Additive manufacturing is often referred to as 3D printing, but is there a difference?
The short answer is yes — although it’s a bit subtle:
Additive manufacturing is a beginning-to-end process of developing and ultimately creating an item using 3D printing technology. The term ‘3D printing’ refers to a more ‘ground-level’ creation.
ADDITIVE MANUFACTURING: 3D PRINTING
Though the technology was pioneered in the 1980’s, the vast breadth of potential applications was only appreciated within this past decade as patents expired, computing technology improved, and various organizations – including NASA — began to research its value to their operations. Since then, the almost magical capabilities of 3D printers have become widely known.
So what does a 3D printer do? A 3D printer creates a desired item incrementally – layer by layer.
It’s a little bit like building with Lego. You start with laying a base of blocks and start building upwards and outwards one layer at a time, adding variations to how the interlocking blocks sit on each other as needed the goal of constructing whatever model you have in mind.
The letter contents would be represented three-dimensionally – length (x), width (y) and now also height (z).
In the case of 3D printing, the building blocks are replaced with a desired raw material – nylon, polycarbonate, titanium, copper – and your hand is replaced with the energy source that will bind or fuse the raw material one layer at a time with the goal of – you guessed it – creating the desired object. And the layers are much, much thinner. The Lego blocks depicted represent a layer height of 3.2mm. Layer heights for 3D printing are measured in microns, or 1/1000 of a millimeter, ranging from as small as 20 microns to 200 microns (sometimes more).
In other words, comparable to the thickness of a human hair.
This incremental layered approach to producing an item is exactly what 3D printing is all about, and it is increasingly pervasive. It can be used to create objects smaller than the head of a pin, but also to build houses, car and aircraft components — even castles and bridges!
There is a wide variety of 3D printing media available, including:
- FUSED DEPOSITION MODELING (FDM): the most well-known and affordable form of 3D printing is mainly used with thermoplastics, though the technology is being adapted to work with other materials (like concrete for houses), and larger scales.
- STEREOLITHOGRAPHY (SLA): the ‘original’ 3D printing, uses UV light – normally in the form of a laser – to catalyze photochemical thermoset resins
- DIGITAL LIGHT PROCESSING (DLP): very much like SLA printing, DLP catalyzes photochemical resins using a projector that crystalizes one layer at a time.
- SELECTIVE LASER SINTERING (SLS): this process uses a laser to sinter (heating to compact without melting) powdered materials like nylon
- SELECTIVE LASER MELTING (SLM): sometimes referred to as powder bed fusion, SLM is arguably the most common and reliable form of metal 3D printing, SLM uses lasers to melt and fuse metals and alloys.
- DIRECT METAL LASER SINTERING (DMLS): this process is for metal 3D printing also, but instead of using lasers to melt and fuse the metal, it sinters it.
- DIRECTED ENERGY DEPOSITION (DED): Creates objects by melting powdered material (most frequently used for metals such as titanium, aluminum, stainless steel or copper) with a focused energy source as it is deposited.
- BINDER JETTING (BDJ): binder jetting creates models by ‘gluing’ a base material powder together using a binding agent which is typically removed in post processing. This process can be used on a wide range of materials including metal, ceramic and sand.
It may sound simple, but in truth the current levels of application, affordability and integration into cross sections of public awareness and industry have only been made possible through the development of digital and computing technology.
ADDITIVE MANUFACTURING: A QUICK OVERVIEW
If 3D printing presents an almost revolutionary way to create items, it shouldn’t be surprising that the process of designing the items to be printed can be equally revolutionary since it allows a previously unavailable production latitude. The bracket to the right is an excellent example of redesigning a component at reduced cost and with less material waste.
While users can always choose to send a file straight to a device and let the device use default print settings, it is usually preferable to include a middle step, rendering and slicing, for a three-step process:
- CONCEPTION AND DESIGN
- RENDERING AND SLICING
- PRODUCTION (PRINTING)
We’ve explained each step below:
1. CONCEPTION AND DESIGN.
The designer’s idea is rendered visually using computer-assisted design (CAD) software. There are a wide number of CAD programs that can create ‘print-compatible’ files with varied levels of complexity, detail and cost.
- Entry-level programs like TinkerCAD are a great introduction to design for people who have no modeling experience. These programs are so user-friendly that they are used in elementary schools.
- More complex programs like Onshape or Fusion 360 have a learning curve, but allow for greater precision in design — shaping and texturing, for example.
- Some programs are free – including Sketch Up and FreeCAD – while others can be paid for monthly or bought outright.
- A number of websites offer downloadable print files. Quality varies.
