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  1. #1
    Join Date
    Jan 2019
    Posts
    1

    CNC Lathe Program

    for turning a radius on a part what does the I & K stand for example
    G1Z0
    X1.75
    G3X2.0 Z-.125I ? K ?

  2. #2
    Join Date
    Jan 2019
    Posts
    74
    It is the distance to the center of the arc.
    X Y Z
    I J K

    See how they go in order?

  3. #3
    Join Date
    Mar 2019
    Posts
    3
    Quote Originally Posted by Dodge68 View Post
    for turning a radius on a part what does the I & K stand for example
    G1Z0
    X1.75
    G3X2.0 Z-.125I ? K ?
    I would use R instead.
    G3 X2.0 Z-.125 R0.125

  4. #4
    Hi guys,

    I am new here as well as in lathe working. And I need an advice if you can help .

    My machine(jnc 25 star) is old but in my opinion it is in good condition.

    And here is my question , what should I do to have a good for example M05 drill threed?
    Do I need tapmatic? Should I use G84 or some better solution...?

    Thanks!

  5. #5
    Join Date
    Apr 2019
    Posts
    3
    hi
    could you please help me about allen bradley characterization axcfil

  6. #6

    Re: CNC Lathe Program

    Quote Originally Posted by kruel037 View Post
    Hi guys,

    I am new here as well as in lathe working. And I need an advice if you can help .

    My machine(jnc 25 star) is old but in my opinion it is in good condition.

    And here is my question , what should I do to have a good for example M05 drill threed?
    Do I need tapmatic? Should I use G84 or some better solution...?

    Thanks!



    Depending on how old the star is you might have to do a a G1 with tap feerate in and then stop spindle,reverse spindle and G1 feed out with tap feedrate.
    Ive seen it done on Citizens cincom F12.

  7. #7
    Join Date
    Aug 2009
    Posts
    230

    Re: CNC Lathe Program

    I would use R instead.
    Depending on the control in question; and the exact geometry involved, the R word can fail to resolve properly. The I, J, and K words are more numerically stable... so if you get odd behavior, try switching to direct offsets.

  8. #8
    Join Date
    Jun 2015
    Posts
    4131

    Re: CNC Lathe Program

    Depending on the control in question; and the exact geometry involved ....
    hi, that is relative to accuracy of the software that generated the program, the way it rounds up numbers, etc; in such a case, errors should be the same, regardless of g-code syntax ( R vs ijk ); depends on post algorithm

    to deal with less accurate coordinates, some cnc controllers may use a parameter to tolerate the in-position of g02/g03s

    to achieve higher accuracy toolpath, one may need to check the accuracy of the software, use zero-tolerance inside the machine parameter, and adjust specs accordingly / kindly
    Ladyhawke - My Delirium, https://www.youtube.com/watch?v=X_bFO1SNRZg

  9. #9
    Join Date
    Sep 2010
    Posts
    1230

    Re: CNC Lathe Program

    Quote Originally Posted by deadlykitten View Post
    hi, that is relative to accuracy of the software that generated the program, the way it rounds up numbers, etc; in such a case, errors should be the same, regardless of g-code syntax ( R vs ijk ); depends on post algorithm

    to deal with less accurate coordinates, some cnc controllers may use a parameter to tolerate the in-position of g02/g03s

    to achieve higher accuracy toolpath, one may need to check the accuracy of the software, use zero-tolerance inside the machine parameter, and adjust specs accordingly / kindly
    It has nought to do with what you have suggested. Typical Motion Control Software, that which generates the motion trajectory, typically uses an Arc Centre, Arc Radius, and the included Angle of the Arc. Also typical, is the numerical precision used in calculations in even the most lacking program generation Software, and is far more accurate than the Least Programmable Increment that is overwhelmingly used with CNC Machines of 0.001mm and 0.0001".

