6.5 Printer calibration

One of the advantages of the Polar3D printer’s underlying polar coordinates architecture, and minimal number of moving parts, is that the Polar3D printer doesn’t tend to require frequent calibration. However, occasionally you may want to check and adjust its calibration.

There are three general types of calibration of the Polar3D printer: (1) the z height of the extruder, (2) the alignment of the center of the build plate along the x-axis, and (3) the consistent levelness of the build plate. (Three dimensions implies three calibration adjustments – but because the Polar3D printer operates in polar coordinates, with a spinning build plate achieving both x-axis and y-axis movements, rather than a separate and distinct y-axis calibration, calibration of the Polar3D printer’s movement in the xy-plane is achieved via x-axis calibration and build plate levelling.)

In more detail, the three calibration areas are as follows:

1.

z height (the most important/most commonly in need of adjustment calibration item): If the z height of the extruder is slightly high, the first print layer (first layer of material extruded) may only be lightly touching the build plate, instead of being “smooshed” so that it adheres to the build plate. If the z height is too low, filament either may not be able to come out at all, or may come out too “smooshed” and actually flattened. You will want to check that the tip of the extruder nozzle is just above (a thin sheet of paper higher than) the build plate surface.

2.

x-axis (more rarely an issue): The center of the build plate¹ should be located directly under the extruder nozzle of the print head when the build plate is homed: neither too far forward, nor too far backward. This is more conveniently checked when the build plate itself is removed from the build plate shuttle: compare the alignment of the extruder nozzle vs. the center of the drive gear bearing on the build place shuttle.

3.

Consistent levelness of the build plate (very rarely an issue): The build plate should remain at a consistent height relative to the extruder tip, even when sliding forward or back. Check the z height with the extruder at the middle of the build plate; then slide the build plate forward² so that the extruder is at the edge of the build plate and confirm that the z height hasn’t changed. If the z height is changing from middle to edge of build plate, then:

(a)

The build plate shuttle arms in the back of the printer (near the Z rod) may be bent downwards. Push these arms up gently until the extruder nozzle stays at the same height across the entire radius of the build plate.

(b)

The pads that the build plate mirror rests upon may be slightly off. This is normally checked at the Polar 3D factory when the printer is assembled, but something might have happened to throw off this alignment after leaving the factory, so it is worth checking to confirm that the mirror is still properly aligned.

Calibrating a Polar3D printer’s z height and x-axis (items 1 and 2) is performed using the printer local web interface’s “Calibration” screen. But the “Calibration” screen, and the process overall, differs between Polar3D 1.0 printers (where the process is more manual), vs. Polar3D 2.0 and 2.5 printers (which have a more automated calibration feature).