Prusa MK2.5 and X-Axis limit switch no longer works.
I have a MK2.5 that has worked flawlessly for years. Recently it started "ignoring" the x-axis limit switch when starting a print. You can hear the stepper drive into the end of the axis (lasts about 2 seconds) and not have a controlled stop like the y-axis for example. It sounds bad, but continues to print fine. I disconnected the X and Y limit switches from the Rambo controller and did the following two checks:
- When the switch is NOT depressed both the X and Y axes have a resistance of 0.5 to 0.6 ohms.
- When the switch is depressed both the X and Y axes measure "open" with multimeter.
This seems normal to me so I'm at a loss to understand what could be causing the X-axis limit switch to be ignored, even though the Y-axis with the same values works as expected.
Hoping the wisdom of this forum will give be some more troubleshooting advice.
Thank You!
RE: Prusa MK2.5 and X-Axis limit switch no longer works.
Did you check the resistance on the micro switch contacts, or on the connector contacts in the plug?
regards Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
RE: Prusa MK2.5 and X-Axis limit switch no longer works.
Good question. The resistance values reported were measured at the connector contacts at the controller end of cable. Said another way, the measurement includes both switch and cabling as I wanted to make sure I didn't have a broken wire.
RE: Prusa MK2.5 and X-Axis limit switch no longer works.
that was my concern...
did you activate the switch, using the X axis Buffer?
https://help.prusa3d.com/guide/3-e-axis-assembly_48816
Steps 64 and 65
regards Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
RE: Prusa MK2.5 and X-Axis limit switch no longer works.
I looked at the part shown in the link and it doesn't look like the one on my printer. That shows a bolt on endstop block whereas mine is integral with the extruder parts, as shown here. i3 MK2/S to MK2.5 Upgrade Printable parts by Prusa Research | Download free STL model | Printables.com
More troubleshooting on my part though: I put a few thickness of electrical tape on the endstop block shown to make it trigger earlier and this seems to have worked, but I only tried it twice so far. I don't see any mechanical interference when I manually push the axis into the stop but clearly there must be otherwise adding the tape shouldn't help.
RE: Prusa MK2.5 and X-Axis limit switch no longer works.
You may have a later version. I took the picture from an assembly guide
Try bending the lever on the switch, a little, make the switch activate earlier.
regards Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
RE: Prusa MK2.5 and X-Axis limit switch no longer works.
I have a MK2.5 that has worked flawlessly for years. Recently it started "ignoring" the x-axis limit switch when starting a print. You can hear the stepper drive into the end of the axis (lasts about 2 seconds) and not have a controlled stop like the y-axis for example. It sounds bad, but continues to print fine. I disconnected the X and Y limit switches from the Rambo controller and did the following two checks:
- When the switch is NOT depressed both the X and Y axes have a resistance of 0.5 to 0.6 ohms.
- When the switch is depressed both the X and Y axes measure "open" with multimeter.
This seems normal to me so I'm at a loss to understand what could be causing the X-axis limit switch to be ignored, even though the Y-axis with the same values works as expected.
Hoping the wisdom of this forum will give be some more troubleshooting advice.
Check the bundle of wires and zip ties behid the extruder for any interference with the frame or electronics box. Power off the Prusa and manually move the extruder and listen for the switch click. My MK2.5 had mechanical resistance with the frame before the switch clicked. It must have been that way for years but somehow pushed through. Then then one day it decided enough was enough and started skipping steps. I ended up printing an alternate cable manager for the extruder.
https://www.printables.com/model/443319-i3-mk25s-extruder-cable-management/comments
It's slimmer which gives another 3mm travel so it always contacts the switch before the frame.