What 3D Slicer Software Does and Why You Need it

Curtis Satterfield, Ph.D.

Curtis Satterfield, Ph.D.

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If you are new to 3D printing you may have heard that you will need a slicing program or slicer for short. In this article we will review what a slicer is and why you need it for 3D printing.

3D printers need specific machine instructions telling them how to print your model. The models downloaded from the Internet or created in a 3D program must be converted to G-Code that the printer can use. A slicing program converts your model into the necessary G-Code for your 3D printer.

The slicer also allows you to change settings that will affect the quality of your print. In addition to calibrating your 3D printer, properly configuring the slicer for your printer will have a huge impact on your print successes. There are numerous settings to work with in a slicer and we will examine some of the most common.

What is the purpose of a 3D Slicer?

When you download or create a 3D model for printing it is stored in a common 3D file format such as an STL or OBJ file. These files allow your computer to read and interpret the information in the file to display the object on your computer screen. However, your 3D printer doesn’t understand how to turn the data from an STL file into a 3D printed object. For that you need to use a slicer to convert the information in your STL file into machine readable G-Code.

G-Code is a language that instructs a machine tool how to carry out tasks. The G-Code tells a motor or motors on a machine where to move, how fast to move, and what path to take. Let’s look at an example. I will slice the 10x10x3mm cube pictured below in Simplify3D.

3D printable 10mm cube in 3D Slicer

In the image below I have sliced. I have changed the view to show only the first layer of the printing process.

First Layer Tool Path in 3D Slicer

The dark grey cylinder represents the tool head, in our case the print nozzle. The color of the line denotes what part of the print it represents. The dark purple is a skirt, the blue is an outer perimeter, the light blue is inner perimeter and the green is a solid layer. Each of these colored lines represent where the printer will extrude filament. Now let’s look at the G-Code that the slicer generated to produce this layer.

The first layer of this print was 187 lines of code long. I have chopped out most of the movement G-Code to shrink it down for an image. In the image below … represents a section of code I removed to reduce the code line count.

GCode from a 3D printer file
Each line in the above code has a G-Code command associated with it. The letters and numbers after the command tell the printer how to carry out the command or rather what parameters to use when doing the command. G-Code is an entire topic and I won’t cover it in detail for this article. The purpose of the image was to show you what the G-Code looks like from the slicer. For our 10x10mm box the entire file was 2,283 lines long. That’s a lot of information for such a small print. The larger and more complex your print the longer the G-Code file will be.

Once the G-Code file has been generated by your slicer you can transfer it to your 3D printer and begin printing. That is the most basic assessment of what a slicer does and why you need it for 3D printing. The above example was a model that was sliced and prepared for printing on an FDM printer. We will talk about resin slicers later in the article. In the next sections we will dive into more detail about different slicers and important slicer settings.

Common Slicer Programs

There are a lot of Slicing programs available today including both free and paid options. Here is a list of some of the most common programs:

FDM Slicers

SlicerOperating SystemsCost
CraftWareWindows, Mac, LinuxFree
CuraWindows, Mac, LinuxFree
ideaMakerWindows, Mac, LinuxFree
MaterControlWindows, Mac, LinuxFree
PrusaSlicerWindows, Mac, LinuxFree
RepetierWindows, Mac, LinuxFree
Slic3rWindows, Mac, LinuxFree
SliceCrafterBrowser BasedFree
Tinkerine SuiteWindows, MacFree
Z-SuiteWindows, Mac, LinuxFree
KISSLicerWindows, Mac, Linux, Raspberry PiFree/$35
Netfabb StandardWindows$1,000 – $4300 annually
SelfCADBrowser$9.99/Month
Simplify3DWindows, Mac$150

One of the most used free programs is Cura by Ultimaker. Cura offers a great program that many in the 3D printing hobby use as their primary slicer. When I first starter 3D printing, I used Cura and it was perfect for my needs. I have since purchased a license for Simplify3D which I now use as my primary slicer. If you are just starting out there is no need to purchase a slicing program with the variety of free slicers available.

