3D printing - introduction
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What is 3D printing?
We begin this blog series with the basic of 3D printing. So what is 3D printing? 3D printing is an additive manufacturing process that involves laying down raw material, most commonly plastic, in a successive pattern until an object is formed. The image below shows a simplified view of the process.
Figure 1: Simplified 3D printer manufacturing process
2. “Printed” material
3. Build plate
Additive manufacturing is one of three basic types of manufacturing:
● Injection Molding
Understanding the differences between the aforementioned can help us realize the advantages and disadvantages of 3D printing when compared to other methods of manufacturing. From the name itself, we can understand that additive manufacturing involves “adding” material to produce a desired object. This method helps in conserving raw material as it only lays down the required amount. Additionally, it also allows for the production of hollow objects.
Figure 2: Ultimaker 2 3D printer, an example of additive manufacturing
Comparatively, subtractive manufacturing involves cutting away from a “block” of material until an object is formed and can be compared to carving or sculpting. Intricate and detailed objects can be produced but at the disadvantage of having no option of being hollow and the waste of all the material sculpted away. CNC cutting or milling are typical examples of subtractive manufacturing and are a relatively common industry.
Figure 3: Metal milling, an example of subtractive manufacturing
Lastly, injection molding is the process in which a pre-made mold is prepared and then injected with the desired material. Rapid and successive production of the same object can be achieved here as there is no time wasted “carving” or “printing” the object. However, this method allows for production of a single object efficiently, but not multiple different objects as a new mold has to be made every time a new object is required which is time consuming.
Figure 4: Injection mold, an example of injection molding technique
In summary, the three manufacturing processes have their advantages and disadvantages and can be summed up with the following. Additive manufacturing (3D printing) is suitable for prototyping and producing a small number of parts. Subtractive manufacturing (CNC) is suitable for large two-dimensional parts, like a large laser cut decorative wooden board. CNC is also superior in producing living hinges. Lastly, injection molding is very practical for relatively larger scale production. For example, a new product can be prototyped using 3D printing and then produced at a small market testing scale (around a 1000 pieces) using injection molding.
How does a 3D printer work?
3D printing is the process of transforming an idea into a 3D model which is then “sliced” in a software into g-code and finally made into a tangible object using a 3D printer.
It is important to break down a 3D printer into its basic components to get a vivid understanding of how it operates. A 3D printer is very similar to a conventional paper printer except for the fact that is has a third vertical axis, the Z axis, which makes the printer “3”D as compared to 2D. These axes are controlled using g-code which is a language specific to 3D manufacturing and is generated prior to printing using a 3D model and a slicing software. Basically, g-code is a set of coordinates that guide the printer to move the extruder to the desired location.
The three axes that make up a 3D printer are the X, Y, and Z. The following picture illustrates their placement in the printer.
Figure 5: 3D printer axes
The main parts of the printer include the extruder, build plate, and axes’ carriages. The extruder is where the “printing” happens. It is composed of a heater block, a nozzle, and a driver motor and its gear.
Figure 6: Main 3D printer components
The extruder is where the plastic is pulled in by the driver motor into the nozzle that is heated by the heater block (AKA hot-end). In the nozzle, the plastic is melted at very high temperatures ranging between 190 - 230 degrees celsius depending on the material type. Once melted, the plastic is pushed out of the nozzle as a fine thread that is laid down on the build plate in the desired shape.
Figure 7: Sliced view of an extruder showing its components
The build plate is where the molten plastic is laid layer by layer. It is also the most important factor in determining the total build area for a printer. Build plates come in two forms, heated and unheated. The current trend is the use of a heated plate for most types of materials. However, build plates need to be heated for only certain types of plastic, most commonly ABS. Otherwise, build plates can be unheated when PLA is being used. Generally, heated build plates offer better adhesion compared to unheated ones, but this not a fixed rule.
Figure 8: A heated build plate
It is of utmost importance that adequate adhesion is achieved upon contact of the plastic with the build plate to avoid dislodgment of the printed object and consequently failure of the print. Adhesion can be improved by regular cleaning of the build plate and the application of certain types of adhesives or tapes.
Another important set of parts of any 3D printer is the axes and their stepper motors. All the movements of the printer occur on these axes. An axis typically consists of the following:
● Smooth rods (threaded rod on the Z axis)
● Stepper motor
● End stop
It is important to perform regular cleaning and lubrication of a printer’s axes’ rods to maintain smooth performance.
The Z axis determines the resolution of the printer which in turn determines the quality of the print. It is equal to the height of each layer that is laid down and is measured in mm (or microns) and usually ranges from 0.1 to 0.3 mm but can be as little as 0.02 mm (20 microns) which is 5 times thinner than a paper. Smaller resolutions mean better quality prints but also much longer print times.
Figure 9: Comparison of 3 different print resolutions. Left: 0.3 mm Center: 0.2 mm Right: 0.1 mm
In conclusion, this article sums up the very basics of 3D printers and their components. Each one of the above mentioned will be explained in more details in upcoming articles. In the next article, we will talk about the different types of materials used in conventional 3D printers.
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Author: Muhammad B. Darwish
Muhammad Darwish is a self-taught 3D printing enthusiast that has considerable expertise in the world of 3D printing and 3D designing. Muhammad is currently studying medicine in Ras Al Khaimah and continues to practice his 3D printing hobby in his free time. He started his 3D printing journey 6 years ago with a DIY MakerBot Thing-O-Matic 3D printer that he assembled and fine-tuned at home. One of his recent projects include a RepRap Prusa Mendel i2 that he sourced and assembled himself. He now offers 3D printing tutorials and courses and can be reached at the following email: mdarwish3D(@)gmail.com