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Axes Maximum Travel + Soft Limit Issue

Discussion in 'CNC Mills/Routers' started by P.Abraham, Sep 19, 2020.

  1. P.Abraham

    P.Abraham New
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    Hi there,

    I'm trying to set up my soft limits. As an example, I'm trying to set my Z-axis max travel soft limit to 80mm. But after setting it, when jogging the machine, it does not go passed 65mm. Having the same issue on X and Y axes. I've calibrated steps/mm and that's pretty accurate (although it theoretically shouldn't matter??)

    I've also followed the instructions for $20 (Enable and Save Homing first before enabling). No idea where to look next :/

    Any guidance would be greatly appreciated.

    Thanks

    Prenny
     
  2. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Is the 65mm measured, or indicated on the DRO

    Keep in mind the soft limits alarm is raised if the commanded move will hit the softlimit (so for example if soft limit is 80, you are on 65, you cannot send a 15mm move as that will violate the softlimit. Error thus pops up at 65, saying you can't move another 15. It will however process a 14mm move)
     
  3. P.Abraham

    P.Abraham New
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    Hi Peter,

    It's indicated on the DRO. I didn't know that soft limits alarms were pre-emptively raised based on the upcoming command. Will definitely keep that in mind! However, thats not what's happening in this instance. My jogging mode is in continuous and stops responding at 65mm. Also, even if I input values up to 80mm into the DRO I still get nothing :/
     
  4. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Interesting then. Our (you are using CONTROL right) continous jog looks at the available distance and sends no more. (max travel - current mPos - 1mm)

    But do try in Incremental too

    Segment of the Serial Console log around the error may also reveal something
     
  5. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Just stops? Or raises the Alarm?

    Either error 15: Jog target exceeds machine travel. Command ignored.

    Or Alarm 2: G-code motion target exceeds machine travel. Machine position safely retained. Alarm may be unlocked.
     
  6. P.Abraham

    P.Abraham New
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    Correct, I am using CONTROL. I'll detail the errors and share it in here in the morning. I've powered off the machine for the night on account of my neighbors sanity

    There are 2 scenarios that occur RE "just stops" vs. "alarm raise".

    Scenario 1: when 65mm is approached (continuous jog), alarm 2 appears.

    Scenario 2: after alarm 2 is unlocked, when hitting Z+ to try and moved passed 65mm, no further alarm is raise, and quite literally nothing happens on the machine although CONTROL log spits out "ok" with each click. No further alarms are raised.

    I'll try it in incremental jog.

    I'll recreate it in the morning and do a more comprehensive write-up that's hopefully more conducive for debugging.

    Thanks a tonne Peter! I really appreciate your help!
     
  7. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    So in the log next to OK will be the command that was sent (calculated as above) - that would be good to screenshot.
     
  8. P.Abraham

    P.Abraham New
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    Hey Peter!

    So here's what I've found. I retried the enabling steps for soft limits as indicated on CONTROL, which seemed to help! I still kept getting a discrepancy between the RDO value and the maximum travel value but realised that I never accounted for the travel between homed-zero and the actual hard switches, which mostly accounted for the discrepancies. However that raised another question for me when I was going through this exercise. Below you'll find the soft limits settings vs. actual travel figures for each axis


    X-axis (824mm soft limit): 818.5 RDO travel + 4.53 zero-hard limit gap = 823.03 total travel | 0.97mm off from 824mm max travel
    Y-axis (1270mm soft limit): 1264.93 RDO travel + 4.57 zero-hard limit gap = 1269.5 total travel | 0.5mm off from 1270mm max travel
    Z-axis (82mm soft limit): 76.06 RDO travel + 4.29 zero-hard limit gap = 80.35 total travel | 1.65mm off 82mm max travel


    Does that seem ok or should we be able to expect a higher rate of accuracy? for example, none of the zero-hard limit gaps are the same. What are the sorts of tolerances we can expect to achieve with this machine if everything has been set up correctly?

    I must also add, that apart from the tolerances, everything else seems to be working perfectly. My hard and soft limits are working exactly as they should! No more crashing haha! and no more alarms.
     
  9. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    In Incremental we don't have to worry about the keyup/keydown delays so you can pretty much jog / run gcode up right to one step before the soft limit. With Continuous there is a less direct control loop (send jog Command for full distance on keydown, send cancel jog on keyup)
     

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