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Thread: Servo motor setup

  1. #41

    Default Re: Servo motor setup

    Hi,
    you are doing what I said not to, namely confusing the electronic gearing parameters within the drive with Mach parameters.

    The fact that you change what you believe is the denominator and it changes at a much larger ratio than you expected tells me that you do not understand the drive parameters
    properly yet.

    Leave Mach entirely alone and concentrate on the electronic gearing parameters until you are 110% with them.

    Then and only then do you start fiddling with Mach to get accurate axis distance movements.

    If your servos do 2500rpm then if you set the electronic gearing to 1:1 then it will require an input pulse rate of:

    2500/60=41.666 revs/sec
    41.666 x 10000=416,666 pulsue per second. This should be within the signalling speed of your MB3 provided you are using differential signaling.

    If you chose an electronic gear ratio of 5:1 then the pulse rate is:
    2500/60=41.666 revs/sec
    41.666 x (1/5) x10,000=83,333 pulses per sec or 83 kHz, which you could do single ended, if you wish.

    All that has changed is the pulse rate required to make the servo run at full speed. The consequence is resolution. In the first instance, with 1:1, ie
    10000 pulse per rev and a 10mm pitch screw each step is 1um. In the second case with 5:1, ie 2000 pulse per rev the resolution is 5um per pulse.

    For a hobby machine 5um is probably entirely enough resolution but your servo and ESS/MB3 combination can do better AND STILL run at full speed.

    You will only get to exploit the full benefit of the hardware combination when you can fully exploit the electronic gearing parameters. So go back to the drawing board
    and figure out which of the parameters is the numerator and which is the denominator and that the servo responds AS YOU WOULD EXPECT when you change then.
    Until that time leave Mach alone.

    Craig



  2. #42
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    Default Re: Servo motor setup

    Ok Craig
    what is more to expect from the electronic gear . I find those number it look like somme thing near 5.xxx:1 because 5:1 =4.9375 and 4.9375/5 = 0.9875 in
    Now I have to figure out how to find the right ratio for the proper number.

    Attached Thumbnails Attached Thumbnails Servo motor setup-ratio-table-screew-2510-jpg  


  3. #43

    Default Re: Servo motor setup

    Hi,
    so you are using inches after all?

    At the moment the distance moved is irrelevant. What you need to do is understand electronic gearing.

    Can you set the gearing to 1:1 or 2:1 or 5:1 at will?

    If for instance you choose 5:1 then 2000 pulses will cause one revolution of the servo. With a 10mm pitch screw:
    distance traveled (one rev of screw)= 10/25.4
    =0.393700 inch.......and it took 2000 pulses to do that. Therefore the pulses per inch (the Mach setting):
    =2000/0.393700
    =5080.0

    Note that the Mach setting is a real number, ie it can have a fractional part. But note also that the numerator/denominator
    are both integers but the division ratio is rational, that is has a fractional part.

    The rule is :
    1) Set the electronic gearing to best balance the resolution and signaling speed
    2) Set Mach's pulses per unit to the value required to achieve accurate movement.

    Craig



  4. #44
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    Default Re: Servo motor setup

    Hi Craig
    I find my ratio for my 2510 , X axe for having a deplacement of 1 inch dro and real the ratio is 32767/6464=5.0691.
    I tried the same number on the Y axe 4010 and it move 0.195 in for dro 1.00 in . After I made it more simple 5:1 .
    On axe X I use PN098 as Numerator (32767) and PN102 as denominator (6464) , for the Y axe I use PN099 (32767) as Numerator and PN102 (6464) as denominator .I taught that the are the same pitch so it should be the same ratio ? nothing move . I hade give the same number in Mach4 for both axe in the pc . Now I realy don`t know what is happening . What do you thing ?
    Thanks
    Alain



  5. #45

    Default Re: Servo motor setup

    Hi,
    you are making it more difficult than you need to.are

    It looks like you have decided 5:1 is about right. So set the drive parameters to 5 and 1 and then leave them alone. That would mean that 2000 pulses to the drive input
    will cause the servo to rotate one turn. That's all you have to achieve

    Now set the Mach steps/unit to whatever value necessary to get one inch of travel. Do not try to use electronic gearing to achieve perfect movements,
    Machs parameters do that. You keep trying to mix them together.....don't do it!

    Craig



  6. #46
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    Default Re: Servo motor setup

    Hi Craig
    I know but this is the method I found. But it help me knowing the system. Small question I put 6 A fuses at the output of my 220v circuit disjonctor and when I make 2 meter the on Y motors and one of the two fuses blows.What size fuse I should on the system does not jump. Mach 4 is at 2500 velocity and 200 acceleration.



  7. #47
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    Default Re: Servo motor setup

    Craig ,
    on the drive the number showen on it during the time the motor run is what ? Rpm of the motor , right ? so for the distance per minute I use (diameter x pi ) (25*3.14159 =78.53 mm/min x rpm) Is it the way to calculating ?
    Thanks and nice week-end !!!
    Alain



  8. #48

    Default Re: Servo motor setup

    Hi,
    if one or more of your drives is blowing fuses it could indicate a fault with that drive/drives......but more likely its just the inrush current
    demand of an accelerating servo.

