Do 3D printers really reach 50 micron (0.05 mm) accuracy? I've always been wondering about the actual accuracy of 3D printing devices. When looking for the perfect machine to buy, I looked at the speed, price, filaments supported etc, but also accuracy. I once asked somebody who could give me some advice on what to look at. 

One of the things I was told about was that many printers don't necessarily have that crazy precision of 0.05&nbsp;mm (50 micron). Another person told me something different - he said most of those printers actually were capable of putting out 50 micron layer height. How is it really? 

Another thing is that the official slicers for those machines also claim that this precision is real, for instance the PrusaSlicer v2.0. 

There are many high-end, very expensive machines and even they sometimes claim their resolution is worse than 50 microns.
There's not a simple answer to this question, or if there is, it's "no". However the situation is a lot more complicated. When printer specs cite accuracy like this, they're usually basing the claim on the nominal size of the smallest movements on each axis by one "microstep" of the stepper motors. There's a great article on Hackaday explaining the how this affects accuracy: How Accurate is Microstepping Really.

At the mechanical positioning level - putting the print head where it needs to be to extrude the material with the desired accuracy - you have at least these factors limiting your accuracy:


Microsteps are generally spaced roughly monotonically between whole steps, but do not necessarily divide the whole step into even portions. How well they do is a matter of the stepper drivers your printer's controller board uses. Generally, microsteps are 1/16 of a step (although there are drivers with 1/8, 1/32, or even 1/256, maybe others too), so if you see a rated accuracy of 0.05 mm, a whole step, which might be the minimum you can get reliable accuracy from, is likely 0.8 mm.
Stepper motors are deflected slightly - up to 2 whole steps but less than one step is more likely if they're not overloaded - under load. So are belts. How much this affects you depends on the design of the printer and how much mass each axis is moving. Direct drive extruders are much worse in this regard. Delta printers are probably best in it.


These can be mitigated somewhat, with tradeoffs, by using stepper motors with more steps per rotation, better stepper driver chips, reduction with gears, etc.

On top of that, you also have extrusion and properties of the print material limiting your accuracy:


The extruder motor is subject to the same accuracy issues as the positioning ones. If you extrude too much or too little material anywhere, you'll necessarily have accuracy issues. You can compute them based on the cross-sectional area of filament, size of extruder gear, extruder motor step and microstep size, etc.
If the filament diameter is not perfectly consistent, you'll also extrude too much or too little material.
If material is not cooled or kept warm appropriately as it's extruded (this varies by material), it will sag, warp, or curl, ending up in a different place from where you wanted it.
The more you vary the ratio between nozzle/extrusion width and layer height from an ideal ratio, the more the shape of the extruded material paths will differ from the model you're trying to print. With thick layers especially they'll become rounded rather than near-flat along the walls.


In theory, a lot of these issues probably could be mitigated a lot better than they are now just by better slicing - the logic that happens on a computer to convert the original 3D model into instructions for where to extrude material.

With all that said, you can get pretty amazing accuracy still, especially with a good or well-tuned so-so printer. On my cheap Ender 3, after dealing with some issues now and then that made glaringly obvious problems, I can get dimensional accuracy within 0.1 mm in the X and Y directions, at least for some models. So I think it's very plausible that a better, or better-tuned, printer could get 0.05 mm accuracy.