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Thread: 1993 Fadal VMC40 with x axis runaway

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    Default 1993 Fadal VMC40 with x axis runaway

    Hi everyone.
    I have a 1993 Fadal VMC40.

    About a year ago my way cover rubber was torn. Coolant got into the X axis motor and destroyed my bearings.
    I took the motor out and put new bearings into it. I borked the tachogenerator and I didn't know what I was doing at the time so I bought another Glentek GM4050. I have been running this one ever since. Let's call the original motor, MOTORONE and this new one MOTORTWO.

    Fast forward to now. MOTORTWO has been running great ever since. No misses, no quirks, great.
    I had an order for 20 pieces, I made 18 and then I went on vacation for a week. When I came back, I turned on the machine, I was already at my CS marks, so I typed CS [enter] and the machine ran away towards X positive until it alarmed out.

    I was stunned. This is definitely not what had happened ever before.

    So... let's get into it:
    THE Y AXIS WORKS FINE.
    THE Z AXIS WORKS FINE.
    I had since ordered a new tachogenerator and swapped it onto MOTORONE. I just assumed MOTORTWO had gone bad.
    I wired up MOTORONE, now with new tachogenerator, and I had some runaway issues.
    The X axis is slowly moving in one direction. Since I changed brushes and what not I tweaked the SIG on the X axis encoder board until the motor stopped moving. I could not CS though, because the motor still ran away.
    I am drifting about .001 every 5 seconds.
    Here's what is very weird though. If I set the increments to tenths, and spin the wheel, the x moves progressively faster. Like the handwheel is a measure of velocity.
    The X drifts slowly at low values, but if I turn the value up or down the X moves faster.
    Does that make sense?
    The x drifts really slowly at .001, but the x drifts even faster at .250, as if the handwheel is controlling the velocity of the X axis. It never stops drifting. If I crank it up too far it alarms out.
    The Y and Z work fine. One rotate click, one movement.
    When it alarms out, the X still drifts as if it's seeing residual voltage, even before I hit manual and jog to reset the servos. After playing with the SIG potentiometer I can get the X axis motor to stay stationary, but if I move x one tenth to the negative it will continue to drift until I bring it back to zero, and then it stops again. If I move one tenth positive it will drift until I bring it back to zero, but unlike moving negative it will continue to drift.

    I swapped the wires (the white and black and 2, 3, 4, 5, and 6) to the amplifier between X and Y and the problem stayed on the motor side.
    Then I swapped the coax wires between the 1040 X and Y boards and the problem stayed on the motor side even though I was now controlling it through the Y selector on the front of the machine.
    Well, that means motor, right?
    So I swapped back to MOTORONE with its tachogenerator and the motor still runs away.

    So what are the constants? I'm still using the same X axis resolver through all of this. And the wiring.

    I take apart the rotary A axis and put the A axis resolver onto the X axis motor. It still runs away, and it's still a velocity generator like it's not getting a signal to stop moving.

    I then take the Fluke meter and put a probe on the motor side and one inside the case. With the help of a friend we probed the wires one by one and jiggled the harness measuring for a resistance drop. There was no resistance drop.

    So I've tested the harness as best I can.
    I've swapped the 1010-4 boards.
    I've swapped amplifiers.
    I've swapped motors.
    I've swapped resolvers.
    I've swapped tachogenerators.

    Here's where things get even more stupid.
    I was flipping through my blue binder and it says
    SLOT 9 is X axis 1010 board
    SLOT 10 is Y axis 1010 board
    SLOT 11 is Z axis 1010 board
    SLOT 12 is B axis 1010 board
    SLOT 13 is A axis 1010 board
    SLOT 14 is Spindle

    The card in slot 9 has a sticker on it that reads X AXIS and has jumpers 5-12, 7-10, 8-9, as the manual says it should.
    The card in slot 10 has a sticker on it that reads Z AXIS and has jumpers 5-12, 6-11, and 8-9.
    The card in slot 11 has a sticker on it that reads Y AXIS and has only one jumper, 8-9

    I'm at a loss.

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    Default Re: 1993 Fadal VMC40 with x axis runaway

    Quote Originally Posted by Paraquat View Post
    I wired up MOTORONE, now with new tachogenerator, and I had some runaway issues.
    The X axis is slowly moving in one direction. Since I changed brushes and what not I tweaked the SIG on the X axis encoder board until the motor stopped moving. I could not CS though, because the motor still ran away.
    I am drifting about .001 every 5 seconds.
    ...should have adjusted the BAL pot to correct drift.

