SLS vs. MJF
Compare SLS and MJF powder-bed polymer printing by qualified material, geometry, surface state, finishing, orientation, powder management and the inspection your part needs.
Both are powder-bed processes; neither is a generic nylon result
SLS selectively fuses powder with a laser. HP MJF deposits fusing and detailing agents across the powder layer before heat is applied. The relevant comparison is the complete qualified route for the intended part.
SLS
Polymer powderA laser scans and fuses selected regions of a powder layer.
Design check: Loose powder supports the part; cavities need a removal path.
MJF
Polymer powderFusing and detailing agents define the part and its edges. Heat bonds the layer.
Design check: Select the qualified powder, then plan depowdering and finish.
Process principles shown in cutaway. Energy colours are schematic. Supports, hardware and layer thickness are simplified; machine configurations vary.
SLS
Laser-fused powder
A broad family of SLS machines and powder products can support PA11, PA12, filled nylons, TPU and specialty polymers. Product data remains machine and condition specific.
MJF
Agent-and-heat powder fusion
MJF material choices are tied to the qualified platform and supplier portfolio. Screen the exact material, color/finish state and process evidence.
Shared
Depowdering and orientation
Both can make complex support-free polymer geometry, but both need powder escape, cooling awareness and a plan for direction-sensitive requirements.
Compare the delivered material route, not a generic process badge
HP itself frames the MJF/SLS decision around budget, mechanical properties, specifications, finishing and quantity. Those questions are more useful than a fixed accuracy or strength ranking.
| Topic | SLS | MJF |
|---|---|---|
| Build mechanism | A laser selectively fuses polymer powder layer by layer. | Fusing and detailing agents define regions in a powder layer before heat fuses them. |
| Productivity to compare | Laser scan paths and fused cross-sections contribute to build work; assess the actual layer count and packing. | Agent deposition and heating use layer passes; assess layer count, packing and the selected system rather than assuming a fixed speed advantage. |
| Material selection | Select a named powder and its supported machine/parameter set. | Select an HP-qualified material and compatible MJF platform. |
| As-printed colour | Depends on the commercial powder; natural, white, gray, black and filled appearances are distinct products. | Depends on the material and MJF process; an as-printed state is not a general colour palette. |
| Internal geometry | Powder escape paths must be designed through every internal volume. | The same depowdering principle applies; do not assume a cavity is clean because it is printable. |
| Finishing | Blast, dye, smoothing, coating or machining must be compatible with the material and final fit. | Finishing likewise needs a material-specific route; dyeing is a post-process rather than a powder selection. |
| Properties | Use the manufacturer’s named powder, printer, orientation and condition. | Use the manufacturer’s named MJF material, printer and condition; do not transfer SLS values to MJF. |
Compare delivered batch timing including cooling, depowdering, finishing and inspection. The machine exposure step alone does not establish order lead time.
PA11, PA12 and filled nylon answer different questions
PA11 can be selected for ductility and impact-oriented use cases; PA12 is often a balanced nylon choice; glass- or carbon-filled formulations trade compliance for stiffness. The commercial powder defines the evidence.
The polymer name is a starting point
A material family can contain multiple formulations. Check the commercial product, process and test condition.
Fillers change the trade-off
Glass beads, glass fibres and carbon fibres are distinct reinforcements. Compare stiffness, elongation, surface and directionality together.
Schematic illustrations; not to scale. Confirm the design for the chosen material, process and final use.
| Part need | Compare | Avoid assuming |
|---|---|---|
| Repeated flex / impact | PA11 product data, orientation and conditioning | That any PA11 part has a fixed hinge life or identical impact behavior. |
| General functional nylon | PA12 product data, surface and finishing | That all PA12 powders have the same density, tensile, elongation or color. |
| Stiff housing / fixture | Glass-bead, glass-fibre or CF formulation and Z-direction behavior | That every “GF” means fibre or that reinforcement makes the part metal-like. |
| Elastomeric part | Named TPU/TPA/PEBA material, hardness and compression or tear data | That the process label alone defines flexibility. |
| Colour / cosmetic part | As-printed colour plus dye or coating specification | That a dyeable powder offers arbitrary colors or that finish leaves dimensions unchanged. |
Make the geometry cleanable and inspectable
Powder supports overhangs, but it also occupies internal channels and moving mechanisms. Design access, then specify the features that must be measured after depowdering and finishing.
A sealed cavity retains material
Hollow geometry does not guarantee a hollow delivered part. Unfused powder, liquid resin or support can remain inside.
Design a cleaning route
Provide accessible openings and a path through the cavity. Opening size depends on process, material, channel length and cleaning method.
Schematic illustrations; not to scale. Confirm the design for the chosen material, process and final use.
- Make powder removal explicit. Include drain and access features that match the channel path, material, wall thickness and cleaning method.
- Mark functional faces. Identify bearing, sealing, thread, locating and cosmetic surfaces before orientation and finishing are chosen.
- Use direction-aware data. A supplier TDS may give X/Y/Z results. Place the actual loaded feature in the context of that evidence, then validate it.
Quote the two qualified routes against the same acceptance plan
The cleanest comparison uses one geometry, the candidate material products, the required finish and the same inspection criteria. That exposes a real difference in feasibility rather than a generic process claim.
Learn from a first article
Use representative geometry, material and finishing to verify the properties that matter before repeating the order.
Control the production recipe
Record material product, build settings, orientation, finishing and inspection criteria. Confirm changes before the next batch.
Schematic illustrations; not to scale. Confirm the design for the chosen material, process and final use.
For product-level evidence, browse 3D printing materials. For geometry details, see the SLS and MJF design guides.
Frequently asked questions
Is MJF faster than SLS?
Build productivity depends on machine, material, layer strategy, nesting, cooling, depowdering, finish and batch geometry. Compare quote-specific throughput and delivered-part timing rather than applying a universal speed claim.
Is MJF stronger than SLS?
Neither is universally stronger. The relevant data are for a named material product, printer, orientation and conditioning. A PA12 result from one route cannot be assigned to another powder-bed process.
Are SLS and MJF parts black by default?
No. As-printed color depends on the commercial powder and process. A different colour may require a separate dye, coating or paint operation, each of which should be specified and approved.
Can I use the same CAD for SLS and MJF?
Often the base geometry can be evaluated in both, but powder escape, wall distribution, orientation, material selection, finishing allowance and inspection requirements should be reviewed for each candidate route.
Sources and further reading
- HP — MJF vs SLSHP process description; compare exact supplier-qualified material routes.
- HP — MJF materials portfolioMaterial compatibility and color/reusability claims are product specific.
- Formlabs — SLS design specifications
Specify the details that make the part work.
Upload your CAD and drawing with the material, quantity, finishing and critical dimensions. Confirm the manufacturing route before production.