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The Nuts and Bolts (and Belts and Other Parts) of 3D Printing
Jennifer Belgin

“People are usually on either end of the spectrum. They assume it’s a simple process or they’re too intimidated that it’s too complicated for them to try.”  - Yupcat

I've lost track of how many times I've been asked something along the lines of, "Which 3D printer should I buy?" or "Can you give me a quick explanation of 3D printing?" on one of my social media accounts. Since this is not a quick answer type of question, I decided it was finally time to sit down and do a write up that will hopefully shed some light on the subject.
Before we dive in, I need to make a couple things explicitly clear. Anyone can learn to 3D print. Printers are dropping in price, becoming more readily available, and there are videos, user groups, and tech pages galore. The support is there. However, it is not easy. IT IS NOT JUST PRESSING A BUTTON. It's also not a cheap hobby. You'll need to learn the mechanics of your particular printer, how to repair it, how to replace parts, how to level your bed, how to properly place your print in a slicer, determine the ideal print settings, minimize stringing, add supports, and a host of other technical factors. If you are the kind of person that is easily frustrated, this is not the hobby for you. If you have a modicum of patience and the willingness to practice and do your research, I think you'll find it enjoyable. Most of the time. When you aren't about to throw your printer out a window.
Another important point is that people really get invested into their particular brand of filament, resin, printer, preferred upgrades and the like. I've seen verbal punches being thrown in all of my printing groups at some point and you can rest assured that someone will disagree with your opinions. While I do recommend doing some research, asking questions like "What is the best printer?" is going to net you 38 different answers. Listen to the people you trust or the user group that makes you feel the most welcome and comfortable.

Types of 3D Printing

The two most commonly accessible forms of 3D printers are FDM (fused deposition modeling) and SLA (stereolithography). SLA is one of the earliest types of 3D printing and is composed of layers of resin that are cured by UV light. You've likely heard of companies like Formlabs, Anycubic, and Elegoo who all produce consumer model SLA printers and whose bed sizes have been growing larger as time goes on. A benefit of SLA is that you get seriously high-quality prints that often don't require much in the way of finishing as the layer lines are barely, if at all visible.

A drawback is that the bed sizes are smaller than most FDM printers, resin is more expensive than most filament, and it puts out caustic fumes that require you to use them in a space with adequate ventilation. When your print is done, you'll need to carefully wash it and cure it with UV light. There are dozens of DIY builds for this or you can invest in a wash and cure station. I don't currently use SLA printers because I'm focused on making larger items but a quick Google will provide you with everything you'll ever need to know.

 

FDM printing utilizes thermoplastics to build items through stacked layers of filament. Prusa, Ender, Monoprice, and Creality are just a handful of known makers who provide machines in a wide variety of styles and sizes for just about every application you can imagine. Some are pre-assembled and only require the placement of a couple screws to get started while others are kits that you fully assemble. 

There is a wide spectrum of filament options for FDM printers that now include metals and biological products. They range in price and ease of use, and some are made for specific machines. I personally use PLA+ which is a thermoplastic made from corn starch products. It has a bit more strength than standard PLA but it's also somewhat biodegradable, less finicky about ambient temperature, and doesn't require an enclosure to manage caustic fumes. However, the print lines are more noticeable and generally require some post-processing. For me this is a non-issue as I'm going to be adding a self-leveling resin for rigidity and strength which will minimize that with a bit of sanding. 

Parts of a Printer

There are a few different styles of FDM printers but they are generally comprised of the same parts, even if the setup varies. I'm currently using all Creality machines so I've chosen the 10S for my example.

Axes

If you've taken Algebra you're probably familiar with the coordinate planes and the X and Y axes. 3D printers add a third dimension with the Z axis for height. Everything you do with models will involve their placement in these three axes and your software will allow you to make adjustments to them in scale, rotation, and translation.

Print Display/Power Unit/SD Card Reader

Here's the brain of your printer. This box contains your power unit, the SD card reader and direct plug into a computer, your motherboard, and the LCD screen that allows you to manage your settings. Since I'm running multiple printers I always use the SD card. Older models have you slide in the card and it can be a challenge to remove them without tweezers or a practiced gripped but the two newer machines I have use a push button release. Press it once to insert, press it again and it pops out. When you buy a Creality printer it will come pre-wired. All you have to do is plug everything in to the right place.

Filament Holder

This comes in a couple of pieces that you twist together and then screw in to the top of the Power Unit. However, I've modified this to sit on the top of my machine instead so that it takes up less space on my table top. It required me drilling larger holes in to the base of the handle but the spacing is perfectly aligned with the two screws that hold in the Z axis rods.

Motors

You'll have four motors to drive your X, Y, and Z axes as well as your filament into the extruder. For the three axes, there are also belts attached to each motor that drive the parts. These are generally already in place and all you have to do is plug in the cords from the power unit. They are all labeled so it's pretty easy to manage. I like to keep an extra motor or two around in case of failure and source mine from Tiny Machines 3D because I prefer using OEM parts and they source them from Creality. You can also grab them from a host of other vendors with many on Amazon offering 2 day shipping.

