Fiber 3D Printing

Why and how is it different from normal 3D printing

Fiber 3D printing is very similar to FDM, or a normal thermoplastic (like PLA) printing. In both case, the material filament passes through the hot extruder, melts the thermoplastic/bonding material in the filament, and then deposits the material as per the g-code.

But fiber 3D printing differs from plastic 3D printing in few things

• Fiber has a fixed width - While plastic can melt and take available space, fiber has a pre-defined width. For FabMachines F3 Fiber 3D printers, it is 2mm. The width of fiber cannot reduce if space is not available

• Fiber cannot take sharp turns - Since fiber has a finite width, and is continuous, it cannot take sharp turns. Instead, it has a minimum turning radius which needs to be taken into account when printing walls and infill with Fiber. As a result, it is difficult to have 100% infill density with Fiber alone. The remaining area can either be filled with plastic, or left vacant depending on the design.

• Fiber cannot overlap - Ideally the fibers should not overlap. An overlap will lead to definite material build-up, unlike plastic printing, where slight overlap just results in additional packing of material in the current layer

• Fiber needs to cut - The biggest difference from plastic printing is that fiber needs to cut after each segment, before moving to next segment. This is because fiber is a continuous entity, and each travel move will require a cut in the fiber.

• Fiber should have continuous walls - In the simplest example, say you are printing only 3 outer walls with fiber. In plastic printing, one can

> Print Wall#1
> Retract and/or travel
> Print Wall#2
> Retract and/or travel
> Print Wall#3

But for fiber, retraction or travel won't cut the fiber, and hence, ideally, all 3 walls need to be printing in a continuous curve (think of a wall curve spiraling in). If you want to print all 3 walls separately, that's also possible, but that will introduce 3 cuts in your fiber wall. A cut in fiber inherently leads to less strength. Hence a continuous wall is recommended

• Fiber cut is hardware dependent - While most of the print params in plastic printing are hardware independent, FIBER_CUT_DISTANCE is an important factor in fiber printing. FIBER CUT DISTANCE is the distance of the cutting point from the nozzle exit point, and it equals the distance which the fiber printing nozzle will travel after cutting the fiber. This happens because the fiber cannot be cut exactly at the point of nozzle exit. Once you cut the fiber, the cut part (attached to the already printing fiber) will continue to print till the end of segment. The next segment of fiber (behind the cut part) will stay behind the cutting point. When the next fiber print segment starts, this new fiber portion will be extruded equal to FIBER_CUT_DISTANCE before the printing nozzle starts moving.

• Fiber print requires minimum length - Since the FIBER_CUT_DISTANCE is a fixed value for a hardware, any curve with length less than this value cannot be printed with fiber. In other words, your fiber-print segment start point and end point should be at least as far as FIBER CUT DISTANCE, otherwise there will be leftover fiber after the segment is printed. This leftover can cause overlaps and other issues. This can also lead to certain perimeters having fibers, while others don't (because of perimeter length being less than FIBER_CUT_DISTANCE