Homing causes motors to turn past limit contact

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  • April 25, 2018 at 9:00 pm #10971
    fixxxer
    Member

    Hey all-I’ve noticed a difference in behavior of (let’s say the y-axis) depending upon whether I am performing a homing operation or a jog/traverse. All of my switches are configured as either homing and limit or just limit. During a traverse operation, the machine shuts down with the proper error code immediately, taking no further steps. However, when running a homing operation, the limit switch is contacted and then it proceeds to step a few steps. I thought maybe this was latch backoff and zero backoff so I set both to “0” but I still get the same behavior. I’m assuming it’s just a configuration variable I’ve overlooked. Anyone know?

    April 28, 2018 at 6:21 am #10972
    cmcgrath5035
    Moderator

    Have you read thru wiki
    https://github.com/synthetos/TinyG/wiki/Homing-and-Limits-Description-and-Operation
    and in particular
    https://github.com/synthetos/TinyG/wiki/Homing-and-Limits-Description-and-Operation#homing-configuration-settings

    Settings values to “0” here probably not a good or workable idea.

    If problems continue, provide a listing of your settings that don’t work.
    Best to post a $$ parameter list to a cloud drive and provide a URL link.

    April 29, 2018 at 12:20 pm #10973
    fixxxer
    Member

    Thanks for the reply, I have read that page several times but I’ve missed the $xJH command. I haven’t adjusted those values and they’re set “[xjh] x jerk homing 40 mm/min^3 * 1 million.” I can play around with the parameters but out of curiosity what do you guys use? I’m assuming that the higher the number, the quicker the machine will stop.

    April 30, 2018 at 1:42 pm #10974
    cmcgrath5035
    Moderator

    I don’t use homing, so can only read the wiki and add comments from others.

    Here are suggested parameters for a Belt MAchine (SHO2) with
    a screw Z axis.

    [xjm] x jerk maximum 5000 mm/min^3 * 1 million
    [xjh] x jerk homing 10000 mm/min^3 * 1 million
    [xsv] x search velocity 3000 mm/min
    [xlv] x latch velocity 100 mm/min
    [xlb] x latch backoff 20.000 mm
    [xzb] x zero backoff 1.000 mm
    [yjm] y jerk maximum 5000 mm/min^3 * 1 million
    [yjh] y jerk homing 10000 mm/min^3 * 1 million
    [ysv] y search velocity 3000 mm/min
    [ylv] y latch velocity 100 mm/min
    [ylb] y latch backoff 20.000 mm
    [yzb] y zero backoff 1.000 mm
    [zjm] z jerk maximum 50 mm/min^3 * 1 million
    [zjh] z jerk homing 1000 mm/min^3 * 1 million
    [zsv] z search velocity 3000 mm/min
    [zlv] z latch velocity 100 mm/min
    [zlb] z latch backoff 20.000 mm
    [zzb] z zero backoff 1.000 mm

    High jerk will be more aggressive in changing velocity, from low to high or high to low. If you have a low mass spindle, Jerk could be higher.

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