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I'm new to 3D printing and have bought an Ender 3. I have printed a few good prints but I'm noticing a worsening issue:

When I select "autohome" the axes head towards their limit switches, but the y axis in particular seems to slam into the limit switch, bending it away, meaning that the platform bounces off and doesn't activate the limit switch a second time

This causes the machine to slam against the back over and over until the limit switch is triggered or power is removed.

I've replaced the limit switch twice

I've tried supergluing the limit switch to its PCB but even with a needle and patience this caused the limit switch to be ruined

What can I do?

Edit: Here are some photos of the switch (2nd replacement). The OEM switch also did the same thing, but I don't have photos of that. The screws are loose in these photos, but this is just because my Allen key is lost - the previous two switches had the screws reasonably tightened with the correct Allen key, provided in the boxenter image description here

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  • $\begingroup$ Photo please? this sounds like the switch is mismounted... $\endgroup$
    – Trish
    Mar 29 '20 at 11:02
  • $\begingroup$ Possibly the gcode speed settings during these homing operations are way too high. Can you post your gcode "preamble" so we can advise? $\endgroup$ Mar 31 '20 at 15:23
  • $\begingroup$ @Carl Witthoft I'm using the Auto Home function found on the Ender 3 - pressing the wheel and going to prepare, then auto home, $\endgroup$
    – Deep
    Apr 1 '20 at 7:00
  • $\begingroup$ Can you move the Y to the opposite end and then time how long it takes to move across? That may be able to tell us if it's going too fast. Also, are you sure the Y limit switch is working? If you press it with your finger while its homing, does it stop? $\endgroup$
    – DoxyLover
    Apr 3 '20 at 4:12
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Personally, I have found that if you bend the arm of the limit switch out, it gets triggered earlier and solves this issue for good, (broke a switch clean off at the bend on the pins, soldered old switch back onto the pins in the board) bent the arm to a greater angle, so the striker triggers 3-5 mm earlier, problem averted!

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The solution seems to be simply triggering the switch earlier, and making sure that it is triggered. The thin arm can end up bent over the actual button of the switch, meaning that the arm can be touching the switch without actually "pressing" the switch. For some, bending the arm seems to have worked, but for me I had to wedge a small piece of plastic between the arm and the switch button, meaning that it is a lot more reliable when you press the switch. The piece isn't stuck in there in any way, simply held by friction. This isn't the best solution as you have to keep an eye on that piece with every homing, but until a better answer is available, I recommend this solution as it was more reliable than bending the arm out or into a different shape.

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