Multi Jet Fusion (MJF) and Selective Laser Sintering (SLS) are 3D printing processes commonly used with black and white nylon, respectively. Both methods fall under the powder bed-based 3D printing category. The process begins with powder being spread onto the printing platform, which is then fused layer by layer through hot melting or sintering of the powder particles. The primary difference between the two lies in their heat sources: SLS uses a laser as the heat source, while MJF employs an ink that absorbs infrared light, which is sprayed onto the powder bed. This is followed by an infrared heat source scanning the platform to fuse the ink-covered areas.
Some Differences in the Properties of the Two Nylons
Process
SLS: A thin layer of powder is initially spread evenly over the platform, which is then heated to a temperature just below the sintering point. A laser scans each cross-section along a predetermined path to sinter the powder. After each layer is completed, the platform moves down, and the process repeats until the part is fully constructed. Once printing is finished, the entire silo must cool down before the parts can be removed from the powder.
MJF: Similar to SLS, a thin layer of powder is first spread over the platform and heated to a near-sintering temperature. An inkjet nozzle sprays a fusing agent onto the powder, while a detailing agent is applied around the edges to prevent unwanted sintering. A high-powered infrared heat source then irradiates the powder bed, sintering the areas where the fusing agent was applied, while the unexposed powder remains unchanged. This process repeats until the part is fully formed. Like SLS, MJF-printed parts are encased in powder and require cooling before removal.
Dimensional Accuracy
Both MJF and SLS deliver industrial-grade 3D printing with high dimensional accuracy. MJF generally outperforms SLS in this area, mainly because the MJF printhead operates at 1200 DPI (approximately 1 dot per 0.022mm), while the typical laser spot diameter in SLS systems is around 0.3-0.4mm. Additionally, the detailing agent used in MJF enhances the ability to print fine details and sharp edges.
Appearance and Surface Quality
Since dark materials absorb heat radiation more efficiently, the fusing agent used in MJF is black, resulting in a light grey appearance for MJF parts. A uniform black finish can be achieved through post-processing steps.
SLS parts typically appear white and can be dyed in any color, offering greater flexibility in terms of color customization.
Both MJF and SLS parts have a granular surface texture, but they can both be post-processed to achieve a smoother, higher-quality finish.
Material Properties
PA 12 (nylon) is the primary material used in both MJF and SLS processes. SLS parts tend to be slightly weaker in the Z-axis (print direction), while MJF parts offer better overall strength, flexibility, and more consistent mechanical properties across all axes.
Cost and Delivery Time
Black nylon tends to offer slightly superior performance, but it also comes at a higher cost.
The delivery time for both methods is generally similar. However, black nylon may have a slight edge in terms of delivery time due to better powder recovery and a faster cooling rate.
Tolerances for SLS and MJF at WellCircuits
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