xPP405 Clear Application Notes

Introduction

xPP405 Clear was developed with material partner LoctiteAM/Henkel. It is a polypropylene like material with high elongation and high toughness that has very good impact resistance. This is a translucent material that is ideal for printing end use parts for packaging, bottling, eye wear, and other industrial applications.   

Printing with xPP405 Clear

It is recommended to use Low Power settings (3mW) when printing with this material for high accuracy and improved surface finish. The default print settings available on NexaX software are reliable for medium sized constant wall thickness parts printed between 30-60° from horizontal.

xPP405 Clear parts will show signs of heavy z-overcuring on down-facing surfaces and therefore will require close attention to part orientation and support generation to minimize such issues. In general, any important and/or intricate features (sharp ridges, cavities, holes, text, etc.) need to be facing the vat during printing. Large cross sections (>10mm) should be avoided when necessary for better surface finish. Orienting parts at a slight angle (15 – 30) degrees will help minimize shrinkage and interlayer delamination. All support interfacing surfaces will be subject to over-curing and will result in rounded edges and/or “melted” like surface finish. Additional post-processing will be required to fix those surfaces to achieve sharpness in detail.

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Orientation recommendation for xPP405 clear. All fine features are unsupported and are facing away from the vat. Support interfacing surfaces are uniform and therefore easier to post-process.

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Over-curing nature of xPP405 clear - Top image shows the CAD model with supports generated (sharp edges). Bottom image is the printed parts after support removal where support nubs are over-cured on to the base of the model. It will require additional post-processing effort to achieve a nice surface finish on parts such as these.

Support Strategy

xPP405 Clear has a high elongation and hence certain features on parts can bend away from the support structures, or cause warping during printing. It is recommended to support the parts with default strength - high-density supports, with added cone supports where necessary.

xPP405 clear requires thorough support structures around the overhang features to print them successfully. This is due to the high peel forces combined with the resistance offered due to the relatively high viscosity of the material. Users may notice that parts oriented at a 45degree incline will still require supports along the edges to ensure higher print success. Therefore, the critical overhang angle of this resin is 60 degrees while the maximum overhang distance is set to 1.5mm.

xPP405 clear parts are prone to warping and bending due to the ductile nature of the material. Careful consideration to part thickness is required when designing parts to be printed. In general, we recommend a minimum wall thickness of 2mm to combat the warping properties of the material. Cone supports are an integral part of file prep as it provides a means of controlling warping during printing.

If thin parts (< 2mm wall thickness) are to be printed, we recommend post-curing the parts with supports still attached to minimize part deformation.

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Cone supports (alongside regular scaffolding supports) is an integral part of file-prep with xPP405 Clear. It is important to have cones covering all the edges that’s facing the build platform.

Resin Viscosity

xPP405 Clear is a high viscosity resin, and therefore printing large cross sections using default print settings could prove difficult. In such cases, consider increasing the peel distance (+1mm) along with decreasing the Peel speed (to 100mm/min) to allow smooth separation and additional peeling distance between each cured layer.  Due to the high viscosity, the material tends to get accumulated inside small cavities and prone to cause cupping failure even within the shallowest cavities. Proper part design, orientation and cleaning can help mitigate some of these challenges.

It is recommended to wash the parts immediately after a print is completed to avoid resin getting trapped withing small channels and cavities. Use of an ultrasonic device will help with cleaning out resin from hard-to-reach places on your parts.

Post-processing Tips

Validated Workflows (based on 4mm tensile coupons)

Washing

Post Cure

Tensile Strength

(MPa)

Tensile Elongation

(%)

4min wash in xClean bath (may be 2-stage)

 

Rinse in IPA & air dry

20 min in xCure at room temp.

36

78%

 

 

xPP405 Clear has the tendency to accumulate inside the part cavities and within the supports structures. It is a good idea to allow the resin to fall back in o the VAT before removing the build plate from the machine. We recommend removing supports off of any mid to large size parts to ensure thorough cleaning, and to wash away any uncured resin that could be settled inside small cavities. Compressed air can also be used to remove residual solvent from the surface of the material.

All unsupported features and walls printed with xPP405 clear will display great clarity and a nice translucent finish you’d expect to see from a translucent photo-polymer resin. The main challenge you will come across when post-processing is to achieve similar surface results on the support interfacing surfaces where support nubs will need to be sanded off. Once sanded down from a low grit (200) sanding paper to a higher grit (800 -1000), additional polishing step with a buffing agent is required to get the maximum clarity on those supported areas.

Washing

  • xPP405 Clear parts should be put through 2 xClean baths (dirty and clean) 1-2 mins each. Part can then be rinsed off in IPA as the final bath.
  • Make sure the parts are completely dry (at least 30mins) before post-curing them in the Wash+Cure unit.

 

Curing

  • 20min with UV only in the Wash+Cure is generally recommended. Thicker parts may require a bit more cure time to achieve full scope of material properties.
  • Any over-curing will result in part surface turning yellow/amber.
  • Post cure parts with supports still attached so that they will hold their shapes + minimize deformation during post-curing (parts < 2mm wall thickness).

 

Updated

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