It is critically important to get the first layer of the print right, When the first layer is not the best it can be then it can lead to complete failure, parts detaching, and warping. There are several techniques and recommendations one can heed in order to minimize the chance of this happening.

To understand what makes for good first layers we need to understand Flow Math and the relation that layer height and extrusion width have to the surface area presented by the extruded filament against the build plate (or layer beneath, for layers after the first.)

If you didn't level the bed with SCREWS_TILT_CALCULATE then we should presume the be is not level as the paper method and other techniques will not provide an adequately level bed, becoming exponential more default as the bed size increases. Klipper provides native methods to both check the bed level and to calculate exactly how much adjustment each bed screw requires to be perfectly level.

From the Slic3r docs: “Having a level bed is critical. If the distance between the nozzle tip and the bed deviates by even a small amount it can result in either the material not lying down on the bed (because the nozzle is too close and scrapes the bed instead), or the material lying too high from the bed and not adhering correctly.”

To tell if the bed is level execute the following gcode in the Fluidd console:

 
G28
SCREWS_TILT_CALCULATE MAX_DEVIATION=0.02

You can also include the same gcode in the slicer's machine print start gcode or Klipper's print_start_macro. If the bed isn't level the print will stop.

A well set z_offset is critical for layers to bond and that extends to the first layer bonding to the build plate. It can not be properly set with the paper method.

By slowing down the first layer velocities we can reduce the forces applied to the molten filament as it's extruded, reducing the chances it is stretche too much and won't adhere well to the build plate.

Keep PLA first layer speeds between 20-60mm/s, slower for PETG and TPU. Slow for more intricate and finer first layer designs.

It can not be stressed enough that calibrating your filament is critical for good prints and this certainly extends to the first layer as well.

Make sure you have tuned the extruder rotational distance before any other tuning and calibrations. If this value is off then all Klipper's extrusion calculations about flow will be off.

Make sure you've calibrated for the specific filament you're print with its

• max volumetic flow rate (you can't print faster than this)
• filament flow ratio
• pressure advance

“If too much material is laid down then the nozzle may drag through it on the second pass, causing it to lift off the bed (particularly if the material has cooled). Too little material may result in the first layer coming loose later in the print, leading either to detached objects or warping.”

Using a thicker first layer height provides additional flow and more heat, and better conditions for adhering to the build plate. It better accommodates imperfections in the bed surface and warpage of the plate. Consider it a good practice to bump the first layer height up by 0.04mm for PLA and 0.08mm for PETG. Some recommend first layer heights matching nozzle diameter, more realistically that can't be more that 90% of nozzle height to get enough “squish”.

The fatter the extrusion with the more material will touch the bed and the more surface area it will have to grip the plate. Increasing the first layer line widths above 200% is canonically recommended yet the percentage is based off layer height so unless you're also using thicker first layer heights as well keep the value above 0.42mm minimum. Setting to fixed 0.46mm rather than a percentage is easier in practice.

“The extruder hot-end and bed, if it is heated, can be made hotter for the first layer, thus decreasing the viscosity of the material being printed. As a rule of thumb, an additional 5°C is recommended.”

This reduces the chance of knocking through the extrusions on the plate.

“It makes no sense to increase the temperature of the first layer and still have a fan or other cooling mechanism at work. Keeping the fan turned off for the first few layers is generally recommended.”

No cooling for the first [few] layers.