Our Unified 2 Firmware has specific settings to make auto bed leveling (ABL) probes work properly and provide a good user experience. Many people who are new to our firmware or ABL, in general, are not familiar with how this all works (mainly BLTouch or CRTouch users). The goal of this article is to educate users on how the firmware works to eliminate confusion amongst users who are not familiar with ABL systems. We follow best practices from Marlin and settings that we find through our years of testing ABL systems on actual machines.
The CRTouch is a clone of the BLTouch and it functions identically to the original BLTouch sensor. Any guides and information about the BLTouch apply to the CRTouch and the CRTouch is setup in our firmware using the BLTouch settings.
You also need to have a proper starting GCode in your slicer for any ABL system to work. We recommend using the one we put together for our EZABL kits and this starting GCode works with stock Proximity Probes, BLTouch, and CRTouch probes. See our guide here: ABL Bed Leveling Starting Gcode Guide
When you are using ANY ABL probe with our firmware after homing the Z axis will show 5mm. This is to reset the probe detection to the OFF state. This 5mm is NOT included in your Z offset. This 5mm also does not mean that your Z home location is Z5, it is still Z0. Before setting your offset make sure to move the Z down 5mm to bring the height to Z0.
You should NEVER follow any direction from other sources that tell you to move the nozzle to the bed and then issue a GCode command that “Zeroes out” the Z. If someone is telling you otherwise, they are wrong. Just move the nozzle down 5mm after homing to get to Z0, its that simple.
In general, BLTouch and similar probes (like the CRTouch and other knock-offs) cannot run very fast probing speeds while maintaining accuracy. Our default speed for ALL ABL probes in the firmware is set to 8mm/s.
If you have our EZABL and your printer can handle faster probing speeds you can use the SUPERFAST_PROBE option to get speeds of 15mm/s. If you want to try this uncomment the option and then update your firmware. Run a few M48 tests. If your Z axis is moving smoothly (not losing steps) and your M48 probe test is reporting a result of 0.01 or lower then your printer can use the higher speed. If you enable the SUPERFAST_PROBE and you are getting poor M48 results and/or your Z axis is losing steps (usually this is heard by the motor vibrating/grinding noises) then you should NOT use the SUPERFAST_PROBE option on your printer.
Your Z Offset tells the firmware how much distance is between the nozzle and the bed after the probe detects the bed. Once you have a Z Offset set on your printer it will use this distance to calculate where your actual Z0 position is in relation to the nozzle and the bed. To prepare for this select “Auto Home” under the Motion menu on the printer LCD and then move the Z down 5mm using the printer LCD (Motion > Move Axis > Move Z > Move 1mm – in the LCD menu) if you just homed the machine and it is showing 5mm height on the Z. See the “Z Height After Homing” section above.
Once you have the firmware installed and your probe is working you need to set your Z offset.
If you are comfortable, you can also just set your Z Offset “on the fly” by adjusting it on the skirt of a print. You can see this in action in our EZABL EZTip video below. This is how we set our Z Offsets on all our machines in the TH3D shop and this is more accurate than using other methods to acquire the Z Offset.
Once you have the offset dialed in. Press the LCD button and then go to Configuration > Store Settings to save them to the printer EEPROM. If you do not store the settings the offset will be forgotten when the printer is rebooted.
