What Are The Minimum Reliable Printing Distances?
I've starting designing things in 3D Fusion with intentionally tight clearances on parts. On printing I quickly found that the printed objects just barely didn't fit. Does anyone know what the accuracy tolerances of the printer are?
Best Answer by Diem:
Your basic unit of accuracy is one extrusion width, the default for a 0.4mm nozzle is 0.45mm.
Gcode geometries define the central line of extrusion so the exudate squidges out by 0.225mm on either side.
Generally, with FDM, it's not worth attempting precision closer than 0.1mm; you can go finer but it gets lost in squidge.
Separation between print-in-place parts is easy down to about 0.25mm, you *can* get to 0.1mm but it requires some devious manipulation to prevent re-melting as the printhead passes and the consequent seizing.
You can use soluble filament to separate complex print-in-place parts but then your smallest gap is one extrusion width.
For parts that must fit together, especially keys/sockets, 0.2mm is usually enough tolerance but you may need a little light sanding to remove nubs.
Remember that curves are often exported as high count polygons and be aware that if you are outputting lower precision to reduce file size there is a nasty possibility that convex curves meant to fit concaves might be expressed with a different facet count causing corner misalignment.
And don't forget that your part is printed hot and will contract as it cools, this can make a significant difference with longer extrusions - look up the the coefficient of thermal expansion for the specific polymer and calculate the calibration.
Cheerio,
RE: What Are The Minimum Reliable Printing Distances?
I think this varies from printer to printer. You can print a tolerance test like this one https://www.printables.com/model/116911-clearance-tolerance-test
You print it, try to rotate the nubs and see up to which clearance they work without binding up during printing. This gives you a rough idea on what clearances you need to design in.
Your basic unit of accuracy is one extrusion width, the default for a 0.4mm nozzle is 0.45mm.
Gcode geometries define the central line of extrusion so the exudate squidges out by 0.225mm on either side.
Generally, with FDM, it's not worth attempting precision closer than 0.1mm; you can go finer but it gets lost in squidge.
Separation between print-in-place parts is easy down to about 0.25mm, you *can* get to 0.1mm but it requires some devious manipulation to prevent re-melting as the printhead passes and the consequent seizing.
You can use soluble filament to separate complex print-in-place parts but then your smallest gap is one extrusion width.
For parts that must fit together, especially keys/sockets, 0.2mm is usually enough tolerance but you may need a little light sanding to remove nubs.
Remember that curves are often exported as high count polygons and be aware that if you are outputting lower precision to reduce file size there is a nasty possibility that convex curves meant to fit concaves might be expressed with a different facet count causing corner misalignment.
And don't forget that your part is printed hot and will contract as it cools, this can make a significant difference with longer extrusions - look up the the coefficient of thermal expansion for the specific polymer and calculate the calibration.
Cheerio,