3D PRINTING - PART 4

It's Getting Hot In Here

A Guide to Using HP Jet Fusion 3D Printing

With the ever expanding world of 3D printing, a new addition is added to the list and that is Jet Fusion Printing. This new innovative technology has quickly become a popular choice within the industry for its speed, accuracy and cost effectiveness. The technology itself is very similar to binder jetting as discussed in chapter 2, it utiliser’s a liquid binding agent deposited onto the powder bed to generate the different layers of an object; as well as injecting a detailing agent to achieve the finest details and a smooth surface finish.

One of the advantages of this technology is unlike its counterpart SLS (Selective Laser Sintering), it requires less heat to fuse the powder together which in turn reduces the time it takes to cool down.

Please click on the following link to view the process:

https://www.youtube.com/watch?v=XeTdo-w6Qx8

HP Multi Jet Fusion, as a 3D printing technology, is powder-based and does not use lasers. The powder bed, housed in a large chamber, is heated uniformly at the outset. A fusing agent is jetted where particles need to be selectively molten, and a detailing agent is jetted around the contours to improve part resolution. While lamps pass over the surface of the powder bed, the jetted material captures the heat and helps distribute it evenly. Since the powder bed is already heated and melting is not based on laser movement, each printing layer takes the same time, leading to foreseeable build times. At present the machine has a maximum building size of 380 X 284 X 380 mm for raw printing.

When compared to other printing technologies such as SLA, FDM, CJP, the Jet Fusion printing leads the way in its speed, accelerating prototypes for testing and manufacturing. It also does not require any support structures to prevent the design from collapsing during the production. As it is already surrounded by compacted powder, allowing the most complicated objects to be formed, some of which contain interlocking parts, moving parts, living hinges and other highly complex designs. In most cases the generation of support material increases the time for a part to be fabricated. At present, the material used by the machine is PA 12, a polyamide. This type of material consists of a very fine powder grain, capable of producing parts of 80 microns (normally used to refer to the layer height, also known as print resolution) resulting in higher density parts with a much lower degree in porosity.

Modelled digitally then 3D printed using Jet Fusion technology and painted to achieve a ‘fossil quality’ look. Due to the intricate and delicate parts of the model, the HP Jet Fusion was the obvious choice for production.

Image courtesy of – Nasser Samman

The benefit of the fine grain powder lends itself to detailed features and complicated parts without any need for post processing. Once completed, parts removed from the printer have an appearance of concrete, however the material works well with colour dying either soaked in a container or sprayed onto its surface.

With its afforded build size, these light pendants were printed in sections, colour dyed, then assembled. Image courtesy of – Nasser Samman

One significant advantage of the parts produced using this technology is their behavior under load.  Rigid resins are quite brittle and tend to fail in multiple pieces. The polyimide however, has a much greater toughness (the ability of a material to absorb energy and deform without fracturing). 

Parts intended for transportation have a greater chance of arriving in one piece as they are capable of absorbing sudden impacts. The prints produced are lightweight, highly durable and both heat and chemical resistant, making Jet Fusion an excellent choice of producing production parts without the expense of tooling.

Exposure to UV light will not deteriorate the materials properties, such as the case with SLA. The material itself is extremely durable in exterior environment’s and has been used within art installations and exhibits

It is important to remember that the properties of Multi Jet Fusion PA 12 vary depending on the thickness of the model. With a minimum wall thickness of 0.6 mm, your 3D printed object becomes more flexible. To make the object become fully rigid, a 2 mm wall thickness is required.

Image courtesy of – Nasser Samman

Printing Resolution

Layer Thickness               80 µm

Accuracy                          ± 0.3% (with a limit of ± 0.3 mm)

Minimum Thickness and Geometry of Your 3D Model

Minimum wall thickness (flexible):                                  0.6 mm

Minimum wall thickness (rigid):                                       2 mm

Minimum wall thickness stemmed elements:               0.7 mm with support – 0.9 mm without support

Minimum wall thickness particular design aspects:    1-2 mm

 

The maximum size of your models are limited by the physical size of our 3D printers – nothing can be printed larger than the printer bed. There is no minimum size for polyamide prints, keeping in mind minimum thickness for walls and structural aspects, to ensure the object will not break is 0.6 mm.

 

 

 

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