    ...from Glentek GA370 manual which is about the same for all DC Servo systems
    snip
    5.3 VELOCITY LOOP PHASING:
    For proper servo operation it is necessary for the amplifier to receive negative feedback from the tachometer. If the
    tachometer leads are reversed (positive feedback), the amplifier will run away. To check the phasing of the motor and
    tachometer proceed as follows:
    1. Make sure Current Limit potentiometer, RV5, is full CCW (as shipped from factory).
    2. Make sure that nothing is connected to the Signal Input (J1-2) or the Auxiliary Signal Input (J2-1 or J2-2).
    3. Apply the main power for DC Buss and the 120 volt power for the fans.
    4. Slowly turn the Current Limit potentiometer, RV5, CW. If the motor starts to run away turn the Current
    Limit potentiometer full CCW and reverse the motor armature leads. Again, slowly turn the Current Limit
    potentiometer CW. The motor should be stopped or rotating slowly.
    5. Set Current Limit potentiometer, RV5, to the desired peak current for the remaining adjustments and
    operations.
    Typical settings for Current Limit potentiometer, RV5 (20 turn potentiometer).
    3 turns CW = 30% peak current 10 turns CW = 85% peak current
    6 turns CW = 60% peak current 14 turns CW = 95% peak current

    5.4 TACH GAIN ADJUSTMENT:
    1. At this point the motor will be rotating slowly. Adjust the Balance potentiometer, RV6, until the motor
    rotation is stopped.
    endsnip

    At this point after reading your description of all the things you have changed/tried/swapped around. I would guess the Original runaway problem was/is the Fadal 1010 X axis board, but first need to get the X Amp adjusted correctly. Which AMP's do you have ? Do you have the manual for your Modal number?

    Attached Files Attached Files


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    Default

    Quote Originally Posted by machinehop5 View Post
    ...should have adjusted the BAL pot to correct drift.

    ...from Glentek GA370 manual which is about the same for all DC Servo systems
    snip
    Including his GM4050 DC servos??


    Thanks



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    Default Re: 1993 Fadal VMC40 with x axis runaway

    I've been going nuts reading every forum I can. A lot of people blame the power supply.

    I measured the large capacitor and got 120 VDC.

    I have a 1220-3A power supply board.
    I have 116.4 VAC going into the transformer.
    I have 11.5 VAC coming out of the transformer into the rectifier.
    I get 19.8 VAC coming off wires 1 and 3.
    I get 9.71 VDC coming off 4 and 5.
    I get 116.9 coming out of the power supply board into the 1100-1B board.

    I probed the outputs and 1 and 2 are grounds to the 1060-0 board
    3, 4, and 5 see 5.10 VDC
    6 and 7 get 5.11 VDC
    8, 9, and 10 get 5.12 VDC
    11 and 12 are 12.02 VDC
    13 and 14 are -12.02 VDC

    Power supply looks stable.

    I found an encoder testing page.
    It says measure for 1.7VAC at the J1 bullet connector.
    Z is 1.74 VAC
    Y is 1.69 VAC
    X is 0
    The same sheet says expect 3.5 volts coming in and on the white wire and the ground I saw 3.480 VAC.

    I found a spec sheet for the resolver that says
    Wires 1 & 2 should read 70-80 ohms.
    Wires 3 and 4 should read 190 to 220 ohms
    Wires 5 & 6 should read 190 to 220 ohms

    I measured them on my first resolver and got 0 for everything.

    I found another resolver and also got 0. Turns out there was a spot of corrosion on the pins. A dusting with some scotchbrite red and I was able to get some readings.
    77.6 ohms, 206.4 ohms, and 206.4 ohms.
    I installed this resolver and I saw 1.76 VAC at the bullet connector for X

    The X still drifts. HOWEVER, now when I do a CS the motor jerks one way and then starts to creep the opposite way before it runs away. It's sortof in the right direction towards a resolution. I think it could be a difference of signal and balance now.



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    Default Re: 1993 Fadal VMC40 with x axis runaway

    Oh.
    I forgot to add

    They are Glentek DC GM4050 servo motors.
    The amp is a 4568-4201 board (stamped in the middle) and GA4568EA stamped at the bottom.
    I do not have a manual with me but a bit of searching yielded this:
    https://www.glentek.com/download/ga4...al/?wpdmdl=369

    Glentek offers nothing more than a data sheet for the GM4050 servo motor.