    When a program is generated using IJK in Circular Moves, the centre of the Arc is calculated from the Start Point of the Arc using CAM Software, or manually using a Calculator that is working at a far more accurate level than the Least Programmable Increment of the Machine Control and the values Rounded to the accuracy of the control. Even if the program is Rounded to an accuracy greater than that of the Least Programmable Increment of the Machine Control, the control will truncate the value to its Least Programmable Increment. Accordingly, the centre of the Arc translated to the Control by IJK is as accurate as the control can resolve.

    When the Arc Move in a program use the R Format, the Start and End Point of the Arc are calculated using high precision calculations and are Rounded to the Least Programmable Increment of the Control. The R Format doesn't specify the centre of the Arc directly, as does the IJK Format, and as the Motion Control requires the Arc Centre, the Control must calculate the Centre using the Start/End coordinates and the Radius supplied. However, rather than use data that has a higher precision than its Least Programmable Increment, as does the CAM Software or Calculator, the Control uses data that has already been Rounded to Its Least Programmable Increment. Accordingly, there will be cases where the Arc Centre calculated by the control when R Format is used in the supplied program will be less accurate than when the Arc Centre is translated to the control using IJK Format in the supplied program.

  10. #10
    Join Date
    Jun 2015
    Posts
    4131

    Re: CNC Lathe Program

    hi, considering that code is ok, for both R and IJK variant, the difference between them may shift the center position with 1um, and this is not such a big deal; even diff is generally > 1um

    about how code is generated, this is a different story:
    ... worst case scenario : a G91 toolpath made of many arches, that adds truncation errors, that may lead to shifting the end-point of the toolpath, or even making it impossible for the controller to reach then end point of the tooltapth; here is where, the rad comp parameter of okuma's kick in, so to deal with 'nasty' codes
    ... best case scenario : outputing coordinates with more digits then the controller can display, on a controller that is not truncating

    Even if the program is Rounded to an accuracy greater than that of the Least Programmable Increment of the Machine Control, the control will truncate the value to its Least Programmable Increment.
    truncation does not always happen inside the controller; it may still round up and do the math at a higher level then the axis positioning acuracy; okuma osp was truncating until a while ago, at least for g91 mode, but a recent update just fixed that

    however, there is still an ocasional problem with rounding, but there is a low chance to affect the g02/g03s

    It has nought to do with what you have suggested
    it's always a pleasure to see your comments; i have seen that your skills, about spindle phase & z axis syncronization, when threading, have increased, and the 1st time when i told you about the "desincronization" you have had hardly believed that is true

    give it time angel; so far, you did not teached me anything new / kindly
    Ladyhawke - My Delirium, https://www.youtube.com/watch?v=X_bFO1SNRZg

  11. #11
    Join Date
    Sep 2010
    Posts
    1230

    Re: CNC Lathe Program

    Quote Originally Posted by deadlykitten View Post
    hi, considering that code is ok, for both R and IJK variant, the difference between them may shift the center position with 1um, and this is not such a big deal; even diff is generally > 1um

    about how code is generated, this is a different story:
    ... worst case scenario : a G91 toolpath made of many arches, that adds truncation errors, that may lead to shifting the end-point of the toolpath, or even making it impossible for the controller to reach then end point of the tooltapth; here is where, the rad comp parameter of okuma's kick in, so to deal with 'nasty' codes
    ... best case scenario : outputing coordinates with more digits then the controller can display, on a controller that is not truncating



    truncation does not always happen inside the controller; it may still round up and do the math at a higher level then the axis positioning acuracy; okuma osp was truncating until a while ago, at least for g91 mode, but a recent update just fixed that

    however, there is still an ocasional problem with rounding, but there is a low chance to affect the g02/g03s



    it's always a pleasure to see your comments; i have seen that your skills, about spindle phase & z axis syncronization, when threading, have increased, and the 1st time when i told you about the "desincronization" you have had hardly believed that is true

    give it time angel; so far, you did not teached me anything new / kindly
    You teach the uninformed all that you know and they still know nothing. By expressing your ideas simply exhibits what little you know about CNC machining and programming in general.

