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What is 3D printing? The definitive guide

Learn all you need to know about 3D printing in 30 minutes or less. Whether you are just getting started or you’re an experienced engineer, you’ll find this guide packed with useful tips and information - updated for 2018.

Part 1

The Basics

What is 3D printing? How does it work? What are its key benefits and limitations and main industrial applications?

Here, we answer all these questions and examine how 3D printing compares to traditional manufacturing to help you understand the current state of the technology.

How does 3D printing work?

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.

An illustration of the basic Additive Manufacturing process

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.

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 costed $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.
Early SLS 3D printer

3D printing: beyond the hype

The 3D printing hype cycle

So where is 3D printing today? Is the hype over? Well, maybe but...

The hype of the previous years was based on the idea of widespread consumer adoption. This was (and still is) a misleading interpretation of where the technology actually adds value.

3D printing today has found very specific roles in the world of manufacturing. The inflated expectations of the previous years have given their place to an increased productivity. Many aspects of the technology are now mainstream and adopted by both professional and hobbyists.

Of course, 3D printing is an evolving technology. Every year new 3D printers are released that can have a significant impact on the industry. For example, HP launched their first 3D printing system relatively late (in 2016), but it proved to be one of the most popular industrial 3D printers already by 2017.

Benefits & Limitations of 3D printing

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.

Learn more about the advatages of 3D printing →

Benefits of 3D printing

Geometric complexity at no extra cost

3D printing allows easy fabrication of complex shapes, many of which cannot be produced by any other manufacturing method.

The additive nature of the technology means that geometric complexity does not come at a higher price. Parts with complex or organic geometry optimized for performance cost just as much to 3D print as simpler parts designed for traditional manufacturing (and sometimes even cheaper since less material is used).

DMLS/SLM hip implant
Very low start-up costs

In formative manufacturing (think Injection Molding and Metal Casting) each part requires a unique mold. These custom tools come at a high price (from thousands to hundreds of thousands each). To recoup these costs identical parts in the thousands are manufactured.

Since 3D printing does not need any specialized tooling, there are essentially no start-up costs. The cost of a 3D printed part depends only on the amount of material used, the time it took the machine to print it and the post-processing - if any - required to achieve the desired finish.

cleaning SLS parts
Customization of each and every part

Have you ever wondered why we buy our clothing in standardized sizes? For the reasons we just mentioned, with traditional manufacturing, it is simply cheaper to make and sell identical products to the consumer.

3D printing though allows for easy customization. Since start-up costs are so low, one only needs to change the digital 3D model to create a custom part. The result? Each and every item can be customized to meet a user's specific needs without impacting the manufacturing costs.

DMLS/SLM dental-crowns
Low-cost prototyping with very quick turnaround

One of the main uses of 3D printing today is prototyping - both for form and function. This is done at a fraction of the cost of other processes and at speeds, that no other manufacturing technology can compete with:

Parts printed on a desktop 3D printer are usually ready overnight and orders placed to a professional service with large industrial machines are ready for delivery in 2-5 days.

The speed of prototyping greatly accelerates the design cycle (design, test, improve, re-design). Products that would require 8+ months tp develop, now can be ready in only 8-10 weeks.

3DP 101 - Design iterations with 3D printing
Large range of (speciality) materials

The most common 3D printing materials used today are plastics. Metal 3D printing finds also an increasing number of industrial applications.

The 3D printing pallet also includes speciality materials with properties tailored for specific applications. 3D printed parts today can have high heat resistance, high strength or stiffness and even be biocompatible.

Composites are also common in 3D printing. The materials can be filled with metal, ceramic, wood or carbon particles, or reinforced with carbon fibers. This results in parts with unique properties suitable for specific applications.

multi-material brackets

Limitations of 3D printing

Lower strength & anisotropic material properties

Generally, 3D printed parts have physical properties that are not as good as the bulk material: since they are built layer-by-layer, they are weaker and more brittle in one direction by approximately 10% to 50%.

Because of this, plastic 3D printed parts are most often used for non-critical functional applications. DMLS & SLM though can produce metal 3D printed parts with excellent mechanical properties (often better than the bulk material). For this reason, they have found applications in the most demanding industries, like aerospace.

Functional 3D printed parts non critical parts
Less cost-competitive at higher volumes

3D printing cannot compete with traditional manufacturing processes when it comes to large production runs. The lack of a custom tool or mold means that start-up costs are low, so prototypes and a small number of identical parts (up to ten) can be manufactured economically. It also means though that the unit price decreases only slightly at higher quantities, so economies of scale cannot kick in.