Resin Slicers

SlicerOperating SystemsCost
ChituBoxWindows, Mac, LinuxFree
Formware 3DWindows$155 personal/$360 commercial
Photon Open SlicerWindows, Mac, LinuxFree
PrusaSlicerWindows, Mac, LinuxFree
Zortax Z-SuiteWindows, MacFree

There are not nearly as many resin slicers as budget level resin printers have only become common in the past couple of years. One of the most common slicers used for printing with budget resin printers such as the Elegoo Mars or Anycubic Photon is Chitubox. I use both PrusaSlicer (for automatic support generation) and ChituBox for actual slicing of my models. PrusaSlicer is more well refined than ChituBox but it only generates files for printing on the Prusa SL1. So, I must slice my models in ChituBox to print on my Mars.

Each slicer has its own pros and cons and it is a matter of personal preference as to what slicer you end up using. While I highly recommend starting with Cura or ChituBox, don’t be afraid to try other slicers and see if they offer better features. You may also prefer the look and feel of one slicer over another. Each slicer interface is different in how you interact with the model and the settings for your print.

Common FDM Slicer Settings

Ok, we now know what a slicer is used for and the names of several common slicing programs. Time to dive in and look at the most common slicer settings that you will be changing. When you first download a slicer and run it for the first time it will ask you what type of printer you are using. Most slicers come with a library of printer profiles pre-installed for you to choose from. If your printer isn’t listed, you will have to manually enter your printer parameters.

Cura slicing program add a printer dialog box
The Add a printer dialog box in Cura

Selecting a printer from the add printer list auto-populates the settings with a default profile for the printer. This is a great starting point for most printers and overtime you will begin to tweak these settings to better suit your printer. Part of printer calibration involves finding the best slicer settings for your printer. As you continue to 3D print you will find that you usually only need to adjust a few settings in your slicer before printing. Some of the most common settings you might change are the layer height, extruder and bed temperature, infill percentage, and support generation.

Layer Height

Layer Height Settings in Cura Slicing Program

The height of your printing layers affects the level of detail in your print and how long your print will take. Lower layer heights such as .16 take longer to print but offer better detail. Higher layer heights such as .3 and above will decrease the total print time but you will also lose detail in your print. Using a .2mm layer height is a decent balance between quality and print time. If you are curious about how long 3D prints take you can read my article here.

Extruder and Bed Temperature

Extruder and Bed Temperature Settings in Cura Slicing Program

Each filament brand and type you use will have a certain temperature that offers the best print quality. When you start using a new roll a filament in your printer try printing a temperature tower to find the correct extruder temperature. Then stick with that temperature whenever you use that roll of filament. Printing too hot can lead to stringing and messy prints. Printing too cold can lead to under extrusion and filament grinding.

Infill Percentage

Infill Settings in Cura Slicing Program

Printing every layer as solid in a 3D print will use extra time and material that may not be necessary. The amount and type of infill you use will depend on what you plan to do with the 3D print. If you plan to put it on the shelf as decoration, a low infill percentage of 5-15% is probably fine. If the print will be subjected to loads or stress you may need to increase the infill percentage.

As infill increases, print time and material used increases. The infill pattern will also affect the print time and material use. If you are just starting out, I recommend sticking to cubic as that tends to be the fastest and offers good structural support.

Support generation

Settings for Support Generation in Cura Slicing Program

If you are printing a model with extreme overhangs you will want to use support. Let’s look at an example. The image below is a model of a tabletop miniature for gaming.

3D Tabletop Gaming Model

There are several areas on the model that will need support in order to print properly. Either the angle is too steep, over 45 degrees, or the layer would be printed in mid-air. Adding support helps with the issue. In the next image you will see where the slicer added supports.

Normal Supports added by Simplify3D slicing program

The gray rectangles are the supports that were added by the slicer. The supports are designed to add structure to the model for printing but easy to remove after the print is done. Using supports will allow you to print more complex models, but it will also use more filament. Sometimes the use of supports can also leave damage on the print if the supports do not separate freely.

