How to choose the right 3D printer for your next project
3D printing technology is turning the manufacturing world on its head. By lowering the barrier to entry, hobbyists and small businesses are able to make precision parts and produce rapid prototypes.
However, the world of 3D printing can be as confusing as it is exciting. There are now dozens of machines implementing various methods of additive manufacturing on the market, each with their own specialties.
Not all printers are created equal
Before choosing a printer, there are a few questions you have to ask yourself to arrive at the correct printer that will achieve your goals.
Are you trying to produce rapid prototypes to iterate your product quickly? Or are you trying to produce a finished good?
What quantities are you trying to produce?
How strong does the part need to be?
Does surface finish matter to you?
How complex is the geometry of the object you want to make?
There are multiple methods of 3D printing, and just like anything, they each have their own advantages and disadvantages. It all depends on what you want to accomplish. The choice boils down to three major questions:
- Do you value speed or precision?
- What material do you want to print with?
- How much money are you willing to spend?
Keep in mind that the concept is still the same between all these printing types. They are all additive manufacturing processes that build up the desired part, one cross section at a time, but get to the finish line in different ways.
How 3D printing works
Before we dive into the different methods of printing, here is a quick recap of how 3D printing works.
First, objects are created digitally using specialized 3D modeling software. Designers are able to shape and craft their desired object from scratch or build upon existing models that other users have made already. Professional 3D modeling software has been in the manufacturing industry for years, but a new suite of programs and tools are constantly being developed to quickly educate and train new users.
Once the desired object has been created, the solid model is exported as a .stl file that represents the surface geometry of the model. The internet is littered with .stl files from 3D printing communities such as thingiverse.com. For example, check out this lightsaber created by user infinati.
However, these .stl files need to be processed before they are ready to be printed. The files need to be sent to a slicing program that will “slice” the model into horizontal cross sections to be created and layered by the printer with the printing medium, to eventually recreate the original model.
This data is then exported into G-code, which is the printer’s machine code to control the motors, extruders, heating elements, and other components of the printer.
Now we’re ready to print.
Types of 3D printing
FDM (Fused Deposition Modeling)
This is one of the most common forms of 3D printing on the market today. The simplicity of the machine makes it cheap to produce and easy to maintain.
An FDM printer works very similar to a hot glue gun. Material is fed towards a heated nozzle that then melts and lays out material on a specified path controlled by the printer’s motors.
FDM printers can print in layers as thin as 0.10 mm (the thickness of a sheet of paper). Most 3D printers utilize stepper motors that are extremely precise and, when combined with the accuracy of the nozzle, can create extremely intricate and complex geometry relatively easily.
One benefit to FDM style printing is the exhaustive catalog of materials and colors to choose from. Plastic is by far the most common material used for 3D printing due to its cost, low melting point, and mechanical properties that make it strong enough for most applications. Users can purchase different spools of plastic wire filament to use with their printers and only need to configure the heat settings to use it.
The boundaries are constantly being pushed as people have successfully printed with materials such as wood (seen below) and glass.
FDM style printing is one of the fastest methods of printing, however, the exterior finish of the part can be rough when compared to the other methods. In most cases, the layer lines are still visible creating a rough surface texture. There are methods of post processing that can smooth out the surfaces that require sanding and painting.
Overall, FDM style printers are prime candidates if your goal is to iterate through designs quickly and you value speed over precision. FDM printers also generally have the largest print area to manufacture larger parts.
SLA (Stereolithography)
Another common method of 3D printing is liquid resin based SLA method. Like all 3D printers, they construct the object one layer at a time. Where it differentiates from FDM printing is the way it generates each layer. In FDM, plastic is melted, positioned, and then cooled back to a hardened state. With SLA, the build platform is submerged in liquid resin that hardens as it cures when exposed to UV light. The printer utilizes a UV laser to trace out each cross section, curing and creating each layer in the process.
DLP (Digital Light Processing) is a version of SLA but uses a projector to expose the entire cross section at a time versus tracing it out, saving time and accelerating the build process.
SLA printers generally have a higher print resolution (thinner cross sectional layer) and can be as fine as 0.025mm or 1/4th a sheet of paper. This results in a greater surface finish than their FDM counterparts at the expense of speed. The higher the resolution you have, the more layers you need to create. FDM prints can be processed to achieve a similar finish, however it requires extensive sanding and painting of the part.
There is still some post processing required for SLA prints which includes washing away excess resin by using isopropyl alcohol, but the process doesn’t take more than half an hour. The final part is also UV sensitive, which may experience discoloration and become increasingly brittle if left out in the sun.
There are many different types of resin out there but generally speaking, material selection is not as wide and is generally more expensive than FDM filament.
SLA printing is great for those who require fine details in their parts and want a smooth surface with minimal post processing. SLA printing is often used for generating molds for jewelry and toys.
SLS (Selective Laser Sintering)
Selective Laser Sintering is a printing method that has yet to hit the desktop manufacturing market. Like SLA printing, SLS uses a laser to construct the object. However instead of using liquid resin as the print medium, the SLS method prints over a bed of the material in powder form, and uses a laser to melt and fuse the particles together.
The process itself is much more dangerous than the other methods described above. The laser is much more powerful, the print bed must be held within a gas chamber with proper ventilation, and the machinery required to lay a smooth bed of powder is complex.
One of the main advantages of SLS is the absence of support structure. Both FDM and SLA prints require printed supports to provide structure to the part during the printing process. Certain geometries with overhangs cannot be printed without supports since the cross-sectional layers cannot be printed over thin air. With SLS, the unused powder surrounds the part during the print and provides a platform for each layer during the printing process resulting in no wasted material.
A subset of SLS is DMLS (Direct Metal Laser Sintering) that allows you to make metal parts from metallic powder. By bumping up the power of the laser to reach the melting point of various metals such as aluminum, steel, titanium, and inconel, DMLS printers are able to create extremely strong and durable parts.
The SLS process is typically slower than SLA and much slower than FDM printing due to the resetting of the bed after every layer, but the benefit is a strong print in all axis (FDM is weak in the Z direction) with a fine finish once you brush off the residual powder.
Choosing your 3D printer
With this, you should have a better understanding of the subsets of 3D printing. Obviously, there is no clear winner as the ‘best’ 3D printer — there is only the proper printer for the proper job based on your needs. For rapid prototyping and iterating, FDM leads the pack. If you require finer detail, your best bet might be SLA. If you have the budget or require additional strength in your part, you might want to look at SLS. Overall, 3D printing is a great technology that can jumpstart your business and can shorten the time from ideation to production.
