Torus Pro Servo + Pathpilot = Lost Motion

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Thread: Torus Pro Servo + Pathpilot = Lost Motion

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    Default Torus Pro Servo + Pathpilot = Lost Motion

    So, I finally got my Torus Pro Servo mill and Pathpilot situated and wanted to start making some parts. I load up a program that spots two rows of holes roughly 5 inches apart, along approximately 12" of travel. Next tool then comes and drills the through hole. Well I watched in horror as drill #2 comes down, makes a hellacious noise and I can see the drill bit bending while drilling. I stop and look at the the one and a half holes I drilled are ovaled. They were at least an 1/16 to an 1/8 off in both the x and the y axis. So I look at the code, and double check all the co-ordinates for holes are the same. So I do a bunch of testing, and find I can easily replicate the error, by zeroing out a dial indicator against a vise, raising Z. then rapiding from one end of the X axis to another and back, and then lowering Z and reading the offset. A single pass test on the X axis would randomly generate an error of .018 to .028, randomly in that range. The more passes I did, compounded the error. I found some great LinuxCNC tutorials for calibrating the ball screw, and checking backlash. ball screw setup was correct, my backlash measurements were ever so slightly off vs what is in the files being passed around by everyone for PathPilot on the TPro. One thing I discovered when doing all the testing though, is that if I used the Shuttle and manually stepped through testing it was fine. I wrote some G-code to streamline the testing, and it starts skewing again. So as a last resort, I took a look at the ini file, and backed the max velocity and acceleration off big time. Now it behaves perfectly, even with the rapids.

    TL;DR
    1. Massive positioning errors discovered and verified to be a machine (not g-code) issue.
    2. Error goes away when maximum velocity and acceleration are lowered.
    3. Concern that servos aren't servo'ing, or at least meeting my expectation of what servos are supposed to do.

    Questions:
    1.Is this down to PathPilot being configured for a stepper based system and does not look at the feedback loop?
    2. Is the motion controller even in the loop at all? or does it just pass off a request for X number of steps to the servo drive, and the servo drive has the feedback loop and responsibility for keeping sync?

    Looking for any help or guidance if anyone has anything to share. I'm a hobbyist, so if ~200ipm and slower acceleration is all this machine can do than I can cope, but I paid extra for servos because I thought positional feedback was an important element to making good parts. Side note, I understand that PP is not what the machine ships with and is way out of bounds from a support perspective from John@Novakon. Not a knock or gripe about the mill, this is entirely of my own doing and I accept that. I know that native LinuxCNC is totally capable of working with Servos, so if I have to go that route eventually, I will.

    Bonus: Take the time to check backlash on all 3 axis and adjust the ini file accordingly. Each machine is a snowflake, My machine is essentially brand new and the backlash actually ended up being less than what the config is that folks are passing around. My X and Z were both .0005 off what was in the config. That error will compound with every change of direction. I'm not making anything that's going in to space, but make everything as good as your can.

    Similar Threads:
    Jason --CNC Newbie--


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    Default Re: Torus Pro Servo + Pathpilot = Lost Motion

    Sorry to tell you this so late in the game, but he Pro doesn't have a closed loop servo system. I knew that going in when I bought mine. I bought them for the speed and strength, but they will definitely lose steps if the accel/decel are set too aggressively. Here's a vid from when I was playing with mine a few years ago. I'm only running 250ipm rapids at this time.


    Don't have to be too bright to be me :)
    bluehandsvideo on youtube


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    Default Re: Torus Pro Servo + Pathpilot = Lost Motion

    WTF;
    I'm definately not a linux educated person and would love to see the changes you made to your velocity and acceleration settings (and where to find them). I switched to PP a while back and when I finally got it running, I was quite thrilled. However, I used the files that were available here in the zone so I only corrected errors in the setup until it worked. The basically means that I have no idea where and what my settings are! I also want to look at the setting for the spindle cause my spin up and down (with breaking resistor) are definately much longer in PP that in Mach (which I somewhat understood).
    Thanks and sorry for your woes! However, maybe this will help some of us understand what is going on so all is not lost!
    Bill

    billyjack
    Helicopter def. = Bunch of spare parts flying in close formation! USAF 1974 ;>)


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    Default Re: Torus Pro Servo + Pathpilot = Lost Motion

    Mike,
    If that is truly the case, than I am a little disappointed. It's not the end of the world though. Now that I know, I can just take the appropriate measures. I am curious if the encoders are there, but not wired, or what the deal is. I've got a backlog of things that I need to make, but once I get them all done, I will likely dig in to this a little further.

    Bill,
    If you go in to the tmc/configs/tormach_mill/novakon_mill_base.ini file in your favorite text editor, (gedit, vi, vim) you will see sections towards the end that contain settings for each axis.Here is an excerpt from my Axis 0 (X) what they were, and what I changed them to.


