The Introduction to HP MJF 3D Printing
Though not strictly a 3D printing company, HP has devoted its time to leveraging 3D printing technology for mainstream manufacturing. It is making inroads with its Multi Jet Fusion technology and in 2017, it unveiled the world’s first state-of-the-art laboratory to help companies develop, test and deliver the next generation of materials and applications for 3D printing.
What’s HP MJF
What is MJF (Multi Jet Fusion) ? Some folks may haven’t heard about it before. People usually are more familiar with 3D printing terminologies like FDM(fused deposition modeing), SLA (Stereolithography), SLS (Selective Laser Sintering) and so on. Multi Jet Fusion is different from those 3D printing as its basic printing process goes as follows:
1. Prepare the 3D printing powder (nylon powder PA12, PA12GB, PA11 are the most common material used by HP 3D printer)
2. Multi jet the fusing agent to the forming area. The fusing agent in black color helps nylon powder to absorb heat.
3. Multi jet the detailing agent to the edge of the parts at the same time. Detailing agent in grey helps to "block" the heat inside the forming area and result in a clearer edge of the final product.
4. Melt all the powder by the heat lamp
Step 1~4 will be repeated until the part are fully printed layer by layer. The thickness of each powder layer is only 0.08mm, which makes precision 3D printing possible. The detailing agent helps to prevent the melting of the powder outside the designated printing area. The remaining powder can be recollected and used for next printing process.
HP MJF Printing Nylon Material
HP MJF 3D Printer 4200/4210
HP 3D printer 4200/4210 consists of a 3D printer, a 3D build unit, and a processing station with fast cooling. The build unit’s internal dimension is 380*380*28.4mm, which is also the max dimensions of a component to be printed. If a 3D build unit is filled with as many parts as it could, the total time needed for printing will be 15 hours. After this, 3 kinds of cooling methods may be used for the components, one is rapid cooling at the processing station, one is natural cooling under room temperature and another is rapid cooling + natural cooling. The time needed for rapid cooling will be almost the same as the printing time. Natural cooling takes about 3 times of the printing time. And mixed cooling take about 23 hours.
There are all together 4 types of 3D printing mode to meet different customer demands.
1. Balance mode
Balance mode is the default mode. This mode is suitable for components that must be accurate, have good color uniformity, and do not affect mechanical properties.
Advantage: Achieve the right balance between appearance and feel, dimensional accuracy and mechanical properties.
2. Mechanical mode
This mode is suitable for printing parts with pin bolts that must be bent, or parts that must pass the impact test.
The printing member has the most suitable elongation at break and impact resistance.
1. As the printing temperature increases, component accuracy becomes more and more difficult to ensure, and the color uniformity is worse than the balanced or fast printing mode.
2. Not recommended for parts that may warp.
3. Fast mode
This mode is suitable for low tensile strength components and low cost components.
1) Save printing time and printing reagents, reduce printing costs;
2) The printing accuracy is almost the same with the balance mode.
1) The tensile strength of the component is weakened;
2) Due to the decrease of printing temperature, the possibility of wrinkling on the surface of the product increases.
4. Appearance mode
This mode is to eliminate dents and abraded top layers. It is especially recommended for products where dents may occur.
1) Reduce the dents on the surface of the product
2) The top surface of the part achieves the lowest surface roughness
1) Affects mechanical properties, but not as obvious as fast mode (especially in the Z direction)
2) Due to the decrease of temperature, wrinkles (especially at the edges) are more likely to occur.
Advantages of Nylon Parts Made By HP MJF
Compared with normal resin parts made by SLA printing, HP MJF printed nylon parts have better air tightness,high-temperature resistance, tensile strength, rot resistance. Resin parts will become beige after a long time and can break easily while nylon parts will withstand a long time storage without any color change and could bear strong physical impact. Because of this, we would highly recommend our customers to use the HP MJF printed parts for some functional prototypes, such as gears. If customers only want to check the outlook, then SLA printed resin parts can be a more cost-effective option.
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