3.3. FIRST SLICE
Lower speeds.
Slowing down the extruder for the first layer reduces the
forces applied to the molten material as it emerges, reducing the chances of
it being stretched too much and not adhering correctly. 30% or 50% of the
normal speed is recommended.
Correctly calibrated extrusion rates.
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. For these reasons it is important to have a
well-calibrated extrusion rate.
First layer height.
A thicker layer height will provide more flow, and
consequently more heat, making the extrusion adhere to the bed more. It
also gives the benefit of giving more tolerance for the levelness of the bed.
It is recommended to raise the first layer height to match the diameter of
the nozzle, e.g. a first layer height of 0.35mm for a 0.35mm nozzle. Note:
The first layer height is set this way automatically in simple mode.
Wider extrusion width.
The more material touching the bed, the better
the object will adhere to it, and this can be achieved by increasing the
extrusion width of the first layer, either by a percentage or a fixed amount.
Any spaces between the extrusions are adjusted accordingly.
A value of approximately 200% is usually recommended, but note that
the value is calculated from the layer height and so the value should only
be set if the layer height is the highest possible. For example, if the layer
height is 0.1mm, and the extrusion width is set to 200%, then the actual
extruded width will only be 0.2mm, which is smaller than the nozzle. This
would cause poor flow and lead to a failed print. It is therefore highly
recommended to combine the high first layer height technique recommended
above with this one. Setting the first layer height to 0.35mm and the first
extrusion width to 200% would result in a nice fat extrusion 0.35mm wide.
Bed material.
Many options exist for the material to use for the bed,
and preparing the right surface can vastly improve first layer adhesion.
PLA is more forgiving and works well on PET, Kapton, or blue painters
tape.
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