Most clear "transparent" prints lose their gloss and transparency becoming hazy, translucent, and even whitish, when they are cleaned with isopropanol, ethanol or even with our milder Cleaning Fluid Bio. Additionally, the use of alcohols also reduce significantly the mechanical properties of most clear and colored prints, weakening and making them brittle. Learn more:
- Comparison of different methods for cleaning and post processing 3D printed resins
- IFU for colored 3D prints
For printing biocompatible resins for dental, orthodontic, implants, and other biomedical applications read: IFU for biocompatible resins
- a low cost wash & cure machine of 100 Euro can be used, such as Wash & Cure machine or a similar one can be used for cleaning and light postcuring prints:
- light boxes with too high power with too long postcuring time can cause some yellowing and decrease of mechanical strength "embrittlement" due to over curing
- a thermal oven (optional, needed in method 2 is used)
Cleaning and post processing protocols
The following cleaning and post processings protocols are cost effective, fast, and easy. They are ideal for obtaining maximum mechanical, gloss, and transparency of clear prints. Follow our post professing instructions without cutting corners for getting optimum results:
Method 1: Light box post curing of wet prints by immersion/dipping
- fast & easy process, recommended with the required usage of Cleaning Fluid UNW1 Bio or Cleaning Fluid UNW2 Bio for increased gloss, transparency, and biocompatibility:
- Cleaning Fluid UNW1 Bio has very good cleansing yield, very low viscosity and a balsamic fragance
- Cleaning Fluid UNW2 Bio has medium viscosity and it is odorless
- both have MSDSs free of hazards and risks
- choose Cleaning Fluid UNW1 Bio if maximum clarity is needed since tends to provide improved clarity with most 3D printed resins
- choose Cleaning Fluid UNW2 Bio if increased biocompatibility is mandatory
- without the usage of Cleaning Fluid UNW1 Bio or UNW2 Bio maximum gloss and transparency of clear resins will not be obtained independently of the resin used, since alcohols, such as ethanol or isopropanol IPA, cause whitening and embrittlement of prints
- remove prints from the build platform with a spatula
- cut the supports
- dip prints inside a washing basket in a washing container filled with Cleaning Fluid UNW1 Bio or UNW2 Bio for removing any uncured resin from the prints while stirring with a magnet stirrer (wash mode of the Wash & Cure machine)
- once prints and washed and cleaned dip them again in another transparent container filled with fresh and clean Cleaning Fluid UNW1 Bio or UNW2 Bio
- postcure prints at room temperature inside Cleaning Fluid UNW1 Bio or UNW2 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 UNW1 Bio or UNW2 Bio from the surface of the prints by spraying isopropanol on its surface to remove any rest of Cleaning Fluid UNW1 Bio or UNW2 Bio
Options and different possible scenarios:
- if the prints are too sticky without yellowing, increase the light postcuring time inside clean Cleaning Fluid UNW1 Bio or UNW2 Bio
- if the prints are non-sticky with yellowing and embrittlement, decrease the light postcuring time inside clean Cleaning Fluid UNW1 Bio or UNW2 Bio until yellowing and embrittlement decrease
- once the prints are non-sticky and without yellowing nor embrittlement the optimum settings have been determined
Method 2: Light box post-curing of dry prints in air atmosphere
This alternative method does not require the use of any cleaning fluid, but requires the use of a thermal oven for dripping out the uncured resin from the prints after printing.
- ideal for dripping out of the uncured resin from the prints by gravity in an oven at <65ºC
- residual and extractables need to be removed for biocompatible applications
- after printing cut the supports and let the uncured resin drip out 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, and rotate them for maximum drip out by gravity)
- the higher the viscosity of the resin the higher the recommended oven temperature for dripping out
- low viscosity resins do not need oven temperatures >50ºC
- high viscosity resins need oven temperatures >50ºC, between 50 and 65ºC
- the higher the viscosity of the resin the longer time needed for dripping out
- avoid temperatures above 65ºC to prevent yellowing
- after postcure the dry prints in a normal light box for 15-30-45-60 minutes* at room temperature
- turn the prints upside down and postcure them for other 15-30-45-60 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)
Options and different possible scenarios:
- if the prints are too sticky without yellowing, increase the light postcuring time
- if the prints are non-sticky with yellowing and embrittlement, decrease the light postcuring time until yellowing and embrittlement decrease
- once the prints are non-sticky and without yellowing, nor embrittlement, the optimum settings have been determined
Final cleansing process
For printing biocompatible devices these final cleansing steps are needed to cure any residual uncured monomer, and/or to remove any extractables, leachables, contaminants, and byproducts.
For biocompatible applications prints:
- can be dipped (recommended) in Cleaning Fluid UNW2 Bio for thermal postcuring at high temperature between 70 and 100ºC for 20-30 minutes, or longer if needed, to cure any residual uncured monomers, and to remove both hydrophilic and hydrophobic extractables, leachables, contaminants, and byproducts
- have to be dipped in water (required) for thermal postcuring between 70 and 100ºC for 20-30 minutes, or longer if needed, to cure any residual uncured monomers, and to remove hydrophilic extractables, leachables, contaminants, and byproducts
- For more information read our more detailed Instructions for Use IFU for biocompatible resins
*Note: The optimum time for curing the resin needs to be determined by experimentation since depends on many variables beyond our control, such as the printer, printing and light box specifications and settings, light power, wavelength, exposure times, total energy dosage, etc.
Discover how method 1 and 2 compare to the cleaning with conventional alcohols which cause matting, whitening, and embrittlement to prints: Comparison of different methods for cleaning and post processing 3D printed resins
When instructions are followed without cutting corners prints with excellent gloss, transparency, surface quality, mechanical strength, and safety can be successfully made. The cleansing yield depends on the dipping time and temperature in Cleaning Fluid UNW2 Bio and water. The higher the temperature the shorter the time needed for fully cleansing the prints.
Some 3D resins have been designed to withstand high temperatures (eg boiling water) without mechanical degradation and yellowing. The higher the temperature the faster and the higher the cleansing yield resulting in increased polymer conversion and removal of extractables, leachables, contaminants, and byproducts.
Some 3D resins can suffer a significant decrease of mechanical strength when exposed to high temperature. In these cases, use lower temperature (eg 60~70ºC) and longer cleaning time to prevent any potential decrease of mechanical strength.
Biocompatible prints will not be ready for usage until maximum polymer conversion and full cleansing are achieved. Biocompatible prints should be free of extractables and leachables.
The safety and biocompatibility of prints are responsibility of medical device manufacturers since their quality and safety depend on the design, implementation, quality assurance and "in house" production of their products with the right printing and post processing protocols and controls.
For more info read: Instructions for Use IFU for biocompatible resins
How to reuse dirty Cleaning Fluid?
Expose the Cleaning Fluid in the washing container to sunlight, or with or without stirring to light in the light box or curing machine. After several minutes the uncured resin will cure as small particles. Then, use a paint filter to separate and remove the cured resin from the recycled cleaning fluid, which can be used again and again for washing prints.