A Basic Primer on 3D Printing
My gosh, two blog posts in a week?! Unpossible!
Anyways, I promised a basic 3D printing primer, so here it is! This is mostly taken from my “Intro to 3D Printing” class, so if you want a bit more depth, take a look at that.
So let’s get started!
What is 3D Printing?:
3D printing is the process and equipment used to take a digital file that has been rendered in 3 dimensions and producing a physical object from that digital file.
What’s so different between 3D Printers and traditional machining processes?:
3D printing is often referred to as “Additive Manufacturing”, which means that material is built up or added in layers to create an object, as in in the below gif:
Traditional machining processes have been dubbed “Subtractive Manufacturing” due to the fact that they start out with a solid block of material, and using various cutters and bits, they remove material till the object takes final shape—as in the below YouTube video.
When did 3D Printing come out?:
In the late 1970s the theoretical groundwork was laid for 3D printing, with the first machine being developed in 1983 by an individual named Chuck Hull ( here is a quick article about him, and the first 3D Printer, the SLA-1). During that time the concept and technology were referred to as “Rapid Prototyping” due to the speed in which a product could be produced as opposed to more traditional methods.
The technology stayed in the domain of manufacturing over the next 20 some years until 2009, when the first consumer machines hit to market.
What is the process for 3D printing?
After a 3D model is designed, it needs to be saved in a file format that can be read by a 3D printer. The first file format, .stl (NOT to be confused with the .stl for certificate trust lists) was created by our friend Chuck Hull and stood for “Stereolithography”. While still a popular format to 3D print from, others have popped up in the last few years such as .obj put forth by Wavefront Technologies.
After the file is saved as a supported file type, the file needs to be cut or sliced into vertical layers to facilitate being printed. There are quite a few open source programs that can do this; sometimes they’re packaged with the printer, and others you’ll need to get on your own. Some examples are Cura, Slic3r, Astroprint and Repetier Host. After the slicer program cuts the model down into layers, the program outputs what is called ‘g-code’. G-code is machine language that tells the printer where to move the hot-end, how fast to extrude the plastic, what temperature things should be at—everything the printer needs to actually print.
What types of 3D printers are there?:
Short answer? Lots. However, most of them have very specific uses, are incredibly expensive, or both. For consumer use, there is really only two types, FDM (also called FFF) and SLA.
FDM stands for “Fused Deposited Material, which is the same thing as FFF or “Fused Filament Fabrication”. In this process, a plastic (usually) filament is heated up to around 200 degrees Celsius (392 degrees Fahrenheit) for PLA plastic or 260 degrees Celsius (500 degrees Fahrenheit) for ABS plastic* in what is called the ‘hot-end’. The hot plastic is then forced through a small opening in the hot head in a process called extruding. The extruded filament is then forced on the build plate in verticle layers, which creates the object.
SLA stands for “Stereolithography”. Stereolithography uses a photo-reactive resin that is exposed to a light source which hardens the resin. The Form 2 we have uses a laser tuned to a specific wavelength to do this, but there are printers that use DLP projectors to do this as well. In the case of the Form 2, a build plate is lowered into the resin, a laser draws a layer of the object, and the build plate then moves up a slight amount (the height of the layer) and the process starts over.
What’s the practical Difference between FDM and SLA?:
FDM printers are more inexpensive. This is true for both the machines and the consumables. PLA can be had for under $30 for a kilogram (2.2 pounds). FDM machines are also easier to work on. Belts, hot-ends motors, etc can typically be accessed (though you may void the warranty) with little difficulty for the end-user. That being said, the quality of the print is limited by the fact that semi-melted plastic is being forced through a small hole. At some point, that hole can’t get any smaller which means the layer height can’t get any smaller. I like to compare FDM printers to dot-matrix printers, perfectly usable to make text documents, but you’re not printing the family portrait out on it.
SLA printers are pricey. While the physical machines are coming down in price they’re still pretty costly. The photoreactive resin can also be pretty costly, Form’s resin, for example, is around $150 a liter ($570 gallon). Other SLA printers have other resins and they’re are 3rd party options available as well, and while cheaper, there are other issues. I’ll probably do a post later on printing cheaper with the Form 2. That being said the quality is far superior to the FDM printers, with the ability to go from printer to casting copies with a very minimum of work. This is your high-end photo inkjet for comparison.
What else should I know about 3D Printing?:
Tons, but this is already a pretty long blog post. 3D printing is brand-spanking new in terms of technology, you’re probably going to have to put in work to get everything to work right. Even printers like the Ultimakers need periodic adjustments and cleaning, etc. The more inexpensive the printer, the more sweat-equity you’re going to have to invest. There’s also supports that often have to be removed with varying levels of difficulty (and frustration), misprints, poorly designed models, bad filament… the list goes on.
This stuff is really, really cool. Seriously. And I’m really glad I’ve gotten the opportunity to learn this at work and get paid to teach it. I plan to get back into more hobby related posts here with a ‘3D printing for hobby use’, but I figured I should at least do a ‘basics’ post. I’d be happy to answer any questions you have!
*These temperature numbers are approximate and may vary by filament and printer manufacturer.