Today’s designers and engineers are presented with a wide array of choices when it comes to 3D printing technologies and materials. Among these innovative solutions, Mjf Printing, or Multi Jet Fusion, stands out as HP’s cutting-edge 3D printing technology, proving to be a highly effective option for a multitude of complex and industrial applications. This article will delve into the workings of mjf printing, its numerous benefits, and help you determine if it’s the ideal technology for your specific part manufacturing needs.
To further explore the diverse 3D printing technologies available through Protolabs Network, we invite you to visit our comprehensive 3D printing service page.
What is MJF Printing?
Multi Jet Fusion (MJF) printing is an advanced 3D printing process renowned for its ability to rapidly produce highly accurate and intricately detailed complex parts using powdered thermoplastics. This technology, often referred to as mjf printing, has quickly become the preferred additive manufacturing (AM) solution for industrial applications due to its consistent and fast delivery of parts characterized by high tensile strength, fine feature resolution, and well-defined mechanical properties. Mjf printing services are commonly utilized for manufacturing functional prototypes and end-use parts, especially those demanding consistent isotropic mechanical properties and intricate, organic geometries.
For a concise yet detailed overview of mjf printing, consider exploring video resources that visually explain the process and its advantages.
The Evolution of MJF Printing Technology
Introduced to the market in 2016 by HP Additive, mjf printing technology is the culmination of HP’s extensive expertise in inkjet printing and precision mechanics. However, the roots of mjf printing can be traced back several decades prior to its commercial launch.
During the 1990s, additive manufacturing (AM) began its shift from being primarily a tool for research and development towards real-world, industrial applications. Manufacturing industries recognized the potential, but speed became a significant bottleneck in this transition. Compared to traditional methods like injection molding or metal stamping, most early 3D printers were considerably slower in part production.
One early strategy to enhance production speed in 3D printing was employing “farms” or arrays of multiple machines to increase output. HP, however, pursued a more integrated and automation-centric approach to overcome this challenge and revolutionize mjf printing.
At their global AM hub in Barcelona, HP engineers developed a system that builds parts layer by layer within a large powder material bed, integrated with automated post-processing machinery. This innovative system, sharing similarities with SLS printing service and other powder bed fusion technologies, ultimately evolved into the sophisticated mjf printing technology we know today.
How MJF Printing Works: A Detailed Process
Mjf printing leverages an inkjet array to deposit both fusing and detailing agents across a bed of powder material. These agents selectively fuse the material into a solid layer, precisely according to the digital design. After each layer is fused, the printer redistributes another thin layer of powder, and the process repeats, building the part layer by layer.
Here’s a step-by-step breakdown of the mjf printing process:
- Build Unit Placement: The moveable build unit, which acts as the container for the part being printed, is placed inside the mjf printing machine.
- Powder Deposition: The material recoater carriage carefully moves across the build area, depositing a uniformly thin layer of the chosen powder material, ready for mjf printing.
- Preheating: The printing and fusing carriage moves across the build area, preheating the powder to a precise temperature. This preheating ensures material consistency and optimal fusion during the mjf printing process.
- Agent Deposition and Fusion: An array of inkjet nozzles precisely deposits fusing agents onto the powder bed. These agents are applied in patterns that correspond exactly to the geometry and desired material properties of the part being created through mjf printing.
- Layer Completion: After each layer is completed, the build unit retracts slightly to make room for the next layer of material to be deposited, continuing the mjf printing build.
- Process Repetition: Steps 2-5 are repeated meticulously until the entire part is fully formed within the powder bed, completing the mjf printing build job.
Once the mjf printing process is finished, the build unit contains both the newly printed part and the surrounding unfused powder. A separate processing station, designed to attach directly to the moveable build unit, is then used for cooling and unpacking the printed part. Crucially, this station also allows for the efficient recovery of excess powder, which can be reused in future mjf printing runs, minimizing material waste. Finally, bead blasting is employed to remove any remaining powder clinging to the part, preparing it for any further cosmetic or functional post-processing steps.
Materials Used in MJF Printing
The materials compatible with mjf printing generally fall into two main categories: rigid plastics and flexible plastics. Rigid plastics commonly used in mjf printing include Nylon PA11, Nylon PA12, and PP. Flexible plastics options feature materials like Estane 3D TPU M95A. HP’s mjf printing systems are primarily designed around polyamide materials, many of which have been specifically developed by HP and their partners to optimize performance in mjf printing.
For a detailed overview of the materials readily available for mjf printing, you can explore the materials available on the Protolabs Network platform. This resource provides comprehensive information on material properties and applications relevant to mjf printing.
| Material | Description |
|---|---|
| HP PA 12 (Nylon 12) | Nylon 12 is a highly versatile and robust thermoplastic, offering excellent all-around physical properties and chemical resistance. It is ideally suited for both functional prototypes and end-use applications requiring durable mjf printing. |
| Glass-filled HP PA 12 | Glass-filled nylon is reinforced with glass beads, resulting in parts with enhanced stiffness and thermal stability compared to standard nylon. This material is excellent for mjf printing applications demanding higher structural integrity and heat resistance. |
MJF Post-Processing: Efficient and Streamlined
Similar to most manufacturing processes, parts produced with mjf printing often require some level of post-processing to be fully ready for prototyping or end-use applications. However, compared to other additive manufacturing technologies, post-processing for mjf printing is generally quite streamlined and less intensive.
