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MJF vs SLS: What Are The Differences?

Selective Laser Sintering - 28 June, 2024
MJF vs SLS: What Are The Differences?
Author
Vicki May
Date
28 June 2024
Category
Selective Laser Sintering
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When it comes to 3D printing, especially in high-performance industries like motorsport, energy, and aerospace, the choice of technology can significantly impact the final product’s strength, functionality, and cost. 

Two of the most popular 3D printing technologies for producing high-quality, durable components are Multi Jet Fusion (MJF) and Selective Laser Sintering (SLS). 

Below, we’re putting SLS and MJF head to head so that you can make an informed decision about which manufacturing process is right for your parts and project requirements.

Overview of MJF and SLS

Multi Jet Fusion (MJF)

Multi Jet Fusion (often called HP Multi Jet Fusion because it was developed by Hewlett-Packard in 2016), is a relatively new technology in the additive manufacturing landscape.

The Multi Jet Fusion process is multi-step. A thin layer of plastic powder material is spread on the print bed and heated just below its sintering point. A fusing agent is applied to form a cross-section of the part. A detailing agent is then applied to enhance edge sharpness. An infrared light passes over the printed parts, sintering the particles to create the final part.

This process results in a highly detailed, precise part with excellent mechanical properties. MJF is often chosen over SLS because it’s suitable when larger quantities of precise parts are needed quickly.

Selective Laser Sintering (SLS)

Selective Laser Sintering has been a staple in the 3D printing industry for decades. SLS uses a high-powered laser to selectively sinter powdered material, bonding it together to create a solid structure.

SLS is a powder bed 3D printing technique used to create precise, functional parts from thermoplastic materials. The process involves a CO2 laser selectively fusing plastic powder material by tracking each cross section of a part layer by layer. After each layer, the print bed lowers and a new layer of powder is added.

If you’re familiar with direct metal laser sintering, selective laser sintering is very similar to this additive manufacturing technology, but uses polymer powder rather than metal. Parts created on SLS printers don’t require support structures like those printed on DMLS, though. This means production costs and times are reduced.

This technology is renowned for producing robust and complex geometries that are often difficult to achieve with traditional manufacturing methods. SLS printing supports a wide range of materials, so it’s ideal for functional testing, or finished parts. From food-grade to flame-retardant materials, there are plenty of materials for a host of applications.

Both SLS and MJF achieve similar robust mechanical properties, but SLS technology is slightly slower. However, the choice of high-performance materials and the possibility of creating complex geometries without support structures, means that SLS is a good choice if you need to produce durable parts with complex shapes and aren’t manufacturing them to scale.

Key Differences Between MJF and SLS

Now that you’ve got a better understanding of SLS and MJF, here are some key differences.

Print Quality and Detail

MJF: MJF emerges slightly ahead of SLS when it comes to producing parts with superior surface finish and finer feature resolution. The technology allows for finer feature details and smoother surfaces right out of the printer, reducing the need for extensive post-processing. This makes MJF an excellent choice for parts where aesthetics and intricate details are critical.

SLS: SLS also produces high-quality parts with high dimensional accuracy but generally requires more post-processing to achieve a smooth finish. The layer lines can be more pronounced compared to MJF. However, SLS excels in creating complex geometries and robust parts suitable for functional prototypes and end-use applications.

Material Properties and Choices

MJF: MJF typically uses nylon powders, such as PA12 and PA11, which offer excellent mechanical properties, including high tensile strength and durability. The uniform heating process in MJF results in consistent material properties throughout the part, making it ideal for load-bearing applications.

SLS: SLS has a broader range of materials, including various nylon grades, TPU, and carbon composites. This versatility allows for greater customisation of parts based on specific performance requirements, such as flexibility, heat resistance, or biocompatibility.

Production Speed and Efficiency

MJF: MJF is known for its rapid production speed. The simultaneous printing and fusing process, combined with efficient thermal management, allows MJF to produce parts faster than most other 3D printing technologies. This makes it suitable for both prototyping and large volume production runs.

SLS: An SLS printer can also be efficient, but the process is generally slower than MJF due to the single-point laser sintering method. However, SLS machines can run continuously for long periods, making them good for long runs of parts where speed is less of a concern. They also have larger build chambers, so we can build larger parts in a single piece, or more parts at once.

Cost Considerations

MJF: MJF allows for efficient use of materials, with a high degree of recyclability of unused powder. The overall cost per part is also often lower for MJF prints than SLS prints due to the speed of production and reduced need for post-processing.

