Material jetting explained: droplets, multiple materials, and support removal

01

Jetting the part material itself

In material jetting, one or more printheads place droplets of build material at selected locations ¹. Drop-on-demand systems fire droplets only where commanded; other jetting technologies may use a continuous stream with selection or deflection. Many commercial polymer systems deposit thin photopolymer layers and cure them with UV energy. Wax jetting can instead rely on cooling and solidification, particularly for patterns and specialized workflows.

This differs from binder jetting, which deposits a liquid joining agent onto a separate powder feedstock. It also differs from vat photopolymerization, where light selectively cures material already held in a vat. ISO/ASTM vocabulary matters because the machines may all advertise jets, light, or multiple materials while producing very different feedstock histories, post-processing needs, and hazards ².

02

From droplet formation to a cured layer

A jetting system conditions material for stable viscosity, supplies it to a printhead, forms controlled droplets, places them relative to the build surface, levels or manages the layer, and solidifies or cures it. Nozzle health, temperature, waveform, droplet velocity, placement, satellite droplets, head alignment, substrate distance, and surface wetting all influence the deposited pattern. The mechanical Z step must then preserve layer registration across the build.

Stratasys describes its PolyJet implementation as jetting photopolymer droplets and curing them with UV light ⁶. PolyJet is a trademarked commercial implementation, not the generic family. Other machines may differ in head configuration, materials, cure strategy, support, and maintenance. A vendor’s nominal layer value or color palette should be accompanied by measured dimensional artifacts, surface evaluation, stability data, and the actual supported material combinations.

• Stable droplets require controlled material condition and maintained nozzles.
• Multiple heads require geometric and material calibration.
• Cure and leveling influence dimensions as well as appearance.
• Missing or deflected nozzles can create structured defects across a build.

03

Multi-material is an interface problem

Material jetting can place different colors or formulations within one layer and may create blended digital materials. This supports anatomical models, visual prototypes, soft-hard transitions, textures, labels, assembly simulation, and patterns. The design file must preserve assignments, and the build software must translate them into head-level deposition. Color management, translucency, surface finish, layer orientation, and support contact all influence what the viewer sees.

A smooth gradient in appearance does not prove a smooth gradient in modulus, durability, biocompatibility, or aging. Interfaces may respond differently to bending, heat, water, UV, cleaning agents, and time. Formulations described as rubber-like are not necessarily equivalent to vulcanized production elastomers. Treat each combination, interface direction, thickness, cure state, and environment as a defined material system requiring evidence rather than averaging two brochure values.

04

Supports and cleaning determine surfaces

Many material-jetting geometries require a second material beneath overhangs, inside gaps, or around delicate features. Removal may involve water jets, manual tools, dissolution, heat, or a specified chemical bath, depending on the system. Contact surfaces can differ from upward faces, and narrow channels may retain support. Design openings and clearances for the actual removal equipment and verify cleanliness rather than assuming accessible geometry on screen.

Post-processing creates exposure and waste. Photopolymer residues, contaminated water or solvent, removed support, wipes, filters, and failed parts need handling under their SDS and local rules. NIOSH identifies liquid resin and post-processing hazards across AM processes ³. Guard pressure-washing equipment, contain splash, protect eyes and skin, ventilate chemical operations, and prevent uncured material or contaminated liquid from reaching ordinary drains without an approved disposal route.

• Identify every trapped or blind support volume during design review.
• Protect thin features from cleaning loads.
• Measure critical surfaces after complete support removal.
• Track support and cleaning waste in cost and environmental reporting.

05

Use the process where its evidence fits

Material jetting is powerful for communication models, surgical planning models, ergonomic studies, fit checks, patterns, color prototypes, and selected end-use parts supported by appropriate data. Choose it when fine deposited detail, multiple materials, or integrated color creates measurable value. Compare build time, consumables, support burden, cleaning access, aging, surface requirements, and inspection—not only purchase price or pixel-like specifications.

For regulated or consequential uses, the complete process matters. FDA guidance emphasizes controls from model preparation through printing, post-processing, verification, and final testing ⁴. NIST likewise identifies surfaces, internal defects, anisotropy, and complex internal geometry as qualification challenges ⁵. Record machine, heads, materials and lots, file assignments, orientation, support strategy, cure, cleaning, and acceptance results. A visually convincing model and a qualified functional component are different deliverables.

Build economics should separate machine exposure, build and support material, head cleaning and purge, preventive maintenance, labor, waste, and yield. Because nozzles can fail selectively, a nominally completed build may contain repeated structured defects. Track head checks, rejected regions, and failures by build location. This turns material jetting from a showpiece process into a measurable production route and clarifies whether color or multi-material capability earns its operating burden ¹⁵.

• Define whether the purpose is visual, tactile, geometric, mechanical, medical, or casting-related.
• Test the exact material combination and interface direction.
• Include cleaning access and disposal in design and cost reviews.
• Recheck calibration after printhead or material-system changes.