Homing issue

Hi,

I asked this question too in general but that seems not to be the right forum for it (that can be deleted).

Currently i'm building a Prusa i3 with Marlin firmware and i'm on the verge of printing but for some reason i can't get my homing right.

When I + the X axis it moves to the left (endstop is on the left).
When I + the Y axis it moves towards me (endstop is my side).
When I + the Z axis it goes down (endstop in on the bottom).
When i home the printer is homes nicely and stays in the corners.
So this all is working as expected i assume.

But when i try a 20mm test cube is goes the wrong way. driving the carriages into itself.

So I tried to reverse the axis and the endstops but now it moves away from the endstops.

What is the correct homing location
1. in a corner or 2. in the middle?

I just don't seem to get it right.

Thanks in advance

Peter

min endstop should be a X left, Y back (ie head is front in relation to bed) and Z down positions.

X - should move towards the left X endstop
Y - should move the bed back, towards the endstop at the back
Z - should move down, towards the Z min endstop.

So there is an issue with all 3 axis.

X moves the wrong way
Y endstop is at the wrong end, but is going the correct way
Z moves the wrong way

ie you need to change the following

#define INVERT_X_DIR true
#define INVERT_Z_DIR true

and physically move you Y endstop.

#define X_HOME_DIR -1
#define Y_HOME_DIR -1
#define Z_HOME_DIR -1

are all correct.

Edited 1 time(s). Last edit at 04/27/2014 07:25AM by Dust.

Ok... I changed some things.

Homing position is now in the front left corner of the heatbed.

X moves left towards left min endstop
Y moves back towards back min endstop
Z moves down towards bottom min endstop

This all works without issues but...

I don't know if this is right but all the axis use positive values (i.e. +1.23) when homing to all min endstops??

And when i select the testcube gcode it tries to go to the middle of the heat bed using also positive values, resulting in a crash.

inverting the direction would probably revert the direction but then it woud move away from the min endstops??

Is there a way to invert the homing direction without changing the endstops?

I'm a bit lost.

Thanks for your help

Edited 1 time(s). Last edit at 04/27/2014 02:57PM by peterv3210.

"Homing position is now in the front left corner of the heatbed." Correct

"X moves left towards left min endstop" X minus or X plus? It should be X minus
"Y moves back towards back min endstop" Y minus or Y plus? It should be Y minus"
"Z moves down towards bottom min endstop" Z minus or Z plus? It should be Z minus"

"I don't know if this is right but all the axis use positive values (i.e. +1.23) when homing to all min endstops??"

how can you say this just after I've told you -ve should move towards the endstops.
Where are you reading this?

"And when i select the testcube gcode it tries to go to the middle of the heat bed using also positive values, resulting in a crash."

It should go to the middle of the X,Y and start at first layer hight.. how is this crashing?

When you home it set that location as 0,0,0, you then can move from 0-200 in x, y and z with no issues. You can only move -ve after you have move +ve some.

If you have done what I said, its correct, your issues are else where, not homing.