Using HP Multi Jet Fusion for Watertight Prototypes

3D printing technologies have improved significantly in recent years opening a floodgate to new possibilities in design, engineering, and application.

Nylon PA12 HP Post Processing

3D printing materials have been developed to withstand extremely high temperatures, resist impact, and tolerate extreme pressure. But until recently, fluid-tight (watertight) components could not be achieved with the polymer materials used in most additive manufacturing processes due to their high porosity. These materials require additional post-processing, coatings, and sealants to achieve water tightness.

Image: HP Inc.

Image: HP Inc.

With the advent of Multi Jet Fusion (MJF), came the ability to 3D print fluid-tight parts. HP’s Nylon PA12 and MJF process have been proven to produce watertight parts without the need for any additional post-processing. Additionally, HP PA12 parts are extremely durable, have good elasticity, and are resistant to chemicals and high fatigue. These factors make Multi Jet Fusion an ideal solution for end-use hydraulic components, or functional prototypes used in underwater applications.

Image: HP MJF parts pre-assembly

Image: HP MJF parts pre-assembly

The large parts shown here were components in a large prototype intended for functional testing. The parts required the selection of a high-density, durable, and watertight material that could be produced as quickly and cost-effectively as possible. Empire Group opted to use MJF technology and Nylon PA12, and produced the components in sections in our Rapid Prototyping Lab, then assembled and bonded the parts together in our model shop.

Other process might be considered for creating this part, including CNC Machining (subtractive manufacturing), or Selective Laser Sintering (SLS). But Multi Jet Fusion provided our customer with several advantages that these plausible options did not.

  • Faster cooling times means that MJF results in shorter lead times than similar additive technologies such as SLS.

  • The recyclability of HP PA12 Nylon powder results in cost-efficiency over CNC Machining where much of the material is discarded.

  • Sterolithography (SLA) materials have a high rate of absorption, can become brittle over time, and are not a viable option for underwater applications.

  • The large build volume of HP MJF also allows larger parts to be manufactured quickly.

Large Multi Jet Fusion Component
Multi Jet Fusion Nylon PA12 Defense

Process Comparison:

Image: Assemby & bonding of MJF components

Image: Assemby & bonding of MJF components

SLA SLS CNC
MJF
Prototype Cost* $10,231 $9,113 $15,500 $7,010
Lead Time 2-5 days 5-8 days 3-5 weeks 2-5 days

*Cost for SLA based on Accura ClearVue Material, SLS cost is an estimate based on 30% average cost-efficiency over MJF1. Material Assumptions MJF (HP Nylon PA12), SLS (Standard PA 12 Nylon), CNC (Cast Nylon CP 6/12)

MJF Best Uses:

  • Fit checks

  • Complex assemblies

  • Material testing

  • Durability testing

  • End use production

  • Watertight applications

MJF Advantages:

  • Heat resistant up to 170C/350F

  • High-density, durable material with balanced mechanical properties

  • Watertight for parts with wall thickness greater than 4 mm with no additional post-processing

  • Excellent chemical resistance to oils, greases, aliphatic hydrocarbons, and alkalies

  • Achieve low cost per part

  • Optimization of product through design unification

Image: HP Inc.

Image: HP Inc.

Image: HP Inc.

Multi Jet Fusion Nylon PA12 Thick Parts
Multi Jet Fusion Nylon PA12 Sectioned Parts
Parts prior to post-processing & powder removal

Parts prior to post-processing & powder removal

Mike Harrington - Our friendly neighborhood RP Manager and your best friend for quick turn parts

Mike Harrington - Our friendly neighborhood RP Manager and your best friend for quick turn parts