A Primer On 3D PrintingBy John Carson on July 1, 2018 | comments
As we all know, 3D printing is a super hot topic right now. It’s everywhere - on TV shows, in the movies, in manufacturing and in healthcare. Why, you ask? It’s obvious - 3D printing is just super cool!
If you have thought about adding printing to your practice, cool! If you’re just not sure what to think, I get that, too. Either way, keep reading, as I will share some tips and information that you will find helpful.
We talked about 3D printing being all over Hollywood, and as such, the first thing to get out of the way is that it is way different (for the most part) than what you see in the movies. In the movies and TV, you hit a button and a little later, out comes a finished product ready to use. As is often the case, real life is quite different. One thing is for sure: 3D printing can indeed save you time and bring new workflows to your office; just know it won’t be quite like the movies.
Clearly, the first decision to make is which printer to buy. As you would expect, there are a lot of different units to choose from and significant differences between many of them. Due to this fact, for the purpose of this article, rather than make a specific recommendation on a printer, I am going to give you a list of different things that apply to just about any printer to aid you when evaluating printers and which one might be best for your practice.
- How accurate is it? One I don’t really have to mention much is accuracy - as a dentist, you are going to ask about this without me telling you to.
- How much does it cost? The other obvious one that I don’t have to tell you about is cost. Printers can range from under $1,000 to tens of thousands of dollars and anywhere in between. The maybe not-so-obvious thing to ask about when considering cost is maintenance costs. Just like your laser or ink-jet printer, there are consumables in 3D printers, so it’s a good idea to know what they are, how often they need to be replaced and their cost.
- What resins can you print? Maybe not as obvious are what resins you can print with said printer. This is really important, as these resins are often task/product-specific and can be printer-specific as well. For example, let’s think about three common things used in our offices: dental models, oral appliances and surgical guides. Yes, you can print all three and get the best results if you use different resins for each item. You can print them all, but to do it right, you need to use three different resins. This is the reason you need to know what resins you can use in any printer you are considering! If you are wondering why there are different resins for each thing, the answer is simple: the different things require different properties and, at least for surgical guides and appliances, you need and want a resin that has been approved for use in the mouth. So if you’re thinking, “okay, that’s two materials, not three, because I could use the same resin for appliances and surgical guides,” you’re on to something … unless you want to sterilize your surgical guides as well as use a resin specifically for guides with FDA approval for such. The last thing about picking your printer is a tie back to tip 2 above: the resins for different printers can vary significantly in price, so a cheaper printer that uses more expensive resin may cost more in the long run.
- How fast does it print? The next thing to consider is how quickly the printer prints. This can vary wildly from printer to printer and depending on how your printer prints (no, they don’t all print the same way). It can even vary on the same printer depending on how many things you are printing. This is due to the fact that some printers print by essentially curing each vertical layer all at once, so the only thing that really dictates print time is the vertical height of the print, while others cure on more of a point basis, so both the vertical and horizontal size of the print effect the print time.
- How big is the print bed? Lastly, you need to know and compare the print bed size of each printer you are considering. The print bed is the platform that your print is printed on and determines how large of an item you can print and/or how many different things you can print.
I have already mentioned post-processing; now we will dive into it and what you need to know. The first thing to know is that post-processing is a really big deal if you want consistent, high-quality products, and I think we can agree that, as dentists, we need to be about high quality and consistency.
So what is post-processing? Simply put, post-processing is what happens once you take the printed item out of the printer to give you a usable product. For reference, here is an image of some prints coming out of my printer.
Keep reading for an overview in the different steps involved in post-processing 3D prints.
1. Wash the print with Isopropyl Alcohol (IPA). This “washing” removes the extra, uncured resin on the print that clings to the partially cured resin that makes up your print. There are many ways to carry out this wash, ranging from do-it-yourself setups to automatic commercial units. In my opinion, both the DIY and commercial units do this job really well. It really comes down to personal preference and budget - at least, that’s my experience so far. The DIY setups typically consist of two baths of IPA agitated by either an ultrasonic or magnetic stirrer. The first bath is used to get the bulk of uncured resin off the polymerized resin and the second is used as a touch-up or final rinse to make sure every last bit of excess was removed and you have a perfectly clean print. Once you start printing, you will quickly learn why you need two different baths. It is quite remarkable just how much excess resin you rinse off your prints. Take a look at this IPA bath after rinsing only a few model prints.
See all the gray stuff in the IPA? That is the excess, uncured resin that was rinsed off! This image is what the prints from above look like after washing.
As far as commercial units, there are lots, and the just like 3D printing itself, that list is always changing. I will not cover those in-depth here in this prime, except to say you should know that they exist. No matter which route (DYI or commercial) interests you the most when it comes to washing your prints, know that this step is critical.
Therefore, my suggestion would be to talk to the manufactures of your printer and the resins and see what they recommend. Why is this critical? If you underdo it, you will have problems with excess resin remaining on your print that will get cured to your print, resulting in an inaccurate print. If, on the other hand, you overdo it, you will also have issues with either weak or distorted prints due to the resin being overexposed to or over-saturated with the IPA. The key here is to follow the resin manufacturer’s recommendations when it comes to washing methods and times.
2. After washing, your print is now ready for post-curing, and if you want consistent, high-quality prints, then (just like the washing of your print) this step is critical. As the term itself implies, post-curing is the process of completing the polymerization of the resin. That’s right, the printer itself does not fully polymerize the resin. Just like the washing step, we again have choices to make in how we carry this out. For this step (in my opinion) the choice you make here has a greater chance at impacting the consistency of your products versus which washing method you choose, as resin curing is a way more technical thing than simply washing away extra uncured resin.
The simplest method employed by some is simply exposing the print to natural sunlight.While it does not get any simpler than that, as we all know, not all sunlight is the same. I mean, think about “sunlight” in Seattle vs Scottsdale - slightly different, right? So if we are after consistent products, I would not recommend this method.
The next method many employ is the use of UV nail salon curing lights. My take on this is that I know they can work and while I would certainly expect more consistent results than the “sunlight” method, personally I would rather have something more purpose-built for what we are doing, as I would expect something built for curing 3D prints to be even more consistent.
For me, this means a commercial unit specifically built for curing 3D prints, like mine pictured here.
Just like the commercial washing stations, the commercial units for post-curing are always changing too. Along that line, while the unit I bought was a relatively new model when I bought it, shortly after buying it the company introduced a new model!
The big things I would look for when looking at curing units are: what is the wavelength they use (and is that wavelength compatible with the resins you plan to use)? Do they have a heater (if you can control the temperature inside the unit, curing will be more consistent)? Do they have automatic timers (who does not want to set it and forget it)? And lastly, how many items can they hold?
Editor’s note: Dr. Carson wrote this article based on a SpearTALK discussion board post about 3D printing. If you’re a Spear Online member, you can participate in the discussion here.
John R. Carson, DDS, PC, Spear Visiting Faculty. www.johnrcarsondds.com