I got an email recently asking about all the various options in Slic3r, the awesome gcode generator by Alessandro Ranellucci. Specifically, my friend wanted to know how to configure Slic3r so that his 3D prints would use much less plastic.

It was long overdue for me to sit down and figure out exactly how all the various Slic3r options altered plastic consumption. So armed with the latest version of Slic3r (0.9.2 at the time of writing), it was time to crunch some numbers! First I needed a fairly complicated model with a mixture of overhangs, tall skinny elements, and large slab elements. Hopefully a shape that was fairly ‘average’, as the shape of your object will alter how each of the print settings affect plastic consumption. By using an ‘average’ shape, hopefully the following can be used as a rough guide for tweaking plastic consumption in your 3D prints.

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I decided the robot design from the Rise of the Machines workshop was a fairly decent starting point as an ‘average’ model. First I ran it through Slic3r with some fairly default settings and opened the resulting gcode in pronterface. The right hand terminal displayed exactly how much plastic filament the print is going to consume:

1670.63834 mm

This gives us a baseline to work from, now it is just a case of running the robot design through Slic3r numerous times, only adjusting one setting at a time. Both halving and doubling, the value. Then opening it up in pronterface to see how plastic consumption has changed:

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Layer Height:

  • Height: 0.8mm - untestable. The nozzle diameter on my 3D printer is 0.5mm, and you can’t print a layer height greater than the diameter of your nozzle.
  • Height: 0.2mm - 1670.63651mm (0.00%)

Perimeters:

  • 4 - 1938.63426mm (+16.04%)
  • 1 - 1604.73862mm (-03.94%)

Solid Layers:

  • 4 - 1892.90031mm (+13.30%)
  • 1 - 1572.47925mm (-05.88%)

So the above settings are all about the outside shell of a 3D print. How tall each layer should be, and the thickness of the shell. So nothing hugely surprising here, a thicker shell means you use more plastic. However, I did find the negligible difference from changing the layer height interesting. I guess I thought a smaller layer height would have also translated into thinner walls.

So what about the settings that configure what is going on inside the outer shell?

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Fill Density:

  • Fill: 0.4 1866.93105mm (+11.75%)
  • Fill: 0.1 1596.03338mm (-04.47%)

Fill Pattern:

  • Concentric: 1736.08333mm (+03.92%)
  • HoneyComb: 1760.13316mm (+05.37%)
  • HilbertCurve (slow): 1630.34629mm (-2.41%)
  • Archmedeanchords (slow): 1630.84554 (-2.38%)
  • Octagramspiral (slow): 1601.16466mm (-4.16%)

Top/Bottom fill Pattern:

  • Concentric: 1684.75343mm (00.84%)
  • Hilbertcurve (slow): 1667.46809mm (-00.19%)
  • Archmedeanchords (slow): 1667.56679mm (-00.18%)
  • Octagramspiral (slow): crashed.

Ok, so increase the fill density use more plastic. Decrease and use less. However, what is interesting is the Fill pattern, use 5% more plastic just by selecting honeycomb? Now that is a little surprising, I was expecting negligible results more inline with the Top/Bottom Fill Pattern. I would have thought that the fill density to be the constraining factor - I only want the volume inside of the shell to be 20% full of plastic, use this pattern to specify the gaps.

Overall, the three most important parameters for plastic consumption are:

  • Fill Density
  • Perimeters
  • Solid Layers

Doubling values for these settings has a tendency to increase the amount of plastic used in a print by about 10%. While halving them only decreased plastic usage by about 4%.