xFLEX402 Application Notes

 

xFLEX402 is a flexible black material with high-rebound capabilities and shore 73A hardness. It is the stiffest of the flexible LSPc materials and ideal for lattice structures or other flexible applications where  resilience is required. This material is available on NXE400Pro, XiP, and XiPPro, but not early model NXE and NXD printers. 

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Figure 1: xFLEX402 Lattice Insole

 

Further consideration is needed regarding material handling and print set-up compared to other industrial materials due to the high viscosity of the material and low green stiffness. Viscocity is about 14,500cPs, a bit more than honey. This results in a slower z-axis movement which is reflected with longer print times. Due to viscosity of the material, it is only available in 1kg wide mouth bottles. 

This material prints best on the thinner Everlast2 membrane when available. 

Material Handling

Material changes and handling require extra time and different techniques due to the nature of the material. Syringe and peristaltic pumps are not effective for this material to remove from the vat of NXE400Pro printers, and it does not easily flow from the XiP cartridge with silicone valves.

Pour material into the vat directly from the wide-mouth bottle. A silicone jar scraper is useful.

Pour out of XiP or XiP Pro vats with the help of a silicone squeegee. To remove from NXE400Pro vat a silicone scoop or spoon is recommended. Use only soft materials and avoid rigid or sharp edged plastic scoops that will damage the membrane. The 190um filter is too fine for filtering resin and you may omit filtering material or use a larger mesh filter if there are known contaminants in the material. Heating the resin a bit will reduce the viscosity and make handling and clean up of tools easier.

Scooper Removal Method

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Figure 2: Silicone Scoop

 

A rubber-lined scooper similar to Figure 2 is recommended when handling room-temperature material. Use a squeegee to help push resin into the scooper as seen in Figures 3 & 4, then filter the resin going back into the container using the paper filters provided.

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Figure 3 & 4: Using scooper & squeegee to remove resin from vat

Resin Heating 

Another option to assist in the removal of material from either the container or the vat would be to increase the temperature of the resin. Heating up the resin to 40°C will allow for more traditional material handling techniques, such as using a syringe to move material. Table 1 outlines how xFLEX402 viscosity will decrease as the temperature is increased.

Temperature (°C) Viscosity Value (cP)
25 14500
35 8400
40

6000

 

Table 1: Relationship of material temperature and viscosity

 

Reducing the viscosity of resin will aid in resin recovery and ensure that less resin is wasted by being left in the container or in the vat. 

Print Considerations

There are additional considerations involving print set-up when printing with flexible materials. The considerations covered here are similar to those for xFLEX475.

Avoid large aspect ratios with tall, thin, and vertical unsupported features as seen in Figure 5. Due to the flexibility of the material and the high viscosity, the part is more likely to have movement as it enters the resin which can result in shift lines in the print.

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Figure 5: Geometry to avoid and movement it could experience during printing

To avoid this issue, angle parts with large aspect ratios such that they are supported throughout the print. Another option would be to slow down the retract speed. Print speeds are exceptionally slow with this material due to the high viscosity already, so it is recommended to make modifications to the orientation and support structure instead of slowing down the print further.

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Figure 6: Correct orientation & supports for parts with large aspect ratios

 

Angle large, flat surfaces to reduce the cross-sectional area. It is recommended to angle parts 30-60 degrees off of horizontal to maintain low peel forces.

It is not recommended to try and decrease print time by increasing print speeds or reducing wait time. These conservative print settings are required in order to successfully print with xFLEX402. 

Post-Processing

xFLEX402 will be tacky prior to post-curing. A specialized workflow must be followed in order to obtain desired material characteristics. Extended time in the solvent will result in altered material properties and interfere with dimensional accuracy. Washing in IPA (isopropanol) only is also acceptable and requires less drying time before curing.

 

Washing Post-Cure Tensile Strength (MPa) Tensile Elongation (%)

2 minutes rinsing in xClean or IPA with manual brushing

 

2 minutes in IPA with Ultrasonic

30 minutes in xCure at room temperature 4.66 245
60 minutes in xCure at room temperature 4.77 259
15 minutes in XiP Wash+Cure Station 4.53 258
30 minutes in XiP Wash+Cure Station 4.87 254

Table 2: xFLEX402 validated post-processing workflow

 

Clip supports prior to washing and post-curing to ensure that the support-interfacing surface of the part is clean. It is recommended to leave 3-5mm of the supports until after post-cure. Removing the last section of supports after post-cure helps prevent tearing or damage to the part since it has obtained more strength.

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