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Thread: Auto leveling

  1. #21
    Super Moderator DrLuigi's Avatar
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    I do have the feeling you would need to change the Arduino file quiet often,
    As the servo isnt precise every time,
    It will almost always be Print able, But i do notice that when i switch from ABS to PLA that PLA has air between lines,
    Its still print able, the next layer will be close to perfect, but its just something i wanted to say, that this isnt something that will be once set, always good to go.

    Example today, I had it perfect for ABS, once i switched to PLA it was like i said earlier, a bit to high.

  2. #22
    Super Moderator RobH2's Avatar
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    I'm getting the same kinds of anomalies. I'm always having to tweak my gap in 'configuration.h'. But still, it's nice to have.

    One odd thing I have is the servo is "twitchy." When it's up and a print it running, it makes little noises and twitches ever so slightly. I just unplug it when it bothers me but then I always forget to plug it back in. I thought that it might be a bad servo so I took the time to switch it out. Same thing. It appears that some stray current pulses through that header and causes the servo to twitch. I doesn't cause any print issues but I worry about it damaging the servo or wearing it out. Any thoughts?
    Bambu P1S/AMS
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  3. #23
    Super Moderator Roxy's Avatar
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    Quote Originally Posted by RobH2 View Post
    I'm getting the same kinds of anomalies. I'm always having to tweak my gap in 'configuration.h'. But still, it's nice to have.

    One odd thing I have is the servo is "twitchy." When it's up and a print it running, it makes little noises and twitches ever so slightly. I just unplug it when it bothers me but then I always forget to plug it back in. I thought that it might be a bad servo so I took the time to switch it out. Same thing. It appears that some stray current pulses through that header and causes the servo to twitch. I doesn't cause any print issues but I worry about it damaging the servo or wearing it out. Any thoughts?
    Two comments. First, you might want to check out your

    #define PROBE_SERVO_DEACTIVATION_DELAY 500

    If you don't have a value specified, it will stay on all the time. Probably, you don't want that.

    The other point is you might want to make some type of stop at the right position so the servo can only travel so far. Then you can tell the servo to go slightly past that stop and it will be pressing hard and not twitching. I also made my probe such that when it is pressing on the bed, the probe gets pressed a little bit against the stop. That way the repeatability of the measurements is better.

  4. #24
    Super Moderator RobH2's Avatar
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    Thanks Roxy. Perfect suggestions. I'll do that now.
    Bambu P1S/AMS
    NVision4D http://nvision4d.com

  5. #25
    Engineer clough42's Avatar
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    Has anyone else had issues with the probe striking the bed when extending and retracting? I had to modify my firmware to raise the Z axis 2mm before retracting. It's an ugly hack (raise 2mm, retract servo, lower 2mm) and I'm not super keen on releasing it in its current form.

    Anyone else dealt with this?

  6. #26
    Super Moderator RobH2's Avatar
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    Quote Originally Posted by clough42 View Post
    Has anyone else had issues with the probe striking the bed when extending and retracting? I had to modify my firmware to raise the Z axis 2mm before retracting. It's an ugly hack (raise 2mm, retract servo, lower 2mm) and I'm not super keen on releasing it in its current form.

    Anyone else dealt with this?
    Yes. There is a long thread discussing aspects of this that Roxy is doing a lot of work on. Try this thread: http://3dprintboard.com/showthread.p...1267#post21267
    Bambu P1S/AMS
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  7. #27
    Engineer clough42's Avatar
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    Quote Originally Posted by Roxy View Post
    Two comments. First, you might want to check out your

    #define PROBE_SERVO_DEACTIVATION_DELAY 500

    If you don't have a value specified, it will stay on all the time. Probably, you don't want that.

    The other point is you might want to make some type of stop at the right position so the servo can only travel so far. Then you can tell the servo to go slightly past that stop and it will be pressing hard and not twitching. I also made my probe such that when it is pressing on the bed, the probe gets pressed a little bit against the stop. That way the repeatability of the measurements is better.
    Second that.

    The other thing you can do is use a Z probe design that has the button (or tip of the lever) is directly in line below the servo shaft. This way, the error is the cosine of the absolute servo arm position error, which is pretty much nil in this situation. If it isn't in line below the pivot, the error can be significant.

    I think the reason the servo twitches is because the Arduino isn't able to schedule the interrupts for the servo pulses reliably. As load on the MCU changes, it has a hard time maintaining the pulse width, exactly. This is particularly the case when the mechanics are moving. Marlin (correctly) prioritizes the stepper motors at the expense of servo precision.

  8. #28
    Technologist Tachout's Avatar
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    Just wondering once I install this will it eliminate the stupid Z endstop microswitch? I hate that thing. Mine has a creep in it or something. I turned on the printer today after not using it for more than a week. Printed the first file perfect. Nothing changed from first file to second file in my slicer configs, and even tried printing the exact same gcode file and somehow the z stop moved from where it was to about a 1/4" to high. I have to figure out that one.

  9. #29
    Super Moderator Roxy's Avatar
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    Quote Originally Posted by Tachout View Post
    Just wondering once I install this will it eliminate the stupid Z endstop microswitch? I hate that thing. Mine has a creep in it or something. I turned on the printer today after not using it for more than a week. Printed the first file perfect. Nothing changed from first file to second file in my slicer configs, and even tried printing the exact same gcode file and somehow the z stop moved from where it was to about a 1/4" to high. I have to figure out that one.
    It can be implemented a number of ways. But the typical method that most people are doing is to use the Z-Probe as the end stop. With that said, most people add a switch to the Z-Probe and leave the existing end stop in place and unused. Some people get more fancy and have both active using the existing Z-End_stop as a backup in case something goes horribly wrong to stop the nozzle from driving into the bed.

    One thing I know for my printer is without the auto bed leveling, it makes a big difference whether the bed is hot or not. If I had the Z End-Stop set so it worked good with a cold bed, it did not work well with a hot bed. And vice versa. The Auto Bed Leveling made that a non-issue.

  10. #30
    Super Moderator DrLuigi's Avatar
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    damn i guess my servo is broken... again..

    Auto leveling is nice, but if i have to keep switching these servos i aint sure if i will use em for alot longer realy..

    The motor seems to still work tho,
    Its pretty weak and my 3D printer seems to get to little eletricity due the servo being broken i guess..

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