SLS: The cost per part can be higher on an SLS printer due to slower production times and more extensive post-processing requirements. Material waste can also be higher, impacting overall cost efficiency. However, the SLS printing process is an excellent choice due to the range of materials that you can use.

Applications

MJF: MJF is particularly well-suited for applications requiring high precision and fine details, such as medical devices, consumer electronics, and intricate aerospace components. The technology’s ability to produce isotropic parts with uniform strength makes it ideal for functional prototypes and end-use parts.

SLS: SLS is preferred for applications needing complex geometries and durable mechanical properties. Plus, the wide range of material options means there’s a host of applications in many different sectors that require functional prototyping and robust functional parts. It’s commonly used in automotive components, aerospace parts, industrial tooling, and customised manufacturing.

Mechanical Properties

When selecting a 3D printing technology, understanding the mechanical properties of the printed parts is crucial, especially for high-performance sectors like motorsport, energy, and aerospace where strength, durability, and reliability are paramount. Multi Jet Fusion (MJF) and Selective Laser Sintering (SLS) offer excellent mechanical properties, but notable differences mean each technology excels in different areas.

Multi Jet Fusion (MJF)

Tensile Strength and Durability: Parts produced with MJF typically exhibit high tensile strength and durability. The technology ensures a uniform fusion of particles, resulting in isotropic properties where strength is consistent in all directions. This makes MJF parts particularly suitable for load-bearing applications and components subjected to mechanical stress.

Flexibility and Impact Resistance: MJF parts, especially those made from materials like TPU, offer a good balance of flexibility and impact resistance. This combination is beneficial for applications requiring parts that can withstand shocks and vibrations without fracturing.

Dimensional Accuracy: MJF excels in producing parts with tight tolerances and excellent dimensional accuracy. The precision of MJF allows for the creation of intricate designs and complex geometries while maintaining structural integrity. This is essential for applications where dimensions are critical for assembly and functionality.

Heat and Chemical Resistance: MJF materials, such as PA12 and PA11, exhibit good resistance to heat and chemicals. This makes MJF parts suitable for environments where they may be exposed to high temperatures or harsh chemicals, such as in aerospace and industrial applications.

Selective Laser Sintering (SLS)

Mechanical Strength and Robustness: SLS parts are known for their mechanical strength and robustness. The laser sintering process creates parts that are highly durable and capable of withstanding significant mechanical loads. This makes SLS ideal for functional prototypes and end-use parts that need to endure demanding conditions.

Material Versatility: One of the strengths of SLS is its ability to work with a wide variety of materials, each offering distinct mechanical properties. For instance, SLS can produce parts from flexible TPU, which is highly elastic and impact-resistant, or from reinforced composites that offer enhanced stiffness and strength. This versatility allows for the customisation of mechanical properties to meet specific application needs.

Porosity and Surface Finish: While SLS parts may have slightly higher porosity compared to MJF, this can be controlled and minimised through process optimisation and post-processing finishing techniques. Additionally, SLS parts often require post-processing to achieve smoother surface finishes, which can affect mechanical performance by reducing friction and wear in moving parts.

Thermal Stability: SLS materials, particularly certain polymers, offer excellent thermal stability. This makes SLS the best choice for parts operating at elevated temperatures or in thermally challenging environments, such as within engines.

Comparing MJF and SLS

When comparing the mechanical properties of MJF and SLS, it’s clear that both technologies have their unique advantages. MJF is superior in terms of isotropic strength, precision, and speed, making it ideal for parts requiring consistent mechanical properties and fine details. MJF also wins the battle of production speed, ideal for faster prototyping.

SLS excels in producing parts with complex geometries. With its broader material range and robustness, it’s ideal for specific mechanical requirements tailored to challenging environments.

Choosing the Right Technology

The decision between MJF and SLS should be based on the specific mechanical demands of your application. For instance, if your project requires highly detailed parts with uniform strength and smooth surfaces, MJF might be the better choice. Conversely, if you need robust, durable parts capable of withstanding high mechanical loads or high temperatures, SLS could be more suitable.

Not sure which type of 3D printing is right for your parts or project? Get in touch with our team today and we’ll help you choose the best additive manufacturing technology for your parts. We are equipped with both MJF and SLS technologies and can provide expert guidance to help you choose the right process for your specific needs, ensuring that your parts meet the highest standards of performance and reliability.

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