Precision in printing means two different things that are often conflated: the smallest feature a process can form, and how closely a dimension across the whole part matches the model. A process can be excellent at one and mediocre at the other, and knowing which one your part needs is what makes a supplier conversation useful.
Feature resolution against dimensional accuracy
Resolution is set by the spot size, the pixel or the nozzle diameter, and it decides the finest detail. Dimensional accuracy is set by shrinkage, thermal history and machine calibration, and it decides whether a hole thirty millimetres from a datum is where the model says. A machine with very fine resolution can still be dimensionally mediocre over a large part.
The hierarchy in practice
Photopolymer processes lead on both resolution and accuracy for small parts. Material jetting is comparable and better on multi material work. Powder bed polymer is good but varies with thermal history across a densely packed build. Metal powder bed is good for geometry and unsuitable for fits. Filament printing is the loosest on both counts.
What limits it
Shrinkage during cure or cooling, and the fact that shrinkage is not uniform across an uneven part. Thermal gradients in the build chamber. Support contact deforming downward faces. Post cure movement in photopolymers. And on metal, residual stress relieving itself when the part comes off the plate, which can move a large part visibly.
Micro printing and the finishing route
Two photon polymerisation reaches features measured in micrometres for microfluidics, optics and micro mechanical parts, in very small build volumes. For everything else, the practical answer to a precise printed part is a hybrid: print with stock on the features that matter and machine or ream them afterwards, which is standard industrial practice rather than an admission of failure.
Questions people ask about precision 3d printing
Which printing process is most accurate?
Photopolymer processes for small parts, on both feature resolution and dimensional accuracy. Filament printing is the loosest and metal powder bed is unsuitable for fits.
What is the difference between resolution and accuracy?
Resolution is the finest feature a process can form. Accuracy is how closely a dimension across the part matches the model. They are limited by different things.
How do I get a genuinely precise printed part?
Print it with machining stock on the features that matter and machine or ream them afterwards. That hybrid route is standard industrial practice.
What is micro printing?
Processes such as two photon polymerisation that reach features measured in micrometres, used for microfluidics, optics and micro mechanical parts in very small build volumes.