Z axis crashing into the bed instead of moving away

Hi guys

I'm having a little bit of a problem with my setup, I'm running it on a AzteegX3 with repetier firmware on it. The homing for all the axis goes well, but when it starts printing it moves the z axis into the head each layer instead of moving away from it. Now I have tried inverting and reversing it to get it to work, and it does work, but then the controls on the host for the Z axis are inverted.

so my dilemma now is;
- Host control for the z axis work properly ( press up goes up, down for down) but the bed crashed into head during print instead of moving away from it
- or host control for the z axis are inverted ( press up goes down, down for up) and the print starts good and I will get a good print.

Is there a way I can fix this? the z axis motor is placed on the top of the printer, the printer is like the ultimaker but the z axis stepper motor is placed on the top instead at the bottom. I don't want to rearrange the stepper motor so I am wondering whether there is a way to fix this either in the firmware or in the repetier host software.

thanks!

Your problem is most likely the location of the end stops. There are only two locations that will give you an "up" +Z axis. The other two locations will give you a +Z axis that is down. It's a cartesian geometry / right hand rule sort of thing.

As you look down at the print bead from the top, the zero position needs to be either in the upper right or lower left hand corner. Depending on how your bed travels and whether you use min or max end stops your switch locations will be in this or that position to make that all happen.

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uncle_bob
As you look down at the print bead from the top, the zero position needs to be either in the upper right or lower left hand corner. Depending on how your bed travels and whether you use min or max end stops your switch locations will be in this or that position to make that all happen.

do you mean that the X and Y endstops have influence on which direction the Z axis will move during print ? maybe I didn't understand you correctly...

thank you for the effort and time

The location of the X and Y end stops define either the max or the min ends of the X and Y axis of the printer. If you have them set up as minimum stops, they define the 0,0 location. Once you define the 0,0 location on a corner of a surface you have identified which quadrant it lies in. If both X and Y are positive, and the quadrant is defined, you have no choice for Z. It's already defined for you. That's just the way cartesian geometry works.

Simple answer - 0,0 must be in certain corners or it simply will not work with normal slicing software.

Yes, you could write a bunch of Python code to redefine everything. It's quicker / easier / more rational to just put the end stops where they belong.

Thanks again for your time, I asked the same question at the repetier section and it seems this is normal for the host software of repetier and it was my wrong interpretation of the host softwares Z buttons, check here for the answer to the question;

[forums.reprap.org]

In your top post in this thread, you specified that you were *printing* and the head went Z negative. That has nothing at all to do with the buttons in repeater (or Pronterface). Moves during print are controlled by the slicing software.

Edited 1 time(s). Last edit at 12/20/2013 11:08PM by uncle_bob.

In my original post I mentioned there were to potential setups I tried and each had it's own problem.

"

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so my dilemma now is;
- Host control for the z axis work properly ( press up goes up, down for down) but the bed crashed into head during print instead of moving away from it
- or host control for the z axis are inverted ( press up goes down, down for up) and the print starts good and I will get a good print

."

In the first option , the host control for z axis work as expected, and during print the Z went indeed negative due to the way I setup the endstops.
with the second setup, the print starts good and I will get a good print, but the Z axis appeared to be inverted.... which now seems not to be the case and I was wrongly interpreting the host buttons .

apologizes if any confusion caused , all working well now .... well it actually was working well haha

Edited 2 time(s). Last edit at 12/21/2013 02:28PM by sam80.