Post-processing comprises of all the steps that are required once a printed piece is removed from the 3D printer. It can be generally divided into two categories: primary and secondary post-processing. The former includes some of the mandatory steps required for all of the parts once they are created. These steps depend on the printing technology in use and usually involve cleaning, removing the support structures, etc. This essentially prepares the printed item for secondary post-processing. The second kind is concerned with improving the finish of the print, whether it is for the aesthetic or functional purpose. The steps that fall under this category include sanding, priming, dipping, painting, as well as sometimes plating or machining. This article will highlight some of the best post-processing techniques for SLA printed pieces.
Post-processing of 3D prints can be an automatic, semi-automatic, or manual operation. You can learn more about post-processing FDM printed parts. You can also buy the best SLA 3D printers from the Bionic Inventor shop.
What is SLA 3D Printing?
SLA or Stereolithography is an additive 3D printing technology. Unlike FDM, instead of consuming plastic filament to print objects, SLA works with liquid resins. When the resin is introduced to a specific type of light, it hardens the liquid to take the form of the model. SLA models are also printed layer by layer, but by zapping a tank filled with resin solution, instead of extruding filaments. The device is loaded with a 3D file containing commands for directing the UV light. When the printing starts, the liquid solution is exposed to a UV light. It carefully targets the resin layer from the bottom and builds upwards.
Resin printing can produce high-quality 3D prints that have accurate features and details as tiny as 0.3 mm. It can be used to print miniatures, figurines, high-quality structural models, etc. Due to its ability to print such fine details, it can create complex prototypes. These are just a few examples of things SLA 3D printing can generate. One of the drawbacks of this printing technology is that it can create tiny pieces, and usually, models need support structures to form certain angles. They can leave marks and blemishes, resulting in uneven surfaces. Luckily, SLA printed pieces are generally the easiest to post-process. There is a variety of finishing techniques that can fix the models and take care of any shortcomings.
POST-PROCESSING TECHNIQUES FOR SLA PRINTED PIECES
Always Remember - Safety First
All 3D printable resins and fresh SLA pieces need to be handled carefully. Pay attention to the advised precautions such as wearing protective glasses, gloves, and other such gear. As for gloves, try to use the neoprene or nitrile gloves to keep your hands protected. When the parts are removed from the resin tank, they often drip, which can be wiped with paper towels. Keep the printed piece away from UV light before the final curing, as photopolymer resin could get polymerized if exposed to UV light.
Rinsing Off the Resin
After the printing process is complete and the piece is taken out of the vat, it has uncured resin all over it. The first one of the post-processing techniques for SLA printed parts, is to rinse off any excess liquid. There are different approaches for cleaning SLA prints, such as an ultrasonic bath and ‘Dunk and Rinse’. The more professional and relatively costly method is the use of an ultrasonic bath. It is also used for cleaning jewelry. The process involves placing the piece inside the tub filled with the cleaner fluid for around two minutes. It removes the uncured resin layer still left on it. Once done, the print will come out with a smooth and clean finish.
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The Dunk and Rinse approach can be used if you do not have access to an ultrasonic bath. You can simply dunk the printed piece into a vat of isopropyl alcohol to remove the uncured resin. Once the part is dipped into the liquid, move it around and rinse it thoroughly. It is a quick and straightforward technique but not as effective as the ultrasonic bath. You may also have to repeat it a couple of times to achieve the desired results.
After the uncured resin is taken care of, you can focus on the supports attached to the printed piece. It is recommended to remove them before curing the model, as removing cured supports can cause them to shatter and take small parts of the material with them. The best approach is to handle them before the curing process. You can snap the supports using flush cutters or other similar pointy pliers. Try to nip them off as close to the surface as possible. In most cases, they will come off quickly. As for prints with more delicate details for supports in hard-to-reach places, you will have to be extra cautious to minimize the risk of damaging the piece.
Curing the Print
One of the most crucial post-processing steps for SLA printed pieces is curing the item. Curing the print with ultraviolet light finalizes its material properties. The different approaches of curing include Commercial Curing Station, Nail Polish Lamp, DIY Curing Chamber, and Sunlight.
- Commercial Curing Station
A number of SLA 3D printer makers also offer commercial curing stations. These stations are optimized and fine-tuned to work more effectively with their resins. This option is most suitable for professional settings and larger prints.
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- Nail Polish Lamp
It is an inexpensive and convenient approach to cure the printed item quickly. You can cure your piece by merely letting the model rest under a nail polish lamp overnight. You can also place a rotating platform like a turntable to optimize the curing process.
- DIY Curing Chamber
Homemade curing chambers are also one of the inexpensive options. A lot of enthusiasts create their own makeshift variants of the commercial-grade curing stations. A simple way to make one is by lining the insides of a box with aluminum foil and then adding a UV light. A rotating platform can be used to place the printed object for even exposure to all parts of the print.
- Curing in Sunlight
Using the UV rays from the sunlight can also cure a printed item. Simply place the item outside on a bright, sunny day, and the sunshine will cure the piece. This method does require a lot of patience, as you may have to wait for a few hours.