After completing an mjf printing job, you’ll find the printed part embedded within a three-dimensional bed of unfused powder inside the build unit.
The primary steps in mjf printing post-processing are:
- Cooling: Initial cooling takes place directly within the build unit. HP also offers modular cooling units that facilitate natural cooling. These units are designed to optimize workflow, allowing a build unit to cool offline while the mjf printing system can be utilized for a new print job, significantly improving throughput.
- Unfused Powder Recovery: Once the build unit has cooled sufficiently, it is moved to the processing station. Here, a vacuum system is used to carefully remove the unfused powder and transfer it into a container for potential reuse in future mjf printing projects, promoting material efficiency.
- Bead Blasting: To eliminate any residual powder clinging to the printed part, bead blasting is employed. This can be done using air blasting or water blasting techniques as well. The process can be manual or automated using equipment like tumblers, ultrasonic cleaners, or vibratory finishing machines, depending on the scale and precision required for the mjf printing output.
Following the removal of all residual powder, additional post-processing might be necessary depending on the specific requirements of the part. For instance, applications requiring very precise surface finishes or tolerances beyond the standard capabilities of mjf printing, such as mating surfaces, bores, or internal threads, might necessitate further machining. Similarly, achieving specific cosmetic or technical standards might require manual sanding or other finishing techniques after mjf printing.
Key Advantages of MJF Printing
If your objective is to create functional prototypes or manage relatively small production runs of end-use parts, mjf printing emerges as an outstanding solution. Mjf printing excels at producing parts with significantly greater strength compared to technologies like Selective Laser Sintering (SLS). Parts manufactured using mjf printing achieve impressive tensile strengths, reaching up to 48 MPa/6,960 psi in both XY and Z axes, as measured by ASTM D638 standards.
Furthermore, mjf printing is exceptionally adept at delivering consistent mechanical properties across all directions of a part’s geometry. This isotropy is particularly crucial for parts with complex, multifaceted designs that also incorporate fine, robust features. For such applications, mjf printing stands out as the most viable and reliable manufacturing option.
Mjf printing enables the production of functional, end-use quality parts with minimal post-production intervention. Compared to many other additive manufacturing technologies, mjf printing is faster and offers superior automation capabilities. This translates to significantly reduced lead times and the creation of high-quality surface finishes with minimal human involvement, enhancing the efficiency of mjf printing workflows.
To achieve its remarkable speed, mjf printing systems consistently scan the surface of the part being printed with each pass, even when printing multiple parts simultaneously. This continuous scanning allows for faster build speeds compared to other technologies, particularly when dealing with larger quantities of parts in a single mjf printing job.
Why MJF Printing is Ideal for Manufacturing End-Use Parts
Mjf printing distinguishes itself from other additive manufacturing processes primarily because it is specifically engineered for producing higher volumes of parts that demand a combination of complexity, fine detail, and structural integrity. This makes mjf printing a highly sought-after solution for manufacturing precise and durable components like electronic component housings, mechanical assemblies, enclosures, and specialized jigs and fixtures.
Modern mjf printing machines often incorporate a build unit that is designed as a rolling cart, directly integrated with a processing station. Once a print job is complete, the powder bed can simply be moved to the processing station for efficient removal of excess powder. Post-processing can be effectively performed in batches, depending on the specific technical requirements of the parts being produced through mjf printing. Often, the need for manual hand finishing is minimal, further streamlining production. This efficient workflow positions mjf printing as exceptionally well-suited for higher volume production runs of functional parts.
The powder bed system inherent in mjf printing eliminates the necessity for support structures. This allows for efficient nesting of parts within the build area, maximizing the utilization of each mjf printing run. Moreover, the unused powder from each build can be reclaimed and reused in subsequent mjf printing production cycles, contributing to cost-effectiveness and sustainability.
MJF vs SLS 3D Printing: Understanding the Differences
While Selective Laser Sintering (SLS) shares similarities with mjf printing, there are key distinctions between these two powder bed fusion technologies. Like mjf printing, SLS printers also deposit powder material layer by layer in a build area. However, SLS machines utilize a laser to fuse material, sintering powder particles together and to the layer beneath.
In SLS, the material properties of the part can be adjusted by modulating the laser’s power, though the range of control is somewhat limited. In contrast, mjf printing offers a broader range of material property modulation through the use of HP’s diverse selection of chemical agents. These agents provide more extensive opportunities to fine-tune the properties of each voxel (3D pixel) of the part during the mjf printing process, offering greater design flexibility and control over material characteristics.
MJF vs. Injection Molding: Choosing the Right Process
Mjf printing not only excels in comparison to other additive manufacturing technologies but also presents itself as a compelling alternative to traditional injection molding. Injection molding involves upfront costs for mold creation and requires extensive Design for Manufacturing (DFM) analysis before production can begin. It also poses limitations in terms of part geometry and typically involves longer lead times, primarily due to the time needed to produce the mold and complete other processing steps.