In most cases, this turning point is at around 100 units, depending on the material, 3D printing process and part design. After that, other technologies, like CNC machining and Injection Molding, are more cost effective.

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Learn more about economies of scale →

3D printing larger volumes - metal Binder Jetting
Limited accuracy & tolerances

The accuracy of 3D printed parts depends on the process and the calibration of the machine. Typically, parts printed on a desktop FDM 3D printer have the lowest accuracy and will print with tolerances of ± 0.5 mm. This means that if you design a hole with diameter of 10 mm, its true diameter after printing will something between 9.5 mm to 10.5 mm.

Other 3D printing processes offer greater accuracy. Industrial Material Jetting and SLA printers, for example, are able to produce parts down to ± 0.01 mm. It is important to keep in mind though, that these results can only be achieved after optimisation for specific features in a well-designed part.

Metal 3D printed parts for critical applications are often finished via CNC machining or another process after printing, to improve their tolerances and surface finish.

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Read an in-depth comparison of the accuracy of the different 3D printing processes →

Accuracy of SLS 3D printed parts
Post-processing & support removal

Printed parts are rarely ready to use off the printer. They usually require one or more post-processing steps.

For example, support removal is needed in most 3D printing processes. 3D printers cannot add material on thin air, so supports are structures that are printed with the part to add material under an overhang or to anchor the printed part on the build platform.

When removed and they often leave marks or blemishes on the surface of the part they came in contact with. These areas need additional operations (sanding, smoothing, painting) to achieve a high quallity surface finish.

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Learn more about supports in 3D printing →

FDM bracket with soluble support structures

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.

Aerospace
Automotive
Robotics
Tooling
Healthcare
Design
Cinema
Education
DIY

Aerospace

Aerospace and Space engineers use 3D printing to manufacture high-performance parts. The ability to create topology optimized structures with high strength-to-weight ratio and the possibility to consolidate multiple components into a single part are particularly appealing.


Optisys LLC is a provider of micro-antenna products for aerospace and defense applications. They used metal 3D printing to reduce the number of discrete pieces of their tracking antenna arrays from 100 to only 1. With this simplification, Optisys managed to reduce the lead time from 11 to 2 months, while achieving a 95% weight reduction.


Read the full story in the 3D Printing Handbook →

3DP 101 - applications - space

Automotive

The automotive industry has benefited greatly from the fast turnaround and the ease of customization offered by 3D printing.


Volkswagen traditionally used CNC machining to create custom jigs and fixtures. CNC has typically longer production times and higher cost. The same jigs and fixtures could be 3D printed overnight and tested on the assembly line the next day. Feedback from the operators was incorporated almost immediately and a new jig was ready to test the next day until the perfect tool was created.


Read the full story in the 3D Printing Handbook →

3DP 101 - applications - automotive

Robotics

In the field of robotics & automation, custom one-off parts are very often needed to develop new robotic mechanisms. 3D printing has evolved into one of the main manufacturing technologies of this industry, because of its speed, great design freedom and ease of customization. The large range of material options with unique properties, also allows the creation of unique structures, such as "soft" robots.


A team of engineering students from the University of Antwerp built a humanoid robotic arm that can translate speech into sign language and they used 3D printing almost exclusively to manufacture all custom structural parts of their robot.


Read the full story →

3D printed robotic hand

Industrial tooling

The development of new 3D printing materials with high heat resistance and stiffness, combined with the ability to create custom parts quickly and at a low cost, pushed 3D printing to find multiple applications around industrial tooling.


For example, 3D printing is used today to manufacture low-run injection molds. These molds are used to produce a few hundred parts (compared to the 10.000+ of metal molds), but come at a fraction of the cost of a "traditional" mold and can be manufactured overnight. This makes them ideal for low-volume, low-cost production or small tests runs before full scale manufacturing.


Read the full story →

A 3D printed mold for low-run injection molding

Healthcare

Did you know that today in the US hearing aids are manufactured almost exclusively using 3D printing? In fact, the companies that did not adopt the technology, very fast when out of business, as they could not keep up with the competition.


The healthcare and prosthetics field has benefited greatly by adopting 3D printing. Custom shapes, such as hearing aids, no longer need to be made through manual labor. With 3D printing, they can be manufactured quickly from a digital file (by 3D scanning the patient's body, for instance). This brings substantially lower costs and lower production times.


