Bed Auto Leveling.. check this out

#define X_PROBE_OFFSET_FROM_EXTRUDER -30.6
  #define Y_PROBE_OFFSET_FROM_EXTRUDER 5.9
  #define Z_PROBE_OFFSET_FROM_EXTRUDER -15.5

  #define Z_RAISE_BEFORE_HOMING 16       // (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 3000         // X and Y axis travel speed between probes, in mm/min

  #define Z_RAISE_BEFORE_PROBING 16    //How much the extruder will be raised before traveling to the first probing point.
  #define Z_RAISE_BETWEEN_PROBINGS 5

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derletztename
I tried a lot and read a lot about this and i'm near to get it working, But I just don't get the Nozzle to touch the Bed after Probing. It just stays where it was after the Probe triggered.
The Servo retract as it should, but after that the printer won't turn any lower.
And therefor prints into the air...
I added my config.h - maybe someone sees my stupid mistake?
I am using an (PRotos) like the old Prusa and recently updated it a little...

Thanks a lot

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derletztename
Thanks for the answer
If I change the value of Z_PROBE_OFFSET_FROM_EXTRUDER nothing changes after probing.
The nozzle stays at the high it was during probing. And there it stays during printing.
The nozzle should be near to the bed after I perform a G28, right?

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derletztename
Okay, the G1 Z0 Command does help. But it varies where zero is.
Maybe there is some connection that after the probing the z-axis move faster than it could and therefore lose some steps sometimes. How can i get this slower? It doesn't seem to be affected by the homing speed settings in the config.h

Whats wrong with my #define Z_RAISE_... Has it to be bigger? As big as my "Stick" for the probe is?

Do I have to activate the EEPROM Settings for the leveling? Where else does it save the values?

And how can I test if the leveling did actually worked? Just via printing or should it even work while manually moving the x and y axis?

As I am no good with Software I did not want to install the Enhanced G29 code, before understanding the usually one...

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derletztename
Okay, I did everything as you suggested. Probing takes more time now but seems to be accurate.
Theres just one thing i don't get. After G29 the nozzle is a little bit higher above the bed than after a G28 (I send a G1 Z0 after both).
How could that be?
The height after G28 is perfect, but after the G29 it's about 1mm to high...

A FAQ would be great btw. Than people could help themselfs... Or is there something like this?

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derletztename
Okay, I did everything as you suggested. Probing takes more time now but seems to be accurate.
Theres just one thing i don't get. After G29 the nozzle is a little bit higher above the bed than after a G28 (I send a G1 Z0 after both).
How could that be?
The height after G28 is perfect, but after the G29 it's about 1mm to high...

A FAQ would be great btw. Than people could help themselfs... Or is there something like this?

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otas
I have made microswitch sensor operated by electromagnet for auto bed levelling. Has anybody managed to control electromagnet instead of a servo? Especially on Melzi - using a fan switch transistor to do that?
I would appreciate any suggestions.

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otas
Thanks, but not much luck there. Never mind, I will perservere. I think the servo is a bit too wobbly and microswitch too inaccurate for this purpose for an accurate measurement. I am working now on optical, contactless switch, which does not need moving parts and retraction. So far I managed on the prototype 10mm clearance gap, 1 micron accuracy with 30 micron hysteresis. The idea is to mount it 4 mm above the nozzle level, leaving 6mm below the nozzle for the table clearance. Still need more work on the electronics. But in principle I am there.

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zonerx
Anyway to implement BAL with Melzi board? there isn't any port for servo on Melzi board..

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regpye

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zonerx
Anyway to implement BAL with Melzi board? there isn't any port for servo on Melzi board..

Have a look in the SmartRap forum, we are using no servo Auto Bed Leveing now. You may be able to do something similar.
SmartRap forum

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Brainscan
Thanks regpye if I'd tried looking a bit harder I probably would have found it, not so easy navigating on my iPhone while my laptop is broken. Strangely you seem to have had the exact same idea I had for my mendelmax. I made a j head mount with a hinge and spring and used the hotend as the probe. I use hall o sensors as they can be set extremely sensitive so the slightest touch will activate the endstop, problem was I don't currently use a Bowden hotend and the retract was moving the hotend up and down. I hadn't spent much time designing it so I could probably improve the way it works with a bit more effort. I've switched to a servo activated probe for the moment but I'm trying to design a new lightweight x carriage/extruder that doesn't have a stepper motor on it and doesn't use a Bowden cable. Not sure if it's going to work yet but I'm hoping it will be a good alternative to my current set up.

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regpye

Sounds like a challenging idea but well worth following.
The only thing about using a Bowden is that it is light weight, otherwise I would be using it directly with an extruder and hotend combined.
How does the hall o sensor work? Is it magnetic?

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Brainscan

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regpye

Sounds like a challenging idea but well worth following.
The only thing about using a Bowden is that it is light weight, otherwise I would be using it directly with an extruder and hotend combined.
How does the hall o sensor work? Is it magnetic?

I like how lightweight Bowden setups are and my nozzle probe would have worked a treat if I'd been using one as the retraction wouldn't pull and push the hotend up and down (I'm only talking 0.1-0.2mm) but it was enough to affect print quality. I don't want to switch to a Bowden as I want to be able to use soft filaments like ninja flex. I'm hoping to mount the extruder stepper on an x end and have a lightweight x carriage/extruder/probe combo so I can up my print speed.

Yes hall o sensors are tiny and very cheap and detect magnetic fields, they are also extremely accurate and don't wear out. I use them on the boards designed by rrd but you can just plug them into a servo lead and away you go. There are a couple of articles showing how they can be set up like that.