times with the errors in -Y holding fairly constant and ranging from .0021" to .0026' and that could simply be my old eyes looking at the indicator and over/under shooting the zero a couple of 1/10'ths. +Y moves were very different, in that, the error ranged from .0117" to .0185".
Test-2: With an indicator mounted in the spindle and indicating on a fixed surface on the table, and both the indicator and controller position zero'd, the axis was moved an arbitrary distance away (say 5"). Then by rocking the axis back and forth and back and back and forth about a half a turn each time on the hand wheel in the .010 per click, the axis was moved to starting point as determined by the indicator. Although the controller position should read .0000 (or really really close), it is now over .100" off. When this same exercise is repeated, the error continues to grow.
What Has Been Checked and Ruled Out:
Encoder - This machine has the older "Red Cap" servo motors (Model: 105 Type: A06B-0315-B032#1001) with 2500 Pulse/Rev encoders (ABS Pulse Coder A860-0320-T112). I honestly thought it was going to be an encoder problem, but after swapping between axes, the issue did not follow the encoder and the unit in question worked fine on the other axis.
Servo Motor Drive Board: - The drive board (A208-1003-0090/02) was also swapped in the same fashion as the encoder with no change noted.
Motor / Ball Screw Coupling - Not slipping
Ball Screw End Play - Way covers pulled back and a ball bearing placed in the center-drill hole of the 10mm pitch ball screw with indicator on that. With aggressive axis movement, indicator did not show axial movement of the ball screw beyond about .0005"
Ball Nut to Table - Not moving
Back Lash: - It is an old machine with a minimal amount of backlash; however, what little lash it has was removed before indicator readings described above were taken.
I know that there are parameters to which changes are made when tuning a ball screw; however, I am at a loss when it comes to an issue like this where the magnitude of the error is 6 or 7 times grater in one direction. Not sure where to go from here.......Fortunately; there are no pressing jobs that have to be run on this machine at this time. So; if there is anyone out there that may have encountered a similar issue with a similar control system (i.e. old Fanuc 10M control) - I would love to hear how it was resolved.
Re: Axis Movement Issue - Fanuc 10M Control on Mori MV-45
Thanks Partner for the reply! I checked the end play of the ball screw and found there to be minimal movement (i.e. .0005" or so back and forth) as the axis is moved positive then negative again and again.
Re: Axis Movement Issue - Fanuc 10M Control on Mori MV-45
Is this a new problem? sure sounds like a loose coupler. Did you put a magic marker line from the actual screw to the motor shaft?
I dont like your first test. You are relying on your indicator setup to be perfectly parallel to your axis stroke to have any accuracy. I prefer some length artifact/std like a long gage block and a test indicator that is going to only be looking for zero.
Even saying that you should be testing it with memory operation, not handwheel tomfoolery. Interpolate an angle while indicating a straightness bar, or better yet an angle master. Sweep a hole and set zero there and move away from it and back, see if it repeats. Cut a circle. What do those things show.
Re: Axis Movement Issue - Fanuc 10M Control on Mori MV-45
Thanks for your interest in helping me solve the problem. As stated in my post; the motor to ball screw coupling is not slipping, and witness marks were utilized to make that determination. Although you don’t like my methods, they are adequate to detect and describe the particular issue using memory operation and/or hand wheel. Using the very same methods on the X axis renders a totally different result; one with accurate repeatable movements. If we were tuning a ball screw on a machine that was operating properly; your suggestions would be spot on. However, the problem I am having can be detected with a tape measure! The exacting methods you would like to see are overkill at this stage of the trouble shooting process. The last program I ran (the one that made evident the inaccuracies) involved center drilling, helical milling of a pocket, peck drilling, and chamfering. The helical milled pocket looked like hell and the chamfering operation was way off in the Y axis where the problem lies.
Re: Axis Movement Issue - Fanuc 10M Control on Mori MV-45
I only asked again about your coupler because locally here I had a similar lost motion problem on a Makino V55. "the coupler is tight" they said. It was but was not enough.
What does the following error look like.
So if you were making good parts and then out of the blue it is doing this? what about your ways and gibs?
"Back Lash: - It is an old machine with a minimal amount of backlash; however, what little lash it has was removed before indicator readings described above were taken."
do you mean you set the comp value to zero or you comped it to zero. Whats the value you are using
Im not familiar at all with the 10, But I would try to swap the encoder-control control-drive cables . So X becomes Y. I am guessing the encoder goes to the control.
Re: Axis Movement Issue - Fanuc 10M Control on Mori MV-45
The problem did not happen out of the blue. The machine was not utilized for six or seven months as far as running production jobs. During that time, it was exercised on several occasions running a program just cutting air. A week or so ago, we needed to use the old mill to run a production job and a new program was loaded and the problem showed up at that time.
As far as backlash is concerned; there is about .002" in the Y axis movement. When I said that it was removed before indicator readings were taken, it was done in hand mode in the same fashion as you would do when running a manual machine by making sure that the lash was eliminated in the direction of movement before the reading which marked the start of the measured movement.
Today; I figured out which connectors to move to what locations on the main board to "swap" the Y axis servo motor and encoder cables with that of X axis - and YES the encoder cable goes back to the main control board. When powering on after the "swap" I get alarms indicating soft overtravel in both X and Y. When going to hand mode at that point; I can move both the X and Y axis, but in only one direction. I understood, from other research, that the thing to do was to power up while pressing both the "." and "-" keys at the same time to enter the IPL screen. Then select "settings" followed by turning off the "CHECK SOFT OT AT POWER ON" This; however, does not work to eliminate the alarms of "OT001 X + OVERTRAVEL (SOFT 1)" and "OT002 Y - OVERTRAVEL (SOFT 1)". My next challenge is to figure out how to overcome the soft OT alarms when I've got the X and Y axis swapped so I can move each axis in both directions to determine if the problem moves from Y to X. If it does, I'm afraid the problem is on the main control board ("backboard" as some call it).
Another way the problem can be made evident (before the "swapping" exercise) is by doing the following. Mount an indicator on the table and touch off on the spindle with the indicator in mid travel and set to zero. In hand mode with the wheel on zero, your thumb at 9 o-clock and your index finger at 3o-clock and in the .01"/click setting rock back and forth about 1/4 turn about 10 times and then put the wheel back to the zero. The indicator which should be back to zero is now a hundred thousands off. Do it again and the error just keeps getting bigger. When repeating the same exercise on the X axis, the indicator will return to zero every time.
Re: Axis Movement Issue - Fanuc 10M Control on Mori MV-45
OK - So I was able to position the table almost to the hard stops in X positive and Y negative and get past the soft over travel alarms while having the X and Y cables swapped in the main board. The problem did, in fact, follow the axis. In other words; with the servo motor and encoder cables swapped on the main board (X for Y), the original problem that was in the Y axis is now in the X, and Y moves accurately as it should. Now the big question is; what to do next? Any ideas anybody? If it is of any help; here is some data from the main board and the three cards that plug in to it:
Main Board:
FANUC 10
Type A02B-0074-B501
No. 17217 1987-07
Re: Axis Movement Issue - Fanuc 10M Control on Mori MV-45
Finally - Problem solved. After installing a refurbished main circuit board (not the "daughter" axis control board I thought would be the problem), the machine movements are accurate as they were prior to the problem that got this thread started. Thanks for those the offered help. By the way; I learned that the Fanuc-10 has circuitry on the main board to control two(2) axis as for a lathe, and when installed on a mill, the axis control daughter board is added to control the 3rd axis.
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Axis Movement Issue - Fanuc 10M Control on Mori MV-45
