On this page we will discuss the concept of slicing - as a broad, top-level topic, not the specifics of slicing in individual software environments.
I.e. we will discuss the concept of layer height, but not the location of the layer height setting in any specific piece of software - because each software will vary.
Thus we're only going to talk about concepts of slicing.
Slicing as word implies turns the digital 3D object into slice upon slice of data for the 3D-printer to print, layer by layer.
Think of the process in reverse. You have a physical plum tomato. Using a serrated paring knife you cut the tomato into a dozen slices. Now the tomato is fleshy and soft so it oozes liquid and each slice will lose its form, but you could still re-stack the slices to resemble a tomato. Slicing software works in a similar way with varying options: it slices digital objects in order to stack them layer by layer using a 3D-printer to turn that data into a recognizable object.
(The point about the serrated paring knife is an important analogy: depending on the type of knife you use, results will vary. The same goes for slicing software and slicer settings. The choices you choose - the settings - matter.)
Slicing is primarily concerned with the following concepts: shell, speed, and volume (including both layer height and infill) - and also temperature. Other concepts like raft, brim, and even supports may not be necessary - but you will want to learn them in order to produce successful prints.
So we know the .STL is an outline, the contours of a 3D shape. The .STL is a 'shell' in the same way an egg has a shell - there is an exterior layer protecting all the stuff inside. When you prepare a shape for 3D-printing you decide how many shells the print will have.
2 shells is generally considered a good balance of integrity & strength versus time & consumption of material. Most software will be defaulted to 2 shells.
In the example below the orange is the outer shell, and the yellow are inner shells. You can see in one frame the shape has 2 shells, and 3 shells in the other frame. Doesn't seem like such a huge difference:
But then take a closer look at how changing a simple setting has different output results:
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2 shells:
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3 shells:
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Slicer software will usually provide you with very useful data about material consumption & time - all based on your settings. In this example we see how setting the print to have 2 shells uses 2.33 meters of material and requires 57 minutes and 47 seconds of time to complete the print; setting the print to have 3 shells uses 2.51 meters of material and requires 59 minutes and 49 seconds of time to complete the print. The difference of 0.18 meters of material and 2 minutes may seem negligible, but if you had to produce x12 of the same print that minute setting change will require 2 extra meters of filament and nearly ~30 minutes of time! If you were buying your own material and factoring in time to your costs, these settings would be important.
Rule of Thumb: 2 shells is a good balance of strength versus time and material usage.
As the name implies, Layer Height is the 'height' of each layer of the print. The standard for measurement is micron. One micron is equivalent to one millionth of a meter. This is equivalent to one thousandth of a millimeter - 0.001mm. Thus 100 microns is equivalent to 0.1mm - therefore it takes 10 layers at 100 micron layer height to produce a 1mm high print. Whew!
At this point you'll notice we're using a lot of metric measurements - even if you 'design' your object in Imperial units you will ultimately use metric for 3D-printing. It is a good idea to learn both, and to know which one you are using at any given time.
As previously noted the .STL is just a shape - it is hollow on the inside.
And if the shells determine how many outlines the print gets, what fills up the inside?
The infill has two primary properties: density & pattern.
The density is a number, a percentage - e.g. 5%, 15%, 50%.
The pattern is descriptive of a design - e.g. linear, honeycomb, triangles, etc.
15% may sound like a small number, but when filling in empty space with physical material it winds up being a lot - for 3D-printing it is often plenty, and remember every choice is a balance of time versus material usage, etc.
So for example in the following image 4 different patterns are shown, each with a 15% density:
(Click the image for a larger version.)
The patterns available will vary software to software - so the above examples are examples only. Density is more standard: again 15% is generally considered a good balance of time and material usage. 15% tends to provide enough strength to the integrity of the print while allowing it to print quickly and not use too much material.
Similar to the 2 shell / 3 shell table above, we can see the time & material differences affected by the infill density:
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5 percent infill:
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15 percent infill:
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25 percent infill:
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50 percent infill:
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You may think you need to 'push the limit' and infill your print with 50% or more, but generally speaking 15% is fine. 15% is a good balance of time and material - as seen in the table above - while providing the model with enough internal support to hold everything in place. In fact once you begin increasing the infill density the pattern itself may be unrecognizable - in the image below this is the same honeycomb pattern set to 75% infill:
Keep in mind the print head has to follow each of those outlines - known as moves. Each move takes time, uses more material, and only increases the chance of something going wrong. So simply increasing the infill density to 75% requires nearly twice as much material as 15% infill density, it nearly doubles the overall weight of the print, and would take nearly 60% longer to complete. With no added benefit.
Rule of Thumb: 15% infill density is a good baseline when getting started with 3D-printing.
Temperature as the word implies is a measurement of heat - of the hot end of the 3D-printer's extruder.
Temperature is almost always discussed in Celcius - not Fahrenheit. So if you write a number down or find some random number online associated with a material, it is likely Celcius.
A quick analogy: Have you ever gone into a deli? You probably have. Have you ever noticed that there are different types of water for sale? You probably have. What's up with that? Different types of water. And they all taste different! But water should just be water, right?
The question is rhetorical because we all know the answer is that it depends on where the water comes from, how it is treated and purified, etc.
The same goes for PLA. There is no universal PLA, but lots of different brands, vendors, and material compositions. Because of this there is no universal temperature setting.
But generally speaking PLA has a temperature range of 190℃–220℃.
