All Glossary

3D Slicer

A slicer is software that can cut a 3MF, OBJ or STL 3D model file into hundreds or even thousands of layers and then control a printer to print them layer-by-layer.

Key phrases linking here: slicer software, the slicer, 3d slicer, stl files, a slicer, g-code - Learn more

Details

Slicing software converts an 3D STL, OBJ or 3MF file (exported by CAD software) into slices of G-Code print-head movement, extrusion and temperature instructions. Many free and paid slicer products are available. These formats can exist because of standards developed over the years in the 3D design industry. Slicers handle infills (e.g. a honeycomb pattern instead of printing pieces solid) and print supports to hold up sections that flare outward (most 3D technologies cannot print over thin air!).

Each 3D design package saves files in a format that geometrically describes the shape (along with parameters, features, and history), a fully functional "blueprint". They export 3D geometry into these standardized formats that slicers can import. STL files have enabled the companies producing 3D design software to offload the complex slicing task (and driving the hundreds of available 3D printers) to other companies. They also enable the existence of online distributors of printable 3D model files (like TurboSquid, Thingiverse, Printables).

We have experience with Slic3r (of which Prusa Slicer is a fork), Simplify 3D and Cura. We drove my first cheap 3D RepRap printer via USB cable using Simplify 3D (it costs about $150), that machine was frustrating but that slicer eased things quite a bit (it was very good at generating support and had drivers for hundreds of printers). Simplify 3D has also turned out to be better in some ways than the version of Cura used in our Creality K1 Max. But Prusa Slicer wins, it is a truly beautiful piece of software. We use it in on our Prusa MK3S and MK4S (it's free and included). It’s major advantage is how intimately it is tied with all their printer models. Through its default settings and easier interface I have discovered rafts, better fills, manual filling, better overhang printing, cutting, placing, rotating, sizing. And its native project format is 3MF.

I have learned to depend on tools in the slicer for things that I used to do in the CAD software (especially replication and cutting objects up to print them in multiple pieces and orientations). Experience with using your slicer can cut print times dramatically (especially with avoidance of printing support), I am doing prints now it one-quarter the time simply because of being smarter about it.

The advantages of printing via an SD-card or USB stick and letting the printer handle everything are also significant (e.g. it is possible to pull the plug out of the wall and recover a partial print on restart!). That being said, printers now have web interfaces, either by directly acting as an independent access point or as an agent tied to cloud services of the printer provider. This sounds great but, like me, the frustration of getting and keeping that complexity working may send you scurrying back to printing via memory stick.

One issue with printing is that sometimes models are not "airtight". Some slicers can simply fail a print, others are able to join any unconnected lines and print the item anyway. This happens when doing surface modelling (e.g Blender or editing STL files), not likely in solid modelling where the software generates all the surfaces from the geometry of the piece.

Slicers can also handle the burden of updating the software in a 3D printer (when printing is being done from a computer via USB or Wifi and the slicer is tied to a particular brand of printer). Typically, when the slicer itself updates it can also download printer firmware or configurations.

Related Information

G-Code 3D Printer instructions

This picture has its own page with more detail, click here to see it.

Simplify3D knows how to convert the 3D geometry generated by Fusion 360 into G-Code (shown in the black text window lower right). I have just told Fusion 360 to print this and it automatically launched this and passed the 3D geometry to it. Simplify3D is a "slicer" because it knows how to convert a 3D object into slices that a 3D printer can lay down (one on top of the other). Simplify3D is fairly expensive and competes with a number of free products (like Slic3r, Cura). It gives me a 3D view of the object and enables positioning and rotating it on the bed and configuring dozens of parameters. It is about to deliver the G-Code (via a USB connection) to my RepRap 3D printer (although it is often preferable to use the "Save Toothpaths to Disk" button to generate G-Code and write it to an SDCard which the printer can accept). The black text-edit window shows what the G-Code looks like. It is just text. With hundreds of thousands of commands that mostly move the head to successive X-Y positions and a defined filament feed-rate.

3MF vs STL vs OBJ files for 3D printing

This picture has its own page with more detail, click here to see it.

Shown here are Creality Slicer, Prusa Slicer and Simplify 3D. Each of these can import STL, OBJ and 3MF files. Each permits resizing, rotating, reflecting and duplicating individual items and can efficiently place and space multiple items and groups. Each saves or exports as 3MF files. On the right is the Fusion 360 print dialog where I can choose which slicer and which format to send.

OBJ files were introduced in 1980 for visual rendering (e.g. animation, gaming, special effects). Files store surface geometry as interconnected triangles and define surface textures, materials and colors. These features were overkill for early 3D printers.

STL (Stereolithography) files were developed in 1987 by 3D Systems specifically for CAD and 3D printing, having a single focus on geometry. They were simple and computationally efficient (and also unitless like OBJ, assuming mm). STLs permitted only one object. They dominated early 3D printing processes (FDM, SLA, SLS), where color or texture was irrelevant and provided a simple standard for industry growth. However, modern printers can now do color, texture and multi-material, thus...

3MF (3D Manufacturing Format) files were introduced in 2015 specifically for more advanced 3D printing. To OBJ they add object orientation, units, printing instructions and meta information. Objects in 3MF files can be manipulated separately in the slicer.

All three formats are generated by modern CAD software (for handoff to a slicer app). 3MF is the preferred one.

Prusa Slicer keeps getting better

This picture has its own page with more detail, click here to see it.

I have just 3D printed from Fusion 360, it has handed over the geometry to the Prusa Slicer app (shown here). Slicers are not just for printing, they are getting more and more powerful at manipulating, orienting and sizing images before printing - relieving the CAD program of some of the burden. As an example, I have cut this mold in two and turned the top section upside down. In view of the fact that this creates an unneeded join, why do it? Because it minimizes the amount of printed support needed (the insert on the bottom shows the support it deems necessary). The flat tops of both pieces are down therefore they require zero support. And, because prints are precise the two halves fit together so well that the seam is barely visible.

The Prusa Slicer generates G-Code for 3D-printing

This picture has its own page with more detail, click here to see it.

This slicer ships with, and is recommended for, the Prusa line of 3D printers (when you click to print something in your 3D design software (e.g. Fusion 360) it sends the 3D geometry to your chosen slicer software, that software drives the actual printer). Simplicity and the exact visual reproduction of the printed bed make this a good choice for slicing (slicing is the mathematical process of cutting a 3D object into layers that can be printed successively). Another advantage is that online help for this printer will generally assume the use of this slicer. There are a myriad of settlings and parameters that printing software must respect to adapt to each type of 3D printer and the pairing of the Prusa printers with this slicer will be the best.

Links

By Tony Hansen Follow me on

Got a Question?

Buy me a coffee and we can talk