**What autobedleveling do**
> ABL is not a rectifier , but only a repeter of t…he bad surface on all your object
> ABL is just made to make adhesion but the price of adhesion is your object deformation
> ABL copy your surface and will make the same surface for all layer of your object
> ABL don't modify extrusion for some first layers , to make a plane vertical ,
> and parallel to the ' X & Y ' rods
> ABL , construct a tower perfectly perpendicular to the calculated probed plan
> ABL is not serious , you must have an absolute PERFECT PLAN SURFACE ,
> it's not serious to build and object on a mountain buildplate , the perfect surface is the first tool needed to build and object
> LINEAR or BILINEAR ? , now I think you can find by yourself , linear will make a 'possible plan'
> by using the max height of your bent bed', it's a risk to make zero adhesion
> if too high somewhere, and BILINEAR make a mesh , adhesion is perfect , but mesh is respeated infinitly
**The magic of FADE_HEIGHT**
>ENABLE_LEVELING_FADE_HEIGHT is the only option that will linearise the print plan, you can add this option in the firmware for all leveling system and now only you are in harmony with all the axes of the printer. iIt gradually reduces leveling correction until a set height is reached, set with M420 Z<height>
_Now you know all about Autobedleveling .
**Unified Bed Leveling**
> UBL , is a bilinear with fade height too , but very complete to make precision mesh , but in theory , everybody have a ' correct ' bed and will not need to probe some other points after the automesh generated. UBL is an ULTRA BIG TOOL to probe where it's needed 'if needed ' to use a bad bed , but if you have a good bed , it's easy too, it has Tools and Utility to try a print test and more. As I said before , UBL must be simplified and I'm sure in a few weeks , UBL will be a smart system with only one click . I recommend you use it to report all informations to help the developers to make it more simple.
You can save your mesh , and use it on each print
No need to enter dimensions values in firmware , total area is used automaticly
You can make a mesh without probe and with an endstop ' manually meshing '
You can make it with hot bed and nozzle at different temps
You can adjust , add a new probed point if needed outside of the predefined grid
You can make a test print to validate if you are not sure of your mesh
**Why UBL ?**
> Because , all devellopers have decided to make war to the first layer. It's a good idea because , it's really possible. And it's made now , UBL will scan all the surface ' 10x10 points by defaut' , will make a smooth mesh that can be very precise with the interpolation between probed points . If we set a good mesh 'UBL is made for this ' , we can have the first layer perfect like the second layer lol !! No you're not dreaming , play with UBL and you will have this results. It's why , I have made this guide , to guide you to the most Advanced AUTOBEDLEVELING.
Thks to @Roxy-3D
**For better results**
> For information , the only material that can help you to have a perfect bed immediatly ,
> is the vitroceram glass or borosilicate , 3mm glass can hold 2kg of plastic without bending ,
> if you can buy 4mm or 5mm glass , you will have a buildplate impossible to bend with the heat or the weight of the object
> My buildplate is 400x400 and 3mm and with this , i don't need autolevel , the bed is so perfect ,
> i just use the probe , just for swapping the nozzle and adjust offset by firmware .
> So , the first job , is to make 'mechanicaly' an amazing buildplate , and if you have this , you can use a probe ' bltouch' or other to probe the zero , because when you change the nozzle , you don't have to touch your bed screw , but just to find the offset by software , no mechanical modifications
> The probing with sensor offer to never touch the bed screws , but , sometimes , you can verify it lol
> To make a perfect bed on another already installed , cut a borosilicate glass and fix it , to fix it you can glue it with silicone '5mm of perimeter glued is enough and very solid ' , and place under one or two coats of aluminim paper to equal to the height of the silicone of the edge , this solution works , the bed can be unmounted and back to origin mounting and the heat conduction is good.
