This guide will walk you through the process of calibrating the position of the T1 toolhead with respect to the T0 toolhead. This calibration is necessary for any prints which use both toolheads on the same model. This includes support material prints.
1.1 When to calibrate the X and Y tool offsets
Calibration of the X and Y tool offsets must be done every time a hot end assembly (or toolhead) has been manipulated in a way that affects the nozzle’s relative position to the carriage. This is part of normal operation and the machine may require minor adjustments and re-calibrations over time.
Procedures requiring re-calibration of the X and Y tool offsets:
- Changing nozzles – AON3D recommends that you replace the entire heater block assembly rather than individual nozzles
- Removing the heat sink from the Z-probe fixture
- Removing the heater block assembly (HBA) from the heat sink assembly
1.2 Objective of X and Y calibration
The objective of the calibration is to line up the material printed by T1 with material printed by T0. Without this procedure, the two tools may be misaligned and the material printed by the two toolheads will be shifted in the X and/or Y axis.
2 X and Y Calibration Process
Required Tools & Equipment
- The two spools of ABS filament included with the M2 printer
- Calipers or another measuring tool
M218 G-code command will be used to modify the coordinate system of the T1 tool with respect to the coordinate system of the T0 tool. Please note, for this process, the T0 toolhead remains “static”, while the
M218 command changes the T1 position with respect to the T0 position. When changing the offset we are looking to move the printed features of T1 rather than T0 and treat the positioning of T0 as correct.
The X offset obtained from the calibration represents the distance in X from the origin (placed at the front left corner of the build plate) to the nozzle tip of the T1 toolhead in its parked position, as shown in the figure below. The Y offset is simply the distance in Y from the nozzle tip of the T0 toolhead to the nozzle tip of the T1 toolhead, in their parked positions.
- Ensure probe offset calibration has been performed for both tools prior to conducting this procedure
- Do not attempt to modify the X and Y offsets of the T1 tool during the printing process
- Offset calibration should not require changes of more than 10 mm from the nominal offset value
- You can use filament other than ABS, but different print settings, including operating temperatures, may be required
2.1 X and Y Calibration High-Level Procedure
- Home all axes
- Determine T1 tool home position
- Start test print
- Observe printing behaviour and record offset error
- Modify T1 offset values via the terminal and
- Restart test print to verify offset change
- Observe printing behaviour and verify that offset error has been reduced
- Repeat the cycles as required to achieve the desired level of precision in your calibration.
The following sections outline the detailed execution of the process summarized above.
2.2 X and Y Calibration Factory File
Download the X and Y calibration G-Code file. The file contains a simple square shape. The process is configured to have five “brim perimeters”. Temperatures have been set for use with AON3D validated ABS filament: 230°C extrusion temperature, 105°C bed temperature, and 80°C chamber temperature.
If you haven’t already, load the two spools of ABS filament provided with your machine on T0 and T1. Note that the filaments are different colours to easily distinguish the printed features on T1 from the printed features on T0. You can also download the X and Y calibration factory file which allows you to create customized G-Code scripts to accommodate dual toolhead calibration using filament material other than ABS. Once the G-Code script is created, you can upload it to the printer.
Before starting a print, the printer must be at thermal equilibrium. Make sure to preheat the bed and chamber to the operating temperatures for your chosen material. For ABS, you should be at 105°C bed temperature, and 80°C chamber temperature. The operating temperatures for other AON3D-validated materials can be found here.
2.3 The Calibration Test Print
Once you hit print, each toolhead will print 5 "brim" perimeters. A brim is a single track of material deposited around the outside perimeter of a part. T0, the left toolhead, will print 5 brim perimeters first (blue). T1, the right toolhead, will then print 5 brim perimeters inside those printed by T0 (green).
At this point, the T0 tool will take over to print the first layer of the part.
For the rest of the print, T0 will print the perimeters while T1 prints the infill.
When the print finishes, the toolheads will move back to their parked positions in X. The hot ends are turned off so as to avoid clogging filament inside the heater block while adjustments to the offset are made. The chamber and bed heaters are left on to allow you to start another print shortly after.
2.4 Calibrating the Printer
All units are in mm!
- Ensure the calibration G-Code file has been uploaded to the printer
- Note the initial T1 tool offset:
M218 T1in the terminal tab
- Note the X and Y values output on the screen. An example output is shown below. If the X and Y values read "0", the offsets have not been adjusted from their factory state, and will be X:526 and Y:0.
- Start the calibration test print by tapping Print beside the calibration print G-code file in the files tab.
- Observe the printing process. Note the position of the T1 print relative to the T0 print.
- Once the print has finished, estimate or measure the T1 offset in X and Y. These will be
∆Yto the X and Y values from step 2. These will be your new X and Y offsets.
- Increasing the
X offsetvalue will move features printed by T1 to the operator’s left
- Increasing the
Y offsetvalue will move features printed by T1 toward the front of the printer
Y offsetvalue should be smaller than +/- 2 mm
X offsetvalue should be larger than 500 mm
- To modify the T1 X and Y tool offsets, make sure the print has stopped, and enter the following G-code commands to the terminal:
M218 T1 X[X offset] Y[Y offset] G28 M500
M500 command saves the offset values entered.
- To fine-tune the calibration, repeat steps 3-7 until you are satisfied with the relative printing position of the two toolheads.
Once you have calibrated the T1 X and Y offsets, it is necessary to probe the bed with T1 again to compensate for the changed probe positions in the X-Y plane.
2.5.1 X and Y Offset Calibration Example
- G-code file is uploaded to the printer
- Determine initial T1 offset:
< M218 T1 > Hotend offsets: X:0.00 Y0.00The offsets have not been adjusted from factory state.
- Test print: Run the X and Y Calibration G-code
- The following was observed by the operator:
The T1 tool is printing to the right of the ideal position
The T1 tool is printing in front of the ideal position
- The offsets are measured:
∆X = 3.5 , 3.5 mm to the right of the ideal position
∆Y = -0.6 , 0.6 mm in front of the ideal position
- The new offsets are X529.5, Y:-0.6
X + ∆X = 526 + 3.5 = 529.5
Y + ∆Y = 0 + (-0.60) = -0.6
- The T1 X and Y offsets are modified by entering the following into the terminal:
M218 T1 X529.5 Y-0.6 G28 M500
- To fine-tune the calibration, the operator runs the X and Y Calibration G-code file again. This time, no offset is visible while printing. When the print is completed, the operator measures the gap between the infill (T1) and the outline (T0) and finds there is still a small offset:
∆X = -0.2, 0.2 mm to the left of the ideal position
∆Y = 0.1, 0.1 mm to the back of the ideal position
X + ∆X = 529.5 + (-0.2) = 529.3
Y + ∆Y = -0.6 + 0.1 = -0.5
The T1 X and Y offsets are modified by entering the following into the terminal:
M218 T1 X529.3 Y-0.5 G28 M500
To confirm the calibration, the X and Y Calibration G-code file is run again. This time, no offset is observed, and no offset is measured.
- The operator probes the bed with T1 again to compensate for the changed probe positions in the X-Y plane.
The X and Y tool calibration process is complete. You are now ready to start dual-material printing with your AON-M2.