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Thread: Taig CNC-Controller Replacement-Dynomotion Suggestion

  1. #25
    Member TomKerekes's Avatar
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    Default Re: Taig CNC-Controller Replacement-Dynomotion Suggestion

    Hi Peter,

    There isn't any tuning involved with steppers they are open loop. It is really just a matter of finding your limitations on velocity, acceleration, and Jerk. You might read this. I see from your screen capture that you have Velocity set to 60,000 steps/sec. For a KStep with 3200 steps/rev that is 1125RPM whic is quite fast for a stepper motor. Your test plot only gets up to about half of that so you should test a bigger move size.

    Adding encoders will allow you to detect stalls and miss steps instead of just running blind. It will also allow you to recover after a fault or if the axis is disabled as the position will be maintained. It can also improve accuracy slightly as compensation for position lag can be corrected by running closed loop. Linear scales to control the actual axis position is ideal. You might read this.

    Regards
    TK http://dynomotion.com


  2. #26
    Member PeterTheWolf's Avatar
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    Default Re: Taig CNC-Controller Replacement-Dynomotion Suggestion

    ...
    ...

    Thanks Tom .......

    So, I am assuming, 1000 RPM is the best a stepper will do then it really does not matter what setting I have tested, as long as I am using a velocity setting that gives me 1000PRM or less.
    For my next test I used V=55000 ... which give 1031 RPM. It would seem the motor would spin faster on the bench based on the sound and rotation of the shaft I am seeing.
    However, I am not seeing any difference on acceleration until it gets lower than 250,000. Anything over 300,000 shows no difference.

    So, I am thinking these would be my setting for the 3rd order motions.
    V=44,000 (20% of 55,000)
    A=320,000 (20% of 400, 000)
    J=4e+06 (If I decrease this to 4e+05 it never reaches the top V, if I increase this to 4e+07 to 08 ... it will hit V almost instantly).

    Taig CNC-Controller Replacement-Dynomotion Suggestion-002_stepper_test-png


    Taig CNC Machine Quick Links
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    KFLOP Power Suppy

    Stepper Motor Power Supply Used

    Stepper Motor Used on Taig

    Taig CNC Machine Counter Weight Design

    Taig CNC Machine Counter Weight Design - 3D STEP File
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  3. #27
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    Default Re: Taig CNC-Controller Replacement-Dynomotion Suggestion

    If Tom thinks 1125 rpm is fast id probably going going slower then 1000. Steppers really loose torque fast at high rpm. So its safer to set rapids on the slow side. Most of my problems with my old Taig would occur during rapids. Looking back now, if i cut my rapids in half it may have worked fine. I think I set my rapids at like 30 IPM. But you have a higher voltage system which should work better at higher speeds.

    Maybe on a little machine like that you could put a vise on the table and push against it (should be much stronger then you) to verify you still have some torque left at rapid speed. Just want to be sure your not on the edge, completely loosing position due to an overloaded and stalled rapid move is absolutely no fun at all. The machine will just continue going maybe several inches off from where its supposed to be, destroying parts, tooling, everything in its path, even the machine itself. I speak from experience lol.



  4. #28
    Member PeterTheWolf's Avatar
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    Default Re: Taig CNC-Controller Replacement-Dynomotion Suggestion

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    .....


    Tom,

    Can I please get you to review my calculation for the KmotionCNC Trajectory Planner Perameters?

    Taig CNC-Controller Replacement-Dynomotion Suggestion-calculationscuttingperameters-jpg Image LINK



    Here is the a link to the Word Doc: My Calculation for the Trajectory Planner


    Taig CNC Machine Quick Links
    ....
    ....
    KFLOP Power Suppy

    Stepper Motor Power Supply Used

    Stepper Motor Used on Taig

    Taig CNC Machine Counter Weight Design

    Taig CNC Machine Counter Weight Design - 3D STEP File

    Word Doc. of my Calculation for the Trajectory Planner
    ....
    ....



  5. #29
    Member TomKerekes's Avatar
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    Default Re: Taig CNC-Controller Replacement-Dynomotion Suggestion

    Hi Peter,

    On the bench steppers can run really fast. You really need to have them connected to the machine to see what they can actually do loaded then back down to provide a good margin. Here is a video of 4 motors running 3000 RPM with a 36V supply. But they realistically have no torque at that speed. Its also important to understand that your mechanics can have resonances that can cause stalls at certain speeds. Accelerating quickly through those speed may not cause a stall where maintaining a speed for a while may. CNC machines must be able to work continuously at any speed in their range. So I like to also check under very low acceleration to slowly sweep through all speeds as a test.




