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[How do I?] 4th Axis Settings In Mach3

Discussion in 'CNC IN THE HOME SHOP' started by jbolt, Oct 23, 2016.

  1. jbolt

    jbolt United States Active User H-M Supporter-Premium

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    I have the 4th axis wired I just need to do the stepper drive settings and the Mach3 settings.

    For the stepper drive I can set the micro steps to:
    400
    800
    1600
    3200
    6400
    12800
    25600
    51200
    1000
    2000
    5000
    10000
    25000
    50000

    The stepper motor is a 1.8 so 200 steps per rev.

    The rotary table is 4 deg per turn so 90:1

    Armed with that info what should the drive be set to and what would be the "Steps per" in the motor tuning of the A axis? If I chose say 1000 on the stepper would the setting be (1000*200)*90 = 180,000,000????? or am I totaly off?

    Once that is set then there is, Velocity?, Acceleration?, G's? Step Pulse? and Dir Pulse?

    Are there any other setting in Mach3 I need to configure?
     
  2. rdean

    rdean United States Active User H-M Supporter-Premium

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    The rotary axis is set to degrees and a 90 to 1 gear ratio will make a very accurate setup.
    The 4th axis in Mach3 should be setup as the A axis and make it rotary.
    The diameter compensation does not work on all Mach3 versions. I recommend version 66 as being the least likely to cause problems.
    On the config tool path section there are several items that need to be checked.
    Rotational radius is set for each job on the settings tab to set the speed of the work.
    There may be some others but I can't think of them right now.

    Ray
     
    Last edited: Oct 23, 2016
  3. jbolt

    jbolt United States Active User H-M Supporter-Premium

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    I think my math was wrong. If I recall the micro step value on the stepper drive represents the actual number of motor steps and the "Steps per" in mach3 for the rotary axis are degrees so it would be (1000*90)/360 = 250 per degree.

    On the tool path configuration under "Rotations" when the "A-Rotations Enabled" is checked does that mean it is substituting the selected axis above? Or is it referencing the rotational axis of the part as defined in the CAM? Does this mean it cannot do X, Y, Z & A at the same time?
     
  4. rdean

    rdean United States Active User H-M Supporter-Premium

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    Well I am a little more awake this morning so for the version number I like 062 the best but 066 does work.
    On the Settings tab "Rotational Radius" compensates the speed of the 4th axis for the size or diameter of the part when substituting A for X or Y in the cam program. Tool path page orientates the part with which axis the rotary aligns with. It is used for the tool path display. All 4 axis are still active and if you have a cam program that can write true 4 axis programs all are working.
    "Axis Calibration" will get you close to correct steps just enter 360 and check if the rotary made one full rotation and adjust from there.
    Step and direction should be setup as your other axis are if you are using the same or similar controller but you may have to make adjustments for the direction of rotation.
    It has been several years since I setup my 4th axis and I need to check the machine for more accurate information.

    Ray
     
  5. jbolt

    jbolt United States Active User H-M Supporter-Premium

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    Thanks Ray, I'll dig into a little more.

    I hit a snag with not getting any response from the stepper driver. It powers up and the BOB is sending step and direction signals but the drive does not respond so I need to get that sorted out first.
     
  6. rdean

    rdean United States Active User H-M Supporter-Premium

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    I went out to the machine to check out just what I had.
    The stepper controller is set at 800 steps per revolution.
    The gear ratio is 36 to 1.
    Mach3 setup A axis motor is set to 80 Steps per degree, the Velocity is at 8000, and the Acceleration is set at 400.
    This is for my setup yours will be different but the principle is the same.
    What cam package are you using?

    Hope this helps.

    Ray
     
  7. jbolt

    jbolt United States Active User H-M Supporter-Premium

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    Thanks for the settings. At least it is a starting point.

    For CAM I have HSMWorks & Aspire.

    Not sure yet if the 4th axis post I have for mach3 actually works.
     
  8. rdean

    rdean United States Active User H-M Supporter-Premium

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    I also use Aspire and wrote a post processor for it to automatically enter the radius compensation in Mach3.
    Send me a PM if you would like the information.

    Ray
     
  9. Metal

    Metal United States Active Member Active Member

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    is this normal to gear down that far? I am designing a 4th axis right now and was looking at only 8:1 reduction with a 1600oz/in stepper I could throw an extra level of gearing in there if needed, but resolution sounded OK from my vague math at only 8
     
  10. rdean

    rdean United States Active User H-M Supporter-Premium

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    It depends what diameter part you will be turning as the forces exerted at 1" are many times less that those at 6" of diameter. What material you are cutting also comes into play and the holding ability of the motor when the part is not turning but other cuts are in progress is very important. Most steppers use a reduced voltage when standing still to reduce the heat generated internally so the holding power goes down also.
    Don't forget the backlash issue as the diameter increases the amount of movement increases exponentially with the diameter. A 1" diameter part that has 1 degree backlash can move about 0.009 but that same backlash at 6" in diameter is 0.052. Not acceptable.
    It all depends on what you are doing and how accurately you want it to be.

    Ray
     
  11. Metal

    Metal United States Active Member Active Member

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    Ah
    Yeah, I had thought about that, I'm resolving most of it by building a brake into it rather than let the motor try and fight the forces through a few levels of gearing directly
     
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  12. jbolt

    jbolt United States Active User H-M Supporter-Premium

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    Thanks for the link to that.

    I changed out the stepper drive and now have it turning. I ran the axis calibration and no changes were necessary. I'll try dry running a program this week and see how it goes. I'm curious to find out if my HSMWorks 4th axis post actually works.

    Thanks for the help.
     
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