Inherited a 4x8 machine that has some issues....


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    Default Inherited a 4x8 machine that has some issues....

    Hi All,

    So I started a new job and as a part of that I have inherited the duties of fixing thier existing CNC machine. Having built my own 4x4 Avid/Mach3 machine I am not a complete newbie but this one I am working now has some interesting challenges.

    The X and Y axis' in this machine are LinTech rails with NEMA 34 sized servo's on them. Everything seems to be wired and mechanically functioning properly.

    So the first challenge is that the Y axis slave will initially start to move in perfect unison with the Y axis but after 4-5 inches it dramatically slows and as such it racks the Y axis. It does this in both directions and all along the axis. I have checked the motor tunings between the two in Mach3 and they are the same there. It is also interesting that if I keep the speed slow enough, it does not do this... Anything over 70ipm and I have racking issues but not below that speed.

    Needless to say.. I would rather not run at 70ipm if at all possible.

    The second issue is that the Y axis is losing position... I can run a program and bring it back to home and it can be a half an inch off in either direction... I will be running different tests today to see if I can narrow it down to a single servo or if they are doing it in tandem.

    Any idea or suggestions would be greatly appreciated.

    Thanks in advance,

    Mick

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    Default Re: Inherited a 4x8 machine that has some issues....

    Quick followup... I just double checked and I was incorrect about the slave axis slowing down after a few inches... they both do it... and in both directions.. there is no set way that it happens....



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    Default Re: Inherited a 4x8 machine that has some issues....

    Is the signal too fast? Commenting so I get updates on this.

    Sent from my SM-G996U using Tapatalk



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    Default Re: Inherited a 4x8 machine that has some issues....

    Quote Originally Posted by ubergeekseven View Post
    Is the signal too fast? Commenting so I get updates on this.

    Sent from my SM-G996U using Tapatalk
    I have no clue to be honest. Is that a setting in Mach3?



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    Default Re: Inherited a 4x8 machine that has some issues....

    Quote Originally Posted by MicFarlow View Post
    Quick followup... I just double checked and I was incorrect about the slave axis slowing down after a few inches... they both do it... and in both directions.. there is no set way that it happens....
    You said it has servos, for it to do this there must be a problem with the servo motor or drive, when you have servos with encoders, they don't loose position. what is the name of the servos and drives.

    Mactec54


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    Default Re: Inherited a 4x8 machine that has some issues....

    The drivers and the servos will have a specific frequency they should respond to. If you didn't get the control computer with mach configured already with the machine. Maybe the frequency isn't set correctly in Mach. The drivers and servos have to have those specs.
    It could be the amperage settings on the drivers as well. I suppose that the faster you try to move them, the higher draw they would have. If set too low, then they may not be able to get enough juice to keep them going at the rate specified. Too high isn't good either though.
    The drivers should have some method of changing the output amperage. Probably switches that determine the setting and would definitely be in the manual. Then just reference the servos manual for the optimal input amperage.


    Sent from my SM-G996U using Tapatalk



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    Default Re: Inherited a 4x8 machine that has some issues....

    Quote Originally Posted by ubergeekseven View Post
    The drivers and the servos will have a specific frequency they should respond to. If you didn't get the control computer with mach configured already with the machine. Maybe the frequency isn't set correctly in Mach. The drivers and servos have to have those specs.
    It could be the amperage settings on the drivers as well. I suppose that the faster you try to move them, the higher draw they would have. If set too low, then they may not be able to get enough juice to keep them going at the rate specified. Too high isn't good either though.
    The drivers should have some method of changing the output amperage. Probably switches that determine the setting and would definitely be in the manual. Then just reference the servos manual for the optimal input amperage.


    Sent from my SM-G996U using Tapatalk
    It will be using Set/Dir, sent to the servo drives, the servo loop is closed in the drives, it will only depend on the encoders CPR as to what may be needed to be set as the kernel speed in Mach3 45000Hz to 65000Hz setting should be fine for what he has.

    There is no amperage setting on servo drives.

    Mactec54


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    Default Re: Inherited a 4x8 machine that has some issues....

    Are they 'proper' AC servo's or more like hyybrid stepper types?.

