First a list of identified problems :
Hardware problems
• the holes on the spider to fix the probe mount are not correctly aligned making the probe getting stuck when going too low.
• the screw in the lock ring is of poor quality making difficult to put the spring under tension.
• the microswitch used to detect the levelling of the z-probe is reliable when used to detect the closing of the circuit (ie for end-stop), but not when used to detect the opening.
• to close the microswitch the spring around the z-probe should have enough tension to be stronger than the internal spring of the microswitch. To be sure that each time the z-probe goes down the microswitch will close, you have to put the external spring under a big tension, meaning big risks of spider tilt when pushing the probe.
Software problems (on the official version of the marlin software : 1.0.3 dev )
• If you launch a G29 command without a closed z-probe circuit (ie the z-probe down) the behavior is not predictable, the spider is likely to go one way without stopping on end-stop but forcing the mechanical stop until you stop the power (I broke ball bearings that way).
• normally for the initial adjustment you should modify the z-probe height by the M851 gcode. Unfortunately it does not do anything with the official marlin version. So you have to recompile for each try.
• The auto-levelling is not compatible with multi extruders in this version of marlin (at each extruder change the spider will go up a little)
there is no command to put in a script to wait until the z-probe is up or down.
What to do to repair that ?
Hardware change :
first point : change the grub screw of the probe lock ring. To detect a reliable level, the tension of the spring should be constant, the grub screw is too difficult to tighten!.I used a remaining #15 screw but you may use any M3 screw (see photo). Be careful the the head of the crew does not touch anything that could block the probe.
- first point.png (58.15 KiB) Viewed 4904 times
Third point : Change the microswitch. it is impossible to use the provided switch for auto levelling. But luckily it is very easy to find better ones. I bought mine in a local electronic shop (see photo), it is almost the same, it has the same form factor, it cost twice the price of the original (but just a few bucks) and its lever has a hinge, so it needs much less force to switch and is considerably more reliable.
- 20170725154132.png (57.77 KiB) Viewed 4904 times
At this point your Auto-leveling should work. But to make it really usable I made some software change. I use Marlin 1.0.3 of the RKMB_GT2560_G2S package provided by GEEETECH so all the following modification are for this version only.
first software change : Block the use of auto-levelling if probe is not down to prevent erratic behaviour.
in marlin_main.cpp file in function gcode_G29() at line 2568 after the line :
st_synchronize();
add the following code :
#define MSG_PROBE_NOT_DEPLOYED "G29 probe not deployed"
if (!deploy_probe_for_each_reading) { // if the probe is not to deploy for each point,
// it should be deploy at this point.
// otherwise return in error
boolean probestate=true;
#if HAS_Z_MIN
probestate=READ(Z_MIN_PIN)^Z_MIN_ENDSTOP_INVERTING;
#endif
#ifdef Z_PROBE_ENDSTOP
probestate=READ(Z_PROBE_PIN)^Z_PROBE_ENDSTOP_INVERTING;
#endif
if (probestate){ // test the probe state state
LCD_MESSAGEPGM(MSG_PROBE_NOT_DEPLOYED);
SERIAL_ECHO_START;
SERIAL_ECHOLN(MSG_PROBE_NOT_DEPLOYED);
return;
}
}
second software change : Correct gcode_T() function to use two extruders and auto-levelling.
in marlin_main.cpp file in function gcode_T() at line 5128 after the line :
// Offset extruder (only by XY)
change the following code :
for (int i=X_AXIS; i<=Y_AXIS; i++)
current_position += extruder_offset[tmp_extruder] - extruder_offset[active_extruder];
// Set the new active extruder and position
active_extruder = tmp_extruder;
#endif // !DUAL_X_CARRIAGE
#ifdef DELTA
sync_plan_position_delta();
#else
sync_plan_position();
#endif
// Move to the old position if 'F' was in the parameters
if (make_move && IsRunning()) prepare_move();
by this one :
if (extruder_offset[X_AXIS][tmp_extruder]==0 && extruder_offset[Y_AXIS][tmp_extruder]==0 &&
extruder_offset[X_AXIS][active_extruder]==0 && extruder_offset[Y_AXIS][active_extruder]==0){
active_extruder = tmp_extruder;
} else {
for (int i=X_AXIS; i<=Y_AXIS; i++)
current_position += extruder_offset[tmp_extruder] - extruder_offset[active_extruder];
// Set the new active extruder and position
active_extruder = tmp_extruder;
#endif // !DUAL_X_CARRIAGE
SERIAL_ECHO_START;
SERIAL_ECHOLN(" send plan position");
#ifdef DELTA
sync_plan_position_delta();
#else
sync_plan_position();
#endif
// Move to the old position if 'F' was in the parameters
if (make_move && IsRunning()) prepare_move();
}
Third software change : Enable the use of M851 for probe level setting.