Read the full report →

3D printed hearing aids

Product design

With the help of 3D printing, product designers can easily customize their products at no extra costs. They can also create high-quality functional prototypes for a new product concept. This accelerates the design cycle and proves that their product idea works before a larger investment is made.


For example, Paul Kohlhaussen designed and created a functional prototype of his ultimate camera. He combined camera parts from different models and merged them together with a custom 3D printed body. He then took his idea to Kickstarter to succesfuly get funding for his project.


Read the full story →

A functional 3D printed prototype of a camera

Entertainment

3D printing is one of the favorite tools of movie makers today, due its ability to create believable props. The high design flexibillity of 3D printing helps entertainment professionals bring to life objects of their imagination. This can now be done quickly and at a much lower cost than the past.


One example comes from Vitaly Bulgarov, a concept designer whose resume includes working with movie studios. like Paramount and Dreamworks. He used 3D printing to quickly turn his computer sketches into a usable physical objects for a film he was working on.


Read the full story →

3D printed movie prop

Education

The 3D printing technology has great potential in educational environments. With 3D printing, the course subjects can be brought to life through scaled replicas. This equips the students with practical (and very valuable) real-life experience.


Aerospace engineering students from the University of Glasgow worked together with Rolls Royce to create a functional 3D printed jet engine model. The model gives instant feedback to the students about changes they make during it operation, helping them gain very valuable practical experience.


Read the full story →

A functional 3D printed jet engine model used in education

Makers

For makers that constantly explore new ideas, 3D printing is the perfect tool. One of its key benefits is the ability to produce unlimited spare parts and new designs without relying on external vendors. They can develop and customize their designs enabling them to create new and better concepts.


Jack Davies, for example, is a product design student from Nottingham Trent University. He created his own electric skateboard using 3D printed parts. His boosted board has capabilities comparable to a commercially available electric skateboards, but for about a third of the price.


Read the full story →

The parts of a 3D printed e-board

3D printing vs. Traditional Manufacturing

3D printing is an exceptional tool for manufacturing custom parts and prototyping. Due to its unique characteristics though, it is best suited for specific applications.

When choosing between an additive (3D printing), subtractive (CNC machining) or formative (Injection Molding) manufacturing technology, then there are a few simple guidelines that can gudie your decision.

As a rule of thumb:

"3D printing is the best option when a single (or only a few) parts are required at a quick turnaround time and a low-cost or when the part geometry cannot be produced with any other manufacturing technology."

Choosing a subtractive technology (CNC machining) makes more sense in the following scenarios:

  • Medium volumes: When producing parts in the 100's, then CNC machining is typically more economical. This is because the economies of scale start to kick in.
  • Relatively simple geometries: Especially for metal parts, when the design can be manufactured easily through a subtractive process then CNC machining is the best option.
  • High material requirements: When excellent material properties are essential, then CNC machining is a better option, as 3D printed parts typically have a lower strength.
  • High dimensional accuracy: For functional parts with tight tolerances, CNC machining is the best option. For complex geometries, a hybrid approach (print first, CNC machine afterwards) is also be a viable option.

For larger production (> 1000 parts), formative technologies (like Injection molding) are more cost effective and usually make the most financial sense.

For a quick reference in the unit cost, use the graph below. In this simplification, it was assumed that all technologies can produce the part geometry. When this is not the case, 3D printing is generally the preferred manufacturing solution.

3DP 101- Cost-vs-quantity

To summarize:

"3D printing offers great geometric flexibility and can produce custom parts and prototypes quickly and at a low-cost, but when large volumes, tight tolerances or demanding material properties are required traditional manufacturing technologies are often a better option."

Read an extensive article with practical examples →

Part 2

3D Printing Processes

After reading this section, you will have a complete overview of today's 3D printing landscape.

Quickly learn about the most popular processes and materials, as well as actionable decision making tools to help you select the optimal 3D printing process for your application.

The different types of 3D printing

Additive Manufacturing Technologies poster

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


An infographic with all currently available 3D printing technologies is available for download here. It illustrates the seven 3D printing categories, the main materials each group can print with and the most popular printer manufacturers.

The next sections will introduce you to the basic operating principles and pro's and con's of the six main 3D printing processes today.

After reading this chapter, you will be able to make educated decisions about which 3D printing technology is best suited for your particular application.

