An Overview of FFF/FDM 3-D printing

Sep 24, 2019 Ian Darwin

Quick links:


"Within a few years, 3D printers will be nearly as common as paper printers." At least, that’s what some pundits have been telling us. I do not believe that the current crop of 3D printers are consumer-ready. Not, say, like deskjet printers, or laptops, or smartphones. But they are here, and they matter. So we’d best learn a bit about them.

7b1ff3df 6276 4d47 8d21 6715a92f0b52
Figure 1. A Prusa MK4 3D Printer

A 3D printer, as the name implies, prints in three dimensions. If you remember the old "dot matrix" printers, or have looked inside an inkjet printer while it’s working, you’ll have seen a physical print head moving back and forth as the paper moves up. That is 2D printing: back and forth, and, up and down, are the two dimensions. Now imagine the paper flattened out and held in place, with the print head moving back and forth as well as left and right - this is how old style mechanical pen plotters moved in 2D. Now imagine the print head or the "paper" - actually a metal print bed - can move up and down as well as front to back and left to right, and you’ve got 3D. Change the ink to molten plastic and you’ve got an idea how most consumer 3D printers work. These are called Fused Deposition Modelling or FDM printers. Technically FDM is a trademark, so we’re supposed to call them 'fused filament fabrication' (FFF) printers, an alias that was created due to the trademark. But most documents still call them FDM.


The idea of FDM printing is not new; it’s been around for several decades. The main credited inventors are Hideo Kodama of Nagoya, Japan’s Municipal Industrial Research Institute, and Chuck Hull of 3D Systems Corporation (USA). Hull’s contribution is the design of the STL (STereoLithography) file format that is widely used today in all types of 3D printing. The first widely-known do-it-yourself printers are from the RepRap project, started in 2005 by Adrian Bowyer and still going strong, though the website maintenance is starting to slow down. RepRap intends to provide self-replicating printers, i.e., those that can print all their own parts. Since some of the parts need to be metal rather than plastic (for accuracy and for strength), we’re not there yet. Some projects based on RepRap have reached about 75% of the self-replicating goal; they still don’t make the metal parts. The majority of consumer-priced 3D printers today (early 2020’s) are based to some degree or another on the RepRap project’s design.

The Original Prusa MK4 (pronounced "Mark Four"), shown in the lead photo, is by one of the major early contributors to RepRap, Josef Prusa. After contributing a lot of code to the RepRap project, Josef started a company to popularize the RepRap style of 3D printers, and has been very successful. Like most of the people in the world he did not trademark his last name, so many low-cost imitators use the name "Prusa" in their ads. Beware of imitators! The Prusa companies do hold tradmarks on a number of terms, including his full name 'Josef Prusa', the full product name 'Original Prusa', 'Prusa 3d' and others (see the title page of any of their manuals downloaded from the website for a complete and updated list). If a printer’s advertisement doesn’t say "Original Prusa" in the name, it’s a knock-off. If it does say "Original Prusa" and it turns out to be not from, please report it!

There are several sub-types of FDM printer, based on how the mechanism is organized:

  • "Bed slinger", the most common type, moves the bed in the X and Y directions and the print head up for each new layer;

  • "CoreXY" printers, a newer design, move the bed up and down, starting a print with the bed at the top and pushing it down for each new layer;

  • "Delta" printers, relatively uncommon, use 3 arms to control the print head’s x, y and z locations.

Other kinds of 3D Printing

There are also 3D printers that use liquid plastic resin (called stereolithography, SLA for short). These use light to turn liquid resin into solid plastic, flashing a layer at a time. I like to say that "an FDM printer melts solids into liquid, while an SLA printer fuses liquid into solids." Other types deposit molten metal or use other materials, other methods. They’re out of scope for this discussion, which is focussed on the FDM/FFF style.

Slicing (and dicing?)

Just as you have to format a document before printing it in 2D, you have to design or model your object before you can 3D-print it. Or, as you can photocopy an existing document, you can 3d-scan an object, clean up the model file, and print from that. There are also lots and lots of model files you can download (mostly for free, sometimes for pay) from the Internet. One of the longest-running and best-known sites for free downloads of 3D-printable models is (funded by long-time print manufacturer MakerBot Industries,). one of the earliest commercial makers of consumer-oriented 3D printers). Another is, funded by long-time manufacturer Prusa. There are many other sites where you can download model files to print, share new designs, modify existing ones, and so on.

The FDM printer has to print all the filament at a given height, one motion of the Z axis, before moving up to the next. This is called one "slice" of the print. There is thus a second step, called "slicing", which converts your generic model file from STL/STEP/3MF or other model format into 'g-code', device-specific low-level code to drive the printer. A G-code file is specific to a given model of printer with a given nozzle and type of filament in it. Going back to the printing-on-paper scenario, slicing is analogous to the printer driver software installed in your desktop computer. There are dozens of software tools, both free/open source and commercial, for both stages, the modelling and the slicing.

The Ink’s The Thing

The plastic "ink" for FDM printers is called "filament" because it comes in long thin shape, like a string, or like overly-thick fishing line, usually 1.75 mm in diameter. It’s a form of meltable plastic; the most common types are :

  • PLA (poly lactic acid, biodegradable);

  • PETG (also harder, can be food-safe).

  • ABS (harder plastic, longer lasting, higher melting point);

  • Nylon, carbon fiber, even some metals (these need tougher nozzles).