    # 110 in/min
    MAX_VELOCITY = 5
    MAX_ACCELERATION = 50
    # 20 % higher
    STEPGEN_MAX_VEL = 6
    # 2.5x
    STEPGEN_MAXACCEL = 50
    BACKLASH = 0.0014

    Here is what I changed mine to:


    # 110 in/min
    MAX_VELOCITY = 3
    MAX_ACCELERATION = 15
    # 10 % higher
    STEPGEN_MAX_VEL = 3.3
    # 1.67x
    STEPGEN_MAXACCEL = 25
    BACKLASH = 0.0008


    I believe* that the MAX_VELOCITY and STEPGEN_MAX_VELOCITY are values in inches per second, so x 60 to get to the more common inch per minute. so a value of 3 is 180ipm. The MAX_ACCELERATION and STEPGEN_MAXACCEL I believe are in ips². I changed both STEPGEN values based on instructions I found here:
    INI Configuration

    I believe that the issue is around the acceleration, not necessarily the maximum velocity. I will likely continue to test and alter these settings to see what I can safely attain, but for now I have parts to make.



    Thanks,
    Jason

    Jason --CNC Newbie--


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    Default Re: Torus Pro Servo + Pathpilot = Lost Motion

    I might add that this error may or may not have been occurring since the beginning, but it may not have manifested itself until now because I added a second DX6 vise to the table to make some really long parts. How's that for science kicking you where it hurts?

    Jason --CNC Newbie--


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    Default Re: Torus Pro Servo + Pathpilot = Lost Motion

    Quote Originally Posted by WTFover View Post
    So, I finally got my Torus Pro Servo mill and Pathpilot situated and wanted to start making some parts. I load up a program that spots two rows of holes roughly 5 inches apart, along approximately 12" of travel. Next tool then comes and drills the through hole. Well I watched in horror as drill #2 comes down, makes a hellacious noise and I can see the drill bit bending while drilling. I stop and look at the the one and a half holes I drilled are ovaled. They were at least an 1/16 to an 1/8 off in both the x and the y axis. So I look at the code, and double check all the co-ordinates for holes are the same. So I do a bunch of testing, and find I can easily replicate the error, by zeroing out a dial indicator against a vise, raising Z. then rapiding from one end of the X axis to another and back, and then lowering Z and reading the offset. A single pass test on the X axis would randomly generate an error of .018 to .028, randomly in that range. The more passes I did, compounded the error. I found some great LinuxCNC tutorials for calibrating the ball screw, and checking backlash. ball screw setup was correct, my backlash measurements were ever so slightly off vs what is in the files being passed around by everyone for PathPilot on the TPro. One thing I discovered when doing all the testing though, is that if I used the Shuttle and manually stepped through testing it was fine. I wrote some G-code to streamline the testing, and it starts skewing again. So as a last resort, I took a look at the ini file, and backed the max velocity and acceleration off big time. Now it behaves perfectly, even with the rapids.

    TL;DR
    1. Massive positioning errors discovered and verified to be a machine (not g-code) issue.
    2. Error goes away when maximum velocity and acceleration are lowered.
    3. Concern that servos aren't servo'ing, or at least meeting my expectation of what servos are supposed to do.

    Questions:
    1.Is this down to PathPilot being configured for a stepper based system and does not look at the feedback loop?
    2. Is the motion controller even in the loop at all? or does it just pass off a request for X number of steps to the servo drive, and the servo drive has the feedback loop and responsibility for keeping sync?

    Looking for any help or guidance if anyone has anything to share. I'm a hobbyist, so if ~200ipm and slower acceleration is all this machine can do than I can cope, but I paid extra for servos because I thought positional feedback was an important element to making good parts. Side note, I understand that PP is not what the machine ships with and is way out of bounds from a support perspective from John@Novakon. Not a knock or gripe about the mill, this is entirely of my own doing and I accept that. I know that native LinuxCNC is totally capable of working with Servos, so if I have to go that route eventually, I will.

    Bonus: Take the time to check backlash on all 3 axis and adjust the ini file accordingly. Each machine is a snowflake, My machine is essentially brand new and the backlash actually ended up being less than what the config is that folks are passing around. My X and Z were both .0005 off what was in the config. That error will compound with every change of direction. I'm not making anything that's going in to space, but make everything as good as your can.


    What brand of servo drives? You still need to tune your servo drives. The PID internal to the servo drives needs to be tuned.

    I am running PathPilot on Yaskawa AC servos +-10V system Denford NovaTurn Lathe.
    My system is fully closed loop.
    The servo drives are running in torque mode and had to be tuned first, followed by settings in PathPilot.
    I will soon be refitting a Denford Triac mill and a Infimatic Freedom NC200 controller.

    Hope this helps,

    Iron Man

    Last edited by Iron-Man; 12-13-2018 at 02:15 PM. Reason: additional info.


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    Default Re: Torus Pro Servo + Pathpilot = Lost Motion

    I'll have to look and see if there are any identifiable markings when I get home today. I don't remember there being any but I didn't really look that close either. I know the Servo Drives are AC and are the "Mige AP1". I am not sure if the drive and servo are a package unit because the manual https://www.dropbox.com/s/12oe4jh1ef...Drive.pdf?dl=0 shows some of the motor options. It even alludes to using the "small motor" because of the 220v single phase. It certainly appears that the servo drives has all the A/B/Z signature inputs that you would need to do this.