Fused Deposition Modelling (FDM)

In FDM, a spool of filament is loaded into the printer and then fed to the extrusion head, which is equipped with a heated nozzle. Once the nozzle reaches the desired temperature, a motor drives the filament through it, melting it.

The printer moves the extrusion head, laying down melted material at precise locations, where it cools and solidifies (like a very precise hot-glue gun). When a layer is finished, the build platform moves down and the process repeats until the part is complete.

After printing, the part is usually ready to use but it might require some post-processing, such as removal of the support strucures or surface smoothing.

Schematic of a typical FDM 3D printer

FDM is the most cost-effective way of producing custom thermoplastic parts and prototypes. It also has the shortest lead times - as fast as next-day-delivery - due to the high availability of the technology. A wide range of thermoplastic materials is available for FDM, suitable for both prototyping and some functional applications.

As of limitations, FDM has the lowest dimensional accuracy and resolution compared to the other 3D printing technologies. FDM parts are likely to have visible layer lines, so post-processing is often required for a smooth surface finish. Additionally, the layer adhesion mechanism makes FDM parts inherently anisotropic. This means that they will be weaker in one direction and are generally unsuitable for critical applications.

Learn more about FDM 3D printing →

add_circle_outline Low-cost prototyping
add_circle_outline Fast turn-around (less than 24 h)
add_circle_outline Functional applications (non-critical load)
remove_circle_outline Limited dimensional accuracy
remove_circle_outline Visible layer lines (can be post-processed)
remove_circle_outline Anisotropic mechanical properties

Stereolithography & Digital Light Processing (SLA & DLP)

SLA and DLP are similar processes that both use a UV light source to cure (solidify) liquid resin in a vat layer-by-layer. SLA uses a single-point laser to cure the resin, while DLP uses a digital light projector to flash a single image of each layer all at once.

After printing, the part needs to be cleaned from the resin and exposed to a UV source to improve its strength. Next, the support structures are removed and, if a high quality surface finish is required, additional post-processing steps are carried out.

Schematic of a typical SLA 3D printer

SLA/DLP can produce parts with very high dimensional accuracy, intricate details and a very smooth surface finish ideal that are ideal for visual prototypes. A large range of speciality materials, such as clear, flexible, castable and biocompatible resins, or materials taylored for specific industrial applications, are also available.

Generally, SLA/DLP parts are more brittle than FDM parts, so they are not best suited for functional prototypes. Also, SLA parts must not be used outdoors, as their mechanical properties and color degrades when they are exposed to UV radiation from the sun. Support structures are always required in SLA/DLP which may leave small blemishes in the surfaces they come in contact with that need extra post-processing to remove.

Learn more about SLA/DLP 3D printing →

add_circle_outline High accuracy & intricate details
add_circle_outline Smooth surface ideal for visual prototypes
add_circle_outline Large range of specialty materials
remove_circle_outline Produces relatively brittle parts
remove_circle_outline Degrade with exposure to sunlight
remove_circle_outline Removal of support marks required

Selective Laser Sintering (SLS)

The SLS process begins with heating up a bin of polymer powder to a temperature just below the melting point of the material. A recoating blade or roller then deposits a very thin layer of powder - typically 0.1 mm thick - onto the build platform.

A CO2 laser scans the surface of the powder bed and selectively sinters the particles, binding them together. When the entire cross-section is scanned, the building platform moves down one layer and the process repeats. The result is a bin filled with parts surrounded by unsintered powder.

After printing, the bin needs to cool before the parts are removed from the unsintered powder and cleaned. Some post-processing steps can then be employed to improve their visual appearance, such as polishing or dying.

Schematic of a typical SLS 3D printer

SLS parts have very good, almost-isotropic mechanical properties, so they are ideal for functional parts and prototypes. Since no support structures are required (the unsintered powder acts as support), designs with very complex geometries can be easily manufactured. SLS is also excellent for small-to-medium batch production (up to 100 parts), since the bin can be filled throughout its volume and multiple parts can be printed at a single production run.

SLS printers are usually high-end industrial systems. This limits the availability of the technology and increases its cost and turn-around times (compared to FDM or SLA, for example). SLS parts have a naturally grainy surface and some internal porosity. If a smooth surface or watertightness is required, additional post-processing steps are needed. Beware that large flat surfaces and small holes need special attention, as they are susceptible to thermal warping and oversintering.

