When using a dual extrusion printer it is important to calibrate the distance between the nozzles in X and Y direction. A properly calibrated printer will produce parts without a visible shift between sections printed with the left and the right extruder. In this article I wil discuss the use of a calibration program to find the offset between the nozzles on the Flashforge Dreamer.
It can be quite difficult to measure the offset between sections printed with each extruder on actual parts. Therefore several 3D printers manufacturers use a calibration routine similar to that used in inkjet printers with 2 or more cartridges. A 2D pattern is printed on which the user can determine the correct offset in X and Y direction by looking for the best aligned marks.
I found a calibration routine on the Sailfish firmware website that seemed like a nice straight forward method for calibration.
Since I did like the idea behind this procedure, I replaced the G and M codes to make the program compatible with the Dreamer and made some changes to the pattern, like extending the center line in the pattern (target line) and I added a small square to prime the nozzles before the start of the print.
Update 15-04-2018: updated program to Rev2, which now includes z-hop (lifting nozzle) between each line to minimize risk of nozzles scraping lines off the platform.
The calibration Gcode file for the Dreamer can be downloaded using the link below:
Click the link and copy the text into a text file with the file extension “G” instead of “TXT”. The Gcode file can be transferred to the printer using an SD card or by using the Flashprint software.
The calibration procedure works as follows: a line pattern is printed with both extruders. The pattern contains horizontal and vertical lines, of which only the line in the middle of the pattern is perfectly aligned between the two extruders in the Gcode. The other lines in the pattern are increasingly misaligned the further they are away from the center line, with 0.1mm increments. This means the first line next to the center line has a 0.1mm offset between left and right extruder, the second line a 0.2mm offset and so on. See screenshot below (click to enlarge).
My specific printer has an X offset of 34.2mm and a Y offset of 0.0mm. The offset can be found under Tools -> “On Board Preferences” in Flashprint.
When you change this offset and confirm by pressing OK, the new offset is uploaded to the printer and becomes effective immediately. Note that the offsets are limited to one decimal.
When the calibration program is printed, look for the set of marks that are best aligned. In the example below the printer is properly calibrated (center marks show best alignment):
It may be difficult to check alignment when simply looking at the print. Taking a picture and reviewing it on the PC makes it much easier to assess the pattern.
Now let’s take a look at a test print when the X and Y offsets between the nozzles are intentionally misaligned. X is gives an additional offset of +0.2mm and Y +0.4mm. (In this specific example the X offset becomes 34.4 and Y becomes 0.4mm in the onboard preferences menu)
The results for this test are shown below:
As can be seen in the enlarged detail views, the misalignment in the software settings carries over to the printed pattern. This means the calibration procedure works as intended.
Below is a video of the entire procedure in action:
If you have any questions about this procedure let me know in the comments.