Bubbles and internal voids are defects that can compromise both the surface quality and internal integrity of parts printed by vat photopolymerization. These defects may appear as trapped air pockets, internal cavities or irregular gaps in the printed object.
Although often overlooked compared with exposure-related defects, bubbles and voids can strongly affect dimensional accuracy, mechanical performance and reproducibility.
Main causes of bubbles and voids
Trapped air in the resin
Air may become entrapped during resin handling, stirring or pouring into the vat. If not released before printing, these bubbles may remain trapped during exposure.
Incomplete resin refill
If fresh resin does not fully refill the exposed region between layers, localized gaps or partial voids may develop.
High resin viscosity
Highly viscous resins refill more slowly, increasing the probability of incomplete filling or trapped bubbles in fine geometries.
Fast mechanical cycle
Lift and retract movements that are too aggressive may disturb the resin surface and promote bubble formation.
Typical symptoms
- internal holes or gaps
- irregular cavities in printed sections
- bubble marks on surfaces
- reduced mechanical integrity
Corrective actions
- allow resin to rest after agitation
- reduce lift speed if necessary
- improve refill time
- manage resin temperature and viscosity appropriately
Engineering interpretation
Bubbles and voids are often related to resin flow dynamics rather than optical curing problems alone. Their occurrence depends on resin rheology, geometry, mechanical cycle parameters and handling practices.
A structured classification of resin printing defects is available in the 3Dresyns® Photopolymer Printing Failure Atlas , which organizes common vat photopolymerization failures according to their observable morphology and most probable physical causes.