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    Default Re: 1993 Fadal VMC40 with x axis runaway

    good to hear you found a dirty plug. Plugs are always a weak point. Check them all...not sure if the1993 Fadal's had the Service Programs available back than because memory was expensive but, there was a program to adjust SIG and Balance using the Lag Display for each axis. At the COMMAND prompt type TA,2 enter
    https://www.fadalcnc.com/media/pdf/t...e_Programs.pdf
    thanks for the update
    enjoy



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    Default Re: 1993 Fadal VMC40 with x axis runaway

    My manual lists three programs that have survived in my brain since the last time I did this.

    The first was a 20 inch move back and forth that was supposed to take exactly 72 seconds in order to set the master clock.
    One moved all three axes 6 inches, back and forth, and I was trying to set the gain to 1.440 volts on the positive sweep.
    The other was for the balance, and I had to bring it down to 0-1 on the display.

    I'll post an update when I'm running again.



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    Default Re: 1993 Fadal VMC40 with x axis runaway

    I still get a horrible mismatch between the X and Y axes, like they aren't synchronized. Linear motions are smooth as butter.

    I double checked the backlash settings along X. I started with 3, 4 and 4. I zeroed out all three variables and conducted my tests. I ended with 3, 3, 4

    I double checked the tightness of my three piece, three finger union. The spec I found in the book was a gap of .060 between the coupler and the fingers.

    The master clock is set to 72 seconds, right on the money.

    I ran the program in the manual that moves all three axes 6 inches, and allows me to tune to 1.440 +/-.001 VDC. I tuned them all to this value. I then adjusted the balances to get them all to 0, +/- 1
    I repeated this process two more times to ensure everything was stable.
    When running the program that moves all three axes 6 inches I observed two things worth noting:
    My following error on X (supposed to be 595) reads 585.

    While moving in the positive direction, X is tuned via the signal gain to 1.440, Y is tuned to 1.440 (but dips to 1.437 in the middle of its travel, and spikes to 1.442 by the end of its travel) and Z stays pretty good at 1.440 VDC.
    While moving in the negative direction, X drops to 1.420 ish, Y drops to 1.432 ish, and Z stays 1.439 VDC.
    I don't know why the dramatic dip in the voltage of X while moving in the X minus direction.

    I found this post:
    https://en.industryarena.com/forum/s...d--100379.html
    Where a user states
    One other thing when I have the following error at 595 the digital meter reads 1.45 not 1.44, when I Adjust via digital to 1.440 the following error reads 560-570

    the x and Z following errors flukuate about 4 points, the Y flucuates about 28 points cant get it to settle down( hence why i am going to try a different tach.)
    (Which makes me suspect my brand new tach)
    to which another user replies:

    the 1.45 is ok. The 1.44 is a suggested starting adjustment. All motors and amplifiers will adjust slightly differently. That is why it is necessary to re-tune when ever an amp, motor or controller card is replaced.
    So I'm less concerned with the 1.440 value now, and I will be focusing on the displayed following error tonight.

    I need to borrow a 45 degree gage block which is why I didn't do the 45 degree test last night.



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    Default Re: 1993 Fadal VMC40 with x axis runaway

    ...sounds like the Y Amp is not working correctly or as smooth as X Amp and that will affect them working together. Circles out of round etc...for sure. If, its not a mechanical problem with Y axis...might want to swap eeprom/drip socket jumpers and swap from Z amp to Y amp but, there is a stored Tool Change offset number on the Z Card maybe (not sure about 1993) look in the Fadal Survey command should write it down and save it just in case. Y axis would also have some kind of Offset Parameter too.



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    Default Re: 1993 Fadal VMC40 with x axis runaway

    I tweaked the signal and the balance on the Y axis. It's on the 0 to -1 side of balance while sitting on the auto screen.
    The Y axis following error is real close to hovering around 595 but once in a while it fluctuates as high as 604 or as low as 588. I had to record it as a video and play, pause, play, pause, to see the deviation.
    The X and Y were perfectly synchronized the majority of the time, but I saw deviation up to .010 between the axes, granted, this was only a split second.

    I ran the survey last night and I double checked my backlash.

    All the survey parameters for the Y axis were 0. X had values stored, and Z had values stored.

    I bought extra transistors. I wonder if it's worth replacing them just to eliminate transistor failure on an amp card as a possibility?

    I had some 1x1 aluminum stock. I stood it up, and programmed a .950 diameter circle. I forgot I had -.010 wear offset from the last tool that was in there so I'm expecting a .940 diameter boss.

