Auto Bed Leveling doubt

Hi All,

So I built my first cartesian 3D printer and and I am planning to do a few tests as a CNC Router.

At this moment I have a dremel attached to the Z axis, using an endstop as Z Max Position. For bed leveling, I use an aligator clip on the bit of the dremel and the other contact is a old PCB that I have (1.65mm thick). The wires are connected to Z min Endstop.

After bed leveling (3 point) I can check the matrix created and it seems ok. Removing the PCB and sending the Z axis to 0 gives me exactly 1.65mm above the bed but I was expecting the bit to touch the bed since I have #define Z_PROBE_OFFSET_FROM_EXTRUDER -1.65 // Z offset: -below +above [the nozzle]. Have already tried +1.65 but it gives me the same result.

I have also commented //#define MIN_SOFTWARE_ENDSTOPS and set #define Z_MIN_POS -5

Could you tell me if this is ok?

Appreciate any help you guys can provide.

Do you have the EEPROM enabled? If so... You need to pre-load the default settings into the EEPROM with a M502 and M500 pair. Just because you have a value specified in the Configuration.h files does not mean that value is being used.

You can see the values being used by giving it a M503. It might be good to check and see what Z_PROBE_OFFSET_FROM_EXTRUDER is being used.

Hi Roxy,

Thanks for you advice. After sending the M502/M500 command I had the 1.65 mm offset showing up in the display but it also messed up with everything else .

If you could be so nice, I have other questions that you may provide answers. They are:

• After issuing M502/M500, none of the motors were moving. Investigating the issue, I found that my feedrate (500 mm/s) was too high. Therefore, I started to play around and found that 12mm/s made them work again (X,Y). Z was alway 5 mm/s. Don´t you think this value is too low? I am using lead screws TR14, 3 mm pitch and all my drivers are set to 1/16.
• As I mentioned before, I am using an endstop as Z-Max and an alligator and old pcb as Z-Min. So, when the bit touches the PCB the firmware knows it is zero. Before the M502/M500 the 3 point auto leveling was working fine but now everytime I send a G29 my Z axis moves until Z-Max endstop is no longer active (goes down and then home again), then X and Y proceed to the next point where Z-Axis again moves down just a little bit until Z-Max is not active. The same process goes on for the third point. Do you have any suggestion on where to look at?
• The last one, once I make the Auto Bed leveling work again, how do I implement the corrections needed? I mean, what commands do I need to send to have the matrix stored and applied to further movements?

Thank you so much for you patience.

Regards,

Marcus

It is hard to say if 12 mm/sec is too fast. You will need to do some prints and see if you get any 'layer shift'. You might be able to turn up the power to your stepper motors and if so, that should let you run faster. It is OK for the stepper motors to be so warm (hot) that you can only hold your hand on them for 5 or 10 seconds.

For checking out if your endstops are working... You can use M119.

As far as bed leveling... I can answer any UBL question, but there are 5 different bed leveling systems supported by Marlin. And the answers are going to vary depending on which one you are using. (And you didn't specify this.)

Hi Roxy,

Thanks once again for your support.

I am pretty sure my endtops are working properly. They were before the M502/500 command but maybe this is not what you meant.

What I can not understand is why the software seems to consider the Z-Max Endstop as the Min. I assume this is the reason why the Z axis begins to move downards to the table and, as soon as the Z-Max Endstop is not active, it comes back and resume to the next point. Homing Z works perfectly.

I am using a 3 point Automatic Bed Leveling.

Forgive me if I misunderstood something.

Thanks!

Marcus

Do you have your axis moving in the right direction? Do you have PronterFace working so you can send commands to the printer? If you tell the Z axis to move down, does it move up?

If an axis moves the wrong direction, you can flip these definitions:

// Invert the stepper direction. Change (or reverse the motor connector) if an axis goes the wrong way.
#define INVERT_X_DIR true
#define INVERT_Y_DIR true
#define INVERT_Z_DIR true

Hi Roxy,

Yes, everything is moving to the right direction. I am using Repetier host.

Yesterday I downloaded the new FW version (1.1.6) and, before sending it to MEGA, I had to reconfigure several parameters. Taking advantage of this, I have also enabled Unified Bed Leveling.

So, I sent a M502 / M500 to store the parameters into the EEPROM, G28 to home the axis and then I sent a G29 P1 to begin the automated procedure. What I could notice is that it seems several points are being taken in the "air". What I mean is that I was expecting the proble to go all the way down until it touches the bed and then proceed to the next point. This happens from time to time (going all the way to the bed and triggering the endstop) but sometimes I see the probe going down, then it stops above the bed (let´s say 30 mm) and then it moves to the next point.

Could you explain what to expect after the G29 P1? Does the probe touch the bed right after the G29 P1 (after moving to X and Y)?

Thanks once again for your clarifications.

Marcus

First... Get your printer working well enough it can print a small object (Calibration cube???) in the center of the bed. Don't try to bring up UBL without being able to do this.

Once you can print a small object in the center of the bed with no issues... The G29 P1 should probe the entire bed working out from the starting location. It should not probe in the air. It kind of sounds like you have the Z-Probe endstop inverted???? You can check that with M119. It should report Open when in the air up above the bed and Triggered when you press and hold the switch.

Edited 1 time(s). Last edit at 10/27/2017 12:18PM by Roxy.

Hello,

Thanks for you reply.

I will do as you suggest and try to print something at the centre of the bed.

I´ve already tested the Endstops and they are all working properly. When the probe goes all the way down to the bed, it hits the plate used to close the circuit and the probe goes up again. I did the same test manually and can confirm the firmware sees Z-min end stop triggered when M119 is sent.

I´ll let you know how it goes once I print something in there.

Thank you and regards,

Marcus