Behind the Acronyms: A Look at the Letters Behind 3D printing Methods and Materials, Part I: FDM
“FDM. SLA. SLS. Pjet. PC. ABS. Huh? I just want to 3D print my design so I can hold it in my hand? What’s all this stuff?”
The media is all abuzz with 3D printing. You hear that 3D printers are so affordable that within 5 years, we’ll all have them in our homes printing everything we would otherwise buy at Target. But there’s a little more to it than that.
Ok, a lot more to it.
There’s a number of 3D printing methods available, each with its own pros and cons. Durability, strength, material choices, workability, temperature resistance, and of course cost are just a few. Over the next few articles, we’ll take a look at some of the most common 3D printing methods used in consumer product design and development.
One of the most widely used forms of 3D printing and best 3d printers under 500$ are good and Fuse Deposition Modeling, or FDM. FDM is currently the media’s belle of the 3D printing ball. With the prices of machines like the Makerbot Replicator dropping below $3,000, it’s easily the most accessible form of 3D printing available for those hoping to tinker in their own home.
But FDM is also one of the most tried and true printing methods in the professional realm, with Stratasys machines leading the pack in this arena. While consumer grade small scale FDM machines can be had for $1,500, a professional grade mid-size machine with an 8″x8″x12″ print bed can run you closer to $50k, and machines with huge print beds go into 6 figures.
An FDM machine is fed with a spool of weed-whacker like material, typically ABS or PC. The material is heated and extruded out of the printer head layer by layer, with the head and/or print bed moving with each layer. Support to overhanging features in the model is supplied either by support structures designed into the build from the same material (which are subsequently cut away), or supplied by a secondary “support” material, which is cleaned away after the print is done. Typically this support material is either simple to snap away from the model material, or it is soluble in a special liquid and can wash away.
The benefit of this soluble support is that interlocking and even moving parts can be printed as a single assembly. Higher end professional machines typically use support material. These machines come with software that will help you orient your part, pack your build tray, and will generate support material structures for you.
You can even choose to run parts solid, or with a semi-hollow honeycomb like internal structure. If you don’t need the strength or weight of a solid part, this will save you quite a bit of build time and material. And while on material savings, the way you orient your parts can make a big difference as to your support material usage as well.
FDM machines are relatively simple to maintain and operate, and don’t really require getting too messy, even if you have a wash tank for soluble support material. This makes them a great choice for home use, or office use where a fully stocked and sectioned off project lab isn’t in the cards. While many low cost options are available, they simply can’t offer the consistency, resolution, and quality of parts run on higher end machines.
FDM prints can be great for overall form studies, and will yield fairly robust parts that can even be put through good amounts of force in function testing. PC is a bit stronger than ABS, though both can take quite a bit of strain. The biggest consideration when putting pressure on these parts is your build layers.
Parts are far more susceptible to breakage along these layers, so keep in mind in which axis you need the most strength while orienting your build. While FDM parts can be strong, they also have very little flex to them, so they aren’t the best for fine detailed snap features or small elements like that. Also, because of the comparably large layer size, your resolution isn’t super high, so FDM isn’t great for when you need fine details, like fine embossed or debossed elements.
And because of these layer slices, curvature in the vertical plane may get a stair-step-like effect to it, kind of like a topographic map. This is another thing to keep in mind when orienting your part.
Aesthetically, FDM parts, as I mentioned above, are not high-res, and have clear lines at each layer. These are pretty noticeable visibly as well as by feel. While FDM parts can take a sanding, you can’t really get rid of these lines unless you’re prepared to spend an afternoon with Bondo, primer, sandpaper and paint.
Overall, FDM is a solid go-to choice for prototyping, certainly good for form studies, a basic level of fit and function, and a good first round prototyping option. While build time isn’t the fastest, they require little time and effort to clean up after a build. Having one of these pro level machines in my office certainly paid for itself within a year.
In my experience, it is the first option I’ll use to prove out a design. If I get to a point where I need better aesthetics, smoother surface finish, finer detail, or material with a little more give (which is not always needed), I’ll move on to either SLA, SLS, or Pjet, which we’ll dive into later in this series.