There are many terms when it comes to 3D printing, but shell thickness is one you may have come across recently. It definitely has its importance in the results of your prints. In this post, I will detail how to get the perfect shell thickness settings for your prints.
How do I get the perfect Shell Thickness settings? The default wall thickness in Cura is 0.8mm which provides a minimal amount of strength for standard 3D prints. For prints that need durability, a good wall/shell thickness would be around 1.6mm and above. Use at least 3 walls for more strength.
This is the basic answer on how to get the perfect shell thickness, but there are some useful details that you can learn in the rest of this post. Keep reading to brush up on your knowledge of shell thickness settings.
What Is Wall/Shell Thickness?
Wall & shell means the same thing in 3D printing, also known as perimeters so you’ll see these used interchangeably. Cura refers to is as walls so that is the more standard term.
Put simply, shells are the walls of your prints that are exposed to the outside of your model, or just the exterior of your object.
Bottom layers and top layers are also known to be a type of wall because it’s on the exterior or outside of the object.
The main settings you’ll come across is the number of walls and the wall thickness. They both work together to create a certain sized wall around your print. Shell or wall thickness is a combination of your wall width in mm and the number of walls.
If you have a low wall thickness and several walls, it will basically be the same as having a high shell thickness and fewer walls.
How Does Wall Thickness Benefit My Parts?
The main benefit of increasing wall thickness is to add to the strength and durability of a part. These are necessary for prints that serve some kind of functionality, such as a mount, holder or handle.
Adding to your wall thickness is a good alternative to adding tons of material for a higher percentage of infill as found in the video below by CNC Kitchen.
One of the key features you can do for wall thickness is to adjust your prints to have more wall thickness or walls in weaker areas where parts are likely to break.
You do need to keep in mind, adding a large wall thickness for parts that require precision can alter its shape enough to make it unfit for purpose.
It’s not the end of the world because parts can be sanded down to accurate dimensions but this will take extra work, and depending on the part design and complexity, might not be possible.
Larger wall/shell thicknesses creates a sturdy, durable model and also decreases the chance of any leaks. On the other hand, a lower wall thickness can significantly reduce filament used and print times.
How is Wall/Shell Thickness Calculated?
The usual practice for shell thickness is to have a value which is a multiple of your nozzle diameter.
For example, if you have a nozzle diameter of 0.4mm, you want your shell thickness to be 0.4mm, 0.8mm, 1.2mm and so on. This is done because it avoids print imperfections and gaps occurring.
In terms of figuring out shell thickness, it’s usually calculated to be a value of two nozzle diameters, being 0.8mm for a standard 0.4mm nozzle.
In Cura, the wall thickness is already calculated for you and overridden by line width so when you change your line width input, wall thickness will automatically change to be line width * 2.
When you’re printing with a weaker, brittle material, overall shell thickness can make or break you (excuse the pun), so make sure you’re clued-up on these settings.
To adjust overall shell thickness, you’ll have to change the wall line count setting. Having a shell thickness of 0.8mm means a wall line count of 4 would give you a 3.2mm wall.
How to Get the Perfect Wall/Shell Thickness
Now on to getting the perfect wall thickness.
Honestly speaking, there is not one particular perfect wall thickness that will work the best for your prints, but you usually want to be in a 0.8mm-2mm range.
The first thing you should know is that every print has its purpose and functionality. Some are printed simply for looks and aesthetics, while some are printed to under a load or physical bearing.
You need to determine the use of your part before you can identify what the perfect shell thickness would be for you.
If you’re printing a vase, you wouldn’t need such a wide thickness because durability isn’t a necessary characteristic for its use, although you don’t want it to break, so you’ll need a minimum.
On the other hand, if you are printing a wall mount bracket, you’ll need the right material, infill and plenty of walls to make the part as strong as possible.
An example is if you print a part with 0% infill and just a 0.4mm wall it will be very weak and easy to break, but add a few walls to it, and it will make it a lot stronger.
So, this will be trial and error from gaining experience with different shell thicknesses. Once you get the hang of it and understand how it works and looks, you’ll be able to determine the perfect shell thickness with ease.
What is the Minimum Wall Thickness for 3D Printing?
You rarely want a wall thickness that is below 0.8mm. For models that need durability, I’d recommend 1.2mm and above because according to IMaterialise who deliver custom 3D prints, these are most likely to break during transit. There isn’t really a maximum but you don’t really see above 3-4mm in normal cases.
If your model has fragile parts and thin structures such as the limbs on a figurine, shell thickness would help out a lot.
Having a 3D print wall too thick can also cause issues so watch out for that. This happens with more detailed designs where parts of the print are close to others. At a certain shell thickness, there will be overlap between parts so try to balance it out at a level where you see fit.
If you want your prints to have some flexibility, a thick shell won’t work too well for that as it makes your prints more rigid. Another thing you should know is an overly large wall thickness creates internal stress that can actually result in warping and print failure.
Some slicers have an in-built function to stop people adding too large of a wall to their models.
There is a minimum thickness that a 3D printed part needs to have to be able to hold up at all.
When it comes to how thick 3D printed parts should be, Fictiv found that 0.6mm is the absolute minimum and also the thinner your part’s shell thickness, the higher the chance that something goes wrong during the process.
The reason this happens is because of the nature of 3D printing and its layer by layer process. If melted material doesn’t have a good foundation underneath, it can have trouble building up.
Models with thin walls are more prone to warping and gaps in the print.
What is a Good Wall Thickness for PLA?
For PLA 3D prints, the best wall thickness is around 1.2mm. I’d recommend using a wall thickness of 0.8mm for standard prints that are for looks and aesthetics. For 3D prints that require strength and durability, try using a wall thickness of 1.2-2mm. Walls are the best method to improve strength for PLA 3D prints.
For the top/bottom thickness, you can use the same measurements whether you have a 3D printed like the Ender 3 V2 or Anycubic Vyper.
3D Printing Wall Thickness Vs Infill
Wall thickness and infill are two factors in 3D printing to increase the strength of your 3D prints. When it comes to wall thickness vs infill, it’s better to use wall thickness for strength. A model with 0% infill and a 3mm wall will be very strong, while a model with a 0.8mm wall and 100% infill won’t be as strong.
The level of strength by increasing infill percentage decrease as you go up in infill percentage.
Hubs measured that a part that has 50% infill vs 25% is around 25% stronger, while using an infill of 75% vs 50% might increase the part strength by around 10%.
3D prints will be more durable and less prone to breakage when you have a strong wall thickness, but using a combination of wall thickness and a high infill percentage is the best.
You’ll have an increase in material and weight with both of these factors, but wall thickness uses less material in comparison to how much strength it adds.
Check out the video below for a great illustration of this.
Part orientation is also important with strength. Check out my article Best Orientation of Parts for 3D Printing.