Introduction
3D printing has forever changed how the game is for how we build things, all the way from prototypes to ready-for-production parts. The technology builds objects from the ground up, one layer at a time, from a digital model that is then converted into G-code. It is far more flexible of a manufacturing process compared to subtracting methods such as CNC Machining.
What Material is Used in 3D Printing
Understanding what material is able to do is key to grasping how 3D printing processes work. It also dictates how materials can be processed. Each material is optimized for specific purposes.
FDM or fused deposition modeling, or fuse filament fabrication FFF, is the most liked and preferred printing method for 3D printing technology. FDM materials usually consist of a thermoplastic filament, which is heated and extruded through a nozzle to produce layers that cool into a solid. Most FTM printers melt materials and create a flow of filament by heating within a range of temperatures, mainly around 180° C to 250° C.
Stereolithography SLA uses a laser to take a liquid resin and transform it into a solid layer with UV light. SLA printing is preferable because of its ability to print high-resolution models and smooth surfaces. Industrial Industries prefer SLA to print prototypes and products that need a high degree of finished quality. Selective Laser Sintering (SLS) and Multi Jet Fusion (MJF) use a laser or binding agents to fuse powder particles. SLS and MJF are appropriate for nylons, polyamides, and metals in order to create sturdy, isotropic parts without needing support structures. Powder bed fusion processes allow complex geometry to be manufactured in engineering-grade materials.
Source: https://www.digitalengineering247.com/article/the-dos-and-donts-of-metal-3d-printing
Additionally, there are other processes available, such as Binder Jetting, leading to ceramics and metals, and Direct Energy Deposition (DED) for larger metal parts. Each of these technologies has different constraints regarding available materials and material processes. For example, Fused Deposition Modeling (FDM) supports filament provided that there is the correct FDM type, Stereolithography Apparatus (SLA) utilizes resins as its stock materials, and SLS utilizes powder. The entry point for each process is typically given by the properties of the material, such as tensile strength or heat resistance.
Choosing a process is all about balancing trade-offs. The way the material behaves will shape your design just as much as the printer itself. With FDM, printing is straightforward and you can dial in the dimensions with precision. The catch? The printed layers have a weaker bond in one direction, so you need to design with that in mind. For SLS-based processes, while both isotropic and the part geometry strengthen themselves, the finishing process, such as removing the remaining part powder, must be managed.
The Primary Materials Plastics and Thermoplastics
Kingroon 10KG PLA/PETG/TPU Filament
Thermoplastics are the main core type of material for FDM 3D printing. Ranging from hobbyist to industrial-level prototypes. They are the most common types of printing material because of their low cost and convenience, as well as their availability. Thermoplastics can be melted and reshaped in any form again without a lot of loss of malleability in the plastic.
The most common type of thermoplastic for 3D printing is polylactic acid or PLA is manufactured from common renewable resources like cornstarch and sugarcane. It's also a biodegradable type of plastic and is considered to be environmentally friendly compared to the petroleum-based types of plastics. PLA melts between 180 and 220 degrees Celsius to extrude smoothly. This type of thermal plastic has a low odor and prints with minimal warping. It is also low-cost, costing roughly $15 per kilogram.
Its properties include a tensile strength between 50 - 70 MPa, good dimensional accuracy, and a glossy finish. It’s a beginner’s dream material inexpensive, widely available in almost any color, and forgiving if you’re still dialing in your printer. The downsides are that it can snap under tension, softens if it gets too warm, and fades or cracks if left outside in the sun. Typical applications for PLA include: decorative objects, prototypes, and educational models.
ABS is also a well-known material that is very durable and tough. Acetone vapor can be used to smooth ABS and improve appearance. ABS needs more heat — around 230°C or higher — but in return, you get a tough, impact-resistant material. That’s the same stuff LEGO bricks are made from, so you know it can take a beating. An example of ABS is a LEGO brick or parts in an automobile, based on strength. Pros: Resistant to heat (up to 100 °C), flexible, and stable.