2. RENDERING AND SLICING.
Step Two in the additive manufacturing process converts the completed computer visualization of the object into a print-compatible file format (typically an .STL or .OBJ file). The computer graphic of the object is then “sliced” and converted into numerical computer code. That code will guide and direct your 3D printer as it creates the physical object.
Slicing software typically allows the user to make a variety of selections that will govern the material used, strength, and quality of the end item.
Choosing correct settings can be tricky to master as each setting will influence quality of the end product. Learners can use default settings recommended by device software, but if finer detail, higher speed, greater strength, supports, or greater adhesion is required, precise slicer settings will be very important.
3. PRODUCTION (PRINTING)
Third, the sliced file is sent directly to the 3D printer. The code in that file now directs the 3D printer to physically construct the item layer by layer in accordance with the settings and material you have pre-selected.
Note how streamlined this process is!
‘Direct-to-Device’ production is one of the most powerful aspects of additive manufacturing. The designer can create and immediately upload a file him or herself. There is no down-time and no need to involve another party. In addition, the process requires comparatively little ongoing oversight.
The implications of CAD to print and the incremental build process are substantial. Here are some of the benefits that can result:
- RAPID PROTOTYPING: One of the most well documented benefits of AM, additive manufacturing facilitates and removes many of the costs associated with the production of a high fidelity prototype by cutting out many of the additional steps involved in more historical methods.
- GREATER DESIGN COMPLEXITY: Since components are constructed one layer at a time, traditional manufacturing restrictions and design requirements like draft angles, undercuts and tool access typically do not apply to additive manufacturing.
- SUPPLY CHAIN MANAGEMENT: In much the same way as additive shortcuts the production of prototypes, AM adopters can rethink and shorten their supply chain to reduce reliance on 3rd parties and shorten lead times.
- REDUCED ASSEMBLY REQUIREMENTS: Redesigned parts can simplify assembly by removing fasteners like flanges or hinges, both reducing labor requirements and the net weight of the final component
- REDUCED WASTE: Even when accounting for possible support structures, 3D printed parts produce less waste than traditional methods like CNC milling that can result in 50% or more material weight.
- CONTROL OVER INTELLECTUAL PROPERTY: Implicit in the capacity to manage an organization’s supply chain is the ability to limit access to proprietary intellectual property.
- GREATER CUSTOMIZATION: Changes to a design whether for iterative prototypes or to enhance end-user satisfaction can be produced without incurring capital and set up costs associated with traditional methods.
- REDUCED INVENTORY RELIANCE: Approved designs can be produced on demand rather than require an exhaustive and capital intensive inventory process.
- NETWORKED DIGITAL PRODUCTION AND INVENTORY: Approved designs can be stored as digital files that can be forwarded to producers as needed for production.
ADDITIVE MANUFACTURING: DIFFERENT FROM CONVENTIONAL MANUFACTURING
One of the great artists of the Renaissance, Michelangelo, is reputed to have said:
“Every block of stone has a statue inside it and it is the task of the sculptor to discover it.”
Conventional forms of production are likewise largely “subtractive”. The designer starts with a raw material and pares it down until left with the desired item. Of course this is true with sculpting, but it is also true of other conventional production processes. For example, furniture-making requires trees. Once harvested, those trees will be delimbed, debarked, sawed and resawed, planed. Before the carpenter ever begins to put a chair together, that wood has already gone through a series of ‘subtractive’ processes. Even with the help of the many machines involved, we have a laborious, time-consuming and expensive process.
Methods of subtractive manufacturing include casting, molding, joining, machining, and forming.
The video link to the left offers a look at a Computer Numerical Control (CNC) milling machine. It shows the CNC mill in various stages of milling different items. Notice that during all stages, the milling machine is subtracting filings or shavings from the stock material. A lot of waste is created.
This graph demonstrates the relationship between cost/unit and number/units. The red line denoting conventional manufacturing, is used to indicate how different conventional methods have evolved to suit higher volumes. The blue bar denotes additive manufacturing.
The green shaded area denotes the area of quantity/cost superiority offered by additive manufacturing. As additive manufacturing technology improves, its projected impact is to speed up the production process and thus reduce the AM quantity/cost line relative conventional manufacturing.
This graph illustrates the relationship between unit complexity and unit cost.
The red line denotes the growing costs involved in conventionally creating more complex components. This may include extra labor, more specialized machinery or fixtures/jigs.
The blue line denotes additive manufacturing which is able to more easily reproduce design complexity without requiring requiring extra inputs.
ADDITIVE MANUFACTURING vs TRADITIONAL MANUFACTURING
Who wins in this match-up?