Two weeks ago the ShopBot was working ok. Today when I initially tried to home all, Y and Z homed ok but X tried to run the gantry onto the floor to the East. If not for the safety blocks at the end of the rails, it would have. Emergency stop had to be engaged.
After resetting once, the X limit triggered during homing which stopped the gantry at the bolt in the rail where it should but the ShopBot still failed to home. When I tried to touch off the X afterwards (the others touched off fine), I got the error " Can’t issue MDI command when not homed"
Tried to home a few more times. Half the time, the emergency stop is required. Will not home the X.
Intermittent faulty X limit switch or something else? Any ideas?
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Just ran it through the homing cycle, all axes as well as each individually, and it never hiccupped. I’m not sure why it was acting up for you. Did you notice whether the led lit as the sensor passed over the bolt?
It’s normal to not be able to touch off of the machine isn’t homed. That’s a feature, not a flaw.
The only concerning thing I noticed is that the z limit switch is getting moved every time it’s bumped, so z home isn’t consistent. I don’t think it’s an issue where the screw isn’t tight enough. It’s been held in place by a screw and some carpet tape. I may need to make a better bracket for it, but it’s been working for years the way it is.
I do believe the travel speed during homing is faster than it used to be? I don’t know who might have changed it, but I understand why. Homing the machine when the spindle was at the end away from the limit switches took forever. But I wonder if the z needs to be slowed down. To me it acts like it’s just moving too fast to stop once the switch is tripped. I’ll have to look into that some more unless somebody else has ideas. @Kim_Kirwan
Thinking about this more, the z limit switch should probably be reoriented so that the block on the carriage can over run the switch without hurting anything.
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I’m guessing the little sensor is just misaligned with the bolt. Like it got knocked in a goofy, non- functioning direction. Probably an easier fix than you’d think. I’ll check on it first thing Saturday morning.
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On Thu, Apr 24, 2025, 8:15 PM Brian Wiles via MakeICT Forum <noreply@talk.makeict.org> wrote:
| thephantombrain MakeICT Member
April 25 |
Two weeks ago the ShopBot was working ok. Today when I initially tried to home all, Y and Z homed ok but X tried to run the gantry onto the floor to the East. If not for the safety blocks at the end of the rails, it would have. Emergency stop had to be engaged.
After resetting once, the X limit triggered during homing which stopped the gantry at the bolt in the rail where it should but the ShopBot still failed to home. When I tried to touch off the X afterwards (the others touched off fine), I got the error " Can’t issue MDI command when not homed"
Tried to home a few more times. Half the time, the emergency stop is required. Will not home the X.
Intermittent faulty X limit switch or something else? Any ideas?
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I looked at that. It was very slightly not vertical, maybe 5 degrees, so I nudged it straight and checked that the screw was snug. But it homed for me in the not straight condition. Maybe I was just lucky and it was barely ok there. Thanks!
Fwiw, the sensor on y was about the same and I also straightened it. It might be interesting to do some experimenting to see how for out of alignment it has to be to start causing problems.
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At the CAD Meetup on May 10, Jimmie increased the homing speed , that’s why it seems faster. I like the change.
Thanks for looking into this so quick @whateg01
The plan is for me to be back this evening and I’ll give my cuts another shot and keep an eye on the sensor orientation as I proceed.
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Overall, I like the faster homing as well. But the way the z limit switch is oriented, it can’t handle the overshoot that occurs as the z hits the limit then tries to stop. I’ll look at how to address that now.
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The homing operation is supposed to be set up so that it finds the home switch quickly, then backs off of it, then approaches very slowly a second time, now that it has some idea where the switch is. I’ll check on it this weekend.
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The issue seems to be that as it approaches quickly, it overruns the available travel on the reed switch and ends up pushing the reed switch out of the way a little. It’s cumulative so the switch just keeps getting pushed farther away. I agree that it should locate the right position quickly then back up and approach slowly.
I’m headed to KC for a family thing today but I’ll be back this evening. Do you know when you’ll be at the space?
If you mean me, I’ll be there Sunday because I’m double-booked from 3-5pm to take Resin Printing Class and to host Electronics Meetup. I can be available from 5pm-late, also Maker Monday evening, if either of those would work for you.
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