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Introduction to 3D Printing
From industrial art to medical applications to automotive parts, 3D printing has a wide range of diverse uses. As the technology develops and becomes more cost-effective and accessible, we’re seeing a boom in its use both by professionals and hobbyists.
Across industries, 3D printing is helping people iterate faster, cut outsourcing costs, optimize production processes, and unlock entirely new business models. It’s revolutionizing the way businesses and hobbyists manufacture objects, facilitating more cost-effective processes and less environmentally harmful methods.
But what exactly is 3D printing and how does it work? Here’s a rundown on 3D printing: what it is, how it works, and how it’s changing the way we manufacture objects.
What is 3D printing?
3D printing involves creating objects from a digital model. Typically plastic is used, but sometimes composite material or metal can also substitute. Most 3D printers add material to an object layer by layer. Because of the way it’s “printed”, 3D printing is defined as additive manufacturing.
What is additive manufacturing?
Calling it “3D printing” isn’t necessarily accurate. Traditional printers typically operate row by row. 3D printers, on the other hand, operate like plotters – they move a print head on both the Y and X axis to “illustrate” a pattern in either plastic, metal, or composite material. Once a pattern is illustrated, the print surface moves down (or the head moves up) and the next pattern is mapped out over the first.
How does a 3D printer work?
There are many different types of 3D printers, but the two most common are:
- Stereolithography (SLA)
- Fused-deposition modeling (FDM)
SLA 3D printers use resin, a light-reactive thermoset material. When this resin is exposed to certain wavelengths of light, short molecular chains join together, polymerizing oligomers and monomers into solidified flexible or rigid geometries.
The SLA 3D printer works by lowering a build tray into resin and slowly exposing each layer of the object to light until the object is fully formed.
FDM, on the other hand, uses filament as its base material. This filament generally comes in strands that are rolled onto a spindle. The FDM machine heats up the filament, aims it with the use of an extruder nozzle, and maps out layers of the material on a build surface. These layers are very thin and very hot. As each layer is printed on top of the one previous, it fuses partially as it cools.
Over time, an object is created from these layers which can number in the hundreds or even thousands.
SLA is the most typical form of light polymerization 3D printing while FDM is the most typical form of material extrusion 3D printing. Both have achieved a low enough cost level that hobbyists, educators, entrepreneurs, small businesses, and consumers can afford them.
Additional forms of 3D printing include:
- Electron beam freeform manufacturing
- Powder bed 3D printing
- Directed energy deposition
- Laminated object manufacturing
SLA and FDM printing are typically used to make plastic objects while other forms of 3D printing generally focus on metal or other materials.
The commonality of all these forms of 3D printing is that they’re creating new objects through the incremental addition and fusing of raw material.
Strengths and weaknesses of FDM and SLA printing
SLA and FDM printers are the most common types available on the market today. Typical consumer variations are priced at a few hundred dollars while professional machines can range from $3,000 – $6,000.
Each kind of printer comes with its pros and cons.
There are a number of factors that have kept SLA printers out of the mainstream:
- The liquid resin used is quite toxic when uncured. If your skin is exposed, it can cause painful rashes or burns.
- Finished objects must be processed in a bath and then cured. They can deform during this process and remain toxic during that time as well.
- Due to the liquid resin and the bath, SLA printers are very messy to work with when compared to FDM printers.
SLA printers also often have prohibitively small build areas meaning you can only generally create tiny objects. A given printer usually has specially formulated resin as well, resulting in users being locked into a vendor’s offerings.
Despite these limitations, SLA printing is starting to become more popular. They’re able to produce prints with very fine detail and few layer lines. This makes them especially suited for:
- Prototyping jewelry designs and molds
- Small dental and medical designs
- Model railroading
- Gaming miniatures
The first common 3D printing technology, FDM printing is still in the lead in terms of product offerings and brands. If you’re new to 3D printing, odds are you’ll want to start with an FDM machine.
The key challenge in 3D printing is getting the final product to print successfully. There are many factors that can go wrong, including:
- Layers don’t bond successfully
- The deposited material heats or cools too quickly
- Filament jams in the extruder
- The print detaches from the build plate
FDM printers print a number of plastics, each with different characteristics. This can make printing more difficult or easier. Each also yields different characteristics in the final objects.
Some of the most common plastics include:
- PLA (polylactic acid): the most common filament type, it’s very easy to work with but can be fragile and will deform in heat or sunlight.