    East - West I had .9406
    North - South I got .9405
    North east to south west I got .9403
    But from south east to north west I got .9395

    I think that's the best the machine has ever done since I've gotten it, but the surface finish still lacks quality and has vertical break lines.



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    Default Re: 1993 Fadal VMC40 with x axis runaway

    1993 Fadal VMC40 with x axis runaway-screenshot_20210819-084030_gallery-jpg
    1993 Fadal VMC40 with x axis runaway-screenshot_20210819-090742_gallery-jpg
    1993 Fadal VMC40 with x axis runaway-screenshot_20210819-090729_gallery-jpg

    Here are some pictures from last night. I still haven't done the 45 degree test.



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    Default Re: 1993 Fadal VMC40 with x axis runaway

    Last night I did the 45 degree program moving from southwest to northeast, as prescribed in my manual.
    For funsies, I reprogrammed it to run southeast to northwest.
    Both showed good. I didn't see anything more than .0005 during the travel, although SE to NW was a bit choppier.

    I then cut a 6.0 inch square, with 11/32 chamfers (so the length of the hypotenuse would be 8 inches)
    I measured 5.999 and 6.000 across X and Y with digital Mitutoyo calipers, and I measured 7.998 across the two, 8 inch hypotenuse spreads with Mitutoyo dial calipers.
    It seems X and Y are good, positionally, but the 45 degree chamfers looked like garbage like they are not synchronized.



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    Default Re: 1993 Fadal VMC40 with x axis runaway

    ...I wonder if you have a cracked/broken resolver/encoder Coupler on Y axis If, your machine uses them. I'm not real positive what Glentek used......If, its the 2 thin Plate type...they can crack around the Rivets and not easy to see the damage.
    https://itscnc.com/catalog/product/v...3/category/38/



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    Default Re: 1993 Fadal VMC40 with x axis runaway


    I have the coil ones with the two set screws.

    I replaced the brushes on the servo last night. Short of that I'm at a loss. Throw out the motor and buy a new one?
    I'm done with this.

    I did notice my new tachometer ring only had counterbored screws, where the old one had a countersink for flat heads.
    I wonder if the tachometer ring is not concentric and that's creating an erratic signal?

    I replaced the old tachometer ring, leaving the new coil on the shaft.

    The motor was flip flopping directions but not alarming out. I was able to adjust the SIG and BAL to get it to slowly creep in one direction, but it won't sit still. I was able to CS and get into the auto screen to see the X axis balance was cycling between 200 to 3250.

    Now the motor is running away again. I'm stuck on tuning the SIG and BAL. Every document I has says "just tune the SIG and BAL", but I've spent hours tweaking them. Is there some baseline? I don't know how to adjust this so the motor sits stationary.
    The weird thing is, if I put my volt meter across the SIG and SIGCOM I can watch the voltage climb from 1 to 10 volts, and back to 1, climbing up to 10, like I'm seeing some kind of ripple?



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    Default Re: 1993 Fadal VMC40 with x axis runaway

    I called KMAC and they had suggested to ohm out the tachogenerator and I was looking for 40-60 ohms at various locations. I got anywhere from 48.8 to 50.0 ohms.

    I found some stock settings for the amplifier boards. I started from there and I was able to get the motor stationary. From there, I was able to CS and then run the x6,y6,z6 program to tune the following error to 595.
    That didn't fix it.

    I measured 1.659 volts from the Y axis resolver.
    I replaced it anyway and now I get 1.745 volts.
    That didn't fix it.

    I pulled the X axis amplifier board and replaced every transistor on it.
    That didn't fix it.



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    Default Re: 1993 Fadal VMC40 with x axis runaway

    Quote Originally Posted by Paraquat View Post
    I called KMAC and they had suggested to ohm out the tachogenerator and I was looking for 40-60 ohms at various locations. I got anywhere from 48.8 to 50.0 ohms.

    I found some stock settings for the amplifier boards. I started from there and I was able to get the motor stationary. From there, I was able to CS and then run the x6,y6,z6 program to tune the following error to 595.
    That didn't fix it.

    I measured 1.659 volts from the Y axis resolver.
    I replaced it anyway and now I get 1.745 volts.
    That didn't fix it.

    I pulled the X axis amplifier board and replaced every transistor on it.
    That didn't fix it.
    ...good Lord are we having fun yet. Sounds like the problem must be with the Fadal 1010 control card. Swapping with Z card is possible but, must record the stored Offset for Tool changer position. The X Card may have stored Offset also. I just had a thought....maybe its Y axis is the problem card.



