Fluid Tightness of HP Multi Jet Fusion PA 12 Components

Beitragsbild Wasserdichtheit von HP Jet Fusion PA12 Teilen

Image: HP Inc.

In the past, 3D printing objects were mostly used for rapid prototyping. The progress of additive technologies has led to an expansion in the use of prototypes. In the meantime, fully functional components can be produced which can no longer only be used as visual or test objects, but which can also be used in the final product. Hydraulic components have so far played an exception in this development, as watertight (fluid-tight) components could not be achieved with most additive manufacturing technologies. The HP Multi Jet Fusion process has closed this gap, as the manufactured objects are now largely watertight.

The differences in fluid tightness of HP Jet Fusion and Laser Sintering

We are comparing these two additive technologies for a simple reason: both use PA 12 as 3D printing material. The biggest difference is in the production method. The objects used in laser sintering are quite porous and therefore not suitable for use with liquids.
To achieve a certain degree of water tightness in laser sintered objects, resin can be used to infiltrate the part. The resin (e.g. epoxy) polymerises within the pores and close up the gaps.
It is not necessary to undergo this process step with HP Jet Fusion, as the material grains are fused together. Although Jet Fusion does not achieve a 100% material density, the gaps are negligible compared to laser sintering. The following figure shows the difference in density between PA 12 components created using the Multi Jet Fusion process and the PA 12 components which were laser sintered.

Material densitity PA 12 HP Multi Jet Fusion vs. Laser sintering

Image 1:
Density [g/cm³] of HP Multi Jet Fusion and laser sintering parts, material PA 12.

Source: Material data sheet HP HR PA 12; EOS PA2200

Influence of wall thickness and geometry

The liquid permeability of 3D-printed objects is significantly dependent on 3 factors:

  • Wall thickness of the object
  • Geometry of the object
  • Pressure exerted on the object

Wall thickness: Not surprisingly, the wall thickness plays a decisive role in determining the pressure up to which the material is watertight. However, the wall thickness is not the only relevant factor, but the shape of the component is also important.

Fuild tightness of HP JMulti Jet Fusion printed PA 12 - wall thicknesses

Table 1: recommended wall thicknesses for fluid vessels depending on pressure.
Source: HP Inc.

Geometry: The shape of the object has a strong influence on the liquid tightness of 3D-printed components. While spherical objects can withstand pressures of up to 10 bar with a wall thickness of approx. 2.5 mm, a cubic object with the same wall thickness can hardly withstand pressures of even 3 bar. It is recommended to make the components as spherical as possible, as this means that the pressure on the walls is more evenly distributed.

Fuild tightness of HP JMulti Jet Fusion printed PA 12 - part geometry

Table 2: recommended geometry for fluid vessels depending on pressure.
Source: HP Inc.

Types of liquids which can be used

Liquid systems often use not only water but also a range of other chemicals. PA 12 is chemically resistant to commonly used chemicals, with the exception of aggressive acids such as chromic acid, nitric acid or hydrochloric acid.
The table below gives you a brief overview of the chemicals which can be used.

Chemical resistance of HP Jet Fusion 3D printed PA12

Table 3: Chemical resistance of PA 12 (HP Mutli Jet Fusion).
Source: HP Inc.

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About 3Faktur: 3Faktur is a 3D printing service bureau. We are specialized on the production of plastic parts, for prototypes and batch production.