Probably the most important step in 3D printing is the slicing- the conversion of a 3D mesh into a set of toolpaths for the extruder in the form of gcode. There are several options for software to do this, and they will all create gcode a little differently, giving slightly different results for the same model.
I wanted to do a survey of a few different slicers and really get a definitive feel for how they differ. My choices were-
Slic3r 0.9.7-, the latest version. It was released after I started printing, so I also used-
Slic3r 0.9.5/6- Though one release back from 097 there were distinct differences. Slic3r is the most configurable of the slicers, at least in the settings that are more widely understood by printer users. For instance you can set different speeds for outer perimeters, inner perimeters, small perimeters, infill, etc to find the balance between quality and speed.
Slic3r 0.7.2b- After this version, Slic3r had a total rewrite, which many consider a step back in quality. Many users continue to use this version, though it lacks some of the newer features and is prone to running out of memory when slicing medium to large models at .1mm resolution.
Skeinforge 39- This is the version of Skeinforge that Solidoodle includes in their installation. The biggest difference from 50 is that the flow rate is not calculated automatically and must be set by the user. It is written in Python, and can take an hour or more to slice what Slic3r will process in minutes.
Cura- Developed by an Ultimaker user, this is a front end for Skeinforge 50. SF50 has some more features such as Skirt, and the calculation of flow rate by filament diameter. Cura runs it under PyPy, which is a more optimized, faster version of Python.
KISSlicer- developed by a user of Bits from Bytes printers, this slicer is faster even than Slic3r. I don’t think I’ve seen it ever take more than a minute.
I configured all of these to use the same settings, as closely as possible. Not all have as many speed variables as Slic3r, so I set all the speeds to 50. The flow rate modifiers (ie Slic3r’s Extrusion Multiplier) were tuned to output at .42mm thick single wall. There are some differences in cooling, since Slic3r and Cura could run a fan for small layers, but Skeinforge 39 could not. KISSlicer has fan control, but it runs on all perimeters rather than activating for layers that take less than a minimum time.
The first print I did was Make Magazine’s Torture Test, which they used to review printers. I used Tinkercad to add some extra torture to it.
There are some vertical holes one on side to see how the overhangs are handled at the top, as well as roundness.
The arch is a test for overhangs and gradual curves. The overhanging corner is impossible to do cleanly, but we can see how cleanly they manage. There are tiny columns and a wedge that tapers to a fine edge. Also there are interior holes to check for dimensions, and a recessed slot to see how solid top layers midway up the print are handled.
There is an array of columns, two of them turned into tubes one of which has a wall thin enough to require a single thread. Another column has a 45 degree chamfer to the outside and a gradual fillet on the top edge which can create gaps. The array of columns is a test for retraction, to see if there is stringing as the extruder moves from one column to the other. I also added a bar across the top of the cube to test bridging.
A couple of the cube walls are very thin to test the filling of narrow areas. There is a wide cylinder inside with a chamfered edge. The underside of that cylinder also has a chamfer, which is a 45 degree overhanging curve to the inside, in contrast to the outside chamfer on that column on the corner.
In the next post we will get started looking at the results of this print.