Help! My Z axis are homing in the wrong direction! SOLVED!!!!

Hey guys!
I'm relatively new to this, so please forgive any grievous mistakes I may make in this post. So basically I have a scaled up mendelmax that's running on Marlin V1 and Pronterface. It's using an arduino mega 2560 with ramps 1.4 and pololu drivers. My problem is that for some reason the Z axis is homing downwards instead of up towards the endstop. In the Config.h I set the value to 1 which is max position I believe. I've looked through various forums and have tried all the solutions but for some reason it doesn't work for me. When I press the negative button in pronterface the Z axis goes down and when I press the positive button it goes up as expected. However whenever I press the home button for the Z axis it goes down. I've tried to set it as -1 for minimum and it still goes down (kinda expected it too but I just found it odd that it did that). Anyways, I have no clue why it's doing that and attached I have my Config.h file if anyone wants to take a look at it. If you need anything clarified or any more information I'd be glad to give it to you to help you help me
Thanks,
Jeff
P.S. Please forgive the wordiness haha.

Edited 1 time(s). Last edit at 09/12/2013 11:21PM by jy.ding1.

I downloaded your config file, and I didn't notice anything wrong.

So the short answer is this: Move the endstop to the bottom, and home down. This is good. Homing to the Z max is bad. You are going to have a horrible time calibrating your machine homing from the top. It's really easy to wiggle your Z endstop to where you need your 'home' to be.

Long answer: You really don't want to do what you are doing. You are going to want to have your 'home Z' end stop at the bottom. There is nothing wrong with having one at the top, but home is where your bed is. You are going to re-calibrate your machine more than you think:
- Your Z steppers are going to miss a step once in a while, you are going to need to re-calibrate your machine to fix that.
- You are going to want to remove your bed every once in a while, and this will screw up your calibration.
- You are probably going to add all kinds of wacky crap to your bed to get your extrusion to stick, and this requires re-calibration.
- You are going to have to re-calibrate it because your bed warps differently at different temperatures.
- You are going to have to re-calibrate it because you jerked your hand off the hot bed while calibrating it at 110C.
- Your will probably need to re-calibrate after you calibrate it because you were so excited that you finally calibrated it correctly, and then you went and breathed on it funny.

To answer the other part of your question:

Sometimes I noticed that you need to save your config file before you compile and upload. Also, make sure you are compiling your firmware before the upload. If it still doesn't stick, kill all power to your board, pull the USB cable, close all arduino windows, reboot your machine, plug the USB cable back in, and then try to recompile and upload.

I hope this helps.

Edited 1 time(s). Last edit at 09/12/2013 04:07AM by rudemutant.

Hmm, I'll have to try that out. I read online that you want to home the z axsis to the max for the mendel max so that it doesnt crash into your build after it finishes. Would that happen if I home it at its min?

Well, that is a great point, and that is why two end stops are good for each axis. The expense isn't that great... you can run down to radioshack, or whatever, and pick up switches for about $4. Whatever it costs, it's worth it.

The alternative to buying a switch, is to make sure your build cube is set in the firmware. What you do is go with an over-estimated build height, home it to the bed, and then use pronterface to find out how high you can go. Then be a little conservative in your firmware. I don't have the mendel max, I have a little prusia, but I started with 100mm, then counted up until I got worried, which got me to about 80. I then decided that I would go with 60.

You can also set your build cube in slicer, which is easier because you can push the limits without busting out that arduino mess.

When you set the max build height in slicer, the GCode won't go past that height, but that doesn't account for a flaky stepper driver. One thing you have going for you is that if your stepper driver does mess up, normally it messes up by not moving enough and starts gouging the piece you are making instead of going up too high and ripping out your wires.

With a gagdget as big as yours, I'd personally go out and get the other endstop. Endstops are good, crashing is bad.

Edited 1 time(s). Last edit at 09/12/2013 10:20PM by rudemutant.

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The problem isnt crashing though... The axis is homing the wrong way and i dont know why.

jy.ding1 Wrote:
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> The problem isnt crashing though... The axis is
> homing the wrong way and i dont know why.

Try this. In the following section,

//Manual homing switch locations:
#define MANUAL_X_HOME_POS 0
#define MANUAL_Y_HOME_POS 0
#define MANUAL_Z_HOME_POS 0

Set the MANUAL_Z_HOME_POS to the height above the bed your nozzle should be at when you home. See if that helps.

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Sorry I missed a part of your question. I have my endstops at the bed, and never busted up a piece AFTER it was finished. I do however seem to have a knack for destroying them about 5 minutes in.

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Solved! I got it working! I have something stuck in my extruder though Won't extrude filament correctly so I gotta take that apart now. It seems that every time I get something working, another thing broke. Haha, thanks for all the help guys!!!