Metal Binder Jetting vs. PBF
The path to true mass production (batch size > 100,000).
1. Introduction: The Promise of True Mass Production
Laser-based powder bed printing (PBF) is precise and ideal for extremely complex components. But its build rate is limited. If an automobile manufacturer wants to produce 500,000 small gears or brackets per year, PBF fails due to cost and time.
This is where Metal Binder Jetting (MBJ) comes onto the scene - a technology that promises to finally catapult metal 3D printing into large-scale production in the automotive and consumer goods industries.
How does Metal Binder Jetting work?
With MBJ there is no laser to melt the metal! Instead, a print head (similar to an inkjet printer) moves over a powder bed and injects a liquid binder (adhesive) exactly where the component is to be created. The powder is glued together layer by layer. The result is a fragile "green part" that is not made of solid metal, but of glued powder.
2. The process: From the green part to the finished component
The real magic - and complexity - of MBJ happens after printing in special ovens.
- Debinding: The green part is heated so that the adhesive evaporates. The part is now called the “brown part” and is extremely fragile.
- Sintering: The brown part is baked in a high-temperature oven just below the melting point of the metal (e.g. at 1,300 °C for stainless steel). The powder particles fuse together (sinter neck formation).
- Shrinkage: During sintering, the material compacts and the component shrinks by approx. 15 to 20%!
3. PBF vs. Binder Jetting: The direct comparison
| Property | Laser PBF (SLM / DMLS) | Metal Binder Jetting (MBJ) |
|---|---|---|
| Building speed | Low (laser draws contours) | Extremely high (surface printing) |
| Support structures | Mandatory (for heat dissipation) | Not necessary (powder supports the component) |
| Residual stresses (warping) | High (hence massive post-processing required) | Almost none (no local melting) |
| Material costs | High (very fine, round powder required) | Low (can often use MIM powder) |
| Dimensional accuracy & accuracy | Very high (net shape) | Challenging (software must predict 20% shrinkage) |
4. The challenge of shrinkage (sinter compensation)
As the component shrinks massively in the oven, it will never come out of the oven as it was printed. Gravity pulls thick areas down more strongly than thin ones.
This is where highly complex software (e.g. from Desktop Metal) comes into play. The software simulates the sintering process in the oven and intentionally deforms (scales) the CAD model before printing. The printed green part looks deformed, but then shrinks in the oven to exactly the desired geometry ("sinter compensation").
5. Pioneers of the market
- Desktop Metal:The "Production System" is the size of a small factory and is designed to print millions of parts per year.
- HP (Metal Jet): HP transfers its decades of experience in 2D inkjet printing to binder jetting. Large car manufacturers such as VW are already testing these systems for series components.
- Markforged & ExOne (Desktop Metal): Offer systems from small R&D systems to large series production.
6. Conclusion: A complementary future
PBF and MBJ do not compete directly. PBF will remain the technology of choice for gigantic, hollow, highly complex individual parts in space and medicine (titanium). Metal Binder Jetting (MBJ), on the other hand, will shine where Metal Injection Molding (MIM) or investment casting dominates today: the cost-effective mass production of small, complex steel components for the automotive and consumer goods sectors.
