ABL Home Position Question

Hey everyone! After almost a year of having the parts to do so, I've finally followed the ZennmasterM ABL tutorials and have ABL "working"!

For some reason, I can't figure out why my G28 home axes command is putting my hot end in the center front of my bed. Previously, I had my home position set to the rear left corner of the bed out of the way of the print. My concern is that a print will finish and when the printer homes at the end, it will smash into the center of the print.

Has anyone had this problem? Thanks in advance!
gmay3

You probably enabled SAFE_HOMING.

Check for safe_homing. That is what caused that for me

Check safe_homing

Thanks everyone! I'll give that a shot and I'll update with the results.

Update: Commented out safe homing worked like a charm, thank you guys! My hotend is homing in the typical back left corner of the bed.

New question: I tried a first print after sending a G28 and G29 and it seemed level across the bed (amazing) but the height was a little too high where the first layer wasn't squishing. In a typical pre ABL Z endstop I would just change the height of the endstop switch, is the new ABL done by changing a parameter in Configuration.h and reflashing?

Follow the section "Roughly Calibrate the Z Offset" here - http://clough42.com/instructions/marlin-firmware-setup/

Thanks for the link kd7eir! I'll check it out. Appreciate the help!

kd7eir, thanks again my ABL is working now and it is awesome!

I've noticed that my probe servo will chatter back and forth a little while travelling in the Z direction down to the bed. Is this normal? I don't think it's bad enough to upset the ABL plane but could the chattering cause any damage to the servo from and electrical or mechanical perspective?

In the configuration.h file, you will find:

//#define PROBE_SERVO_DEACTIVATION_DELAY 300

I highly suggest you uncomment this line so that it detaches the servo after movement. You have probably noticed the servo jitters while printing if you do not have this line uncommented. This constant jittering will cause servo failure. Note that if you are using a slow servo, you may need to increase the delay.

If you look in marlin_main.cpp you will find two functions:

static void engage_z_probe()
and
static void retract_z_probe()

These are where the calls are made to extend and retract the Z-probe. You will notice they have if statements that look for a value of PROBE_SERVO_DEACTIVATION_DELAY. If that value is >0, the servo is attached and detached. The Arduino will only send a drive signal to an attached servo. This prevents the jittering.

Finally got around to making this firmware change and it works perfectly! No more jitter, thanks so much kd7eir!

Quote:

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Originally Posted by gmay3

Finally got around to making this firmware change and it works perfectly! No more jitter, thanks so much kd7eir!

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Glad that I could help.