    A fundamental principle of electric motors is that current is proportional to torque, and of course torque is proportional to acceleration.
    Thus whenever you change direction or even change speed the servo motor demands current proportional to the torque required to accelerate.
    That current supplied by the drive is delivered in short high current bursts and I suspect that is why you are blowing fuses.

    You should be using 'M' rated fuses, in New Zealand at least we call them motor rated fuses which are more tolerant of inrush current.

    All servo drives and VFDs have a rectifier at the input followed by the DC link capacitors and are renowned for drawing very high currents
    for very brief periods of time. It is the sort of load that fuses and/or circuit breakers are not good at protecting. In industrial practice large servos
    and VFDs are fed via 'line reactors' in large part to 'tame' the input current demand. A line reactor will go a long way to preventing nuisance
    trips.

    You can also tame the servo current demand by de-tuning the drive somewhat. You may have noticed quite a few parameters within the drive related to
    max torque and/or max current. Alternately you could try reducing the acceleration parameter within Mach somewhat. Remember however that the drive
    will accelerate up to its maximum parameter determined torque/current to follow a tool path and that not all high acceleration spikes may be a result of a
    high acceleration parameter in Mach.

    Once you have decided on an electronic gearing ratio there are two methods you can use to determine the required Mach Step/Unit value.
    The first one, and the one I advocate because I am very familiar wit engineering calculations, is to calculate the number.
    The other way, which is common amongst hobbyists whom are not good at engineering calculations, is to guess a number, try it and see whether
    the axis moved the requisite one inch or whatever, and if not tweak it a little and try again. Repeating this process until the correct number is arrived at.

    Either method works and both will end up being exactly the same, after all if it takes 6783 steps to move one inch then wether you guessed it by successive
    approximation or by calculating it, it still takes exactly 6783 steps to move one inch.

    If you wish to calculate it try this idea:
    1) From your electronic gearing determine how many pulse are required for the servo to rotate one turn.
    2) From the pitch of the screw determine te distance traveled per one revolution in the units of your choice.
    3) Divide the number of pulses (from (1)) by the distance (in units from (2)).

    For example lets say you choose an electronic gear ratio of 2:1 and have a 10mm pitch screw:
    1) Number of pulses per rev= 10,000 (native encoder pulses) / 2 (electronic gear ratio)
    =5000 pulses/rev
    2) 10mm pith per rev= 10 /25.4
    =0.393700 inches.
    3) 5000/0.393700
    =12700.

    Thus if you put 12700 in Machs Steps/Unit parameter I would expect that if you issued an MDI of G0 X1 then the X axis would move exactly one inch.
    You should try it and measure as accurately as you can that it has in fact moved one inch to confirm your calculation.

    This calculation is very simple and relies on two pieces of information, the electronic gear ratio and the screw pitch. Both must be known
    PERFECTLY accurately, then and only then will it yield a perfect result.

    A a further example but using more general numbers:
    numerator =17, denominator =61, screw pitch=0.2 inch
    1) 61/17=3.588235294
    pulses= 10000/ 3.588235294
    =2786.885245 pulse/rev
    2) Pitch = 0.2inch.....easy
    3)2786.885245/0.2
    =13934.42622
    Thus if you put this number into Machs Step/Unit value and issue a G0 X1 then I would expect the Xaxis to move one inch. Quite why you would choose such
    unusual numbers for numerator and denominator is not clear, but you could if you wish. It might be that you are applying this servo as a replacement in a machine
    with an unusual gear train for example. In short electronic gearing allows the servo to be flexible in application and thereby secure maximum sales exposure.

    In most cases however the electronic gear ratio is decided on as a balance of resolution verses signaling speed. Once the ratio is set then it will be left alone for the
    entire life of the machine. Only the Step/Unit value of the controller need be calculated/manipulated to achieve accurate distance movements.

    I am not sure what the display is set to. With Delta servos, and many others....and probably these ToAuto servos, you can program the drive to display different
    things. For instance you could have it display speed in revs/second or revs per minute, or you could have it display torque in Nm or servo current in Amps.
    The Deltas I use by default display the current encoder count, a 32bit integer, but could equally well display the input pulse count, or the following error
    in encoder counts.


    Craig



  9. #49
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    Default Re: Servo motor setup

    Quote Originally Posted by joeavaerage View Post
    Hi,
    so you are using inches after all?

    At the moment the distance moved is irrelevant. What you need to do is understand electronic gearing.

    Can you set the gearing to 1:1 or 2:1 or 5:1 at will?

    If for instance you choose 5:1 then 2000 pulses will cause one revolution of the servo. With a 10mm pitch screw:
    distance traveled (one rev of screw)= 10/25.4
    =0.393700 inch.......and it took 2000 pulses to do that. Therefore the pulses per inch (the Mach setting):
    =2000/0.393700
    =5080.0

    Note that the Mach setting is a real number, ie it can have a fractional part. But note also that the numerator/denominator
    are both integers but the division ratio is rational, that is has a fractional part.