Thks for all that want to complete this topic
# **How UBL works**
_For the moment UBL is too young , and not simplified , you have 20/30 menus and submenus but in resuming it's just a one click all in one system , I'm sure in a close future , UBL , will be a total automated system._
**LCD Guide**
**Before**
-Mesh Inset must be good , if not , the probe can not go everywhere , if you choose a 3x3 grid ' in firmware' , your mesh must probe 9 times if not , set better the MESH INSET , or use the manual mode
-Try to inform the firmware of the area the probe can reach , if not , you will have 'unprobed zone ' and you willl have to make it manually and it takes time for nothing.
-INITIALISATION OF MEMORY , if not , you will have bip and bip and nothing else
**After**
Create cold mesh in menu ' you can heat the bed and nozzle if you want precision '
Store in a Slot
Activate UBL
Store EEPROM if you want to keep this settings for the next boot ' the mesh is stored but not activated
**Test**
you make a movement NOT BY LCD , you need a true GCODE INSTRUCTION ,of x or y and you see if z motors move to make correction
If you want the perfect correction you use ' validate menu' and a test print will start
after the print , you can adjust , add points , add new values in manual mode , or increase the auto grid
**Print Behavior**
With UBL precision , your first layer will be perfect mathematicly and it's a problem for users that never have this precise settings. Why ? Because the first layer is not compressed and the risk of bad printing is possible , then , ask to your slicer , to reduce a little the first layer height and SLOW the speed , the extrusion will have no pressure on the build plate and , the fixation of the melt plastic can be corrupted.
it's why , the print test is included in the menus , because , it's not possible to make an UBL without human intervention to validate before use
You can reduce height , but you can increase extrusion too
> Steeve !
>
> If you have win , now , you can tweak value and make your own adventure , you know all is needed to go deep in this abyss
>
> Sorry for my bad english , i'm FRENCH !
**Here are the gcode Steps , equal to LCD steps**
No problem with this , let's follow
```
M502 ; Reset settings to configuration defaults...
M500 ; ...and Save to EEPROM. Use this on a new install.
M501 ; Read back in the saved EEPROM.
```
For better probing , bed and nozzles heated
```
M190 S65 ; Not required, but having the printer at temperature helps accuracy
M104 S210 ; Not required, but having the printer at temperature helps accuracy
```
Homing ' of course '
```
G28 ; Home XYZ.
```
Now you need to probe the needed point or the desired points as you want
```
G29 P1 ; Do automated probing of the bed.
```
Or
```
G29 P2 B T ; Do manual probing of unprobed points. Requires LCD.
```
Or
```
G29 P3 T ; Repeat until all mesh points are filled in.
```
```
G29 T ; View the Z compensation values.
```
Probing is finished , and the map must be stored
```
G29 S1 ; Save UBL mesh points to EEPROM.
```
The miracle now !!! The famous height of the perfect linearised layer with all your axes
```
G29 F 10.0 ; Set Fade Height for correction at 10.0 mm.
Depending of the type of the printed object , must be modified if needed
```
Permanent parameter :: ON/OFF after booting , if saved in EEPROM take care !
No need of G29 , before printing , once activated , you can print directly .
```
G29 A ; Activate the UBL System.
```
```
M500 ; Save current setup.
;WARNING: UBL will be active at power up, before any `G28`.
```
# **Autotesting Pattern**
This tool 'if defined in Firmware ' will heat bed and nozzle as specify and print some lines , you will now see where you need to add some probing points to perfect you mesh but always with the minimum points as possible ' of course'
```
G26 C P T3.0 ; Produce mesh validation pattern with primed nozzle PLA temperatures
; are assumed unless you specify B 105 H 225 for ABS Plastic
G29 P4 T ; Move nozzle to 'bad' areas and fine tune the values if needed
; Repeat G26 and G29 P4 T commands as needed.
G29 S1 ; Save UBL mesh values to EEPROM.
M500 ; Resave UBL's state information.
```
Now I'm sure everybody has a better vision of the AUTOLEVELING system and all types, you can now access to the firmware documentation here
`http://marlinfw.org/docs/features/unified_bed_leveling.html`
Thks For all devellopers !
## `Enjoy !`