Wednesday, July 2, 2014

Choice of slicer for hollow printing...

People occasionally ask me which slicer I use... the answer really is "it depends". It depends what I'm printing. Over time I've found that different slicing packages are good at different aspects of printing. A good example of this was when I tried printing this Worldcup Trophy. It's quite a large object and some reported it taking up to 6hrs to print and consuming around 10m of filament, even with a relatively low infill percentage. I felt printing it hollow was the best approach. This would considerably reduce the print time and material consumed and should be achievable.
Worldcup Trophy, standing about 22cm high including Alzibiff's base.

From experience of different slicer programs I've tried out, I've found Ultimaker's slicer "Cura" to be the best at printing hollow objects that close in at the top. When you slice a large object with Cura and set it to 0% infill it 'scribbles' support material on the inner walls when the walls close to a shallow angle as it nears the top. It can be seen as brown lines in Cura's Layers View Mode (below).
This additional sidewall support works well and allows a hollow object to close in completely without any internal infill or internal support construction. The successfully closed in top of the trophy print can be seen in the picture below. The print is hollow.

To complement the trophy, a nice base was designed and shared by Alzibiff, incorporating some nice raised text. I printed it in contrasting green and gold by simply "guesstimating" the length of green needed for the first part, then feeding some gold, then feeding some green to conclude the print. If the print rate is slowed down, as is possible with the speed slider control in Repetier Host, it's possible to watch the cut filament disappear into the extruder then manually feed the next colour into the extruder by hand until the hobbed bolt grips the newly fed filament.

One point of note if you are trying out Cura to slice for a RepRap printer is that Cura calculates Extrusion distances in "absolute" measures, where as RepRap printers generally expect "relative" extrusion distances. To accommodate this simply place an "M82" command in the Start.gcode section of Cura. M82 makes the extruder interpret the extrusion as absolute. M83 sets relative extrusion.

Thanks for viewing!