- Nylon: flexible and strong but requires more in-depth knowledge to assign its printing settings.
- ABS: one of the strongest materials, however, it cools quickly which can cause the layed layers to curl up, ruining the object. It also smells particularly bad and has mildly toxic fumes.
- Infused plastics: some people infuse plastics with other materials such as wood or metals. Each one changes the finish of the print.
Most mainstream FDM printers sport one extruder from which they can print one filament roll at a time. More advanced printers will print two or more filaments, allowing for color mixes, functional characteristics, and support materials that can be easily dissolved.
Because prints are developed from threads of molten plastic, objects with overhangs are often an issue. FDM printers can typically print angles of up to 45-60 degrees, but larger gaps become a problem as the molten plastic simply settles in the free gap.
To mitigate this problem, printers can generate supports that hold up the bridged areas. Single filament machines simply use the same plastic as the print itself and apply a specific set of settings that make the removal of the supports easier post-print.
Dual filament printers create these supports using support material that is dissolvable. Once the duel filament object is finished, it’s submerged in water until the support material dissolves and the final print is left intact.
The orientation of the printed object is also important as FDM printers print in layers. Linear struts of plastic are often stronger than the bonds between layers – this should be taken into account when choosing bed placement, particularly if the object is likely to be stressed later.
FDM printers come in a range of different sizes. The bigger the printer, the more difficult the print as it becomes more challenging to work the heat characteristics over the entire build area.
FDM printers also sport a wide range of nozzle sizes. The bigger the nozzle, the more material is printed over time but this can make the final object less refined. The smaller the nozzle, the more detailed the print. Depending on which nozzle you print with, it can introduce more challenges including those to do with bridging, heat management, and supports.
Design and prep of prints
To go from idea to print requires the use of two software tools: slicers and 3D-modeling (or CAD) software.
3D-modeling programs or CAD (Computer-Aided Design) is the creative engine for 3D models. Just as you might use image-editing software to build a graphic, 3D-modeling programs are used to develop the design for a 3D model.
There are a number of 3D-modeling software options, each suited to separate tasks. Two of the most common are Fusion 360 and TinkerCAD.
TinkerCAD is a beginner-level program often taught at the school level. It lets the user map out a super-quick prototype of a simple design. Fusion 360, on the other hand, is full engineering design software. It can not only design 3D models but also helps you perform stress testing and motion simulation.
There are a lot of ways you can learn common 3D printing programs. Online classes, college courses, or YouTube tutorials are all abundant.
3D-modeling software produces a virtual model of a 3D object, however, most 3D printing happens layer-by-layer – or in slices. A slicer program takes a 3D design and converts it into machine movements.
Typical slicers make G-code, a numerical language that’s used by many computer-aided fabrication devices.
G-code is the standard, however, vendors will often add modifications and extensions. This means that G-code typically must be made by the slicer for specific models and brands of numerically controlled devices.
Traditional slicers were used programmatically by feeding a 3D design file in and getting G-code outputted, but most present-day slicers have an interactive interface. This lets the user adjust the object orientation and monitor the output process, letting them pinpoint potential printing issues before a design is sent to print.
This is also the time that print settings are configured, such as:
- Print speeds
- Adhesion techniques
- Infill methods
- Nozzle and build plate temperature
- Custom G-code blocks to account for special procedures
There are a number of slicers available on the market today. Two of the most popular are open source: Slic3r and Cura. There are also commercial options like Simplify3D. Some vendors create their own slicers that are connected to their hardware. While there are benefits to this approach, the lock-in often means users can’t use just one slicing tool if they own multiple printers of different brands.
3D print time
3D printing an object can take anywhere from half an hour to 7 or more days. There are several factors that dictate how long a print will take, including:
- Overall size
- Overall geometry
- The 3D printing technology used
Generally, the larger the part or the more complex the geometry, the longer it will take to print.
3D printing is the future
The future of 3D printing is exciting and full of possibilities. Every industry from fashion to automotive to medical is set to benefit from the technique, revolutionizing the way we design and manufacture objects.
As the technology becomes more accessible, we’ll see even more diverse applications. It’s already changed the way most industries operate, offering more cost-effective and environmentally friendly manufacturing options for businesses and hobbyists alike.
Now you have a solid introduction to 3D printing.