Introduction
What’s interesting about 3D printing is the micro-millimetre measurements when it comes to the settings in your slicing software and machine firmware.
When levelling the print bed, and getting the first layer height correct, this is done in 0.1mm increments. The tolerances really are that fine. The only reliable way to get these correct while eliminating guesswork is by using calibration prints.
Calibration
Unless you’ve gone out of your way to test your printer with calibration objects, it’s likely that your prints aren’t quite as good as they could be. The commercial 3D printer I started out with didn’t need vast amounts of calibration. Once I had the bed-height set correctly in the firmware, not a lot else was needed.
The dual head Flsun i3 I purchased and rapidly customised was the complete opposite. Because I replaced many of the original parts, the dual extruders in particular, calibrating this printer was critical.
The bed, frame and extruder alignment needed particular attention, but getting the retraction rates right on the extruders improved print quality significantly. This is where calibration objects came in and simplified the process dramatically.
Calibration Prints
There are dozens of test print models on Makerbot Thingiverse focussed on testing the calibration of your printer.
The two in particular that I found most useful for dual head calibration and retraction tuning were these:
Both are fast easy prints to produce, and it’s easy to measure and calculate the adjustments that you need to make.
- The calibration process itself is relatively simple. Do a test print with one of these as your starting point.
- Adjust the firmware/process settings and determine whether the calibration got better or worse.
- Print and tweak until the calibration is correct.
Marlin G26 - Mesh Validation Pattern
The Marlin firmware can be configured to make printing of a test pattern possible, that allows you to confirm the bed levelling mesh values.
As the Marlin firmware documentation states; “The G26 command prints a single-layer pattern over the entire print bed, giving a clear indication of how accurately every mesh point is defined. G26 can be used to determine which areas of the mesh are less-than-perfect and how much to adjust each mesh point.”
Whether you’re using a auto-level sensor or some other means, this test pattern can help visualise where problems exist. Similarly it can visiually confirm when everything is right.
G26 doesn’t take long to print even on a large bed, and problems reveal themselves immediately.
Summary
Calibration prints take all the guess work out of fine-tuning your printer settings. On big prints when things go wrong, it’s not always obvious what you need to adjust.
Calibration prints are small, fast and allow lots of settings to be tested quickly.
It might be the case that on a larger scale some problems still exist. G26 is particularly effective at helping eliminate these across the print bed, without doing a big print to find them.