[PROBLEM] Homes through endstops

Hello all, I have a problem with my reprap Prusa which I recently just wired up a RAMBo board to. I am still working on getting it printing unfortunately and was wondering if any of you may have had or know how to fix the problem I'm having.

The problem is very temperamental and does not occur 100% of the time, but often enough to keep me from printing. When ever I go to home all of the axis to get it ready for a print, the motors do not always stop as soon as the endstops are triggered. This causes the motors to skip and sends the printer into a seizure which loosens nuts and send the z axis right into the print bed. But sometimes (like when I first start up the printer) it homes every axis no problem but then I can't seem to keep it doing that consistently as the problem usually gets worse as I try to fix it.

What I've done already:

I have tested and swapped out the endstops for my old ones that worked fine with my printrboard that I had before this. Same result.

Checked the voltages across the pins. There appears to be no potential difference between the high or ground and signal pin, not sure if this is normal because there is a voltage difference of 4-5v between high and ground.

Currently have all of the endstops wired in the NC or normally-closed position and connected to the HIGH and signal pins.

And all of the steps/mm have been correctly calculated and entered into the firmware.

Here is the mechanical endstops portion of the configuration:
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// Uncomment the following line to enable CoreXY kinematics
// #define COREXY
#define ENDSTOPPULLUPS // Comment this out (using // at the start of the line) to disable the endstop pullup resistors


// corse Endstop Settings

// The pullups are needed if you directly connect a mechanical endswitch between the signal and ground pins.
const bool X_ENDSTOPS_INVERTING = true; // set to true to invert the logic of the endstops.
const bool Y_ENDSTOPS_INVERTING = true; // set to true to invert the logic of the endstops.
const bool Z_ENDSTOPS_INVERTING = true; // set to true to invert the logic of the endstops.
#define DISABLE_MAX_ENDSTOPS

// For Inverting Stepper Enable Pins (Active Low) use 0, Non Inverting (Active High) use 1
#define X_ENABLE_ON 0
#define Y_ENABLE_ON 0
#define Z_ENABLE_ON 0
#define E_ENABLE_ON 0 // For all extruders

// Disables axis when it's not being used.
#define DISABLE_X false
#define DISABLE_Y false
#define DISABLE_Z true
#define DISABLE_E false // For all extruders

#define INVERT_X_DIR true // for Mendel set to false, for Orca set to true
#define INVERT_Y_DIR false // for Mendel set to true, for Orca set to false
#define INVERT_Z_DIR true // for Mendel set to false, for Orca set to true
#define INVERT_E0_DIR true // for direct drive extruder v9 set to true, for geared extruder set to false
#define INVERT_E1_DIR true // for direct drive extruder v9 set to true, for geared extruder set to false
#define INVERT_E2_DIR false // for direct drive extruder v9 set to true, for geared extruder set to false

// ENDSTOP SETTINGS:
// Sets direction of endstops when homing; 1=MAX, -1=MIN
#define X_HOME_DIR -1
#define Y_HOME_DIR -1
#define Z_HOME_DIR -1

#define min_software_endstops true //If true, axis won't move to coordinates less than HOME_POS.
#define max_software_endstops true //If true, axis won't move to coordinates greater than the defined lengths below.
// Travel limits after homing
#define X_MAX_POS 200
#define X_MIN_POS 0
#define Y_MAX_POS 200
#define Y_MIN_POS 0
#define Z_MAX_POS 100
#define Z_MIN_POS 0

#define X_MAX_LENGTH (X_MAX_POS - X_MIN_POS)
#define Y_MAX_LENGTH (Y_MAX_POS - Y_MIN_POS)
#define Z_MAX_LENGTH (Z_MAX_POS - Z_MIN_POS)

// The position of the homing switches
//#define MANUAL_HOME_POSITIONS // If defined, manualy programed locations will be used
//#define BED_CENTER_AT_0_0 // If defined the center of the bed is defined as (0,0)

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

//// MOVEMENT SETTINGS
#define NUM_AXIS 4 // The axis order in all axis related arrays is X, Y, Z, E
#define HOMING_FEEDRATE {50*60, 50*60, 4*60, 0} // set the homing speeds (mm/min)

// default settings

#define DEFAULT_AXIS_STEPS_PER_UNIT {40,40,1120.858269,406.7091} // default steps per unit for ultimaker
#define DEFAULT_MAX_FEEDRATE {500, 500, 5, 45} // (mm/sec)
#define DEFAULT_MAX_ACCELERATION {9000,9000,100,10000} // X, Y, Z, E maximum start speed for accelerated moves. E default values are good for skeinforge 40+, for older versions raise them a lot.

#define DEFAULT_ACCELERATION 3000 // X, Y, Z and E max acceleration in mm/s^2 for printing moves
#define DEFAULT_RETRACT_ACCELERATION 3500 // X, Y, Z and E max acceleration in mm/s^2 for r retracts

//
#define DEFAULT_XYJERK 20.0 // (mm/sec)
#define DEFAULT_ZJERK 0.4 // (mm/sec)
#define DEFAULT_EJERK 5.0 // (mm/sec)


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These settings have brought me as close to printing as I have gotten with this new board.

I have noticed that the x-axis seems to work a larger percent of the time than the other two. I tried switching all of the stops around and still no consistent cause could be pin-pointed. I am stumped and wish I could figure out what it is.

Any kind of help or suggestions would be much appreciated! Please and thank you!

Matt

mv2woods Wrote:
-------------------------------------------------------
> What I've done already:
>
> I have tested and swapped out the endstops for my
> old ones that worked fine with my printrboard that
> I had before this. Same result.
>
> Checked the voltages across the pins. There
> appears to be no potential difference between the
> high or ground and signal pin, not sure if this is
> normal because there is a voltage difference of
> 4-5v between high and ground.

You should be able to measure +5V at the end stop connector.(points + and - shown on the rambo wiki page)