The middle option in the supports tells the slicer if it should generate supports from only the build plate or everywhere on the model. In the image above supports were set to be generated everywhere. This may not be optimal as the supports printed on the model may leave damage when removed. Below is an image of the same model sliced with supports only from the build plate.

Build plate only supports added by simplify3D

As you can see there is much less support generated with this setting. Because the support is only generated from the build plate it reduces the chances of damage to the model from support removal. The downside is that all the areas that need support may not have it. Experience with printing will help you determine when support is necessary and when you can do without.

Other Important FDM Settings

The settings we talked about in the prior section are not the only settings we need to consider. There are other setting that will greatly affect the quality of your prints that you will need to calibrate and adjust. Once you find a good setting you will not need to change it as often as the previous settings we discussed.

Print Speed

Cura print speed settings

This setting can have the biggest effect on both your print quality and your print time. Running the printer too fast will result in a poor-quality print. Running the printer slowly will improve the quality but will increase the total print time. Spend some time calibrating your printer and testing different print speeds to find out what works best.

Retraction

Retraction settings in Cura

This setting tells the extruder to reverse direction effectively removing pressure that has built up in the nozzle. As the print head moves from one island to the next the built-up pressure will cause the filament to ooze from the nozzle resulting in stringing. By using retraction, the pressure is released on the nozzle and the filament will not ooze during non-print travel moves. There is a bit of an art to getting your retraction settings just right for your printer so this will take some experimentation.

Cooling

Cura cooling settings

Applying cooling to the filament as it is laid down helps it solidify more quickly and helps with bridging. When using PLA, the most common setting is to start your fan at 100% on layer 3 of the print. Starting at a layer lower than three can cause the print to warp and peel off the bed. Be aware that some fans and printers don’t work well at speeds slower than 100%. If you try setting your fan speed below 100% and it hums, buzzes, or doesn’t turn on, you will need to run it at full speed.

Shell

Cura shell settings

The shell settings determine how thick the outside or “shell” of your model will be. Wall thickness determines how thick the horizontal walls of your print are while top and bottom determine the thickness of the vertical surfaces. These settings directly relate to the overall strength of your model and they can also affect the quality.

If your models seem to be fragile and are easily crushed, try increasing the wall thickness. If you have problems with the quality of the top of your print, try increasing the number of top layers. If you have a large open area that the top layers are bridging it will take more layers to get a good solid finish.

Common Resin Slicer Settings

When using a resin printer, you will find that there are less options than an FDM slicer. The main settings that you will change in your resin slicer will be the layer height and the exposure times.

Layer Height

Print settings in ChituBox Resin Slicer

Like FDM printing the layer height affects the quality of the final print. Layer height also affects the total print time leading to a balance of quality versus speed. The big difference is the size of the layers in resin printing. If we look at our 10mm cube example from earlier, the print will have 15 layers using a .2mm layer height. If we slice the same model in Chitubox it will require 60 layers at 0.05mm layer height to print.

The lower the layer height the better the detail but the longer the print will take. If you need high quality prints you may want to try printing at .03- or .025-layer height. However, some people argue that the difference in quality between .05 and .025 is negligible and not worth the added print time. This comes down to personal preference and what you plan to do with your resin prints.

Exposure Time

Each resin that you use will have a different exposure time that results in the best print quality. I recommend running a resin exposure test on each type of resin you use. Having determined what the best exposure time is you can enter that number into the exposure time setting. The bottom exposure time should be about 10-12 times the layer exposure time.

Conclusion

While we did not cover all the settings in a slicer this article should give you a good idea of what a slicer does and why it is required for 3D printing. As you continue with 3D printing you will gain experience with different slicers and their settings. As you gain more experience you will learn what effects slicer settings have on final print quality. Coupled with 3D printer calibration slicer settings have a big impact on the success and quality of your 3D prints.