12 June 2017 15:41
Five Things to Consider When Cleaning Your SLS Prints
Being a powder-based process, any SLS project will be inherently messy, especially during the post-processing, when support materials need to be removed and excess powder extracted before the curing stage. That’s why it’s important to pay close attention to the cleaning process and make sure it is treated as a key part of your post-processing stage. While this may seem simple, it can in fact prove deceptively difficult if you wish to avoid damaging your finished parts. However, with the right approach to cleaning parts, it is possible to achieve results that look great and can be used in a wide range of contexts.
Consider these five points:
1) How fragile is your part?
First of all, consider whether any cleaning method utilised may break or deform fragile parts of your model. SLS prints often have parts that are easily breakable, which means faster, more aggressive cleaning methods may not be appropriate. A gentle wash with hot, soapy water or alcohol will be better for removing excess powder, even if it takes longer, rather than a bead-blast or shot of compressed air.
2) Is your workspace properly prepared?
Make sure you work in a well-ventilated area with a dust extractor and will be able to dispose of any material wastage when you are done, whether that means recycling it or disposing of it safely. Bear in mind that many of the printing materials and chemicals used in SLS can potentially be toxic, so exercise all the appropriate safety measures (as we discussed in our last blog post). For example, if you are using an acetone vapour approach to smooth your part, make sure you follow the instructions on how to safely dispose of the leftover liquid.
3) Is there any excess dye left on your part?
If you’re dyeing your part, it’s important that any leftover dye is carefully removed when it is removed from the dye bed. This is typically done with cold water, but you might want to give your parts a few minutes in boiling water, to make completely sure of a clean result. This is especially important for functional parts, as any excess dye on the surface can subtly affect a part’s dimensions and mechanical qualities.
4) What industry regulations do you need to consider?
Depending on the intended use for your part, there may be industry regulations that need to be taken into account during the cleaning process. For example, 3D printed parts that will be used in the medical field must adhere to the most rigorous hygienic regulations, which means they must be remain completely free of dust and bacteria at all times. This must be factored into the cleaning process, to ensure the end result is completely sterile. In such cases, ultrasonic cleaning would be the most appropriate choice, as this will minimise any chance of the part becoming contaminated in any way prior to finishing. If you will be producing medical parts on a regular basis, consider moving production to a dedicated clean room.
5) How will you ensure your part stays clean?
SLS printing materials are naturally porous, which means they will absorb dirt and bacteria very easily. Once your parts have been cleaned and the right finish achieved, it’s important that they stay pristine in order to both look great and meet all relevant industry regulations. We would therefore recommend you seal your part. This will help protect it from dirt and finger-marks, and also ensure it can easily be cleaned later. There are a number of options available when it comes to finishing, which we looked at in detail in this previous blog post.