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Z axis initialization

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Posted · Z axis initialization

Hello, newbie question here:

When beginning to print, am I supposed to have to manually raise the platform into position?

I have had good success printing, as long as I pre-position the platform at the point where it triggers the top z-axis limit switch (in other words, I manually raise the platform until it is just against the brass nozzle, in position to start printing).

If I don't do this--I mean if I leave the platform a few cm below the nozzle), the printing head will automatically center itself over the middle of the printing platform, but the platform doesn't raise to meet it. So the nozzel just starts extruding plastic into thin air.

Again, the way I am doing it seems to work, but it seems to me that something must be wrong, anyway. Because I don't understand the purpose of the top limit switch, unless the platform is designed to automatically rise up to meet the nozzle when you start printing.

Thanks for any insights, if I'm doing something wrong!


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    Posted · Z axis initialization

    Look at your gcode. Around the 4th line you should see something like:

    G28 X0 Y0

    G28 Z0

    The first line above homes x,y and the second line homes z. If you have this G28 Z0 already then your endstop (limit switch) is signalling already even without it being pushed. Could it be mechnically stuck? Does it click when you push on it? Remove it and the cabling from the machine. Check it with an ohmeter. It should change from infinite ohms (open) to 0 ohms (short) when you push on it. I suspect it is always shorted.

    If the switch is fine, then there is something wrong with your board. Maybe a missing pullup resistor on the circuit that connects to the z endstop.

    See what happens is when it goes to home the z it moves the platform up until the z trips but if it thinks the z endstop is already closed you never notice it moving up.


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