    So, I am thinking these would be my setting for the 3rd order motions.
    V=44,000 (20% of 55,000)
    A=320,000 (20% of 400, 000)
    J=4e+06 (If I decrease this to 4e+05 it never reaches the top V, if I increase this to 4e+07 to 08 ... it will hit V almost instantly).
    Probably reasonable values. With the lower Jerk value you would reach max V if you made a longer move. If you care about making long rapid moves quickly then lower Jerk may help you move in less time. Note lower Jerk increases the move time as acceleration is applied more gradually, but if the lesser disturbances allows higher acceleration and possibly higher velocity then the overall move time may be less.


    Can I please get you to review my calculation for the KmotionCNC Trajectory Planner Perameters?
    64,000 Steps/In seems correct

    2nd order motions don't have any Jerk limiting (Jerk is infinite not smaller) and usually require slightly smaller V and A. But these are all probably good starting points.

    Note V should be entered as 0.6875 Inches/sec on the Trajectory Planner Screen (not per minute). Or maybe 0.7. It sort of bugs me when 4 digits of precision is used for a number we are basically guessing at

    HTH

    Regards
    TK http://dynomotion.com


  6. #30
    Member PeterTheWolf's Avatar
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    Default Re: Taig CNC-Controller Replacement-Dynomotion Suggestion

    Quote Originally Posted by TomKerekes View Post
    Hi Peter,

    ............... 3000 RPM with a 36V supply. But they realistically have no torque at that speed.

    OK ... I understand this; however, I will not be able to test on the machine for a bit as I have it apart and working with the mechanics of it with the counter weight for the Z-Axis.

    Quote Originally Posted by TomKerekes View Post

    Probably reasonable values. With the lower Jerk value you would reach max V if you made a longer move. If you care about making long rapid moves quickly then lower Jerk may help you move in less time. Note lower Jerk increases the move time as acceleration is applied more gradually, but if the lesser disturbances allows higher acceleration and possibly higher velocity then the overall move time may be less.
    As always, this type of information is informative for me to understanding what I am looking at in the Test Response Screen/Graph in the Kmotion. I am sure you would like to think that working with the Tree J325 retrofit you helped me set-up would have given me all the experiences I need for this... I still get confused whenever I have to revisit this type of tuning.


    Quote Originally Posted by TomKerekes View Post
    64,000 Steps/In seems correct
    Cool ..........

    Quote Originally Posted by TomKerekes View Post
    2nd order motions don't have any Jerk limiting (Jerk is infinite not smaller) and usually require slightly smaller V and A. But these are all probably good starting points.
    Yes, thank you for reminding me of this ... it was a question in my head when I was testing. Couldn't remember.....


    Quote Originally Posted by TomKerekes View Post
    Note V should be entered as 0.6875 Inches/sec on the Trajectory Planner Screen (not per minute). Or maybe 0.7. It sort of bugs me when 4 digits of precision is used for a number we are basically guessing at

    HTH
    Yes ... I see that now.... I was too in-tuned with making sure my math/unit conversions were correct. Thank you for pointing out the little things that can make such a big difference when things may not be working correctly.

    Single Digits on calculation approximations .... GOT IT!

    ...



  7. #31
    Member PeterTheWolf's Avatar
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    Default Re: Taig CNC-Controller Replacement-Dynomotion Suggestion

    Quote Originally Posted by TomKerekes View Post
    Hi Peter,
    ...........

    Adding encoders will allow you to detect stalls and miss steps instead of just running blind. It will also allow you to recover after a fault or if the axis is disabled as the position will be maintained. It can also improve accuracy slightly as compensation for position lag can be corrected by running closed loop. Linear scales to control the actual axis position is ideal. You might read this.
    Since an Encoder will help me understand the tuning process with feedback, I would like to add this to the bench top testing of the tuning of the stepper motors. I understand that it will need to be re-tuned once it is mounted on the machine. Plus I will gain the advantage these encoders once i get it up and running on the machine.

    I would like to purchase one of the US Digital E6 Optical Kit Encoder for testing. I know you suggested a Linear scale encoder; however, they seem to cost more then the shaft Optical Encoders.

    Am I going to see issues with using these US Digital E6 Optical Encoders on the back shaft of the stepper motors instead of the Linear Scale Encoders?

    Would something like this encoder work with KFLOP/KSTEP?

    Taig CNC-Controller Replacement-Dynomotion Suggestion-s-l1600-jpg


    Tom,

    Can you please review this US Digital E6 Optical Kit Encoder and the configuration I have selected to verify ease of comparability with KFLOP/KSTEP?

    Taig CNC-Controller Replacement-Dynomotion Suggestion-e6_optical_kit_encoder-png Link to PDF Specs.



    This word Doc. holds the configuration I think I should be ordering ..... Does this look Correct?


    Taig CNC Machine Quick Links
    ....
    ....

    KFLOP Power Suppy

    Stepper Motor Power Supply Used

    Stepper Motor Used on Taig

    Taig CNC Machine Counter Weight Design

    Taig CNC Machine Counter Weight Design - 3D STEP File
    ....
    ...