Learn more about the SLS process →

add_circle_outline Ideal for functional prototypes
add_circle_outline Complex geometries - no support needed
add_circle_outline Small batch production capabilities
remove_circle_outline Higher cost than FDM or SLA
remove_circle_outline Slower turn-around due to batch production
remove_circle_outline Grainy surface & internal porosity

SLS vs. MJF

A competing technology with similar benefits to SLS is MJF, which was introduced in 2016 by HP. Both technologies create parts that are visually and mechanically almost indistinguishable.


Learn about the differences of SLS and MJF →

3DP 101 - MJF nylon part

Material Jetting (PolyJet)

Material Jetting works in a similar way to standard inkjet printing. However, instead of printing a single layer of ink on a piece of paper, multiple layers of material are deposited upon each other to create a solid part.

Multiple print heads jet hundreds of tiny droplets of photopolymer onto the build platform, which are then solidified (cured) by the UV light source. After a layer is complete, the build platform moves down one layer and the process repeats.

Support structures are always required in Material Jetting. A water-soluble material is used as support that can be easily dissolved during post-processing and that is printed at the same time as the structural material.

Schematic of a typical Material Jetting 3D printer

Material Jetting is the most precise 3D printing technology (with SLA/DLP being a close second). It is one of the few 3D printing processes that offers multi-material and full-color printing capabilities. Material Jetted parts have a very smooth surface - comparable to injection molding - and very high dimensional accuracy, making them ideal for realistic prototypes and parts that need an excellent visual appearance.

Material Jetting is one of the most expensive 3D printing processes and this high cost may make it financially unviable for some applications. Moreover, parts produced with Material Jetting are not best suited for functional applications. Like SLA/DLP, the materials used with this process are thermosets, so the produced parts tend to be brittle. They are also photosensitive and their properties will degrade over time with exposure to sunlight.

Learn more about the Material Jetting process →

add_circle_outline High accuracy & very fine details
add_circle_outline Injection molding-like finish
add_circle_outline Multi-material & full-color capabilities
remove_circle_outline The most expensive plastic 3D printing process
remove_circle_outline Mechanical properties degrade over time
remove_circle_outline Produces relatively brittle parts

Direct Metal Laser Sintering & Selective Laser Melting (DMLS & SLM)

Direct Metal Laser Sintering (DMLS) and Selective Laser Melting (SLM) produce parts in a similar way to SLS: a laser source selectively bonds together powder particles layer-by-layer. The main difference, of course, is that DMLS and SLM produce parts out of metal.

The difference between the DMLS and SLM processes is subtle: SLM achieves a full melt of the powder particles, while DMLS heats the metal particles to a point that they fuse together on a molecular level instead.

Support structures are always required in DMLS and SLM to minimize the distortion caused by the high temperatures required to fuse the metal particles. After printing, the metal supports need to be removed either manually or through CNC machining. Machining can also be employed to improve the accuracy of critical features (e.g. holes). Finally, the parts are thermally treated to eliminate any residual stresses.

Schematic of a typical DMLS/SLM 3D printer

DMLS/SLM is ideal for manufacturing metal parts with complex geometries that traditional manufacturing methods cannot produce. DMLS/SLM parts can be (and should be) topology optimized to maximize their performance while minimizing their weight and amount of material used. DMLS/SLM parts have excellent physical properties, often surpassing the strength of the rough metal. Many metal alloys that are difficult to process with other technologies, such as metal superalloys, are available in DMLS/SLM.

The costs associated with DMLS/SLM 3D printing are high: parts produced with this processes typically cost between $5.000 and $25.000. For this reason, DMLS/SLM should only be used to manufacture parts that cannot be produced with any other method. Moreover, the build size of modern metal 3D printing systems is limited, as the required precise manufacturing conditions are difficult to maintain for bigger build volumes.

Learn more about the DMLS/SLM process →

add_circle_outline Highly complex, topology optimized metal parts
add_circle_outline Parts with excellent material properties
add_circle_outline Ideal for high-end engineering applications
remove_circle_outline Very high manufacturing costs
remove_circle_outline Specialized CAD software knowledge required
remove_circle_outline Limited build volume

Binder Jetting

Binder Jetting is a flexible technology with diverse applications, ranging from low-cost metal 3D printing, to full-color prototyping and large sand casting mold production.

In Binder Jetting, a thin layer of powder particles (metal, acrylic or sandstone) is first deposited onto the build platform. Then droplets of adhesive are ejected by a inkjet printhead to selectively bind the powder particles together and build a part layer-by-layer.

