> For the complete documentation index, see [llms.txt](https://monasheng.gitbook.io/zerotohero/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://monasheng.gitbook.io/zerotohero/3d-printing-zero-to-hero/advanced-skills/advanced-slicing/layer-height.md). # Layer Height {% embed url="" %} {% hint style="info" %} :man\_mage:**Important:** 3D printers build up parts *layer-by-layer* - printing each cross section, one-at-a-time, over the last. Because the layers are discrete, and have some thickness, a print is never going to be a perfect representation of reality. {% endhint %} In practice, this imperfection usually manifests through so-called *layer lines* on your print. These generally becomes less pronounced as the layer height decreases.

Surface finish changes as a function of layer height, with *layer lines* visible at large heights. Smaller layers result in a smoother finish, but also take longer to print. Remixed from: https://help.prusa3d.com/article/variable-layer-height-function_1750

Consequently, layer height essentially alters the accuracy/detail of your print - but only in the $$z$$ direction - $$x-y$$ detail is limited by other factors. ### Detail-time trade-off Layer height is directly proportional to print time. For instance, if you want to print a part $$10;\text{mm}$$ tall, with $$0.1;\text{mm}$$ layer height: $$ \frac{10;\text{mm}}{0.1;\text{mm}} = 100;\text{layers}. $$ On the contrary, if you wanted to print the same part with $$0.2;\text{mm}$$ layer height: $$ \frac{10;\text{mm}}{0.2;\text{mm}} = 50;\text{layers}. $$ In-plane print speed is largely invariant to layer height - that is to say it doesn't take any longer to print thicker layers - meaning that a $$2\times$$increase in layer height will usually result in a $$2\times$$decrease in print time. ## Selecting a layer height PRUSA printers are capable of incredibly fine detail - down to $$0.05;\text{mm}$$ layer heights. That being said, there is a strong diminishing return on perceptible detail vs layer height below $$0.1;\text{mm}$$ - leading to the *golden rule of layer height:* {% hint style="info" %} :man\_mage: **Important:** always print at the largest layer height you can get away with. {% endhint %} ### When does detail matter? For engineering parts, we are are often less concerned about detail for the sake of aesthetics, and more for functionality. $$z-$$detail becomes important when you have features that evolve in this direction. Consider the following part, where a hole in the $$z-y$$ plane is being approximated better-and-better as the layer height decreases. At the largest layer height ($$0.3;\text{mm}$$), it is possible that the bolt intended for this hole might not even fit due to loss of detail!

In general, you should avoid printing dimension-critical features like this in the $$z$$ direction, instead changing the [Part Orientation](/zerotohero/3d-printing-zero-to-hero/advanced-skills/advanced-slicing/part-orientation.md) to print them in-plane. ## Variable Layer Height Tool Sometimes $$z-$$features can't be avoided - perhaps a part has dimension critical features in more than one plane. *PrusaSlicer* provides a tool for this very circumstance, which allows you to *vary* the layer height throughout a part - printing at high detail (slow, small layers) where required, and low-detail (fast, large layers) elsewhere. This tool allows you to manually set the layer height throughout the $$z-$$range of the part. For more information, consult the PRUSA documentation: {% embed url="" %} The tool even has an `Adaptive` mode, which will automatically apply smaller layer heights to areas of your part with large changes in $$x-y$$ over small changes in $$z$$. This tool is particularly useful for features with these large changes - e.g. spheres - where they taper to a point of infinite gradient.