SLS and MJF – Powder-Based Manufacturing Explained
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When most people think of additive manufacturing, it is the FDM printer with its spinning nozzle that comes to mind. But there is a whole world of advanced manufacturing methods beyond plastic filaments – and among the most powerful are SLS (Selective Laser Sintering) and MJF (Multi Jet Fusion). These powder-based techniques have long dominated industrial production, and today they are used for everything from aircraft components to custom medical devices.
\n\nIn this article, we explain how SLS and MJF work, what sets them apart, which materials they handle – and when you should choose them over simpler methods.
\n\nWhat is powder-based manufacturing?
\n\nPowder-based methods build parts layer by layer just like FDM and resin, but with a crucial difference: the raw material is a fine-grained powder – typically polyamide (nylon) or thermoplastic elastomers – which is selectively melted or sintered together. The surrounding powder that is not melted automatically acts as support material, meaning complex geometries and undercut shapes can be manufactured without a separate support structure.
\n\nIt is precisely this property that makes SLS and MJF industrial favorites: the freedom to design complex internal channels, lattice structures, and assembled moving parts in a single production run.
\n\nSLS – Selective Laser Sintering
\n\nHow it works
\n\nAn SLS machine spreads a thin layer of powder across the build surface. A powerful CO₂ laser then sweeps across the surface and sinters – that is, heats up and fuses – the powder grains precisely where the part is to be formed. The build bed lowers one step, a new layer of powder is applied, and the process is repeated until the object is finished. The entire build chamber is kept at an elevated temperature to minimize thermal stress.
\n\nMaterials in SLS
\n\n- \n
- \nPA 12 (Nylon 12) – By far the most common SLS material. Good chemical resistance, low moisture content, and excellent dimensional stability. \n
- \nPA 11 (Nylon 11) – More flexible and durable than PA 12, bio-based from castor oil. \n
- \nTPU – Elastomeric powder for flexible, rubber-like parts. \n
- \nPA 12 CF / GF – Carbon fiber- or glass fiber-reinforced nylon for higher stiffness and heat resistance. \n
Advantages of SLS
\n\n- \n
- No support structures required \n
- High dimensional accuracy (±0.3 mm or better) \n
- Excellent mechanical properties – isotropic behavior in the XY plane \n
- Scalable: the entire build volume can be packed with parts \n
Limitations
\n\n- \n
- High machine cost and long warm-up time \n
- The surface is typically matte and slightly porous – may require post-processing \n
- Limited material selection compared to FDM \n
MJF – Multi Jet Fusion
\n\nHow it works
\n\nMJF is HP's patented technology and resembles SLS in its basic principle, but replaces the laser with an entirely different system. A printhead array – similar to that in an inkjet printer – sweeps across the powder surface and deposits two types of liquids: a fusing agent that absorbs infrared radiation and melts the powder, and a detailing agent along the contours that cools and sharpens the edges. An IR lamp then activates the melting.
\n\nThe result: entire layers are sintered simultaneously rather than point by point, which results in significantly shorter build times than SLS.
\n\nMaterials in MJF
\n\n- \n
- \nPA 12 – Standard and most common, comparable to SLS PA 12. \n
- \nPA 11 – Higher toughness and impact resistance. \n
- \nPA 12 GB (Glass Bead) – Stiffer and dimensionally stable at higher temperatures. \n
- \nTPU – Flexible, energy-absorbing parts, e.g., damping elements and shoes. \n
Advantages of MJF
\n\n- \n
- Faster production rate than SLS thanks to parallel melting \n
- Highly isotropic mechanical properties – Z strength is nearly as high as XY strength \n
- Fine detail reproduction and sharper edges \n
- Ability to produce in shades of gray and color with HP's Jet Fusion Color system \n
Limitations
\n\n- \n
- The machines are costly and require maintenance \n
- The parts are dark gray straight out of the machine (jet black from the fusing agent) – require dyeing if aesthetics are important \n
- Powder recycling is slightly lower than with SLS \n
SLS vs MJF – a quick comparison
\n\n| Property | \nSLS | \nMJF | \n
|---|---|---|
| Energy source | \nCO₂ laser | \nIR lamp + fusing agent | \n
| Speed | \nModerate | \nHigh | \n
| Surface finish direct | \nMatte, slightly porous | \nMatte, slightly smoother | \n
| Color options | \nWhite/natural + dyeing | \nGray standard + color system | \n
| Mechanical isotropy | \nGood | \nVery good | \n
| Material range | \nPA 11/12, TPU, CF/GF | \nPA 11/12, TPU, GB | \n
When should you choose SLS or MJF?
\n\nBoth methods are ideally suited for functional prototypes and end-use parts in low-to-medium volume. Choose SLS when:
\n\n- \n
- You need a wide selection of materials – including special materials like PA 11 bio or TPU in thin walls \n
- The project requires proven technology with a long industrial history \n
Choose MJF when:
\n\n- \n
- Production speed is crucial – batches of hundreds of parts quickly \n
- You need maximum isotropy for parts subjected to loads in all directions \n
- Color integration is a plus \n
Common to both: they are superior to FDM and SLA when parts must withstand mechanical stress, chemicals, or high temperatures in active use.
\n\nPost-processing of SLS and MJF parts
\n\nDirectly out of the powder bed, the surface is matte and slightly rough. Depending on requirements, these steps may be relevant:
\n\n- \n
- \nBead blasting – Smooths the surface and provides a uniform matte finish. \n
- \nTumbling / vibratory finishing – Smooth surface without manual effort, great for series production. \n
- \nDyeing – PA 12 absorbs color well; enables aesthetically pleasing end products. \n
- \nImpregnation – Fills pores for increased water tightness and chemical resistance. \n
- \nMachining – Suitable when tight tolerances are required on critical surfaces. \n
Industrial applications
\n\nSLS and MJF are widely used today in:
\n\n- \n
- \nAutomotive industry – Ducts, brackets, and interior components in low volume. \n
- \nMedical technology – Patient-specific orthotics, prosthetics, and surgical tools. \n
- \nConsumer electronics – Chassis, buttons, and enclosures with demanding surface finishes. \n
- \nIndustry and automation – Grippers, fixtures, and spare parts manufactured on demand. \n
How can Race3D help you?
\n\nAt Race3D, we work with a broad spectrum of additive manufacturing methods and help you choose the right technology and material for your specific project – whether it is a single prototype or a short-run series. We guide you through the entire chain: design optimization, manufacturing, and post-processing.
\n\nCurious about what SLS or MJF can do for your product? Contact us – we respond quickly and provide a concrete proposal without hassle.
