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AON-M2 Machine Calibration

X-Y Tool Calibration

This guide will walk you through the process of calibrating the position of the T1 toolhead with respect to the T0 toolhead. It is necessary to make this correction for any prints that involve using both toolheads on the same model. This includes support material prints.

Warning

Before proceeding with the X-Y tool calibration:

* Ensure Z calibration has been performed for **both tools** prior to conducting this procedure
* Load ABS filament material on both toolheads
* Ensure thermal stability of the printer prior and during the calibration process

**Notes:**

* Do not attempt to modify the X-Y offset of 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 material other than ABS, however different operating temperatures may be required

When to recalibrate the X-Y tool offset

Calibration of the X-Y tool offset 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 a normal operation and the machine may require small adjustments and recalibrations over time.

Procedures requiring recalibration of the X-Y tool offset:

  • Changing nozzles – AON3D recommends that you replace the entire heater block assembly instead of individual nozzles
  • Removing the heat sink from z-probe fixture
  • Removing the heater block assembly (HBA) from heat sink assembly
  • Changing heat breaks – AON3D recommends that you replace the entire heater block assembly instead of the heat break

Objective

The purpose of calibration is to line up the material printed using T0 with the material printed using T1. If the procedure is not performed, the two tools will become misaligned and the material printed by the two toolheads will be shifted in either the X or the Y axis.

Procedure

Use the M218 command with appropriate X and Y coordinates to modify the coordinate system of the T1 tool with respect to the coordinate system of the T0 tool. Please note, for this process, T0 tool head remains "static", while the M218 command changes the T1 position with respect to the T0 position. Therefore, when changing the offset one is looking to move the printed features of T1 rather than T0 and treat the positioning of T0 as correct.

Calibration Procedure Outline

  1. Home all axes
  2. Determine T1 tool home position
  3. Start Test print
  4. Observe printing behaviour and record offset error
  5. Stop Test print
  6. Modify T1 offset values, via the terminal and M218 G-code command
  7. Start Test print to verify offset change
  8. Observe printing behaviour and verify that offset error has been reduced
  9. Stop test print
  10. Continue modiyfing offset (#6) or start your print

Repeat steps 3 through 5 as required to achieve the desired level of precision in your calibration. The following sections outline the AON3D recommended calibration factory file and detail the execution of the process.

X-Y Calibration Factory File

Download the X-Y calibration GCode file. This file will help you calibrate the X-Y tool offset. The file contains a simple square shape. The process is configured to have four "brim perimeters" and both hot ends set to ABS operating temperature. Temperatures have been set for use with AON3D approved ABS filaments.

You can also download the X-Y calibration factory file which allows you to create customized GCode scripts to acconmodate dual tool head calibration using filament material other than ABS. Once the G-code script is created, you can upload it to the printer.

What does the calibration print do?

Tool heads printing alternating brims

Once you hit print, each toolhead will print 2 "brim" perimeters. A brim is a single track of material deposited around the outside perimeter of a part. As the print proceeds, the toolheads will alternate, each printing a "brim" perimeter, until each tool has printed 2 times around the outside of the square. At this point, the T0 tool will then take over to print the perimeters of the part, while T1 will print the infill of the part.

Calibrating the Printer

  1. Ensure the calibration G-code file has been uploaded to the printer.
  2. Note the initital T1 tool position by entering the following commands via the Terminal:
    • G28 ; Home all Axes
    • T1 ; Select T1 as the active toolhead
    • M114 ; Report current or initial X and Y tool coordinates
  3. Take note of X and Y coordinates.
  4. Press print! Observe the printing process. Point of interest is in understanding where the T1 tool is printing with respect to the T0 tool.
  5. Once the T1 offset is estimated, stop the print. Alternatively you can let it finish.

To Modify the T1 X-Y Tool Offset

To modify the T1 X-Y tool offset, stop the print, and enter the following G-code command to the terminal:

M218 T1 Xn Yn
G28
M500

Where the coordinates X and Y are calculated with:

Xn = Xinitial + ∆X
Yn = ∆Y

Initial Location Xinitial is obtained from homing the T1 tool, then polling the printer with the M114 command. The addition of Xinitial is only required when setting the X offset because of the orientation of the gantry system and the parked positions for the two tools.

∆X and ∆Y are obtained from visual inspection of the printing behaviour of the two brims and using calipers if required.

Recall:

  • Increasing the X value will move T1 to the operator’s left
  • Increasing the Y value will move T1 toward the front of the printer

Please Note: All units are in mm!

Example:

  1. Determine T1 Home position.
    G28
    T1
    M114
    > X:527.90 Y:-40.00 Z:0.00 E:0.00
    
  2. Test print: Run the X-Y Calibration G-code.
  3. The following was observed by the operator: ∆𝑋 = 10 , The T1 tool is printing 10 mm to the right of the ideal position ∆𝑌 = 10 , The T1 tool is printing 10 mm to behind the the ideal position
  4. To correct this, we need to bring T1 forward and to the left of the current printing location. This is accomplished by entering the following into the terminal:
    M218 T1 X537.9 Y10**
    G28
    M500
    

Verify Offset Performance

Once calibration of the X-Y offsets is complete, run the X-Y calibration G-code once more to verify that appropriate changes have been made. This procedure may need to be repeated to achieve the correct offset positions.

Z Probe Calibration

Lastly, once calibration of the T1 X-Y offsets is complete, you will need to probe the bed with T1 again to compensate for the changed probe positions in the X-Y plane.

Congratulations!

The X-Y tool calibration process is complete. You are now ready to start dual-material printing with your AON-M2.