After the print is complete, the part is removed from the powder and cleaned. At this stage it is very brittle and additional post-processing is required. For metal parts this involves thermal sintering (similar to Metal Injection Molding) or infiltration with a low melting-point metal (for example, bronze), while full-color parts are infiltrated with cyanoacrylate adhesive.

Schematic of a typical Binder Jetting 3D printer

Binder Jetting can produce metal parts and full-color prototypes at a fraction of the cost of DMLS/SLM or Material Jetting respectively. Very large sandstone parts can also be manufactured with Binder Jetting, as the process is not limited by thermal effects (for example, warping). Since no support structures are needed during printing, metal Binder Jetting parts can have very complex geometries and, like SLS, low-to-medium batch production is possible by filling up the whole build volume.

Metal Binder Jetting parts have lower mechanical properties than the bulk material though, due to their porosity. Due to the special post-processing requirements of Binder Jetting, special design restrictions apply. Very small details, for example, cannot be printed, as the parts are very brittle out of the printer and may break. Metal parts might also deform during the sintering or infiltration step if not supported properly.

Learn more about the Binder Jetting process →

add_circle_outline Low-cost batch production of metal parts
add_circle_outline Full-color prototyping in acrylic or sand
add_circle_outline Very large printing capabilities in sand
remove_circle_outline Inferior material properties to DMLS/SLM
remove_circle_outline Design restriction due to post-processing
remove_circle_outline Fine details may not be printable

How to select the right 3D printing process

Selecting the optimal 3D printing process for a particular application can be difficult. There are often more than one process that are suitable and each of them offers different benefits, like greater dimensional accuracy, superior material properties or better surface finish.

For this reason, we have prepared decision making tools and generalized guidelines to help you select the right 3D printing process.

Generally, there are three main things you always need to consider:

  • The required material properties: strength, hardness, impact strength etc.
  • The functional & visual design requirements: smooth surface, strength, heat resistance etc.
  • The capabilities of the 3D printing process: accuracy, available print volume, layer height etc.

With these considerations in mind, identifying the best solution for your application should become straightforward. We have prepared a detailed guide to help you with the technical details or you can se this decision trees bellow for a quick reference.

Read the full selection guide →

How to select a 3D printing process

Part 3

3D Printing Materials

3D printing materials are closely connected to 3D printing processes. In this section, you will learn more about the most popular materials that are used today in 3D printing and their key applications.

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.

3D printing materials

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.

Plastics

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.

Do you want to learn more about 3D printing plastics? We have prepared extensive guides for you.

Compare the most popular FDM materials →

Compare the most popular SLA materials →

Metals

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.

Part 4

Design for 3D printing

This section will give you tips on how to correctly prepare your digital files for 3D printing. We will delve deeper in the best design practices and give you recomendations on what software to use.

If 3D modeling sounds tough (or if you are simply short in time), we give you a list of the best online model repositories to help you find existing designs.

How to get a printable model

All you need to start 3D printing is a model in the STL file format. Depending on your design skills and the time you want to invest, you can either:

  • Design a 3D printable model yourself
  • Find it in an online repository

In the next sections we will explore both options, but first let's learn more about STLs.

The STL file format

  • STL is the industry standard file format that all 3D printers use.
  • STLs use triangles to represent the outer and inner surfaces of a solid 3D object.
  • Think of STLs files as the PDFs of 3D printing: they contain all the information needed to print a model, but they are not easy to edit.


Learn more about the STL file format→

The STL file format

Design for 3D printing

If you are already familiar (or willing to get your hands dirty) with 3D design, then it is easy to create a 3D printable model yourself. Just use your favorite CAD software and simply save your models in the STL file format (all modern CAD software packages can do this).

Design rules for 3D printing poster

Don't forget that despite the great design freedom offered by 3D printing, some restrictions still do apply: anything can be "drawn" in 3D on a digital canvas, but not everything can be 3D printed.

To make your life easier, we created a poster that sums up the most important design rules for each 3D printing process. You can print it and put it on your wall to always have it next to you while designing.

If you want to delve deeper, we've prepared multiple guides describing the key design consideration for 3D printing, full of actionable tips and advice.