    The rule is :
    1) Set the electronic gearing to best balance the resolution and signaling speed
    2) Set Mach's pulses per unit to the value required to achieve accurate movement.

    Craig
    Electronic Gearing has nothing to do with resolution, you can't change what the Encoder resolution is, ( although some high end Servo Drives you can change the Encoder Resolution ) but I doubt he has that feature with these Chinese Drives

    All you are creating with Electronic Gearing is the ratio of steps /per that will drive the motor 1 revolution the lower you have this number of steps per rev the better this keeps the steps / per overall low once you get to the control and do the Gear Ratio with your Ballscrew or Rack and Pinion you will have a starting number plus the machine gearing Ballscrew Etc, that will be your final steps per

    Mactec54


  10. #50
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    Default Re: Servo motor setup

    Quote Originally Posted by daytona19876 View Post
    Hi Craig
    I know but this is the method I found. But it help me knowing the system. Small question I put 6 A fuses at the output of my 220v circuit disjonctor and when I make 2 meter the on Y motors and one of the two fuses blows.What size fuse I should on the system does not jump. Mach 4 is at 2500 velocity and 200 acceleration.
    What size is your servo motor this will determine what size the fuse you would need, most would use at least a 20A so 6A is not going to do the job this Fuse can only be at the main supply power to the servo drive

    Mactec54


  11. #51
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    Default Re: Servo motor setup

    Quote Originally Posted by daytona19876 View Post
    Craig ,
    on the drive the number showen on it during the time the motor run is what ? Rpm of the motor , right ? so for the distance per minute I use (diameter x pi ) (25*3.14159 =78.53 mm/min x rpm) Is it the way to calculating ?
    Thanks and nice week-end !!!
    Alain
    So this won't be so complicated using the manual you have, your servo drive is just a very poor copy of a Sigma II Yaskawa servo drive even the manual has parts copied straight from the Yaskawa manual, so you can look at the Yaskawa Manual which is a lot easer to use to get you Electronic Gearing setup

    Attached Files Attached Files
    Mactec54


  12. #52
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    Default Re: Servo motor setup

    thanks Mactec54
    But for you it may be a reference but for me it's still Chinese. The information for you can be comparable from one model to another but for me I do not see any similarity but I understand that for an expert like you this manual says something but for me it remains practically symbols.
    Alain



  13. #53
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    Default Re: Servo motor setup

    Quote Originally Posted by daytona19876 View Post
    thanks Mactec54
    But for you it may be a reference but for me it's still Chinese. The information for you can be comparable from one model to another but for me I do not see any similarity but I understand that for an expert like you this manual says something but for me it remains practically symbols.
    Alain
    No not all servo drive are comparable, only the servo drives you have they are a copy of a Yaskawa servo Drive a poor one at that, but are a direct copy I discovered this a few years ago when I was helping someone else with the same drives

    It lays it out how too, a setup for the electronic gearing for a 10mm pitch Ballscrew you just have to input the same numbers into your servo drives and that is all you have to do, then you have to set the Steps/Per in Mach3 and you are done, I don't think that could be any easier

    Mactec54


  14. #54
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    Default Re: Servo motor setup

    Mactec54 hi
    .As a newbie in servo you say " just have to input the same numbers into your servo drives" what number and where ? I have Mach4 would it be the same ?
    And please could you say "a copy of xxxxx" and forget the "poor word " we are not all rich .
    Thanks
    Alain



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    Default Re: Servo motor setup

    Hi Craig
    in post #23

    "On page 17, 2.3 CN2 Control Interface,
    and subsequent pages show:
    Pin9 and Pin10 are the drive derived power supply and common return
    Pin6 called SigIn1 is by factory default is the ServoEnable input
    Pin7 called SigIn2 is by factory default the Reset input
    Pin2 and Pin14 are the Step input
    Pin4 and Pin5 are the Direction input
    Pin23 called SigOUT2 is Alarm output
    Pin24 called SigOUT4 is EmergencyStop output "

    if the pin 9 and 10 don't work the pin 23 ,#24 #6 #7 are not needed is that right. That left us with 4 wires 3 , 4, 5 and 14 the pin #2 not working has to be change with pin 3.
    The 6 others wires are not needed . So I wont plug it.

    On other subjet is the proximity sensor on the page 17 of the MB3 BOB they are showing how to wire the sensor , my question is should it be preferable to plug it pnp or npn , to be the best if a wire broke or get loose ?

    Alain



  16. #56
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    Default Re: Servo motor setup

    Craig there are the picture

    Attached Thumbnails Attached Thumbnails Servo motor setup-sensor-jpg  


  17. #57
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    Default Re: Servo motor setup

    Quote Originally Posted by daytona19876 View Post
    Mactec54 hi
    .As a newbie in servo you say " just have to input the same numbers into your servo drives" what number and where ? I have Mach4 would it be the same ?
    And please could you say "a copy of xxxxx" and forget the "poor word " we are not all rich .
    Thanks
    Alain
    It was nothing to do with rich or poor, or the cost of, the copy of the servo drive is a poor copy of the Yaskawa drive

    Mactec54


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