in marlin_main.cpp file in function gcode_G29() at line 2600 after the line :
delta_grid_spacing[1] = yGridSpacing;
change the line
float z_offset = Z_PROBE_OFFSET_FROM_EXTRUDER;
by
float z_offset = -zprobe_zoffset ; // do not use Z_PROBE_OFFSET_FROM_EXTRUDER;
in marlin_main.cpp file in function clamp_to_software_endstops() at line 5748 after the line :
#ifdef ENABLE_AUTO_BED_LEVELING
change the line :
if (Z_PROBE_OFFSET_FROM_EXTRUDER < 0) negative_z_offset += Z_PROBE_OFFSET_FROM_EXTRUDER;
by
if (zprobe_zoffset > 0) negative_z_offset -= zprobe_zoffset;
Fourth software change : Modify M401 (raise z-probe) and M402 (stow z-probe) function to be blocking until the z-probe has been raised or stowed.
in marlin_main.cpp file at line 4569 after the line :
inline void gcode_M400() { st_synchronize(); }
change the line :
#if defined(ENABLE_AUTO_BED_LEVELING) && !defined(Z_PROBE_SLED) && (defined(SERVO_ENDSTOPS) || defined(Z_PROBE_ALLEN_KEY))
by
#if defined(ENABLE_AUTO_BED_LEVELING)
in marlin_main.cpp file in function gcode_M401() at line 4587 after the line :
deploy_z_probe();
Add the lines :
// and block if probe is not deployed
#define MSG_WAIT_PROBE_DEPLOYED "Wait probe deployment"
boolean probestate=true,probe_msg=true;
while(probestate){
#if HAS_Z_MIN
probestate=READ(Z_MIN_PIN)^Z_MIN_ENDSTOP_INVERTING;
#endif
#ifdef Z_PROBE_ENDSTOP
probestate=READ(Z_PROBE_PIN)^Z_PROBE_ENDSTOP_INVERTING;
#endif
if (probestate && probe_msg){ // send waiting message once
LCD_MESSAGEPGM(MSG_WAIT_PROBE_DEPLOYED);
SERIAL_ECHO_START;
SERIAL_ECHOLNPGM(MSG_WAIT_PROBE_DEPLOYED);
probe_msg=false;
}
idle();
}
SERIAL_ECHOLNPGM(MSG_ZPROBE_OUT);
LCD_MESSAGEPGM(MSG_ZPROBE_OUT);
in marlin_main.cpp file in functionn gcode_M402() at line 45ç7 after the line :
stow_z_probe(false);
Add the lines :
// and block if probe is not stowed
#define MSG_WAIT_PROBE_DEPLOYED "Wait probe stowed"
boolean probestate=false,probe_msg=true;
while( ! probestate){
#if HAS_Z_MIN
probestate=READ(Z_MIN_PIN)^Z_MIN_ENDSTOP_INVERTING;
#endif
#ifdef Z_PROBE_ENDSTOP
probestate=READ(Z_PROBE_PIN)^Z_PROBE_ENDSTOP_INVERTING;
#endif
if (! probestate && probe_msg){ // send waiting message once
LCD_MESSAGEPGM(MSG_WAIT_PROBE_DEPLOYED);
SERIAL_ECHO_START;
SERIAL_ECHOLNPGM(MSG_WAIT_PROBE_DEPLOYED);
probe_msg=false;
}
idle();
}
// add a waiting tiile to secure the probe
if (! probe_msg){
millis_t codenum = 3500;
codenum += millis(); // keep track of when we started waiting
while (millis() < codenum) idle();
;
}
SERIAL_ECHOLNPGM(WELCOME_MSG);
LCD_MESSAGEPGM(WELCOME_MSG);
in marlin_main.cpp file at line 5598 after the lines :
gcode_M400();
break;
change the line :
#if defined(ENABLE_AUTO_BED_LEVELING) && (defined(SERVO_ENDSTOPS) || defined(Z_PROBE_ALLEN_KEY)) && !defined(Z_PROBE_SLED)
by
#if defined(ENABLE_AUTO_BED_LEVELING)|| (defined(Z_PROBE_ALLEN_KEY) && !defined(Z_PROBE_SLED))
With all that you should have a perfectly functional auto-levelling function. You may add a glass bed or change it with an other one of difeerent height whithout any recallibration ..
I had the following code in my gcode scripts :
M401; lower probe or wait for it
G29 ; auto-levelling
G1 Z10 F5000 ; lift nozzle
M402; stow probe or wait for it
Here is the auto-level function working:
www.youtube.com/watch?v=H3ro2tZpl1g
Attachments:
[attachment=0]20170725154321.png[/attachment]
