Comparison of different methods for cleaning and post processing 3D printed resins

Some clear prints may become hazy or whitish when they are cleaned with alcohols, such as ethanol and isopropanol IPA, and even with our non aggresive Cleaning Fluid Bio.

Summary:

  • Cleaning Fluid Bio is biocompatible, odorless, does not chemically attack prints but it can cause whitening of clear prints
  • Cleaning Fluid NW1 Bio is biocompatible, does not chemically attack prints, nor cause whitening of clear prints. It is supplied in 2 versions:
    • odorless biocompatible version (ultra safe, non potential skin irritant)
    • balsamic fragance version with antimicrobial, antifungal and antibacterial activity (potential ultra mild or mild irritant of sensitive skin) 
  • alcohols, such as ethanol and isopropanol IPA kill the sense of smell, chemically attack prints, causing whitening and embrittlement

Comparison of different methods for cleaning and post processing

The following cleaning and post processing methods are evaluated and compared for obtaining maximum gloss, transparency, and mechanical properties of your prints: 

Method 1: Light box post-curing of prints in immersion/dipping  (recommended process)

Features:

  • fast & easy process, recommended with the required usage of Cleaning Fluid NW1 Bio (odorless version yields improved transparency and biocompatibility)
  • without the usage of Cleaning Fluid NW1 Bio maximum transparency of clear resins will not be obtained independently of the resin used 

Process:

  • remove prints from the build platform with a spatula
  • cut the supports
  • optional step for maximum transparency of High Viscosity HV versions: after printing (before washing in Cleaning Fluid NW1 Bio) eliminate the uncured resin from the prints by gravity in an oven at 65ºC for 30-60 minutes (temperature above 65ºC may cause some yellowing in some 3D resins)
    • a low cost wash & cure machine of 100 Euro, such as Wash & Cure machine or similar light boxes can be used for cleaning and postcuring aligners
    • light boxes with too high power with too long postcuring time can also cause some yellowing
  • dip prints inside a washing basket in a washing container filled with warm Cleaning Fluid NW1 Bio:
    • it is odorless, ultra safe and non-flammable
    • warm the Cleaning Fluid NW1 Bio to 30-60ºC
    • the higher the temperature the easier to remove viscous uncured resin from prints
    • avoid temperatures above 65ºC with 3D resins sensitive to suffer yellowing
  • remove any uncured resin from the prints positioned in the basket while stirring the warm Cleaning Fluid NW1 Bio at <65ºC with a magnet stirrer (wash mode of the Wash & Cure machine)
  • once prints and washed and cleaned dip them again in the same (or another) transparent container filled with fresh and clean Cleaning Fluid NW1 Bio*
  • postcure prints at room temperature inside Cleaning Fluid NW1 Bio in the light box for 15-30-45-60 minutes (cure mode of the Wash & Cure machine):
    • light box curing times depend on the power and wavelength of your specific light box
    • low light power postcuring units require longer times than high power postcuring units
    • high light power postcuring units can cause yellowing and decrease of mechanical strength
    • too long light box postcuring can also cause yellowing and decrease of mechanical strength
  • after light box postcuring remove Cleaning Fluid NW1 Bio from the surface of the prints by spraying isopropanol on its surface to remove any rest of Cleaning Fluid NW1 Bio and residual stickiness 
Options and different possible scenarios:
  • if the prints are too sticky without yellowing, increase the light postcuring time inside clean Cleaning Fluid NW1 Bio
  • if the prints are non-sticky with yellowing and embrittlement, decrease the light postcuring time inside clean Cleaning Fluid NW1 Bio until yellowing and embrittlement decrease
  • once the prints are non-sticky and without yellowing not embrittlement the optimum settings have been determined, then prints can be dipped in hot water** for 20-30 minutes to remove any residuals, extractables, leachables, contaminants, residual uncured monomer, and byproducts

*Note: ideally use fresh unused Cleaning Fluid NW1 Bio to avoid contamination of prints with uncured resin from previous washings

**Note: despite being Cleaning Fluid NW1 Bio ultra safe it has a bitter taste, which is transfered to the prints. To remove it, instead of dipping the prints in water, use combinations of water and Cleaning Fluid Bio (version 2) at 50%/50% ratio to remove the bitter taste

    Method 2: Light box post-curing of dry prints in air atmosphere (recommended for viscous 3D resins)

    Features:

    • ideal for viscous resins
    • ideal for preventing any potential decrease of transparency by the cleaning fluid

    Process:

    • after printing cut the supports and drain and eliminate the uncured resin by gravity from the surface of the prints in the upside down position in an oven heated at 65ºC from 15 to 60 minutes (leave prints upside down for maximum drainage and leak out by gravity)
      • the higher the viscosity of the resin the longer time needed for drain out
    • postcure the dry prints in a normal light box for 15 minutes* at room temperature
    • turn the prints upside down and postcure them for other 15 minutes* 
    • clean and remove any residual stickiness by spraying ispropanol isopropanol IPA on the prints (use a spray bottle to ensure that clean IPA is always used)
    • optional: wash/clean the prints with boiling water

    *Note: The optimum time will need to be determined by experimentation since depends on many variables beyond our control, such as light power and wavelength, etc.

     

    Method 3: Cleaning with alcohol or IPA followed by light box post-curing of dry prints in air atmosphere (not recommended)

    Features:

    • Alcohols, such as ethanol and IPA, reduce significantly gloss, transparency, and the mechanical properties sinced chemically attack prints, causing whitening and fragililty
      • it is recommended to use as alternative our recommended Cleaning Fluid NW1 Bio,  which does not cause any whitening nor decrease the mechanical properties of prints
    • if transparency is not important, and with colored prints, Cleaning Fluid Bio can be used as alternative to alcohols because it does not attack, nor decrease the mechanical strength of prints (but it can cause whitening as alcohols of clear prints)

      Learn more about Sterilization of 3D printed resins for medical devices