    You don't get it that the Control is working with the data supplied by a program that has been created externally and already Rounded to the Least Programmable Increment of the Control. Posting a program that has been Rounded to an accuracy greater than the Least Programmable Increment of the control does nothing other than unnecessarily consume memory. Irrespective of the accuracy level the Control may be able to perform calculations internally, its limited by the accuracy of the data supplied.

  12. #12
    Join Date
    Sep 2005
    Posts
    267

    Re: CNC Lathe Program

    angelw :cheers:

  13. #13
    Join Date
    Jun 2015
    Posts
    4131

    Re: CNC Lathe Program

    Irrespective of the accuracy level the Control may be able to perform calculations internally, its limited by the accuracy of the data supplied.
    hello again, considering that code is ok, on a 3digits machine, when the control needs to calculate the center, from an R syntax, then the center may be shifted, thus there is a probabiblity

    by probabiblity, i mean that there are cases when the center will be detected with:
    ... full accuracy, like for quadrant arches ( that start or end at 0 90 180 270* )
    ... less accuracy, like <=1um for each axis, and that is really low, <diff, etc, so nothing to worry about

    You don't get it that
    please, don't be sure about what 'i don't get' / kindly
    Ladyhawke - My Delirium, https://www.youtube.com/watch?v=X_bFO1SNRZg

  14. #14
    Join Date
    Sep 2010
    Posts
    1230

    Re: CNC Lathe Program

    Quote Originally Posted by deadlykitten View Post
    hello again, considering that code is ok, on a 3digits machine, when the control needs to calculate the center, from an R syntax, then the center may be shifted, thus there is a probabiblity

    by probabiblity, i mean that there are cases when the center will be detected with:
    ... full accuracy, like for quadrant arches ( that start or end at 0 90 180 270* )
    ... less accuracy, like <=1um for each axis, and that is really low, <diff, etc, so nothing to worry about



    please, don't be sure about what 'i don't get' / kindly
    I'm sure that we're all sure what you don't get

  15. #15
    Join Date
    Jun 2015
    Posts
    4131

    Re: CNC Lathe Program

    hello again, in both cases, the result may be affected by an error :
    ... r syntax : center may be shifted
    ... ijk syntax : r may be shifted
    * even so, effects happens at a scale that is too low, to matter

    considering that code is generated ok, and the controller can run both ijk and r, did someone actually hit into a case where 'ijk' was better then 'r', or viceversa ? and if i may, what was exactly the issue ? if you wish to share the code, i will test it for you / kindly
    Ladyhawke - My Delirium, https://www.youtube.com/watch?v=X_bFO1SNRZg

  16. #16
    Join Date
    Sep 2010
    Posts
    1230

    Re: CNC Lathe Program

    Quote Originally Posted by deadlykitten View Post
    hello again, in both cases, the result may be affected by an error :
    ... r syntax : center may be shifted
    ... ijk syntax : r may be shifted
    * even so, effects happens at a scale that is too low, to matter

    considering that code is generated ok, and the controller can run both ijk and r, did someone actually hit into a case where 'ijk' was better then 'r', or viceversa ? and if i may, what was exactly the issue ? if you wish to share the code, i will test it for you / kindly
    A 360deg circular move can't be programmed in one Block using R Format. In every case where I've seen a full circle programmed using R Format, the user has programmed two Command Blocks, each dealing with 180degs of the full circle; logical on the surface, but not so. Being able to programming the circle in one Block is the first plus for IJK Format in my book.

    If there is an error, caused by rounding, minuscule as it may be, when the Control calculates the centre of the arc and shifts the arc centre, there will be a doubling of the error as the shift of the centres will be in opposite directions in each of the 180deg arcs, but it seems that theoretical accuracy matters little to you.

  17. #17
    Join Date
    Feb 2006
    Posts
    1792

    Re: CNC Lathe Program

    Quote Originally Posted by deadlykitten View Post
    hello again, in both cases, the result may be affected by an error :
    ... ijk syntax : r may be shifted
    It is not a very accurate statement. The arc starts with the start radius. If it cannot reach the target point due to some inaccuracy, it makes a small linear move in the end to reach the end point, provided the radius error is within the specified limit.

