Most clear 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 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 postprocessing protocols
The following cleaning and postprocessing protocols are cost effective, fast, and easy. They are ideal for obtaining maximum mechanical, gloss and transparency of clear prints. Follow our postprocessing instructions without cutting corners for getting optimum results:
Method 1: Light box post-curing of prints in immersion/dipping (recommended process)
- fast & easy process, recommended with the required usage of Cleaning Fluid NW1 Bio (odorless version yields increased gloss, transparency, and biocompatibility)
- without the usage of Cleaning Fluid NW1 Bio maximum gloss and transparency of clear resins will not be obtained independently of the resin used, when alcohols, such as ethanol or isopropanol IPA are used for cleaning since they cause whitening and embrittlement of prints
- 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 65º may cause some yellowing)
- 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 prints
- 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 <65ºC with eg a kettle (always below 65ºC to prevent 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
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
- prints can be dipped in warm water** for 20-30 minutes to remove any residual taste caused by 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 residual bitter taste, which is transfered to the prints. To remove it, instead of using just warm water, use combinations of water and Cleaning Fluid Bio (version 2) at 50%/50% ratio to remove the bitter taste. Boiling water is ideal for removing extractables, unfortunately, not all 3D printed resins will withstand 100ºC without suffering a decrease of mechanical strength. Decrease and adjust the temperature to 60-70ºC if your prints do not withstand boiling water. Excessive temperature and time of dipped prints in water can decrease their gloss.
Method 2: Light box post-curing of dry prints in air atmosphere (also recommended if you have an oven, but do not have Cleaning Fluid NW1 Bio)
This altenative method does not require the use of any cleaning fluid, but requires the use of a thermal oven for dipping 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 without the need for using cleaning Fluid NW1 Bio, which despite being ultra safe and biocompatible confers a bit of bitter taste to the prints
- there is not any residual bitterness caused by Cleaning Fluid but still residual and extractables need to be removed in warm water
- 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 longer time needed for dripping out
- avoid temperatures above 65ºC to prevent yellowing
- 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
- prints can be dipped in hot water* for 20-30 minutes* to remove extractables, leachables, contaminants, residual uncured monomer, and byproducts
*Note: The optimum time will need to be determined by experimentation since depends on many variables beyond our control, such as the resin, the printing and light box specifications, light power and wavelength, 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, light fastness, mechanical strength and safety can be successfully made. The cleansing yield depends on the cleaning time and chosen temperature of 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 (boiling water) without mechanical degradation and yellowing. At the boiling temperature of water the cleansing yield is increased 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 boiled in water. In these cases, use hot water at <70-90ºC and longer cleaning times to prevent any potential decrease of mechanical strength. Excessive temperature and time of dipped prints in water can decrease their gloss.
Safe 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 postprocessing protocols and controls.
Options for reducing yellowing
- it reduces yellowing significantly without affecting the print speed nor the safety of 3D 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.
Learn more about the effect of printer and printing specifications on the properties of tested standards:
- Effect of printing specifications on biocompatibility and mechanical properties
- Effect of fine tuning on biocompatibility and mechanical properties
- Effect of printers on biocompatibility, safety and mechanical properties
- Key variables affecting mechanical performance of 3D prints
- Tg, HDT, and mechanical properties depend on printing specifications