FDM - Helpful Tips
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Fused deposition modeling follows this path for production:
A plastic semi-molten filament is unwound from a coil for the purpose of supplying material to an extrusion nozzle.
The nozzle is heated in order to melt the plastic. It has a mechanism to allow the flow of the melted plastic to be turned on and off.
The mechanical stage, where the nozzle is mounted, can be moved both horizontally and vertically.
As the nozzle is moved over the table in the proper pattern, it gives off a thin bead of extruded plastic, which form each layer. The plastic hardens immediately upon release and bonds to the layer just below.
This system is completely contained in a chamber held at a temperature just below the melting point of plastic.
When the first layer is complete, the platform lowers by one layer of thickness and the process starts all over again.
There are some possible defects associated with the FDM process. Some of these are:
A Staircase Effect – Refers to the surface roughness arising from the layer by layer deposition of the FDM material
Curve-Approximation Errors – This refers to the .stl file triangulating all surfaces of a part, making the curved surface a series of connected triangles.
Inter-Road Defects – This happens when two roads do not bond together
Knit-Line Errors – This refers to the filling of an area being segmented due to software limitations, making internal holes between two segments.
Top/Bottom Errors – This is when there is an undesirable roughness on the bottom of the part due to the first layer being in contact with the foam platform. The top error is a ridged effect due to deposited material making a rounded form
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