One issue with fused filament fabrication is the weakness introduced into the parts at the layer boundaries. I had this simple idea of how especially straight sections of 3D prints could be improved on regular printers. Now I found time to test my idea.
Linking Two Layers at the Perimeter
The principle is simple. A gap is kept open after a few layers between the outer and inner perimeter line(s). The line in this gap is printed as the last operation before the layer change.
The line is split into small, equal-sized sections printed in a zig-zag pattern on the Z-axis. This pattern rises from the current layer height to the next layer height (e.g. 0.2mm).
The illustration above shows how this special link perimeter line is embedded between the outer and inner perimeter lines.
Photos
The link perimeter line has peaks, one layer height higher than the current layer height. In the photo, you can see how the flat area of the printer nozzle shapes this line.
The peaks of the lines are merged with the next layer and bond these layers vertically.
Limitations
Nozzle Movement
As the printer nozzle ends in a flat area around the opening, the length of the segments needs to be large enough to allow the filament to reach that height before it gets pressed down from the edge of the printer nozzle. I found a section length of 2-3mm works well with a 0.4mm printer nozzle.
Outer Wall Angles
The slicer needs to know the position of the link perimeter line on the next layer to move the Z-axis and the printer head into the spot where this line will be. This is only possible up to a certain angle; other strategies must be used.
Pattern Alignment
As the link perimeter line pattern has to be aligned with the next layer, it makes sense to use an absolute height pattern with the same offset for all layers of the part. This ensures that a peak in the line always matches the shape of the line in the next layer.
Demonstration GCode
I prepared demo gcode files for PLA on a Prusa i3 MK3S+ printer.
The file pipe.gcode is a regular print, and the file pipe_vc.gcode is modified with a link perimeter line. Test these prints on your printer at your own risk.
This demo gcode was created by processing a suitable gcode with a simple Python script, adding movements in the Z axis to existing commands. This feature would need to be integrated into slicer software to use the technique universally. Yet, I do not have the required knowledge for full implementation.
Conclusion
Even when the printed zig-zag pattern is crude and imperfect, it breaks the uniformity of the layers. This makes it harder for a crack to propagate into the part along the layer line.
If you have questions, missed any information, or wish to provide feedback, add a comment below or send me a message.
Happy printing!
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