This is a sub-topic of my 3D Printing course.
Introduction
This page is just going to serve as a very basic primer as to what 3D Printing is (I’ll use this term interchangeably with Additive Manufacturing, and sometimes abbreviate it as 3DP). Almost every sentence in this page will be extrapolated to an entire lecture later.
Basic Anatomy
There are several different ways a 3D printer can work, many of which we’ll explore later. But we’ve got to start somewhere, and I choose to start with explaining how the 3D Printer in this class works. Before explain how they work, I’d first like to introduce some of the key terms involved with the physical machine.
1. Extruder – Plastic filament is fed into one end of the extruder, which forces the filament forward by digging into it with teethed gears. This particular style is called a Bowden Extruder because force is applied along a fiber at one point, and exerted at another point on the fiber. One major reason for doing this is that the heavy extrusion motor no longer needs to be mobile (It’s fixed to the frame), so now the End Effector can move more in a more agile manner.
2. End-Effector – The end effector is the “business end” of the printer. The end effector contains a heating element which is used to melt the plastic as it is forced out of the nozzle.
X. X-axis – This is the X axis of 3 dimensional coordinate system that the printer uses.
4. Nozzle – The Nozzle has TWO key features. First, it has a precision hole which molten plastic is forced through. This hole allows for a precise width of plastic to be deposited. The second feature is a flat area around the precision hole. This flat area acts sort of like a clothing iron, in that it smooths out the plastic it moves over, creating a uniform surface to deposit on later.
Z. Z-axis – This is the Z axis of 3 dimensional coordinate system that the printer uses.
6. Power Supply – Supplies 24VDC to the motors, heaters, and control electronics.
7. Print Bed – The Print Bed is the surface in which the plastic part is created on. For this printer, the surface is heated – something that is absolutely necessary for some materials to have proper bed adhesion. Bed adhesion is the materials ability to stick (stay in place) to the bed.
8. Leveling Screws – The Leveling Screws allow for the print bed to be adjusted such that it is completely flat relative to the end-effector. This is something that is necessary to ensure bed adhesion across the entire surface.
Y. Y-Axis – This is the Y axis of 3 dimensional coordinate system that the printer uses.
10. Control Electronics – The Control Electronics are responsible for receiving and interpreting commands to enable heaters, move motors, and receive and act on commands from the human machine interface.
11. Human Machine Interface (HMI) – The Human Machine Interface (as the name implies) is what you will use to send basic commands to the printer to start prints, move axes, or heat up heaters.
Theory
I’ll give you the TLDR (Too long, didn’t read) first. Once you have a digital design, it can be turned into a list of instructions for the printer that tells the end-effector where to move and deposit plastic. This is done layer by layer (each one building on top of another) to produce a plastic piece.
Deposition
Deposition is the act of adding a controlled amount of material at a specified location. The key here is CONTROLLED amount – in order for this to work right, the end-effector needs to consistently deposit a known volume of plastic. This is a process that is calibrated and depends on several factors. In order to be deposited, the plastic also has to be heated up to the glass-transition point. Note this is different from the melting point. This is something we will discuss later in this course. Fundamentally this process works exactly like a hot glue gun.
Note all of the cooling features at the top of the assembly – you don’t want filament to get hot and pliable too far away from the nozzle, otherwise the extrusion process will not work properly because force is absorbed rather than transferred to the nozzle.
Process Overview
Going from idea to final part consists of many different tools and format changes:
- CAD – You first develop your part in some sort of Computer Aided Design (CAD) package. It seems like each package uses their own format (though there are some common formats), but for 3D Printing, it is exported to an STL file (Stereolithography).
- Slicer – A Slicer uses several complex algorithms to determine what movements and depositions the end-effector will need to make in order to recreate the geometry contained in the given STL file. There are boatloads of things that can be modified in these algorithms, which we will get into later in this course. The outputted instructions for the printer are called G-Code
- SD Card – It’s not always necessary to put your G-Code on an SD card, but it can be handy to use so your computer isn’t tied to the 3D Printer.
- Control Motors & Heaters – It’s at this point, that things start happening. The G-Code file is interpreted as a list of movements and depositions, which in turn cause depositions at various points in space. Once the entire G-Code script is completed, your part will now exist physically.
Pros and Cons
You’re probably sick of reading. How about I read for you:
