Welcome! Log In Create A New Profile


Auto bed levelling issue

Posted by Focussys 
Auto bed levelling issue
November 17, 2014 04:33AM
Hi All

My Prusa I3 has been printing fine for a few days now, but I have been having problems getting the ABS to stick to the bed. I decided to add bed levelling to get more accuracy.

So far the levelling part works fine, but when I home all in Pronterface the head tries to bury itself in the bed. I tried adding back the z axis endstop in series with the probe only to find it doing the same thing.

Here's the levelling section of my Marlin if it helps:

//============================= Bed Auto Leveling ===========================

#define ENABLE_AUTO_BED_LEVELING // Delete the comment to enable (remove // at the start of the line)
#define Z_PROBE_REPEATABILITY_TEST // If not commented out, Z-Probe Repeatability test will be included if Auto Bed Leveling is Enabled.


// There are 2 different ways to pick the X and Y locations to probe:

// - "grid" mode
// Probe every point in a rectangular grid
// You must specify the rectangle, and the density of sample points
// This mode is preferred because there are more measurements.
// It used to be called ACCURATE_BED_LEVELING but "grid" is more descriptive

// - "3-point" mode
// Probe 3 arbitrary points on the bed (that aren't colinear)
// You must specify the X & Y coordinates of all 3 points

// with AUTO_BED_LEVELING_GRID, the bed is sampled in a
// and least squares solution is calculated
// Note: this feature occupies 10'206 byte

// set the rectangle in which to probe

// set the number of grid points per dimension
// I wouldn't see a reason to go above 3 (=9 probing points on the bed)

// with no grid, just probe 3 arbitrary points. A simple cross-product
// is used to esimate the plane of the print bed

#define ABL_PROBE_PT_1_X 15
#define ABL_PROBE_PT_1_Y 180
#define ABL_PROBE_PT_2_X 15
#define ABL_PROBE_PT_2_Y 20
#define ABL_PROBE_PT_3_X 170
#define ABL_PROBE_PT_3_Y 20


// these are the offsets to the probe relative to the extruder tip (Hotend - Probe)

#define Z_RAISE_BEFORE_HOMING 5 // (in mm) Raise Z before homing (G28) for Probe Clearance.
// Be sure you have this distance over your Z_MAX_POS in case

#define XY_TRAVEL_SPEED 4000 // X and Y axis travel speed between probes, in mm/min

#define Z_RAISE_BEFORE_PROBING 25 //How much the extruder will be raised before traveling to the first probing point.
#define Z_RAISE_BETWEEN_PROBINGS 5 //How much the extruder will be raised when traveling from between next probing points

//#define Z_PROBE_SLED // turn on if you have a z-probe mounted on a sled like those designed by Charles Bell
//#define SLED_DOCKING_OFFSET 5 // the extra distance the X axis must travel to pickup the sled. 0 should be fine but you can push it further if you'd like.

//If defined, the Probe servo will be turned on only during movement and then turned off to avoid jerk
//The value is the delay to turn the servo off after powered on - depends on the servo speed; 300ms is good value, but you can try lower it.
// You MUST HAVE the SERVO_ENDSTOPS defined to use here a value higher than zero otherwise your code will not compile.


//If you have enabled the Bed Auto Leveling and are using the same Z Probe for Z Homing,
//it is highly recommended you let this Z_SAFE_HOMING enabled!!!

//#define Z_SAFE_HOMING // This feature is meant to avoid Z homing with probe outside the bed area.
// When defined, it will:
// - Allow Z homing only after X and Y homing AND stepper drivers still enabled
// - If stepper drivers timeout, it will need X and Y homing again before Z homing
// - Position the probe in a defined XY point before Z Homing when homing all axis (G28)
// - Block Z homing only when the probe is outside bed area.


#define Z_SAFE_HOMING_X_POINT (X_MAX_LENGTH/2) // X point for Z homing when homing all axis (G28)
#define Z_SAFE_HOMING_Y_POINT (Y_MAX_LENGTH/2) // Y point for Z homing when homing all axis (G28)



// The position of the homing switches
//#define MANUAL_HOME_POSITIONS // If defined, MANUAL_*_HOME_POS below will be used
//#define BED_CENTER_AT_0_0 // If defined, the center of the bed is at (X=0, Y=0)

//Manual homing switch locations:
// For deltabots this means top and center of the Cartesian print volume.
//#define MANUAL_Z_HOME_POS 402 // For delta: Distance between nozzle and print surface after homing.

Not sure what to do next.

Hope someone can help.

Re: Auto bed levelling issue
November 17, 2014 07:54AM

That seems excessive. Is it accurate? This may be why you're seeing the nozzle go into the bed.

MakerFarm 8" Prusa i3v
0.4mm E3D v6 for 1.75mm
Re: Auto bed levelling issue
November 25, 2014 11:29AM
remove the # on Z_RAISE_BEFORE_HOMING and set the value so that the extruder lifts a safe distance before homeing.

#define Z_RAISE_BEFORE_HOMING 5 // (in mm) Raise Z before homing (G28) for Probe Clearance.
Sorry, only registered users may post in this forum.

Click here to login