Introduction: Guide to Slic3r

About: I make stuff. #makermovement

Slic3r, the main g-code processor for RepRap 3D printers, can be a little daunting when you are just starting out with your new printer. It can be very frustrating when one little setting is off by a millimeter and your entire print is wrecked. But that is why I decided to write this guide. I will go through each of the settings and help you decide exactly how the particular model your trying to print should be sliced. So lets get started, and please vote if this is helpful!

Step 1: Understanding Slic3r

Slic3r's job is to take your 3D model (.STL or .OBJ are the most common) and change it into a GCODE file. A gcode file is basically just a bunch of X, Y and Z coordinates that tell the printer constantly where to move the extruder to next. To change the .STL to gcode, though, Slic3r needs a lot of information about how you want your model to print. In the next step I will tell you how to give it this information. Read on.

Step 2: Layer Height

Layer height

Layer height determines the resolution of your print. This is very important if you are printing a detailed or very small model. The lesser you set the layer height, the higher the resolution. But there's a catch: it will take way longer to print, because it has to do more layers. Above is a comparison between some different sample layer heights.

Setting the Layer Height

To set the Layer height in Slic3r, click on the "Print Settings" tab, next to "Plater". In the first category that comes up, "Layers and Perimeters" set the layer height. As a rule of the thumb, I usually do 0.25 millimeters. This is faster than some, but will give a very nice overall print quality. After that, set the "First Layer Height" to 0.35.

Step 3: Shells


Shells are like the outer walls of a 3D print. They cover the infill inside of them and give the print a smooth finish. They also help strengthen the print, so more shells, or more layers of wall, gives a tougher part.

Setting Shells in Slic3r

To set the shells in Slic3r, just scroll down and change them. I usually set all of them to 3, which is pretty strong, but still prints quickly.

Step 4: Infill


To conserve filament and cut down on printing time, g-code generators create a grid like structure inside the object, called infill. This is opposed to completely filling in the object, which would take a very long time to print, or, on the other hand, having a completely hollow print, which would be very weak.

Setting Infill in Slic3r

Click on the "Infill" category under the "Print Settings" tab. Then set the fill density as required. If you want a strong part, do 50 to 100 percent. If you are printing something that will not be under strain, 10 to 50 percent will work fine. The next thing to set is the infill pattern. I usually use honeycomb, as it is very strong even with a low fill density, but any of the others work just as well.

Step 5: Speed


A very important setting in Slic3r is speed. As with 2D printers, 3D printers yield lower quality prints when printed fast, but of course this is the most straightforward way to cut down on printing time. The key with print speed is to know where to tell the printer to go fast, and where to go slow. Here's some general speed tips:

  • More quality = less speed
  • More speed = less quality
  • Perimeter speed should be much slower than infill speed
  • External perimeter speed should be slowest
  • Infill can go fast because no one will see it
  • Support material can go faster than perimeters but should be slower than infill

Setting speed in Slic3r

Click on the "Speed" category under the "Print Settings" tab. Using the tips above and the image of my usual configuration, work out a good speed for your model. Just remember, if you want more detail and quality, go slower.

Step 6: Skirt and Brim


The skirt option in Slic3r is not essential but useful at times. It extrudes a loop around your object that is there simply to get the extruder clear before starting on your print. I usually use it, because it isn't hard to do, and it results in fewer wrecked prints.


Brim is very useful if you have problems with bed adhesion (the object won't stay stuck on the print surface) because

bed adhesion problems usually happen when the bottom of the model doesn't have enough surface area. Brim fixes that by making a single layer hold the model down. If your model is small, you may want to use brim. When I use it, I usually do about 10 mm.

Note: Skirt and brim cannot both be enabled or brim will try to print over the skirt, moving the extruder up. If you have brim enabled, it will do the skirt's job as well.

Step 7: Support Material

Support Material

Support material is very important in 3D printing. Without it, you would only be able to print models without any overhangs. 3D printers cannot extrude filament into the air, because it would of course droop and the model wouldn't print correctly. To fix this, you can print the supports, usually thin pillars, to give the printer something to build on top of.

Setting Support Material in Slic3r

To set support material in Slic3r, click on the "Support Material" tab under "Print Settings", then click the check box to enable it. Leave the "Overhang Threshold" to 0, as Slic3r is pretty good at detecting what areas need supports. Also leave the "Enforce Support for the First" to 0 layers. Skip past the "Raft layers", as we'll cover that later. On the "Options" panel change the pattern to the best choice for your model. The best all around support material pattern is pillars, but if you need a lot of support, go with honeycomb. The pattern spacing should be around 2.5 mm. Leave the "Pattern Angle" at 0, unless you want rotated supports. I always put the "Interface Layers" to 1, because the supports are easier to remove. All 3D printers are different though, so you'll have to experiment with yours. Then leave the "Interface Pattern Spacing" to 0 mm and the 'Don't Support Bridges" box checked.

Now your done with the print settings tab!

Step 8: Filament Settings


Under the "Filament Settings" tab, change the extruder temperature to your filament's melting point. As a general rule, 180C for PLA and 230C for ABS. Also set the bed heat according to your filament's instructions. Right above the temperature, set the "Filament Diameter" to your filament size (usually 1.75 or 3 mm) and leave the extrusion multiplier at. If you are printing in PLA, you may want to turn the extruder fan on while printing. To do this, click on the "Cooling" tab right under "Filament", then click the check box to enable "Auto-cooling".

Step 9: Load Model

Load Model

Now that your done with all the settings, it's time to load a 3D model. Slic3r support .OBJ and .STL files. To load one, go back to the "Plater" tab at the top, then click the "Add" button directly below it. Browse to a 3D file and select it. You can now scale, rotate, and view your model via the command bar at the top. When your ready, click the "Export G-code" button on the right. Browse to a folder to put the g-code file in, then hit save. It will slice (which may take a while) and when it's done, send the g-code to the printer and print away!

Note: If you need some models to print, try these websites: Thingiverse, YouMagine, or Grabcad.

Thanks for reading, hope it was helpful! If it was, please vote!

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