    Are the tools you used to do the tuning embedded within Pathpilot distribution? Or did you tune it on LinuxCNC and then copy the pertinent configuration data over.

    Jason --CNC Newbie--


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    Default Re: Torus Pro Servo + Pathpilot = Lost Motion

    Quote Originally Posted by WTFover View Post
    I'll have to look and see if there are any identifiable markings when I get home today. I don't remember there being any but I didn't really look that close either. I know the Servo Drives are AC and are the "Mige AP1". I am not sure if the drive and servo are a package unit because the manual https://www.dropbox.com/s/12oe4jh1ef...Drive.pdf?dl=0 shows some of the motor options. It even alludes to using the "small motor" because of the 220v single phase. It certainly appears that the servo drives has all the A/B/Z signature inputs that you would need to do this.


    Are the tools you used to do the tuning embedded within Pathpilot distribution? Or did you tune it on LinuxCNC and then copy the pertinent configuration data over.
    My original system was on Linux before PathPilot was available.
    The dropbox link appears to be overloaded?
    Can you post the manual? The software and specs of your drive, plus a indicator, should be all you need to tune the servo drives.
    When this is done, then finish tuning in PathPilot.

    Iron-Man



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    Default Re: Torus Pro Servo + Pathpilot = Lost Motion

    Here it is.

    Attached Files Attached Files
    Jason --CNC Newbie--


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    Default Re: Torus Pro Servo + Pathpilot = Lost Motion

    Quote Originally Posted by WTFover View Post
    Here it is.
    Thanks.

    Start at page 36,4.2 Position control mode . Document any changes you make. Re Check the control modes, P035, P036, P037 etc.
    Re Check your settings:
    "5. Signal filter
    Numeral filters related to the parameter P038 will filter the input signal PULS and SIGN. The bigger the
    P308 value, the larger filter time-constant and the lower maximum repeated frequency of input pulse. If P038 is
    seven, the maximum repeated frequency of input pulse will reach 500 kHz (kpps).
    If the positioning is not accurate, increase the parameter P038 in order to filter noise on the signal cable and
    to avoid counting error. The SIGN filter can close by parameter P039 setting.
    6. Smooth filter
    The parameter P040 carries on the smooth filter to the command frequency. It has the exponential form for
    acceleration and deceleration as showing in the following chart. The filter cannot lose any input pulse, but can
    delay its action time. When P040 is zero, the filter does not have any effect. The parameter value indicates the
    time in which the repeated frequency increases from 0 to 63.2% command frequency."

    Sometimes its by Trial and Error
    Gain adjustment procedure for position control loop
    1. Set the load inertia ratio.
    2. Set integral time constant of the speed loop with a relatively great value.
    3. Under no vibration and unusual sound increase the gain of the speed loop, if vibration occurs then decrease the
    gain a bit.
    4. Under no vibration and unusual sound, decrease the integral time constant of speed loop, if vibration occurs
    then increase the time constant a bit.
    5. Increase the gain of position loop, if vibration occurs then decreases the gain a bit.
    6. Because the mechanical system may have resonating factors and is unable to adjust for a bigger gain, then the
    desired response cannot obtain. Now, adjust the filter time constant (parameter P007) of torque, and then carry on
    above steps again enhancing responsiveness.
    7. If need shorter positioning time and smaller position tracking error, can adjust the feed forward of the position
    loop. Please refer to 4.2.4 section.

    Were you provided with software to tune the drives?

    Hope this helps,

    Iron Man



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    Default Re: Torus Pro Servo + Pathpilot = Lost Motion

    Ok, so I made some progress. The motors appear to be a fairly common item, from a google search on the part # on a label. It is sold through MIGE (same people that make the drive) as well as a host of other companies. I'm still hunting for a manual or documentation, I'm not having a whole lot of luck in that aspect.

    • Output Power:1000W
    • Phase:Single-phase
    • Type:Servo Motor
    • Efficiency:IE 4
    • Frequency:50Hz
    • AC Voltage:208-230 / 240 V
    • Certification:CCC,CE,ROHS
    • Model Number:90ST-M04025
    • Protect Feature:Waterproof
    • Flange:86mm
    • Rated power:1000W
    • Rated torque:4N.M
    • Rated current:4.0A
    • Wire QTY of encoder:2500PPR
    • Protect level:IP64
    • Rotor Inertial:3.7KG*CM^2


    Jason --CNC Newbie--


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    Default Re: Torus Pro Servo + Pathpilot = Lost Motion

    To answer your question, I wasn't provided anything other than the mill, and a demo copy of Mach 3 pre-installed and configured in the control computer. I haven't changed anything in the cabinet except for the Pathpilot conversion, which consists of the Mesa Card, a Parallel cable and an SSD drive. From everything that I see here, it looks like tuning and setting up for encoder feedback is possible, so I will likely dig in to that at some point when I get some more free time, but for now, I have parts to make so will probably leave as is, and start doing some research and planning. Thanks everyone for the help and input.

    Jason --CNC Newbie--


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Torus Pro Servo + Pathpilot = Lost Motion

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