RE : Double Z Limit Switches

[davidhk129]

Questions :
What does that mean ?
What is the advantage(s) ?
Would that eliminate layer shifting issue ?

Thank you.

 

[wafflejock]

Doubling limit switches means the z axis would be able to be "levelled" at least relative to the switches individually (basically if one z axis side is lower than the other right now it will move on an angle as it moves along the x axis, honestly not a problem so long as it is level relative to the bed). You can make sure your x-axis is lined up relative to the machine by raising the z value all the way to the top effectively maxing out the z then turn motors off and manually move the z motor until the x-axis is all the way at the top of both rails. The layer skipping is due to either some sort of snagging or the stepper drivers (chips on controller board) are over heating or not pushing hard enough to overcome some snag or other stuff in the way of the belt (possibly belt skipping if it's too loose as well)

Long story short 3D printers are open loop machines meaning they just send commands to motors and expect everything to move as commanded but no real feedback loop. The MK3 does detect when the amperage on steppers is unusually high to detect crashes and uses auto bed levelling by probing 9 spots on the bed before each print but still takes a bit of fiddling sometimes for big prints.

 

[davidhk129]

Thank you.

The reason I mentioned layer shifting is that, if the Z axis was supposed to move up 0.2mm, but instead it moved less than that, that could create issue on the layer it was supposed to print. Yes ?

 

[wafflejock]

Yeah sure but adding extra z limit has same effect as changing bed level left to right when looking straight at it. If you lower the bed a bit on one side it's the same as if the z axis had stopped a bit earlier. Being too low overall could cause the nozzle to be running into and building up filament on it but would expect that to be visible and probably show as roughness in the first couple of layers of the print as well. I'm mostly suspect of stepper drivers overheating or something with the belt though since it seems isolated to one axis and the print otherwise looks good so sort of eliminated nozzle snagging. Try getting an extra fan pointed right at the control board if possible.