  18. #18
    Join Date
    Jun 2015
    Posts
    4131

    Re: CNC Lathe Program

    A 360deg circular move can't be programmed in one Block using R Format.
    hi / yes, that is true, but a full circle is a particular case, and also R<0 may deliver arches > 180*

    my book
    aaa, do you have a programing book ? i don't know, maybe you do ... if you would have one, i would read it

    theoretical accuracy matters little to you
    i use code as accurate as it could be, folowing error is never 0, there is backlash, and most dimensions have a tolerance >1um

    even when folowing error is 0, cnc motion is not a "real" circle, and also encoders motion <> turret ( or spindle ) motion, since there is a precision lost around the mechanical chain

    It is not a very accurate statement. The arc starts with the start radius. If it cannot reach the target point due to some inaccuracy, it makes a small linear move in the end to reach the end point, provided the radius error is within the specified limit.
    hi sinha, i know my "accuracies" ...

    Code:
              if swd[wo] then t:='G02'
                         else t:='G03';
              if full_circle 
               then 
    about that "small linear move" :
    ... if next block contains an axis move instruction, then the machine won't reach the "end point", but will get close to it until distance < in-position; and there is a big chance to have the in-position > g02 code precision
    ... if next block does not contain an axis move, or it contains whatever instruction that is telling the controller to reach the end point, then, if there is some inacuracy, the machine will move to the end point, not among a linear segment, but among a "non-interpolated segment", that is executed on such a short distance, that the servos won't be able to reach the programmed feed, so servos won't be in sync, but each one will reach the final point on it's own; is possible that only the servo will rotate, but the turret will be allready stationary; kind of a succumbed motion, when the cnc can't reach the programmed feed / kindly
    Ladyhawke - My Delirium, https://www.youtube.com/watch?v=X_bFO1SNRZg

  19. #19
    Join Date
    Sep 2010
    Posts
    1230

    Re: CNC Lathe Program

    Quote Originally Posted by deadlykitten View Post
    hi / yes, that is true, but a full circle is a particular case, and also R<0 may deliver arches > 180*
    But less than 360deg. If one were to use the R Format for a full 360deg, a more accurate overall result would be achieved by programming, say, a 359.5deg arc, and 0.5deg arc. However, is there was an error caused by using rounded numbers in the calculation, a shift of the arc centre would still result.

    Quote Originally Posted by deadlykitten View Post
    aaa, do you have a programing book ? i don't know, maybe you do ... if you would have one, i would read it
    Typical halfwit DK comment.


    What Sinha stated is quite correct. You clearly stated in the Post Sinha referred to that both IJK and R Format are shifted. This is not the case with IJK Format as the arc centre is provided by the part program and is not calculated by the control for that arc specified from the Start Point to the Arc Centre. If the End Point specified results in a different Radius to the specified Arc Centre, to that of the Start Point, and the difference is less than a tolerance set in parameter, the action is as Sinha stated,

    There is a clear pattern of you making erroneous statements and when pointed out, you come back with waffle that simply highlights your lack of knowledge and makes you appear a bigger buffoon.

  20. #20
    Join Date
    Jun 2015
    Posts
    4131

    Re: CNC Lathe Program

    You clearly stated in the Post Sinha referred to that both IJK and R Format are shifted.
    actually i did not said that both formats are shifed, but that they may be shifted, thus there is a probability

    and the difference is less than a tolerance set in parameter, the action is as Sinha stated
    again, here is a probability : it may happen, or not; and when it happens, the movement is not an interpolated segment, because programmed feed may not be reached for that short segment

    There is a clear pattern of you making erroneous statements and when pointed out, you come back with waffle that simply highlights your lack of knowledge and makes you appear a bigger buffoon.
    you are also so full of wisdom ...

    ps: 2252-01 ALARM-B DATA WORD circle calculation A side 1
    Ladyhawke - My Delirium, https://www.youtube.com/watch?v=X_bFO1SNRZg

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