Binder Jetting Simulator: Saturation, Density & Sintering

simulator intermediate ~10 min
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ρ_green = 58% — typical green density for metal binder jetting

At 70% saturation with 55% packing density, the green part achieves 58% theoretical density — after sintering, expect 95-97% density with 15-18% linear shrinkage.

Formula

S = V_binder / V_void × 100% (binder saturation)
V_void = (1 - φ) × V_layer (void volume per layer)
Shrinkage ≈ 1 - (ρ_green / ρ_sintered)^(1/3)

Printing Without Heat

Binder jetting takes a fundamentally different approach from laser-based additive manufacturing: instead of melting powder, it selectively deposits a liquid binder that glues particles together at room temperature. This eliminates thermal stresses, support structures, and the need for inert atmosphere — and it is fast. Industrial binder jetting machines print at rates 10-100× faster than SLM, making them viable for production volumes of thousands of parts per day.

Saturation Science

The critical process parameter is binder saturation — the fraction of interparticle void space filled with binder. Too little binder and the green part crumbles; too much and excess binder wicks beyond boundaries, bloating features. The optimal saturation window (typically 60-80%) depends on powder morphology, packing density, and binder viscosity. This simulator lets you explore how saturation interacts with other parameters to control green part quality.

From Green to Dense

The printed 'green part' is only 55-65% dense — a fragile matrix of powder held by binder. Curing crosslinks the binder for handling strength, then sintering at 1200-1400°C (for metals) burns off the binder and densifies the powder through solid-state diffusion. Parts shrink 15-20% linearly during sintering, requiring precise compensation in the digital model. The simulator estimates sintered density based on green-state parameters.

Speed Versus Resolution

Binder jetting's speed comes from its parallel deposition: industrial printheads contain thousands of nozzles jetting simultaneously across the powder bed. Layer times of 5-20 seconds enable build rates exceeding 1000 cm³/hour. The trade-off is resolution — current droplet sizes (50-80 μm) limit minimum feature size to approximately 200 μm, coarser than SLA or SLM but sufficient for most structural and tooling applications.

FAQ

What is binder jetting?

Binder jetting deposits a liquid binding agent onto thin layers of powder (metal, ceramic, or sand) using inkjet printheads. Unlike SLM, no melting occurs during printing — the binder glues powder particles into a fragile 'green part' that is later sintered in a furnace to achieve full density. This separation of shaping and densification enables very high build speeds.

What is binder saturation?

Binder saturation is the percentage of void space between powder particles that is filled with binder. At 100% saturation, all voids are filled; below 100%, some voids remain empty. Optimal saturation (typically 60-80%) provides enough binder for green strength without excess that causes bleeding and dimensional inaccuracy.

How much does binder-jetted parts shrink during sintering?

Sintering shrinkage is typically 15-20% linear (35-50% volumetric), depending on green density and sintering conditions. This shrinkage must be accurately predicted and compensated in the CAD model. Higher green density (better packing, optimal saturation) reduces shrinkage and makes it more uniform.

What materials can be binder-jetted?

Binder jetting works with virtually any powder: stainless steel, tool steel, titanium, copper, ceramics (alumina, zirconia), sand (for casting molds), and even tungsten carbide. This material versatility, combined with high speed and no thermal distortion during printing, makes binder jetting increasingly competitive with SLM for production applications.

Sources

Embed

<iframe src="https://homo-deus.com/lab/additive-manufacturing/binder-jetting/embed" width="100%" height="400" frameborder="0"></iframe>
View source on GitHub