3D Thursdays are an on-going set of blog posts that dig into the world of 3D printing as we develop our knowledge and skills of the process and then present them to you to further both your understanding and ours.
Once we mastered the very basics of the 3D printing process, it was time to take these steps and extrapolate them into designing and printing our own pieces. Printing pre-made items is a much simpler task when all you are doing is downloading a file and importing into your 3D slicer program, all with previously defined settings.
This post will focus on what exactly slicing means when it comes to 3D printing and how the changes apply when you start going off on your own.
Slicing is a term mentioned before with very little explanation. Slicing programs like Slic3r are the go-betweens to take 3D files we built in Google Sketchup and AutoCAD and turn them into .x3g files that the printer can read.
Slicing imports your design and then gives you hundreds of options as to how you want your item to print. The first steps are setting up your ideal settings with varying results exclusive to each piece printed. [SEE FIGURE 1 & 2]
Some of the variables include ‘rafts’ which are the first things printed that literally create a plastic raft between the heated bottom plate and the beginning of the object printed. Think of it like a wood pallet used in warehouses—it elevates it off the ground just enough that the real product doesn’t get ruined. [WE ALMOST ALWAYS USE RAFTS WITH 4 LAYERS.]
In conjunction with the rafts is indicating both the ‘first layer height’ and the overall ‘layer height.’ The first layer height is typically a bit thicker than the rest of the layers and prevents any heat warping that may occur at the beginning of the print. This is commonly seen when you have sharp edges that get so much heat that the corners contort and curl upwards. When this happens, it might be prudent to stop the print and reevaluate the thickness of your rafts and first layer height before further mistakes are made. [OUR FIRST LAYER HEIGHT IS ALWAYS 0.35mm ALL REMAINING LAYERS ARE 0.2mm.]
Another factor is ‘supports,’ which is literally what it sounds. Extra little pieces are printed that fill the gaps of parts that have little structural support while still in the printing process; they are just big enough to provide stability, but small enough that you can break them off after the process is complete. [WE ALWAYS USE SUPPORTS UNLESS THE OBJECT IS COMPLETELY SOLID AND HAS NO AREAS WHERE DROOPING MAY OCCUR.]
Next comes ‘perimeters.’ This is another term simply named, but can have a multitude of factors dependent upon what you are trying to print. Perimeters are the outer-most layers of the print and typically the thickest parts of the item. It’s at this point where you will quickly see whether or not the printing is going to resemble what you want it to be.
The perimeters create the structure necessary for the next step of determining the printing ‘infill,’ which will be explained next. Before infill begins, the ‘solid layers’ setting also has to be defined, which is just like perimeters but refers to the top and bottom of the print, basically sealing it all up on every side. [WE USE A MINIMUM OF 4 PERIMETERS AND 3 TOP AND 3 BOTTOM SOLID LAYERS, BUT OFTEN UP THAT NUMBER IF WE NEED TO BE STURDIER IF REGULAR FORCE WILL BE APPLIED TO THE OBJECT.]
The aforementioned ‘infill’ majority of the printing process and refers to all of the printing substance within all of the perimeters, both horizontally and vertically. Infill has several settings, the first being the ‘fill density,’ which is the percentage of space you want filled. 100% infill would literally be every single layer is one complete slab on top of each other and would just be a back and forth filling each layer. [ SEE FIGURE 3 BELOW]
Whenever you use an infill of anything less than 100%, you also have to choose a ‘fill pattern’ and the ‘top/bottom fill pattern.’ These patterns vary and include: line, Hilbert curve, honeycomb, 3D honeycomb, rectilinear, Octagram Spiral and Archimedean Chords. These all may seem like complicated math terms, but in reality are just various non-solid methods of giving the printed item inner strength. Without explaining every version of pattern, honeycomb is pretty self-explanatory, as is line, but check out [FIGURE 4 BELOW] to see a visual understanding. [WE TYPICALLY USE A FILL DENSITY OF 40%, FILL PATTERN OF HILBERT CURVE AND A TOP/BOTTOM FILL PATTERN OF CONCENTRIC.]
There are also some standard infill settings that we rarely change within the Slic3r program such as: ‘Combine infill every: 1 layer,’ ‘Solid infill every: 0 layers,’ ‘Fill angle: 45 degrees’ and ‘Only retract when crossing perimeters.’
There are dozens of other general settings that can be tweaked depending on what you preferences are and are typically changed with some trial and error printing. We rarely mess with the rest since we are still fairly new to the process, but the last settings we make sure to change are the ‘filament settings’ [ENTIRELY BASED ON WHAT FILAMENT YOU PERSONALLY BUY AND USE; OURS IS 1.75mm.] and ‘extruder and bed temperature’ [WE’VE LEARNED TO INCREASE THE TEMPS. SLIGHTLY FROM STANDARD TO ENCOURAGE THE FIRST FEW LAYERS TO PRINT FLAT: EXTRUDER TEMPS @ 240 DEGREES CELSIUS AND BED TEMPS. @ 115 DEGREES CELSIUS.]
This may seem like a lot—that’s because it is to start. It took us probably 50 prints before we started getting exactly what we wanted and we still struggle when it comes to printing new pieces. Next post we’ll dig more into our own creations now that we have a decent understanding of how to properly prepare the 3D printing files.