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  1. #1
    Join Date
    May 2009
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    28

    linear motion feedrate problems

    Hi everyone...
    I've just noticed, that my coordinate table moves with different feedrates at arcs and lines... From lazy cam I'm postin Gcode, where the feedrate set to 60 mm/min. On the arclines the feedrate is quite normal(60+-1mm/sec Idon't like this too), but when it's passing the linear states of Gcode the feedrate falls to 49-50 mm/min. But I need straight 60 on all the contour not+-, please help...
    And one more thing...
    When I write this simple Gcode : F60 G0 X25 the axis is moving with feedrate 88-90mm/sec????
    In Motor Tuning options the velocity is 100

  2. #2
    Join Date
    Mar 2003
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    35538
    Quote Originally Posted by tigran View Post
    When I write this simple Gcode : F60 G0 X25 the axis is moving with feedrate 88-90mm/sec????
    In Motor Tuning options the velocity is 100
    F60 G0 will NOT move at 60, it'll move at rapid rate. Why it's not going 100, I don't know, but to go 60, try:

    F60 G1 X25
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  3. #3
    Join Date
    May 2009
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    28
    Thank you for reply Ger21! I'll try it...
    But the most interesting and strange is the behaviour of coordinate table at straight lines... Could it be connected with CV mode, or with Axis Slaving?

  4. #4
    Join Date
    May 2009
    Posts
    28
    Please could you tell me, what feedrate is showing the feedrate DRO in Program run menu?
    Is it X, Y,Z??? Or it is dhowing the speed of movement of tool on the contour? I cant understand, what is feedrate for example 55mm/min if both of axes are moving?

  5. #5
    Join Date
    Mar 2003
    Posts
    35538
    The Feedrate DRO is the commanded feedrate. The Units/Min DRO is the actual velocity of the tool, no matter which direction it's moving.
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  6. #6
    Join Date
    May 2009
    Posts
    28
    Quote Originally Posted by ger21 View Post
    The Feedrate DRO is the commanded feedrate. The Units/Min DRO is the actual velocity of the tool, no matter which direction it's moving.
    Thank you for explaining!
    I'm finally lost!!! Maybe my Mach3 is crazy!!! Because it shows commanded feedrate say 60, but its actual velocity shows 52-53 at straight line, 62-63 at arcs...
    Today I tried to command feedrate 70, the movement velocity was 58-59 at straight line, and 65 at arcs... But i still need 60!!!

  7. #7
    Join Date
    May 2009
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    28
    I've installed Mach 3 on two different computers. The 1st is 3.4GHz CPU 2Gb of ram, and it shows the feedate in CV mode 58-59 instead of 60! On the second comp CPU 3.0GHz 512Mb RAM in case of the same settings it shows 53-54 intsead of 60?
    Is it possible, that the feedrate DRO is showing wrong feedrate or cant fit in time?
    And other question... Where else I can adjust feedrates in MACH 3???

  8. #8
    Join Date
    Mar 2003
    Posts
    35538
    Do you mean the Feedrate DRO or the Velocity DRO? (inches/min)

    The only other place to change feedrate is in the G code with an F word (F60)
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  9. #9
    Join Date
    May 2009
    Posts
    28
    [QUOTE=ger21;636150]Do you mean the Feedrate DRO or the Velocity DRO? (inches/min)

    Sorry my mistake Velocity DRO units/min.
    However two computers are showing different numbers... But settings are the same, and this is getting very big problem, because I need exactly that speed which is given by F command...

  10. #10
    Join Date
    Mar 2003
    Posts
    35538
    How long are the moves? Straight or arcs?

    I read recently on the Yahoo group that feedrate can vary slightly from PC to PC, based on the actual PC clock frequency I think. Try compensating by calling for a slightly faster feedrate and see if you can get it to run at the correct rate by telling Mach to go a little faster.
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  11. #11
    Join Date
    May 2009
    Posts
    28
    I've removed the Mach3 R3.042.020 and installed an older version on my worcing computer... And it works Perfectly!!! This newer version I'm using for experiments on the other PC an its worcing prefectly too!!!
    The difference between clock's arent so much... One shows pulse frequency 24000 and other shows 21000-23000 both of them should work properly... My steps per is 800!!! However, I'm glad that this problem is solved...

  12. #12
    Join Date
    Jun 2004
    Posts
    6618
    The versions of mach in the past year have all had issues with me. Just today I was having issues with my mill computer, tried the latest lock down, and then only partial Gcodes was showing up in the tool paths. Switched back to R2.63 and have no issues with Mach.
    This computer is running Vista. Apparently for no reason after running 1.5 years, it decided to start adding steps downward on my Z during a cycle. That ain't good. I witch to my IBM laptop that runs my router. It has XP. No more issues.
    Not sure what suddenly occured to the new machine, but don't have time to troubleshoot. I'll pick up another IBM laptop off Ebay for $150 and be back in business.
    Lee

  13. #13
    Join Date
    May 2009
    Posts
    28
    Apparently for no reason after running 1.5 years, it decided to start adding steps downward on my Z during a cycle. That ain't good.
    Not sure what suddenly occured to the new machine, but don't have time to troubleshoot. I'll pick up another IBM laptop off Ebay for $150 and be back in business. [/QUOTE]

    Are you sure that the problem comes form mach 3??? I think your GCode writer has problems, because the Mach 3 can't change anything in GCODE, or maybe the SAFE Z settigs have been changed, or Z home position was changed... If you changed your units from mm's to inches this can occur and your machine can do wrong things, check once more...

    About Vista and XP, you can try to install XP on your Vista computer, and have two operation systems, at startup you can choose in wich system you want work... It will take only few hours... much cheaper and easier than new laptop(if this interested I can tell more detailis)...

  14. #14
    Join Date
    Jun 2004
    Posts
    6618
    These were known good codes and using the same XML's. I have backups of all this stuff. I use hundreds of different Gcodes over and over. Proven good code, just the new Mach 3 had issues with it. As I mentioned, not just the latest lockdown, but several different ones over about the past year have reacted differently or simply not worked right for me. Not a big issue, since the oder versions do everything I need.

    Definitely a Mach 3 issue though. It did this both on the Vista and the XP laptop. Reverted to older version in both after that. Different codes as well. Showed incomplete tool paths and odd circles on known gode codes.
    Likely something it doesn't like in the old XML files I use.

    As for Vista, I am happy to get rid of it.
    It is aggravating doing a simple thing like copying files. It asks no less than three times if you want it all copied.
    Nothing at all fast about it actually copying them either.
    It took more than 5 minutes on t to copy the same folder that took 30 seconds on the old laptop.
    This was a brand new dedicated computer about a year or so ago. You may see it on Ebay soon, cheap.
    Lee

  15. #15
    Join Date
    May 2009
    Posts
    28
    This was a brand new dedicated computer about a year or so ago. You may see it on Ebay soon, cheap. [/QUOTE]

    Are these laptops so called NETBOOKS?

  16. #16
    Join Date
    Jun 2004
    Posts
    6618
    The Vista computer is a Compaq desktop style.
    The laptop is an IBM R40 Thinkpad.
    Lee

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