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    Default Re: 1993 Fadal VMC40 with x axis runaway

    I forgot to add, I also put a pry bar on the table and put some lean into it.
    I was able to muster .0003 on the Y and .0002 on the X.
    The results were duplicated when I manually attempted to push the table linearly along an axis.
    I do not believe there is a mechanical issue with the ballscrew, or "lost motion" via the nuts, bearings, or thrust bearings.

    I did swap the 1010 cards at one point. I bought a used, tested x axis card off a vendor who strips down machines.
    The first part I cut was a 3/4 scale version. I investigated:

    I used verniers to measure a Kurt Jaw and I got 5.970".
    I had a vise in the machine, which I knew was trammed square.
    I put an edge finder on the sides of the jaws, did some math and it measured 7.542 long.
    I put the old card back in and it measured 5.970 with the edge finder.

    For whatever reason, the replacement card was measuring ~1.5" longer.
    When I put the old card back in, the measurements returned.
    My understanding is the card just counts, so I figured something was wrong with the number of counts. I messaged the vendor and asked if it was a metric machine and the vendor didn't know. Vendor said it powered up and everything moved so they bought it and stripped it down.

    My latest theory is while I was swapping 1010 cards around, if I erased the survey for the Y axis and that's why it reads zero for every field? (See post 11)
    I did find the survey card from when the machine was new. I was going to try those values just to see if it makes a difference. They won't be perfect since the machine has seen some miles, but I'm hoping it narrows down whether or not that's the problem.

    Testing the boards is what lead me to KMAC. Their website offers to test boards. It might be time to call them again.



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    Default Re: 1993 Fadal VMC40 with x axis runaway

    found a manual that says
    Page 622 says "Runs rough?" Yes, all three? No, yada yada

    CHECK AND ADJUST
    RESOLVER CONNECTOR
    AT AXIS CARD J2 WITH
    SERVICE TOOL ST44
    *
    CHECK RESOLVER

    I already blindly swapped resolvers, so that's not it. What is SERVICE TOOL ST44?




    Found a flow chart.

    The machine was functioning perfect prior to this runaway issue so I'm going to say it's still level, and square (based on the 6x6 square I cut).
    It is not a wavy finish on straight cuts.
    My arcs do leave lines at 90 degree marks, or at least they did when I first got the machine. This flowchart says use SERVICE TOOL ST48 to adjust the sin/cos signal.
    What is SERVICE TOOL ST48?

    Step 11.4 says check axis amplifier compensation settings. I can check that tonight. IIRC it's just turn the dial the whole way.

    These are direct drive, so no belts or pulleys.

    I can't find any description of what either of these service tools are.



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    Default Re: 1993 Fadal VMC40 with x axis runaway

    Ok. The compensation knob on the x axis amplifier was tweaked a hair under. I turned it full, as the manual stated.
    I found the original survey card and I put those values into the Y axis.

    The interpolated edges actually look not too bad. The angular cuts have some vertical lines to them but it's good enough for the parts I sell.

    I started to run a small order of 30 parts (6 at a time).
    After the first operation, I started to get an alarm.

    Spindle controller or driver failure.
    Spindle controller or driver failure.
    Spindle controller or driver failure.
    Spindle controller or driver failure.
    Spindle controller or driver failure.
    Spindle controller or driver failure.
    Spindle controller or driver failure.
    Spindle controller or driver failure.

    (8 times).

    I have a Baldor SWEO drive. I ran the auto tuning feature.
    I have 150 psi of air, regulated to 90 psi of air into the machine. I have way lube oil and spindle oil. Belts are tight.
    I mention these because the flow chart in the manual says to address all of these.

    Here's what I've observed:
    When the machine is powered on, the spindle will not turn to execute a tool change. The spindle will not run, regardless of RPM (tried 20 to 7500).
    I can move the spindle manually to line up the tool change hall effect sensor and then a tool change will be executed as normal.

    If I wait 5 or 10 minutes, the machine will spin the spindle to execute a tool change.
    If I wait 10-20 minutes, the machine will run fine. I ran for 9 hours on Sunday without issue.

    If I power off, the machine needs to wait again. This has me suspecting a capacitor is slow to charge?
    I have a Baldor SWEO drive and I see two large capacitors in there under it. They look like silver cigarette cases.
    I don't know how to measure them.

    A lot of people seem to criticize the "regen resistors". I have no idea what these are, or where they are located but based on my drive I have two of them and they should be 13 ohms each.



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1993 Fadal VMC40 with x axis runaway

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