Filament Detector

I love, love, love my filament detector. I cannot tell you how many hours have been saved because the machine realizes there is no more filament and pauses my print until I'm able to add a new spool. It then picks up right where it left off! The only issue with these is that they are plastic and the filament can wear a groove into them over time. This can cause the filament to lift and the detector thinks you've run out when you haven't..

The first time it happened I just ordered a new one for about $5. Then I realized what was causing the issue and I superglued a washer to the side to readjust the channel and was back to printing in a hot minute. There are also a couple of upgraded versions you can print from Thingiverse if that's more your style.

Bowden Tube Drive

There are two main types of hot ends for FDM printers: direct drive, where the motor for moving filament sits right above the extruder, and Bowden tube drives where the motor is separate. I've come to prefer the Bowden tubes because your motor isn't under constant subject to the heat put out by the hot end. The cog on the extruder feeder slowly pushes the filament through the tube and into your extruder.

As with my motors, I like to keep extra cogs on hand. I was once having issues with filament quality and came to realize that it had worn a groove on to the cog so there wasn't much force trying to push it into the tube. It's a 25 cent replacement part that makes a world of difference. Also, this is one of the few parts that I generally upgrade on my printers. Most of the parts are plastic and subject to wear, so I swap them out for a full metal unit when I notice they need to be replaced. 

Extruder

Your extruder unit is the collection of parts that combine to heat up your filament. Nozzles come in a variety of mm sizes to determine the thickness of the lines that will be pushed on to your build plate. I personally stick to .4 nozzles as they are usually pre-installed and I'm happy with the print quality they produce. They also come in a wide variety of materials which can have an impact on the quality of your extrusion. A cheap nozzle with snags and jags will impact the movement of your hot thermoplastic and can even lead to clogs. However, as I've had no issue with the nozzles that come standard with my machine, I haven't worried about upgrading mine to steel.

The thermistor is hidden in the photo below, but it's a tiny thermometer that keeps track of the temperature of your heat block and lets your machine know how hot it is. There's also a thermistor attached to your heated bed that does the same.

The heater is a cylinder inserted into the heat block that warms everything up. When you prepare a model for printing you'll establish in the gcode what temperature you want everything to print at, but you can also manually control this from your power unit.

 

Cooling Fans

There are two cooling fans on the Creality machines housed in a metal box that covers the extruder. One is responsible for helping to maintain proper extruder temperature and the other cools the filament as it's extruded to help it solidify and prevent warping. The fans and extruder components are all wired into the main power unit and can be replaced individually if you have the electronics skills or swapped out as a whole unit. I don't mind changing out a nozzle but if I've discovered an issue with any of the wired components, I just grab a $30 replacement that plugs directly into the unit in a matter of seconds.

 

 Print Bed

The last main part of your printer is the bed. My Creality machines all have heated beds that come with a glass top. I absolutely love this because I feel the glass does an excellent job of promoting even heating as well as a smooth print surface. Metal beds can bow or warp and the 1/4 inch thick glass negates those problems. I also use Suave extra hold hairspray as an adhesion promoter and if I notice too much of a build up it's easy to remove the clips and clean the glass. 

As I mentioned previously, there is a thermistor hidden under the bed that keeps track of your temperature. Bed levelling is A MAJOR COMPONENT of your printing endeavors. A level bed is absolutely essential to the right layer height and proper adhesion amongst the layers. Your bed should be HOT when you level it, so crank it up to 60 degrees (my preference) or whatever you like and then level that baby using the spring loaded cogs under each corner of the bed.

How do you know if it's level? I use a piece of paper and ensure it can only just pass between the bed and the extruder. The Creality machines have an "auto bed leveling" feature which is kind of misleading because all it really does is move your extruder through the 4 corners and then to the middle. You'll still have to manually check to ensure there's the proper distance between the extruder and the bed. You can also install the BL touch which measures how far your extruder is from various parts of the bed, but it doesn't actually do the levelling for you.

Here's the key thing: If you aren't moving your machines, you shouldn't need to re-level them. Now, if I haven't used a machine for a while, say because it's been down for maintenance, I'll make sure to check the bed level before I start printing again. Or if I have to move it for some reason I'll do the same. Otherwise, you shouldn't need to be adjusting this every time you print. If you are, there could be an issue with the springs or knobs. Perhaps your extruder isn't coming down to home after a print? Maybe you didn't heat up your bed before you leveled it?

Below you'll find a cool video that demonstrates the leveling process and also mentions a printer test you can download from Thingiverse to check your levels.

 

The End for Now

I think that covers the basics of machines and their parts. If there is anything I failed to mention here please feel free to reach out so that I can add it. I'm going to start working on a few more posts including slicing models and getting your prints started, finding and using stl's, basic troubleshooting, and finishing your prints for paint.

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