Practical 3D Printing: Cleaning & Curing

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Cleaning & Curing

06.47

00:00	With the part printed, removed from the build plate and the supports broken off, there will always be some excess uncured resin covering the part.
00:07	It's important that we always handle these parts with our nitrile gloves on.
00:12	In this module we'll be looking at cleaning or washing our parts and then post curing them with dedicated machines.
00:18	While these machines help make the process easier, more efficient and effective, we can get by without them.
00:25	So, we'll also briefly touch on how to take more of a manual approach as well.
00:30	As you'd expect, we'll start with the cleaning or washing process, but before we get to our dedicated parts washing station, it's a good idea to remove the majority of the resin from the part.
00:41	This can be done in a container of isopropyl alcohol, simply by dunking the part in and out, or using a soft old toothbrush.
00:50	We don't want to use anything too harsh or abrasive on the parts, as they're not yet fully cured and we could scratch the surface or even damage fine detailed features.
01:00	By getting the majority of the resin off this way, we'll be able to keep the isopropyl alcohol, or IPA for short, in the wash station in better condition for longer.
01:11	And since the wash station contains a large amount of IPA, this will also keep things a little bit more cost effective.
01:18	This dirty container should have a sealed lid that can be replaced when we're not using it.
01:22	Just like our wash station, to prevent any spills or any unnecessary fumes in our workspace.
01:28	So, after this initial dunk, we're ready to put our parts in the washing baskets and into our main washing station.
01:36	This washing station will circulate the IPA, helping to agitate the remaining resin free.
01:41	This can be controlled by a timer, although there's not really a specific time to use and it really depends on the part and the resin used.
01:50	Where larger and more detailed parts will generally need a longer time, say a over 10 minutes, small or very basic parts may only need 10 minutes or less.
02:00	After this is complete, we can lift up the basket and let the excess IPA drip back into the container.
02:07	It helps to give a little shake and tilt the basket back and forward to release any pockets of IPA caught in the part.
02:14	The aim is to keep as much IPA in the wash station as possible, to keep it relatively clean, so we don't have to replace it so often.
02:22	Now, if we don't have a dedicated wash station, then it's just going to be a matter of more manual work with the initial bucket of IPA.
02:30	Another question you might be asking is what about parts printed with water washable resin that we discussed from earlier in the course.
02:38	As the name suggests, the key attraction of these resins is that they don't require any fancy equipment or chemicals to clean.
02:45	We can simply wash these prints under running water.
02:48	After our parts are washed, we want to dry them off.
02:51	Isopropyl alcohol will evaporate, so we can just set them aside on some paper towels and then leave them for a while.
02:58	Otherwise, using a blow dryer or compressed air can help speed up the process, especially for those parts washed with water.
03:05	Before we move on to curing, we need to be sure that all the liquid resin has been removed from the parts.
03:11	In this case, the surface of the parts should appear a consistent matte finish.
03:16	Any shiny areas indicate leftover liquid resin that still needs to be cleaned off.
03:22	This is usually best done with IPA on a clean rag.
03:26	Naturally, if we're using a special high gloss resin, then it does make it harder to tell.
03:31	The next step is post-curing.
03:32	The current state of the part is what's sometimes referred to as a green state.
03:37	What this means is that, while the printed parts have reached their final form, the polymerization process is not yet fully complete, and so maximum mechanical properties haven't been reached.
03:49	Post-curing with light and sometimes heat is required to achieve this last bump in material properties, and this is especially important for the functional parts we'll print in our automotive applications.
04:00	If we don't have a dedicated curing station, there are some alternatives.
04:05	The first and maybe most obvious is natural sunlight.
04:08	We can simply leave the parts in the sun.
04:11	It's also possible to purchase UV lamps, but it should go without saying that we don't want this light shining in our eyes.
04:17	Low-cost UV nail lights can be a good option for small parts for a fraction of the price of a curing station.
04:25	As parts get bigger, we might need to get a little bit more creative with our setup, especially to ensure even exposure and therefore curing of the parts.
04:34	Dedicated curing stations do make life easy.
04:37	These typically use the same 405 nanometer wavelength used by the printer to cure the resin.
04:43	We don't need to get into the physics here, as it's unnecessary, but this is what's been found to effectively and efficiently cure the resin for the best results.
04:52	These stations are designed with multiple light, sources, reflectors, and turntables so the model is evenly exposed and therefore leads to more consistent properties.
05:02	These also have UV safe hoods so we don't need to worry about wearing eye protection.
05:07	The question you're likely asking is how long does the part need to fully cure and what temperature should be used? This is important as over curing can cause the model to turn yellow and become brittle.
05:19	The unfortunate reality is there's no easy answer here.
05:23	Post-cure resins are designed to depend on your equipment, resin choice, and the part geometry.
05:28	Small models printed with standard resins could only take 5 minutes, whereas larger parts could take from 15 to 30 minutes.
05:36	For our example velocity stacks using the frozen TR300 high temperature resin, a 30 minute cure is recommended.
05:44	For the best results we should always refer to the resin supplier's recommendations.
05:49	That covers off the cleaning and curing post-processors so let's recap our parts straight out of the printer will be covered in excess resin and not be fully cured, meaning they won't have their optimal properties.
06:02	We can wash the bulk of the resin off in a container of isopropyl alcohol before transferring to a dedicated wash station that can do most of the hard work for us.
06:12	Parts printed from water washable resins benefit from the ability to simply be washed under running water.
06:18	Before we move to post-curing the parts should be completely dry.
06:30	These will evenly expose the parts to consistent light and sometimes a heat source as well for a set amount of time.
06:37	Just be sure to refer to the resin supplier's recommendations for curing times and temperatures.