The harder filaments emit particulates and/or noxious fumes when heated, so many printers either are enclosed, or have optional enclosures available.

Do be sure you get filament in a type and size that your printer can use! There are plenty of colors available from dozens of suppliers.

Is it perfect?


Some of the pain points in FDM printing include:

  • Bed leveling - the "bed" or surface that the filament gets melted onto has to be quite level, or the print won’t stick in some areas, and will break off or jam up during printing; this is fixed by the very latest printers from Prusa3d, Bambu Labs, and others.

  • Bed heating - almost all FDM printers made today use a heated bed, so the print can cool down more smoothly and adhere to the bed properly. Getting the temperature right can be an issue.

  • Filament choice - choosing the right type of filament for the job.

  • Filament storage - some filaments, especially the most common "PLA", are hygroscopic - they will absort moisture from the air, which can not only swell the filament causing it to jam or 'clog', but also cause bubbles to form in the molten filament, causing print failures. There are special "filament dryers", but some people use electric food dehydrators to dehydrate their filament.

  • Calibration - making sure your slicing software and your printer are "on the same page" (or should we say "on the same print"?). See this calibration article.

  • Retraction - how to avoid "stringing" as the print head ("hot end") moves around. See this retraction article.

I wrote an article - the start of a series - on "I Tried That", my review site, covering Choosing a 3D Printer. The series includes, among others, writeups on the high-end Prusa i3 MK3 (made in Europe) and the cheaper (in both senses) Chinese Creality Ender 3 Pro (which I bought). See the full list at

Here is an older list of machines that I’ve looked at recently (not updated frequently, alas).


Several Ontario ones are listed in my spreadsheet above.

In addition to the major online shopping malls, several e-tailers specialize in 3D printers, including, and

Numerous companies supply the "ink" or "filament". I am absolutely not going to try to keep a list of filament suppliers up to date. I will mention just one, a local-to-me Toronto-area supplier, But whereever you live, just do a web search on Google, or Amazon, or even Kijiji Classifieds, for, e.g., "abs filament [name of country]" or "pla filament [name of country]" as a appropriate. Note: Quality is far more important than price, so check the reviews! With 1.75mm filament (the most common size, used in most printers), be sure to buy filament with a rated variance of 0.3mm, preferably 0.2mm. Filament whose diameter varies more than these limits can cause prints to fail or even cause your printer to jam up.

Separation of Dust and Heat

FDM printers have moving parts that slide along rods or rails; this makes them very susceptible to dust. They also generate particulate matter, and printing with certain advanced filaments generates fumes. All FDM printers generate heat (obviously). Rigid enclosures keep dust out, and allow particulate matter to be filtered and fumes to be vented to the outdoors. They also keep heat in, which is a dual-edged sword: keeping the temperature around the printer stable and warm will make for more reliable printing. However, if it gets too hot, the electronics in the printer’s power supply may suffer, though some have called this a non-issue. The jury’s still out on that.

A good provider of enclosure kits is 3dSourcerer, run by Joseph Willis. Most of their kits consist of clear side panels and require you to 3d print the corner brackets and other bits. They only ship within the USA, but most of their kits are also available on Amazon’s US site for shipment to Canada. Note if you search for 3DSourcerer Amazon will change it to 3D Sorcerer and give you RPG stuff! I have the 3D Sourcerer "DELACK" enclosure keeping the dust and drafts off my printer; see this review.

Filament Storage

Some 3D filaments are hygroscopic, or prone to absorbing moisture from the air. Filament dryers are useful to reverse this effect, as is storage in closed containers or just the sealed bags they typically arrive in. The little dessicant packs that everybody throws away can be heated to dry them, then placed inside the closed container to absorb the moisture from the filamant.

Have a printer? Get paid to print(?)

When 3D printing was growing in popularity, it was easy to make money by signing up with one of these printing services. Now it’s pretty competitive. But here goes. Here are services that you could sign up with once you have a printer working reliably. They collect the money, send you the STL file, and pay you when you ship. A bit like selling on Amazon, eBay or etsy. I have no experience with any of these, so caveat ventor. These links take you straight to the signup pages; be sure to read the terms & conditions!

Disruption (the good kind)

3D printing can enable "rethink," new approaches to building common items. For example, a company called H3X has printed an electric motor that is 3-4x more efficient in terms of power/weight, making it suitable for use in mid-range all-electric aircraft. They were only able to do this by 3D-printing a redesigned stator coil that allows for better heat distribution, so you can run more current through the same size motor without melting it.

The good and the bad

Speaking of disruption, 3D Printers, like any tool, can be used for good or bad. Hammers can drive nails but also break bones. Cell phones can help you stay in touch, but can also be used by kidnappers, drug cartels, and others for nefarious purpose. Guns can kill and guns can defend against killers. 3D printers can repair things, or make things to help you break things. Such is the nature of human existence.

And so it is possible to 3D-print a small gun like a handgun or an AR-15 rifle, using ABS plastic, but such a gun can only be fired a few times before it breaks (spectacularly). In the U.S.A. and possibly other jurisdictions it is arguably legal for a person to manufacture their own gun in this way. There is at least one company making a 3D milling machine that lets you make the part of the gun that really has to be metal, so it can be fired repeatedly. I’ve no interest in this.

3D Printing Cars

Several companies are using 3D printing in automotive design and even manufacture.

3D Printing Residential Housing

There are quite a few companies/organizations 3D printing homes:

The End

That’s all, folks. Happy printing!

Caveat: all information subject to change.