Here are the top 3 things to look out for:

  • Overhangs & support: 3D printers cannot deposit material on thin air. Walls at an angle greater than 45° will require support, affecting the surface quality.
  • Level of detail: The smallest feature a printer can create depends on the size of the end effector (nozzle or laser) it uses.
  • Layer height: The layer height affects the vertical resolution of a part. It's effects are visible are areas with greater curvature (it appears as stair-stepping).


Follow the links below to read comprehensive design guidelines for each 3D printing process:

| FDM → | SLA/DLP → | SLS → | Material Jetting → | DMLS/SLM → | Binder Jetting → |

Do you want to step up your 3D printing skills? We wrote a book that can help you get there:

What is the best software for 3D printing?

Different software packages can aid you in each different stage of the design process: from CAD design, to STL repair and preparation. In this section we list the best software for 3D printing to help you get started.

Here is the list with the CAD design software we recommend to use for designing parts for 3D printing:

If you are looking for the best tools you can use to modify or repair your STL files before you send them to print, here is a list of the best software currently available:

The process of converting an STL file into machine language (G-code) is called slicing. Here are some of the best and most popular slicing software out there today:

Find a design online

If you are new to design (or if you are simply looking for something to print fast), then one of the many online repositories might already have what you are looking for.

Here are some websites we recommend:

  • Thingiverse → The largest online repository with thousands of free 3D printable files for desktop 3D printing.
  • MyMiniFactory → A popular online repository with free 3D models that are tested for quality and are guaranteed to be 3D printable.
  • Cults → An online marketplace with high quality 3D printable models by professional designers, and curated collections connected to big-name brands.
  • Pinshape → An online marketplace with both free and premium 3D printable files, focusing mainly on hobbyists.
  • GrabCAD → An online repository of many 3D models that also includes some 3D printable files, focusing mainly on engineering professionals.

Part 5

Start 3D printing

It is time to put your knowledge into practice. In this section, we will guide you through the basic steps needed to start 3D printing: from choosing what printer to buy to how to use an online service.

Buy a printer or use a 3D printing service?

Once you have your design ready, it is time to print! Again, you have two options here: you can either buy your own 3D printer or use an online service. It is an important decision to make, so we have collected arguments for both sides to help you make the right choice based on your specific needs.

No matter how you decide to proceed, we give you tips on what you should do next in the following two sections.

Buy a 3D printer if… Use an online service if…
you need to print regularly (10 - 25+ times a week) you will need too few (less than 5) or too many (25+) parts printed per month
you have one specific application in mind for the printer you want to print using multiple processes and materials, including industrial printers
you are ready to make a sizeable investment you want to access the latest technologies at all times
you are prepared to setup, tinker and optimize your machine you prefer to focus your time on designing and perfecting your models
you have the necessary space and time to install and operate the printer you want to test and learn first before deciding what printer to buy

What 3D printer should you buy

Best printer guide 2018

To answer this question, every year we reach out to our global network of 3D printing service providers to learn from their experiences and find out more about the 3D printers they own.

With reviews from more than 10 thousand verified 3D printer owners, who have completed about 1.48 million prints on 650+ different 3D printer models, the result of our research is the most comprehensive 3D Printer Guide available.

How to use a 3D printing service

how to use a 3D printing service

On 3D Hubs we are building the smartest manufacturing solution on the planet.

By combining our global network of manufacturing services with our smart sourcing engine, you can instantly access readily available 3D printing production capacity near your area with the best possible quotes and lead times.

When you upload a part, our proprietary Design for Manufacturing (DFM) software detects any potential design issues before production begins, minimizing cost and delays.

This way you can be certain that you always receive the best price possible at the fastest turnaround times for your 3D printed parts.

Part 6

Useful resources

In this guide we touched upon all you need to get you started with 3D printing, but there is plenty more to learn.

Below we list the best and most useful resources on 3D printing and other digital manufacturing technologies for those who want to delve deeper.

Knowledge Base

Here, we touched upon all you need to get you started with 3D printing. There is plenty more to learn though in our Knowledge Base - a collection of technical articles on all manufacturing technologies, written by experts from 3D Hubs and the manufacturing industry.

The 3D printing handbook

3DP 101 - The 3D printing handbook

If you’re a professional looking to master the key aspects of 3D printing, this book is for you.

What's Inside:

  • Insights into the mechanism behind all major 3D printing technologies
  • An understanding of the benefits and limitations of each technology
  • Decision making tools for technology selection
  • Actionable design advice and guidelines
  • Industry case studies from world-leading brands

Want to learn more about Digital Manufacturing? There are more technologies to explore:

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