co-author: William Brent Wright
II. 3D Printer Anatomy
What are the different types of 3D printing and which one should I choose?
There are a lot of different types of 3D printing. For our purposes, we’ll only focus on FDM (fused deposition modeling), or extrusion 3D printing.
You can think of FDM printing as a computer-controlled hot glue gun. It melts plastic at a specific temperature and flow rate and lays down those strings of plastic one on top of the other to create a 3D shape. FDM is by far the most common type of 3D printing because it has the least expensive machines and materials and does not require a clean space or personal protective equipment, like some of the other printing options. FDM allows you to use most of the standard thermoplastics, but you cannot print in metals.
There are two major downsides of printing with FDM-style machines:
- Support material is required and can be difficult to remove.
- In order to print shapes that do not sit flat on the print bed or do not have material directly underneath a layer to be printed, support material (think of this like scaffolding) has to be printed and subsequently cut away or sanded off of the final device. This can increase print times substantially, and then after the print is finished, be a waste of material and take a good bit of time and effort to completely remove. - Parts often are weaker in the vertical axis because each layer of plastic is incompletely welded to the one below it. This can be mitigated by changing some print settings and with certain post-processing procedures, but you’ll always have to overcompensate for strength a bit when using FDM printing.
While there are some small disadvantages to using FDM printing, the cost of the machines and the availability of materials and technical support make printing with FDM a no-brainer.
What size printer do I need?
What will you be printing? BK’s? AK’s, Symes’s? Bigger printers are not always better. Take a look at your practice and see where you need to save some time or where you have a lot of volume. Starting with BK’s would be the easiest to do. Average size BK would be 5–10” tall without a distal attatchment. Think about circumference as well — this will determine the width and length you need your printer to be.
Printer is divided into 3 axis. X axis is side to side. Y axis is front to back. Z axis is up and down. When looking at build volume a 12 “ X and 12” Y will print up to a 37.68” circumference and then you just have to figure out how tall you want it to go. This combination (l x w x h) is called a printer’s build volume.
What printer frame do I need?
There are two main types of printers:
- Cartesian, which runs in a linear fashion on all three axis and
- Delta, which has 3 printer-arms that move up and down along individual vertical beams to create vertical and horizontal movement based on trigonometric calculations.
For the purpose of this guide, we are only looking at cartesian printers because they are more simple to troubleshoot and because there is a lot more support for cartesian-type printers at this time.
What are the parts of a printer?
Some Definitions
The hardware of the printer includes, among other things, a control board, a print head, an extruder, and a hot end.
Think of the control board as the translator of movement for the printer. This tells the different motors to move the hot end to a specific location so that it is ready to have plastic pushed to the right spot.
The extruder pushes the filament to the hot end at a specific speed to ensure the right amount of plastic is getting printed at the right position.
The hot end consists of a cold zone, heat break, melt zone and nozzle. The filament passes through the cold zone and through the heat break and then into the melt zone and finally out the nozzle. The hot end melts the filament at a specific temperature designated by the user.
The printer bed is often heated or has some sort of sticky material to ensure that the print stays stuck to the bed for the duration of the print.
The filament is a roll of plastic, similar to weed-wacker line, that gets pushed through the extruder, melted at the hot end, and laid down layer by layer to create your model.
Extrusion Types
There are two types of extrusion (how the plastic is pushed from the roll of filament to the hot end). Most cartesian printers use a direct drive system meaning the extruder is pushing the filament directly into the hot end rather than a bowden system that has a seperate motor that pushes filament through a tube and then into the hot end. The image above shows a bowden-style system. A bowden system has one main advantage: it allows the tool head to be lighter since the extruder motor is not connected to it. A light tool head in theory allows for faster prints and quick directional changes, without a lot of whiplash. The problem with a bowden system is that if you use any sort of flexible filament for printing, you’re liable for a lot of jams. Imagine pushing string through a tube and you can understand the problems you might have! We almost always suggest buying a printer with a direct drive system.
Nozzle Size
It is imperative to talk about nozzle size. This is the size of the hole at the end of the hot end. The smaller the hole, the thinner the string of plastic that comes out the end. Nozzle size has everything to do with resolution and speed of a print. Small nozzle sizes allow for a smooth detail finish, but take a long time to print since only small strings of plastic can be pushed out. Alternatively, a large nozzle allows for faster prints but does not create a smooth detail finish.
Filament Diameter
Lastly, there are two main sizes of filament: 1.75 mm diameter and 2.85 mm. Choose one size and make sure all your future machines have the same size. In theory 1.75 mm filament will melt quicker and therefore speeds can be increased. 2.85 mm filament needs to be melted all the way through and some believe that speeds are compromised. Most machines default to 1.75mm, which is what we would suggest.
Our suggestions so far, regardless of use case:
- FDM printer
- Cartesian-style printer
- Direct-drive extrusion
- 1.75mm filament and drive system
- Start with a 0.8mm nozzle
