FDM 3D printing is the process of extruding a semi-liquid thermoplastic through a print head tip along a pre-determined tool path to create models and prototypes. Stratasys has transcended expectations to make the FDM process accurate, repeatable and reliable. In this article, we discuss the step-by-step process of calibrating a printer head to ensure the best possible prints.
The F123 3D printer series from Stratasys offers four different slice heights with an accuracy of +/- .008”, all from a single T14 tip. Not only should print heads be changed when the recommended life cycle has been reached, but also when switching to a different material. For example, let’s look at ABS and Diran 410MF07. The extrusion temperature of Diran 410MF07 is significantly higher than that of ABS. If any residual Diran 410MF07 was left in the head, when you tried to print using ABS the tip wouldn’t reach a hot enough temperature to extrude the remaining Diran 410MF07. This would result in a clogged printing head.
Once the new head is installed, you want to make sure there is no material loaded into the heads and no build tray installed in the machine. Following these best practices will help ensure the material will not become clogged in the head during this step and provide the most accurate calibration.
You can then navigate to the Tools page and select Calibration. Next, you will select Tip Calibration. You then have the option to choose either Automatic Tip Calibration or Manual Tip Calibration.
By selecting Automatic Tip Calibration, the printer will automatically calibrate the tip offset values in the X, Y and Z directions. It is important that these values are calibrated properly as they will determine the accuracy with which model and support materials are dispensed during the build. Failure to calibrate could result in subpar surface finish or print failure if geometries are improperly supported.
Notice that it approximates the automatic tip calibration to be seven minutes. However, this number could vary as the oven must increase or decrease temperature to reach the necessary temperature for this process. The estimated time to completion will update automatically and display on the screen.
Once the automatic tip calibration is complete, press Finish then proceed to initiate the Manual Tip Calibration by pressing Start. The manual tip calibration inspection process involves printing the calibration part, inspecting it using a magnifying glass and inputting the correctional values using the touchscreen user interface. Once you adjust the values, press the Apply button to accept the changes.
*Manual tip calibration is unnecessary for TPU 92A, as the automatic tip calibration will suffice.
Using the magnifier provided in the machine startup kit, inspect the calibration values on all four sides (X1,X2,Y1, and Y2) respectively, and determine where the support material is centered along each side between the alignment indicators. Each number represents .001”. For example, if the support material is most centered at Y1 = 4, then the calibration needs to be adjusted .004”. Use the sliding scale icons to match the location on the calibration part to the location on the touch screen. Repeat this process for the three remaining sides.
Next, remove the support material from the inner square. Using a pair of calipers, measure the Z height on all four sides using the average of the four as the Z offset. For the most accurate measurements, be sure to take them from the center of each side, the space near the corners may provide inaccurate information.
Figure 1: First calibration box
In Figure 1 above, notice where the support material is most centered on each side, circled in blue. You will input these values using the sliding scale that will automatically appear after the manual tip calibration has been completed. Using the blue up and down arrows, adjust the Z height to the reading on the calipers.
Once all the calibration parameters have been input, press Apply, and the changes will be made. Next, simply print another calibration box to confirm that the calibration is accurate. When the tips are fully calibrated, the machine is ready to print.
Figure 2: Final calibration box
In Figure 2 above, the support lines are centered at the zero mark on all four sides indicating that the tips are well calibrated. After checking that the X and Y calibrations are accurate, check the Z height once more using a pair of calipers to confirm that the support slice height is 0.010″. Once all these steps are complete, the tips are properly calibrated and your Stratasys F123 Series printer is ready to begin building.
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