If the nozzle is too close, there will not be enough room for the extruded filament to take the correct shape, and it will be forced to squeeze outwards. In minor cases, the extruded line will be wider than necessary and produce elephant's foot. Prints like this may be quite hard to remove from the bed.
In extreme cases, there will be no way for the filament to exit the nozzle, at best causing extruder stepper motor skipping, and even potentially even jamming the extruder/hot end.
The contents of this page are shown in detail in the following video:
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Manual Levelling Procedure
There are many techniques available, but a common one is to move the nozzle to the various corners of the bed, turning the levelling knobs until a standard piece of office paper can just fit between the bed and nozzle. A 0.1mm feeler gauge can be used, but make sure it doesn't have any oil on it that will contaminate the bed surface. Typically, this procedure is done with the bed at printing temperature (essential), and the nozzle close to printing temperature - just cool enough to prevent filament oozing out (optional).
It is common to follow up with a first layer calibration print, and 'live level' the bed by continuing to adjust the knobs when the print is under way.
-This process is depicted in detail in the video above, and a gcode generator is provided at the bottom of the page to generate a suitable test print:
+This process is depicted in detail in the video above, and a gcode generator is provided at the bottom of the page to generate a suitable test print.
Auto Bed Levelling and Z offset
-Auto bed levelling automates the procedure to some extent. A sensor such as a BLtouch, EZABL, strain gauge or peizo transducer is used to probe the bed in a grid formation. At each location, it measures the vertical height, building up an array of stored values, called a mesh. Manual mesh bed levelling can also be used to probe such a grid, but is still a manual process and hence not considered 'automatic'. Here is a visual representation of a probed mesh, shown with the Bed level visualizer Octprint plugin:
+Auto bed levelling automates the procedure to some extent. A sensor such as a BLtouch, EZABL, strain gauge or peizo transducer is used to probe the bed in a grid formation. At each location, it measures the vertical height, building up an array of stored values, called a mesh. Manual mesh bed levelling can also be used to probe such a grid, but is still a manual process and hence not considered 'automatic'. Here is a visual representation of a probed mesh, shown with the Bed level visualizer Octprint plugin:
During printing, the firmware will reference the mesh and compensate for an angled and/or warped bed by raising and lowering the nozzle using Z axis movement. This means the nozzle can travel up and down to match the contours of the bed, ensuring a good first layer.
In the printer's bed is perfectly flat, it is reasonable to claim ABL is not needed. Some users may still prefer it for the added convenience. In the event that the bed is warped (very common), it can be impossible to get a good first layer without ABL or manual mesh bed levelling. An example of this situation is shown in the video above.
@@ -162,13 +160,15 @@- BLtouch/EZABL/Pinda probe - The nozzle is in mid air when these probes are triggered, which will require a negative Z offset.
- Manual mesh bed levelling - The nozzle and bed will be very close when manually probing, requiring a Z offset close to zero. -
- CR-6 style strain gauge - The nozzle touches the bed and flexes upwards to trigger the probe. This means the trigger poiunt is actually higher than the nozzle tip, and requires a positive Z offset. +
- CR-6 style strain gauge - The nozzle touches the bed and flexes upwards to trigger the probe. This means the trigger poiunt is actually higher than the nozzle tip, and requires a positive Z offset.
If BABYSTEP_ZPROBE_OFFSET is enabled in Marlin, setting the Z offset can easily be done as the first layer goes down. Don't forget to save to EEPROM afterwards. This process is depicted in the following snippet:
- -Another advantages of some ABL systems is that once the Z offset is set, you can interchange build surfaces of various thicknesses, with no changes needed for a successful first layer. Assuming the probe is triggered the same way on the bed surface, the Z offset is applied to this trigger point and the first layer height should be the same. On a manually levelled bed, the four corner knobs would need to be turned in unison to raise or lower the bed in accounting for thickness of the new build surface.
+The following picture shows Z offset for a BLtouch. You can clearly see the vertical difference between the probing point (tip of BLtouch) and the tip of the nozzle.
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+ If BABYSTEP_ZPROBE_OFFSET is enabled in Marlin, setting the Z offset can easily be done as the first layer goes down. Don't forget to save to EEPROM afterwards. This process is also depicted in the video at the top of the page.
+Another advantage of some ABL systems is that once the Z offset is set, you can interchange build surfaces of various thicknesses, with no changes needed for a successful first layer. Assuming the probe is triggered the same way on the bed surface, the Z offset is applied to this trigger point and the first layer height should be the same. On a manually levelled bed, the four corner knobs would need to be turned in unison to raise or lower the bed in accounting for thickness of the new build surface.
First layer gcode generator
The following form will create a series of five squares that you can use to live level your bed or set the Z offset. It is quick to print and features one square in the middle of the bed, with four others in the corners. You can use these to turn the levelling knobs in each corner until they are consistent, or ensure your ABL system is working if you have one in place.
+This test uses a 0.2mm first layer height.