For 3D-printing in the QC Makerspace with PLA, 210℃–215℃ is regarded as a good baseline for most geometries and speeds. (Temperature and speed are closely related and commonly overlooked, especially when it comes to troubleshooting failed prints.)
Simple software will likely only have one temperature setting - this is the temperature setting of the hot end throughout the duration of the print.
'Advanced' or 'expert'-level software will give you granular control of the temperature setting - allowing you to adjust the temperature of the first layer as distinct from the rest of the print.
If you're 'getting started' with 3D-printing we recommend using 210℃ or 215℃ throughout your prints until you really understand how temperature operates layer by layer.
You've read a lot on this page - you've come really far. But unfortunately the most overlooked and perhaps the most difficult setting - speed - was saved for last. So take a break if you need - get up and stretch - and let's dive back in when you're ready.
If speed is a measure of distance during a unit of time, we typically measure speed in millimeters per second.
Speed is relative to many things: the material, the temperature, the infill pattern, etc. All those settings 'pass through' the speed setting - put another way the speed setting is how all those other settings get interpreted, as in at what speed, measured in millimeters per second.
A millimeter may be relatively small to humans, but that doesn't mean we should set the machine to travel as fast as possible. For instance most 3D-printers may be capable of extruding plastic at say 200mm/s, but that doesn't mean it's a good idea. (Spoiler: it isn't.)
Similar to how there is no universal PLA temperature setting, there is no perfect speed setting. You will have to experiment, and learn.
And this is where it gets tricky! With infill you likely only have one setting for density and one setting for pattern. With layer height you generally only have one setting to worry about. With temperature you have usually at most two settings, and usually only one. But with speed, you may have two, three, or even five or seven settings. This is why speed is such a tricky issue.
Simple software typically has:
That's the simple version! More complex software will typically allow you to also set the speed for:
You can see 'speed' has many applications, and it will always depend on what you're printing.
That's why there is no universal 'just use these numbers and you'll be fine' setting, and also why it's vital to look at the settings used by others to determine a baseline approach for your own prints.
OK we intentionally set up speed to sound scarier than it really is. Some software may 'auto adjust' the speed settings in real-time, but if you want control over your print (or if the software doesn't have a 'smart' 'auto' feature) you'll have to learn the various speed settings.
All that said, let's go over some numbers now!
The three main speed settings to keep in mind are:
For travel speed generally somewhere between 90mm/s to 120mm/s is good - even up to 180mm/s can be fine. Remember this is when the printer is not extruding. For example say you have two objects on the build plate, and they're spaced apart. The travel speed is absolute and will apply to the distance between the two objects at the same layer - in this image this is layer # 1071:
When the printer completes the layer on the object on the left, it will then speed up to the travel speed when it is not dispensing plastic and migrate to the object on the right (and vice versa). It will then adjust to the speed of the perimeter setting.
For perimeter speed this is the speed you probably want to pay the most attention to. There really is no 'perfect' setting. It all comes down to the geometry of your print. We're referring to all those polygons of the .STL. You can imagine you probably want to have different shell speed settings for these two example files:
The file on the left has a lot of little squiggles, arcs, and curves; the file on the right is entirely straight lines (and right angles). Mechanically there's a lot less 'work' the machine has to do in the print on the right than the print on the left, even though the print on the right effectively travels farther, and therefore dispenses with more material.
Of course these are just sample single layers from prints that have hundreds if not thousands of layers. You don't change the speed setting layer by layer - you set a single setting for all layers. How to choose the correct speed for all the layers? There is no answer other than trial and error.
If you are only afforded a single perimeter setting something in the range of 25mm/s would be good for the file type on the left (with lots of 'small perimeters' and degree changes) whereas something around 50mm/s should be fine for the file type on the right. (Sadly, some programs are defaulted to 90mm/s (or more) when you open the slicer software, which leads to many beginner getting frustrated with failed prints early on in their 3D-printing adventures.)
¹ The reason for having an "outline" shell that may (or may not) be treated at a different speed than the interior shells, is because the 'outline' is the one you see - it is the most exterior shell. Because the exterior shell is the one you actually see, you may want to give it a different speed setting - typically a slower setting, so as to give it a 'finer' treating.
The final speed setting to really be aware of is the infill speed. Similar to the perimeter speed mentioned above this setting really depends on the two properties associated with infill: density, and pattern. You can imagine a pattern like grid or rectilinear will mostly be straight lines, and could probably be set to a marginally faster speed than stars, honeycomb, or 'specialty' infill patterns. Somewhere between 40-60mm/s is broadly supported, and you may even be able to go higher if your hollow interior is very large and your pattern is very simple.
In the following example of an architectural print - a tower - we see infill density at 15% and 7% (slightly under half of 15%) using a 'diamond' pattern:
Because the print is scaled so large, filling in all that empty space even with 15% density seems like overkill. 7% looks like it should provide plenty of support. Furthermore the 15% density requires nearly 90g of material and 6 hours and 44 minutes of time; the 7% density only requires 65g of material and 5 hours and 31 minutes of time - more than an entire hour shaved from the print time!
The underlying point here is infill density and pattern are also relative to scale. If the print was smaller all the numbers would be closer together; but as the print scales up in size, all the numbers exponentially increase!
You may be able to trim the 15% density print time by speeding up the infill print speed, but again be cautious of the infill pattern you use.