Conversely, mjf printing offers greater design freedom and significantly reduces lead times. Design iterations can be implemented rapidly with mjf printing as there is no reliance on physical molds. For production runs traditionally suited for injection molding, especially those involving high volumes of small to medium-sized parts with complex geometries, mjf printing should be seriously considered as a viable and often more efficient alternative.
Generally, mjf printing is particularly advantageous for creating prototypes and for small to medium production runs. Prototypes can be produced in just a few days, and parts created using mjf printing achieve mechanical properties comparable to those of injection-molded parts, making it a robust choice for functional applications.
Real-World Examples of MJF Printing in Action
One compelling example of mjf printing in action comes from CNC Würfel, a specialist in manufacturing and process automation serving the automotive industry and medical technology sectors, among others. In 2017, CNC Würfel transitioned from using milling machines and lathes to mjf printing for many of their component productions. This strategic shift drastically reduced production times and freed up resources for more extensive prototype testing.
This transition proved especially beneficial in the production of the company’s gripper adapter, a critical part used in conveyor belts that comprises several complex components and gripping systems. Traditional manufacturing processes for this adapter resulted in lead times of eight to ten weeks and required significant manual expertise and intervention, occasionally leading to part damage.
To overcome these complexities, CNC Würfel adopted mjf printing for the gripper adapter. The benefits were immediate and substantial, with production times plummeting from two months to under a week. Utilizing mjf printing also resulted in significant cost savings, with a 95% reduction in part cost compared to traditional manufacturing methods. Additionally, the mjf printing process yielded a part that was 84% lighter yet maintained the necessary durability for its demanding applications.
Another impactful application of mjf printing is HP’s own Z 3D Camera, designed to simplify real-time capture and visualization of documents and objects. Before the advent of mjf printing, HP manufactured the camera using three separate injection molded parts. This approach led to lengthy prototyping phases, spanning weeks, and incurred significant costs for each part.
Switching to mjf printing for the camera production dramatically accelerated the process. The new technology allowed HP to print the camera as a single assembled unit, rather than three separate parts. According to HP, this change reduced the per-part cost from $2.42 to just $0.36 and shortened the prototyping duration from weeks to days. Furthermore, the design freedom afforded by mjf printing enabled HP to optimize the camera’s orientation, enhancing the overall quality of the final product.
Handy Tips and Tricks for MJF Printing
To maximize the effectiveness of mjf printing, consider these practical best practices:
- Reinforce Thin Walls and Large Flat Surfaces: Enhance the structural integrity of thin-walled sections or large, flat surfaces by incorporating ribs or gussets in your design. Additionally, surround holes with raised bosses whenever feasible to improve durability and mounting strength in mjf printing.
- Cosmetic Feature Size: Be mindful that raised text and cosmetic features smaller than 0.5 mm might not withstand secondary post-processing steps. Always review the DFM analysis provided with your part quote for detailed guidelines on feature sizes in mjf printing.
- Wall Thickness Guidelines: Aim for wall thicknesses between 2.5 and 12.7 mm for your parts. Deviating significantly from this range may affect the dimensional tolerances achievable with mjf printing.
- Cosmetic Surface Identification: Clearly identify any cosmetic surfaces in your design specifications. This ensures that the manufacturer can take measures to minimize stair-stepping effects, particularly on oblique angles of the part, optimizing the surface finish in mjf printing.
A collection of parts showcasing CNC machining, 3D printing, and sheet metal fabrication, highlighting the versatility of modern manufacturing technologies including mjf printing.
Frequently Asked Questions about MJF Printing
What are the benefits of MJF printing?
Mjf printing allows for the production of large quantities of unique parts without the need for arrays of multiple printers. It can also serve as a cost-effective alternative to expensive casting or molding processes. Modern HP mjf printing systems include integrated bulk post-processing stations, which significantly reduce the need for manual finishing.
What are the drawbacks of MJF printing?
While offering superior quality and consistency for industrial applications, mjf printing is generally more expensive than some modular printing technologies like Fused Deposition Modeling (FDM).
Are MJF 3D printed parts water resistant?
PA 12 Nylon, a common material in mjf printing, is one of the few 3D printing materials that offers water resistance. For parts to be water-resistant, wall thicknesses of at least 1 mm are required, while wall thicknesses exceeding 4 mm make parts watertight. Mjf printing parts made from PA 12 are also chemically resistant to greases, alkalies, oils, and aliphatic hydrocarbons.
What is the dimensional accuracy of MJF printing?
The dimensional accuracy of mjf printing is typically ± 0.3%, with a lower limit of ± 0.3 mm (0.012”).
What is the maximum build size of MJF printing?
Through Protolabs Network, the maximum build size for mjf printing parts is 380 x 285 x 380 mm (14.9” x 11.2” x 14.9”).
What are the smallest features MJF printing can produce?
Mjf printing can produce minimum feature sizes as small as 0.5 mm (0.02 in). With print layers as thin as 80 microns (0.0003 in), mjf printing is capable of creating very fine surface details and intricate geometries.