PETG is a material between PLA and ABS. PETG is the middle ground between PLA’s easy printing and ABS’s strength. It prints smoothly without much fuss, but adds extra durability and a bit more flexibility for parts that need to last. Like ABS, PETG is both food-safe and moisture-resistant (and can be recycled!) and has a tensile strength of 50 MPa. PETG is also a great choice for parts you might be employing in function, i.e., for a water bottle, a mechanical component, etc. Pros of PETG: recyclable, transparent, and special properties. There are other thermoplastics, such as Nylon (polyamide), which is noted for flexibility and abrasion resistance. Depending on the process, one might choose nylon (specifically Nylon 12) for SLS because of its improved fatigue strength (up to 50 MPa tensile). Nylon is also hygroscopic and will absorb water from the atmosphere. The moisture absorbed can change the properties of the material, losing specific tensile strengths. It is an excellent choice for lower weight in prints like gears and hinges.
Composite thermoplastics improve properties, such as carbon fiber-filled PLA has more stiffness, which is suitable for structured parts, but this also wears in the nozzle. (modulus improves to around 4 GPa). The thermoplastic glass transition temperature in crystallinity determines its print properties and performance. Also, any additives that are in the filament can affect printability.
Beyond Plastics: Resins, Metals, and Emerging Materials
While plastics, the largest category of materials, dominate the consumer and rapid prototyping, a wider range of materials is enabling high-performance 3D printing.
Resins used in stereolithography (SLA) and Digital Light Processing (DLP) are once cured is irreversible. Most standard resins are capable of extremely high levels of detail and resolution, less than 50 microns. With the surface finish being so high resolution, smooth surfaces can be created, or Optical clear type prints using clear resin can be done. There are also engineering resins that provide heat resistance up to 200 degrees Celsius and a shore hardness of 48. Most are high in isotopic strength, along with refined features and details.
A growing category of materials is metals printed from powders (via SLS, SLM, or DMLS). Commonly used alloys are titanium (Ti6Al4V, tensile strength = 900 MPa), stainless steel (316L), and aluminum (AlSi10Mg). The properties of these alloys offer the best strengths, good corrosion-resistance and thermal conductivity, allowing parts to be made for applications in the aerospace sector, like the fuel nozzles made by GE. The advantages of printing with metal alloys are that complex geometries can be printed while keeping weight reduced without sacrificing strength. The disadvantages include cost, the need to print in an inert atmosphere, and having to post-process (ex., heating or heat-treating) parts or products.
Ceramics (alumina or zirconia, etc.) can be successfully printed with a binder jetting process for parts that need to maintain high temperatures (>2000°C melting points). Alissia is biocompatible and has been used for implants and prosthetics; however, parts can break easily when manipulations take place in the green state (before sintering).
Other new materials include bio-materials and bio-plastics (hydrogels, and other compounds) as well as food-grade materials like chocolate. Composite materials containing Kevlar-type or glass fibers can be used to improve toughness, and can include metallic-filled filaments where the aesthetic finish mimics bronze. Some of these products benefit the capabilities of 3D printing processes; however add additional engineering requirements.
Applications and Case Studies
Different applications have different material choices. In healthcare, resins that are biocompatible enable custom prosthetics, and titanium prints are changing implants. In the case of automotive, ABS was used for a dashboard, and nylon for an under-the-hood part.
A great example is the 3D printed metal bridge in Amsterdam, worth studying; they used stainless steel in unique designs that showcase both intricacy and life expectancy. On the consumer goods front, PLA is cheap, so it enables rapid prototypes for toy designs at Hasbro.
Future Trends in 3D Printing Materials
In the future, multi-material printing will combine properties, such as flexible and rigid. Progress in nanomaterials may yield self-healing prints, and/or conductive prints. Bio-printing alive cells suggests organ printing, while sustainable materials like algae-based filaments will help with environmental considerations to lessen waste and pollution. AI and data may help design materials by adapting all the compositions required for materials.
