What is 3D Printing?
3D printing or additive manufacturing is a process of making three dimensional solid objects from a digital file.
The creation of a 3D printed object is achieved using additive processes. In an additive process an object is created by laying down successive layers of material until the object is created. Each of these layers can be seen as a thinly sliced horizontal cross-section of the eventual object.
3D printing is the opposite of subtractive manufacturing which is cutting out / hollowing out a piece of metal or plastic with for instance a milling machine.
3D printing enables you to produce complex (functional) shapes using less material than traditional manufacturing methods.
A brief history of 3D Printing
- The sci-fi author, Arthur C. Clarke, was the first to describe the basic functions of a 3D printer back in 1964.
- The first 3D printer was released in 1987 by Chuck Hull of 3D Systems and it was using the “stereolithography” (SLA) process.
- In the 90’s and 00’s other 3D printing technologies were released, including FDM by Stratasys and SLS by 3D Systems. These printers were expensive and mainly used for industrial prototyping.
- In 2009, the ASTM Committee F42 published a document containing the standard terminology on Additive Manufacturing. This established 3D printing as an industrial manufacturing technology.
- In the same year, the patents on FDM expired and the first low-cost, desktop 3D printers were born by the RepRap project. What once cost $200,000, suddenly became available for below $2,000.
- According to Wohlers the adoption of 3D printing keeps growing: more than 1 million desktop 3D printers were sold globally between 2015 and 2017 and the sales of industrial metal printers almost doubled in 2017 compared to the previous year.
How does 3D printing works?
Every 3D printer builds parts based on the same main principle: a digital model is turned into a physical three-dimensional object by adding material a layer at a time. This where the alternative term Additive Manufacturing comes from.
3D printing is a fundamentally different way of producing parts compared to traditional subtractive (CNC machining) or formative (Injection molding) manufacturing technologies.
In 3D printing, no special tools are required (for example, a cutting tool with certain geometry or a mold). Instead the part is manufactured directly onto the built platform layer-by-layer, which leads to a unique set of benefits and limitations – more on this below.
The process always begins with a digital 3D model – the blueprint of the physical object. This model is sliced by the printer’s software into thin, 2-dimensional layers and then turned into a set of instructions in machine language (G-code) for the printer to execute.
From here, the way a 3D printer works varies by process. For example, desktop FDM printers melt plastic filaments and lay it down onto the print platform through a nozzle (like a high-precision, computer-controlled glue gun). Large industrial SLS machines use a laser to melt (or sinter) thin layers of metal or plastic powders.
The available materials also vary by process. Plastics are by far the most common, but metals can also be 3D printed. The produced parts can also have a wide range of specific physical properties, ranging from optically clear to rubber-like objects.
Depending on the size of the part and the type of printer, a print usually takes about 4 to 18 hours to complete. 3D printed parts are rarely ready-to-use out of the machine though. They often require some post-processing to achieve the desired level of surface finish. These steps take additional time and (usually manual) effort.
The different types of 3D printing ( All processes are explained individually in upcoming articles )
The ISO/ASTM 52900 standard categorized all different types of 3D printing under one of these seven groups:
- Material Extrusion (FDM): Material is selectively dispensed through a nozzle or orifice
- Vat Polymerization (SLA & DLP): Liquid photopolymer in a vat is selectively cured by UV light
- Powder Bed Fusion (SLS, DMLS & SLM): A high-energy source selectively fuses powder particles
- Material Jetting (MJ): Droplets of material are selectively deposited and cured
- Binder Jetting (BJ): Liquid bonding agent selectively binds regions of a powder bed
- Direct Energy Deposition (LENS, LBMD): A high-energy source fuses material as it is deposited
- Sheet Lamination (LOM, UAM): Sheets of material are bonded and formed layer-by-layer.
3D Printing Materials
Each 3D printing process is compatible with different materials. Plastics both thermoplastics and thermosets) are by far the most common followed by metals. Some composites and ceramics can also be 3D printed.
In the tables below, the most common plastics and metals used in 3D printing are summarized. If you are looking for a 3D Printing material with specific properties, you will probably find our Material Index useful.
3D printing plastics are lightweight materials with a wide range of physical properties, suitable for both prototyping purposes and some functional applications.
Plastics are either thermoplastics (with FDM or SLS), which are generally more suited for functional applications, or thermosets (with SLA/DLP or Material Jetting), which are generally more suited for applications that require good visual appearance.
PLA (Polylactic Acid)
The most common and low-cost 3D printing plastic. Ideals for non-functional prototyping with sharp details. Unsuitable for high temperatures.
Commodity plastic with better mechanical and thermal properties compared to PLA and excellent impact strength.
Thermoset polymers that produce high detail parts with and smooth, injection mold-like surface. Ideal for prototyping.
Nylon or polyamide (PA) is a plastic with excellent mechanical properties and high chemical and abrasion resistance. Perfect for functional applications.
PETG is an easy-to-print plastic with high impact strength and excellent chemical and moisture resistance.
TPU is a thermoplastic elastomer with low hardness and a rubber-like feel that can be easily flexed and compressed.
ASA has mechanical properties similar to ABS, with improved printability, UV stability, and high chemical resistance. Commonly used for outdoor applications.
PEI is an engineering thermoplastic with good mechanical properties and exceptional heat, chemical and flame resistance.
3D printing metals are mainly used in applications that require high strength, high hardness or high thermal resistance. When 3D printing in metal, topology optimization is critical to maximize part performance and mitigate the high cost of the technology.
DMLS/SLM are compatible with the largest range of metals and produces parts for high-end engineering applications. For less demanding use-cases, Binder Jetting is gaining popularity due to its lower cost with Stainless steel being by far the most used material.
Extrusion based metal 3D printing systems (similar to FDM) are being released in 2018 which are expected to drive down the costs of metal 3D printing for prototyping purposes.
Stainless steel is a metal alloy with high ductility, wear and corrosion resistance that can be easily welded, machined and polished.
Aluminum is a metal with good strength-to-weight ratio, high thermal and electrical conductivity, low density and natural weather resistance.
Titanium is a metal with an excellent strength-to-weight ratio, low thermal expansion and high corrosion resistance that is sterilizable and biocompatible.
Cobalt-chrome (CoCr) is a metal super-alloy with excellent strength and outstanding corrosion, wear and temperature resistance.
Nickel alloys (Ni) have excellent strength and fatigue resistance. Can be used permanently at temperatures above 600°C.
It is important to understand that 3D printing is a rapidly developing technology. It comes with its unique set of advantages, but also lags behind traditional manufacturing in some ways.
Here we summarize the most important benefits and limitations of 3D printing, taking into account the pro’s and con’s of all 3D printing technologies currently available. Use them to understand where 3D printing stands today and where it is headed in the near future.
Benefits of 3D printing
- Geometric complexity at no extra cost
- Very low start-up costs
- Customization of each and every part
- Low-cost prototyping with very quick turnaround
- Large range of (speciality) materials
Limitations of 3D printing
- Lower strength & anisotropic material properties
- Less cost-competitive at higher volumes
- Limited accuracy & tolerances
- Post-processing & support removal
Applications of 3D printing
Here we collected some examples to show how people used 3D printing and why they chose it for their specific use cases.
- : 3D Hubs at https://www.3dhubs.com/3d-printing/