Introduction
Each 3D Printer is slightly different, but in terms of FDM printers, most of the core components are the same. Of course once we get into different or Novel deposition methods, things can get different. Let’s take a look at some of the core mechanisms for the big 3 of 3D Printing (FDM, SLA, SLS).
FDM Electronics
Filament Sensors
A feature that is pretty useful is a filament sensor. Some of them just give a digital signal (IE is filament present or not), and some specialized sensors can actually detect the width of the filament. Let’s take a look at these sensors:
Auto-Bed Leveling
Some systems include auto-bed leveling mechanisms. The one I am most familiar with is what is featured on the LulzBot Taz:
You’ll notice that in the four corners of the build plate, there are little metal disks. At the start of the print, the machine first homes all axes (so it knows for sure where (0,0,0) is), then it slowly moves the extruder down towards the bottom left disk. The system will detect contact with the tip of the extruder is tied to ground, and the disks are tied to digital inputs on the system. Once the controller sees “0”, that means the extruder is touching a disk. This mechanism effectively measures the height of all 4 corners.
Calculus 3 isn’t a prerequsite for this class, so I don’t want to get too in depth with with how this process works, but once you have the corners, you can interpolate any point enclosed within the square (or more accurately, the two triangles) formed by the points. The Z-height of the print is automatically modified to print consistently no matter how off kilter the plate is. If you ARE interested in how this works, I did something very similar for a milling machine I made, and show the entire derivation of the math behind this. It may in fact be the only time in my life that I could actually use Calc 3 for practical purposes.
- S. Oberloier and J. M. Pearce, “Belt-Driven Open Source Circuit Mill Using Low-Cost 3-D Printer Components,” Inventions, vol. 3, no. 3, p. 64, Sep. 2018, doi: 10.3390/inventions3030064.
Of course – you can use more than just 4 points – in fact the more points you get, the less you have to interpolate. With the Ender 3 V2 Neo Pro – the leveling mechanism takes several points across the entire bed – and stores that information internally. All G-Code commands are augmented by that data to conform the print to the slight curvature of the bed.
SLA Electronics & Mechanisms
This heading is just a smidge misleading. What I really mean is UV-Curable Resin printing – But I use the SLA title because that is how it was originally introduced to you. It shouldn’t come as too much of a surprise that there are variations to Chuck Hull’s original SLA design – and with them, some nice advantages.
SLA Mechanism
SLA (Stereolithography) printers use a UV-laser in conjunction with an XY Scanning mirror. An XY scanning mirror typically consists of 2 mirrors which are attached to stepper motors. The two motors move independently allowing for fine control of where the laser source is projected. Here’s an open source XY Scanner I found on Hackaday to help illustrate how these mechanisms work:
Here’s a generic commercial one I found for sale here: https://scannermax.com/collections/xy-scanning-systems/products/saturn-1-system. How much does it cost? Well the site says “Request a Quote,” so probably more than I’d ever want to pay.
DLP-SLA Mechanism
DLP stands for Digital Light Processing. In plain SLA, only one small portion of resin can be cured at a time, as the beam continuously moves around. DLP, instead uses a projector made specifically for outputting UV Light. This allows you to cure an ENTIRE layer at the same time. However all projectors are rasterized (made of pixels), so they do have a potential decrease of resolution compared to SLA (however SLA use steppers which are also discrete devices). Let’s take a look at how this system operates:
MSLA Mechanism
MSLA stands for Masked Sterolighography. MSLA printers utilize a constant array of UV lights that are masked (selectively covered) using an LCD. They’re typically the cheapest resin printing method due to this mechanism being fairly inexpensive. Like DLP, the masks that are used are rasterized.
SLS Electronics & Mechanisms
SLS is mostly comparable to SLA in that it has a laser that is focused on a certain point to cause the powder to melt and combine with the material underneath. In commercial systems normally the laser is stationary and is focused / moved with mirrors. However some lower cost systems directly move the laser as and end effector.
Powder Delivery / Recoater
One of the key steps of SLS, is after a layer is placed, a fresh layer of powder must be delivered. This normally is done by depositing some powder at the edge of the deposition chamber, and then roll it across the entire chamber. This video on the OpenSLS project demonstrates it well:
You should note that that powder distribution is anything but even. I suspect at the time of recording this project was still very much in the experimental stage and was working on proof of concepts. That sub-optimal powder roll-out will likely cause structural flaws in the finished part.