    If they're hybrids it could be too low a voltage being used on too high an inductance motors.
    70-80ipm was the cliff for me in this scenario.

    If they're the AC type then ignore me.



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    Default Re: Inherited a 4x8 machine that has some issues....

    Ok... so I actually misspoke.. I have steppers, not servos! My sincerest apologies about that!

    So.. They have 60v power supplies and I have measure them all to make sure they are at 60v and they are.

    I did have the Y and A sharing a single power supply rated at 6A so I did separate them so now they each have thier own power supplies.

    Both power supplie show a 60v load of 6A and the steppers labels says they are 6A steppers.

    I have ordered a new breakout board that'll be here Tuesday.

    I also took the steppers completely off the machine and with them setting on the floor with no load, they both worked flawlessly with no issues at all. I also put a single one on the machine and it also worked flawlessly... I don't have any issues until I put them both on.

    Thanks!



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    Default Re: Inherited a 4x8 machine that has some issues....

    Quote Originally Posted by MicFarlow View Post
    Ok... so I actually misspoke.. I have steppers, not servos! My sincerest apologies about that!
    So.. They have 60v power supplies and I have measure them all to make sure they are at 60v and they are.
    I did have the Y and A sharing a single power supply rated at 6A so I did separate them so now they each have thier own power supplies.
    Both power supplie show a 60v load of 6A and the steppers labels says they are 6A steppers.
    I have ordered a new breakout board that'll be here Tuesday.
    I also took the steppers completely off the machine and with them setting on the floor with no load, they both worked flawlessly with no issues at all. I also put a single one on the machine and it also worked flawlessly... I don't have any issues until I put them both on.
    Thanks!
    right .
    So It's highly likely that high inductance is your problem.
    If these motors are the ones that are around 140mm length or above they''ll be the terrible 1600-1700oz things which trap a lot of people.
    (Been there).
    Previous user likely didn't get much further with getting it good it either.
    Those type motors need way more than 60v to be usable.
    Somthing like the DM2282 220vac mains voltage drive is more appropriate.

    Ditch the motors for smaller lower inductance ones (maybe even half the length) keeping them 60v.
    you should see a huge improvement.
    I did this eventually after wasting my time with the large ones
    (I've upped to 80vdc with a DM860T on a smaller motor).

    Bigger isn't always better.

    Last edited by dazp1976; 10-29-2021 at 09:10 AM.


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    Default Re: Inherited a 4x8 machine that has some issues....

    Quote Originally Posted by dazp1976 View Post
    right .
    So It's highly likely that high inductance is your problem.
    If these motors are the ones that are around 140mm length or above they''ll be the terrible 1600-1700oz things which trap a lot of people.
    (Been there).
    Previous user likely didn't get much further with getting it good it either.
    Those type motors need way more than 60v to be usable.
    Somthing like the DM2282 220vac mains voltage drive is more appropriate.

    Ditch the motors for smaller lower inductance ones (maybe even half the length) keeping them 60v.
    you should see a huge improvement.
    I did this eventually after wasting my time with the large ones
    (I've upped to 80vdc with a DM860T on a smaller motor).

    Bigger isn't always better.
    You are indeed correct... The steppers in question are Wantai 85BYGH450C-060 motors... they are 151mm length 1,700 oz motors driven with 60v power supplies. The easiest thing for me to do would be to just put in bigger power supplies.. these motors are mounted to gear reducers and then to a coupling on these LinTech rails and I'd rather not try to re-engineer all that if simply swapping out the power supplies will do the trick.

    Additional info.. The drivers are DQ860MA by Wantai as well... this seems to be a kit off of eBay I think....

    Of course.. looking for 80v power supplies seems to be a challenge here are well. I have a tight'ish cabinet to get these things into and it looks like replacing the steppers will be cheaper too...

    Do you have a link or recommendation for a good motor/driver combination that will work of these 60V (120v mains) power supplies?

    Thanks in advance!

    Last edited by MicFarlow; 10-29-2021 at 12:52 PM.


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    Default Re: Inherited a 4x8 machine that has some issues....

    Quote Originally Posted by MicFarlow View Post
    You are indeed correct... The steppers in question are Wantai 85BYGH450C-060 motors... they are 151mm length 1,700 oz motors driven with 60v power supplies. The easiest thing for me to do would be to just put in bigger power supplies.. these motors are mounted to gear reducers and then to a coupling on these LinTech rails and I'd rather not try to re-engineer all that if simply swapping out the power supplies will do the trick.

    Additional info.. The drivers are DQ860MA by Wantai as well... this seems to be a kit off of eBay I think....

    Of course.. looking for 80v power supplies seems to be a challenge here are well. I have a tight'ish cabinet to get these things into and it looks like replacing the steppers will be cheaper too...

    Do you have a link or recommendation for a good motor/driver combination that will work of these 60V (120v mains) power supplies?

    Thanks in advance!

    Honestly. You will get nowhere with those motors. Search around about the 1600 / 1700oz ebay apedials and you will find out.
    Mine went where it belonged....... in the bin!!!
    If you have gear reduction , why does the machine need so much torque?.

    My 1600oz was on a mill head Z axis. I just swapped to a 1080oz smaller 34 motor. (straight swap).
    This is the best advice I can give. Although yes it doubled my speed as soon as I changed it, I'm still a little disappointed.

    However, the new 1080oz does react to a voltage increase.
    I'm using a 1080oz nema34 (ebay) with this DM860T:
    https://www.aliexpress.com/item/3286...86741310%22%7D
    on this 80v:
    https://www.aliexpress.com/item/32818208276.html?spm=a2g0s.9042311.0.0.27424c4dnCK 9hf
    You can choose psu upto 110vdc here:
    https://www.aliexpress.com/item/4000...c00HUG7bw&mp=1
    There are variable voltage here too:
    https://www.aliexpress.com/item/3295...:%223339%22%7D

    I think you should look into getting some cheap 750w AC servo sets such as Lichuan on Aliexpress to be perfectly honest.
    By the time you've figured out reliable motors/drivers/psu the cost difference will be negligible.




    (I bet your machine would prob work fine with nema24 566oz on 60v beings it has reduction tbf).



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    Default Re: Inherited a 4x8 machine that has some issues....

    Quote Originally Posted by dazp1976 View Post
    Honestly. You will get nowhere with those motors. Search around about the 1600 / 1700oz ebay apedials and you will find out.
    Mine went where it belonged....... in the bin!!!
    If you have gear reduction , why does the machine need so much torque?.

    My 1600oz was on a mill head Z axis. I just swapped to a 1080oz smaller 34 motor. (straight swap).
    This is the best advice I can give. Although yes it doubled my speed as soon as I changed it, I'm still a little disappointed.

    However, the new 1080oz does react to a voltage increase.
    I'm using a 1080oz nema34 (ebay) with this DM860T:
    https://www.aliexpress.com/item/3286...86741310%22%7D
    on this 80v:
    https://www.aliexpress.com/item/32818208276.html?spm=a2g0s.9042311.0.0.27424c4dnCK 9hf
    You can choose psu upto 110vdc here:
    https://www.aliexpress.com/item/4000...c00HUG7bw&mp=1
    There are variable voltage here too:
    https://www.aliexpress.com/item/3295...:%223339%22%7D

    I think you should look into getting some cheap 750w AC servo sets such as Lichuan on Aliexpress to be perfectly honest.
    By the time you've figured out reliable motors/drivers/psu the cost difference will be negligible.




    (I bet your machine would prob work fine with nema24 566oz on 60v beings it has reduction tbf).
    How about this stepper motor from Avid... will it work with these 60v drivers?

    https://www.avidcnc.com/960-oz-in-ne...tor-p-112.html

    At 2mh the inductance is quite low and 960oz should be plenty of holding power... they are a little pricey but I have a friend who has 4 of them on his machine and they are great.



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    Default Re: Inherited a 4x8 machine that has some issues....

    so... an observation.... these steppers have a gear reduction of 29:1... that seems excessive to me. the Avid 960oz Nema 34's work just fine with a 3.2:1 ratio...

    I would think changing the gear reduction to something along the line of 5:1 would be a or 6 fold increase in speed and the expense of some torque....

    What are the drawbacks?



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Inherited a 4x8 machine that has some issues....

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Inherited a 4x8 machine that has some issues....