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  1. #1
    ECCO's Avatar
    Lives in Tamworth, United Kingdom. Last Activity: 23-07-2016 Has been a member for 1-2 years. Has a total post count of 12.
    Preying on peoples knowledge and kindness.
    The mill is set up in metric units. Lack of knowledge and understanding determined this choice, it may have been better to have chosen imperial setup units but with metric ballscrews metric was the choice. Whilst running a small program with G20 in the first line the program executes moves that are wildly incorrect. A move of Z0.100" makes the Z axis move continually in the + direction until physically stopped by operating cycle stop. After lots of messing about a G21 was inserted in the second line of the program. It worked perfectly and accurately in Imperial moves. Absolutely no idea why!!!
    Next problem is trying to setup soft limits. Now completely confused. Homed the system in Machine co-ordinates onto 3 limit switches and the system zeroed X Y & Z. Measured overall possible movements in X Y & Z in mm's. Entered these dimensions into homing and limits as positive distances in X & Y and a negative distance in Z. Whilst moving about manually with Soft Limits activated get a fault message "Soft Limits < Max Min". When executing the afore mentioned program again with Soft Limits activated the error message states " Machine out of Soft Limits for Soft Limit Activation". Are soft limits based on machine co-ordinates or component datums? If its component datum would they have to be adjusted to each different component manufactured?
    Next, have subscribed to Artsoft Wizards on my "House" computer, they set and simulate well. Now need to transfer this permission to the "Workshop CNC" computer, how is this achieved? Is it just a file move from "House" to " Workshop CNC" computer, in which case which file or files?
    Many thanks for any help received.

  2. #2
    Whilst running a small program with G20 in the first line the program executes moves that are wildly incorrect. A move of Z0.100" makes the Z axis move continually in the + direction until physically stopped by operating cycle stop. After lots of messing about a G21 was inserted in the second line of the program. It worked perfectly and accurately in Imperial moves. Absolutely no idea why!!!
    Before you start setting the soft limits you need to check what is setup wrong. You seem say when using G21 you are getting accurate moves with inches. Are you saying that if you command the machine X0 2 it moves 2" or 2mm?
    ..Clive
    The more you know, The better you know, How little you know

  3. #3
    It doesn't matter if you use inch or mm for setting up your motor steps per, if you've done it right the machine will run imperial or metric code accurately.
    .
    The body of each feature in the code is simply in numeric units and G20 or G21 in the header tells Mach 3 if those units will be interpreted as (G21) mm or (G20) inches.
    .
    G20 specifies imperial, G21 specifies metric so if you are getting accurate Inch moves with G21 then you have configured your system incorrectly and your steps per out by a factor of exactly 25.4 and your initial commanded moves in inches with G20 will have been simply huge!

    - Nick
    Last edited by magicniner; 25-06-2016 at 06:54 PM.
    You think that's too expensive? You're not a Model Engineer are you? :D

  4. #4
    Firts thing are you running in Demo mode.? Not having license file can cause all sorts of strange things like this.

    Next not good idea to run imperial G-code when set up for metric units. While G20 will scale the units it doesn't affect feedrate. So take the road runner g-code that comes with mach. The feed rate is set for inche's at 60 so because motor tuning is in metric units thats the feed you'll get.

    It's far easier to setup another profile setup with imperial units and use that. Just copy the Metric profile and scale Steps per by 25.4. It removes any issues.

    Why your getting those wrong moves I'm not sure and you'll have to explain a little clearer because not exactly sure what your meaning.? Are you 100% sure your using Metric units.

    Soft lmits are relative to machine Coords. If you enter your X & Y travel in SOFT MAX put Zero in SOFT MIN. For Z Put Negative travel in SOFTMIN and Zero in SOFTMAX.
    It should work then. I'm guessing your putting Z negative in SOFTMAX and that's the message.

    Wizzards are just like Mach3 License file drop it in the mach folder.

  5. #5
    Quote Originally Posted by magicniner View Post
    It doesn't matter if you use inch or mm for setting up your motor steps per, if you've done it right the machine will run imperial or metric code accurately.
    .
    The body of each feature in the code is simply in numeric units and G20 or G21 in the header tells Mach 3 if those units will be interpreted as (G21) mm or (G20) inches.
    .
    Not exactly correct as explained above.!! . . . It will scale the moves but not the feedrate.
    Try it load road runner and put G20 on first line or type G20 in MDI before running.
    The Feedrate in Gcode will be in inches minute but motors tuning is relative to MM/min. This is why you have to retune the motors if you change from metric to imperial units.
    Last edited by JAZZCNC; 25-06-2016 at 07:44 PM.

  6. #6
    Thanks for that Jazz, that's interesting.
    Given the simplicity of the conversion I'm shocked that they didn't make motor tuning/feed rate automatic for changes in G Code units, I had assumed this was the case but only ever work in Metric,
    Regards,
    Nick
    You think that's too expensive? You're not a Model Engineer are you? :D

  7. #7
    ECCO's Avatar
    Lives in Tamworth, United Kingdom. Last Activity: 23-07-2016 Has been a member for 1-2 years. Has a total post count of 12.
    Many thanks for your replies. The mill is having mechanical parts modified at the moment and as soon as it is reassembled I will do some investigation and get back to you all. Once again thanks.

  8. #8
    ECCO's Avatar
    Lives in Tamworth, United Kingdom. Last Activity: 23-07-2016 Has been a member for 1-2 years. Has a total post count of 12.
    Right the mech parts are now modified ok, back to the problems. could you please check over the following calculations for steps per.
    By the way this is a fully licenced version of Mach3. Have re-installed Mach3 and chosen inch base units.

    Motor Steps= 1.8deg =200 steps per 1 motor rev.

    Motor Micro steps =10 therefor 200x10 = 2000 micro steps per 1 motor rev

    Pitch of ball screws = 5mm = 0.19685 inches per 1 motor rev

    No of motor revs to move 1 inch = 1/0.19685 = 5.08 revs

    No of micro steps per 1 inch move = 2000 x 5.08 =10160 micro steps per inch

    Z axis is a 2:1 reduction ratio so 10160 x 2 = 20320 micro steps per inch

    Many thanks ( More to follow )

  9. #9
    Yes that's correct go to top of the Class.

  10. #10
    ECCO's Avatar
    Lives in Tamworth, United Kingdom. Last Activity: 23-07-2016 Has been a member for 1-2 years. Has a total post count of 12.
    After a quite successful re-set on the miller we now have Imperial units. The machine homes properly onto 3 limit switches and runs a simple program ok and accurately.
    The issue now is what to specify in soft limits and soft limit slow zones. I honestly have not got a clue. I can accurately measure the distances that the machine is capable of moving in all axis.
    These dimensions are from the home positions. X +19.000" Y+7.375 Z-13.500.
    Any help most gratefully received.

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