  8. #32
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    Default Re: Taig CNC-Controller Replacement-Dynomotion Suggestion

    Quote Originally Posted by PeterTheWolf View Post
    OK ... I understand this; however, I will not be able to test on the machine for a bit as I have it apart and working with the mechanics of it with the counter weight for the Z-Axis.
    You may not want a counterweight on the Taig. It has very fine pitch screws and its not going to fall or anything.

    To be honest, I found the weight of the head useful in eliminating backlash in the Z. The taig is terrible for backlash on all axes, and the Z axis backlash would make some parts look really bad. I would always adjust my Z axis gibs just loose enough so the head would fall and eliminate the Z axis slop.



  9. #33
    Member TomKerekes's Avatar
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    Default Re: Taig CNC-Controller Replacement-Dynomotion Suggestion

    Hi Peter,

    Would something like this encoder work with KFLOP/KSTEP?
    Wow 300mm 5um resolution linear scale for $50 + shipping? I couldn't find the pinout but it says TTL/EIA422 (differential) so it should work.


    Can you please review this US Digital E6 Optical Kit Encoder and the configuration I have selected to verify ease of comparability with KFLOP/KSTEP?
    Yes it is compatible. Purchase the differential output because it can then be connected to either a single ended input or a differential input. KFLOP only has single ended inputs. If you have noise problems you can add differential inputs (Kanalog, SnapAmp, or 3rd party differential receivers).

    US Digital sells differential to single ended interface modules. See here.

    Regards
    TK http://dynomotion.com


  10. #34
    Member PeterTheWolf's Avatar
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    Default Re: Taig CNC-Controller Replacement-Dynomotion Suggestion

    Quote Originally Posted by mmurray70 View Post
    You may not want a counterweight on the Taig. ..............
    To be honest, I found the weight of the head useful in eliminating backlash in the Z. The taig is terrible for backlash on all axes, and the Z axis backlash would make some parts look really bad. I would always adjust my Z axis gibs just loose enough so the head would fall and eliminate the Z axis slop.
    Thanks Mark,

    When running this machine off the original stepper motors/controller/power supply I was loosing steps on Z-Axis. It was set-up with MACH3 and I am was getting a loss of .060" in steps in "Z" over 8" move in "X" with a tool-path in 3D on the Y/Z plane with a stepover on "X". The Z-Axis would "kind-of" Chatter on it larger moves down in "Z" when moving fast.

    At the time I was going to retrofit it with KFLOP/KSTEP; however, you talked me into looking for a larger machine to retrofit.... which was the Tree 325J.

    Well here I am almost two years later, back on the this Taig CNC.

    I am really just retrofitting this Taig for fun and to learn more about KFLOP/KSTEP / Stepper Motors. Since now I have the Tree 325J to actually machine parts on for retrofitting.
    Once I learn enough with this project and the steppers, I would like to retrofit a old South Bend Bench Tip lathe with KFLOP. My lathe isn't are nice as the image link.

    ...
    ....



  11. #35
    Member PeterTheWolf's Avatar
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    Default Re: Taig CNC-Controller Replacement-Dynomotion Suggestion

    Quote Originally Posted by TomKerekes View Post
    Hi Peter,

    Yes it is compatible. Purchase the differential output because it can then be connected to either a single ended input or a differential input. KFLOP only has single ended inputs. If you have noise problems you can add differential inputs (Kanalog, SnapAmp, or 3rd party differential receivers).

    US Digital sells differential to single ended interface modules. See here.
    Yes ... I saw that differential to single ended interface modules as well.... I will get one of these as well.

    I still have a question on the E6 Optical Kit Encoder ... What is the best suggested CPR setting (1000?) I should configure it for:

    Taig CNC-Controller Replacement-Dynomotion Suggestion-cpr_selection-jpg


    Taig CNC Machine Quick Links
    ....
    ....

    KFLOP Power Suppy

    Stepper Motor Power Supply Used

    Stepper Motor Used on Taig

    Taig CNC Machine Counter Weight Design

    Taig CNC Machine Counter Weight Design - 3D STEP File

    Word Doc. of my Calculation for the Trajectory Planner

    Word Doc. E6 Optical Kit Encoder

    ....
    ....



  12. #36
    Member TomKerekes's Avatar
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    Default Re: Taig CNC-Controller Replacement-Dynomotion Suggestion

    Hi Peter,

    Yes ... I saw that differential to single ended interface modules as well.... I will get one of these as well.

    I still have a question on the E6 Optical Kit Encoder ... What is the best suggested CPR setting (1000?) I should configure it for:
    Higher resolution is always better until you exceed the count rate of the encoder input at maximum RPM. KFLOP can conservatively accept 1 million quadrature counts/second.

    2000 cycles/rev at 2000RPM would be:
    2000 x 4 x 2000 / 60 = 266K counts/sec

    And at 20 TPI would give a resolution of
    20 x 2000 x 4 = 160,000 counts/inch (6.25ui)

    Regards
    TK http://dynomotion.com


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