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Editor's Notes

• #14: Material parameters: Polymer type its chemical ,thermal and mechanical priorities Build Orientation: It refers to the inclination of the part in a build platform with respect to X, Y, Z axis. X and Y-axis are considered parallel to build platform and Z-axis is along the direction of part build. Raster angle: Direction of the raster relative to the X-axis of build table. Layer thickness: It refers to the thickness of the deposited layer. Nozzle diameter: It depends upon the type of nozzle used. Commercial printers mostly use 0.4 mm nozzle diameter. Raster width: Width of raster pattern used to fill interior regions of the part. Number of contours: The number of contours of the part outside Raster to raster gap (air gap): It is the gap between two adjacent rasters in a same layer. Negative air gap refers to the overlap of rasters. Positive air gap allows space between rasters. Printing with zero air gap is highly recommended. Infill density: The amount of material that is used to build the part inside. For example; the inner layers of the part can be printed in hexagonal or rectangular pattern.
• #15: Since Direct extruders are located above the hot end with little space between them, a Direct extruder keeps the distance that filament must travel from the extruder to the hot end to a minimum. This leads to the main advantages of this style of extrusion. 1.Better Extrusion and Retraction Since there is less distance for the filament to travel, extruding and retracting the filament becomes much easier. Essentially, the filament is more responsive to the extruder. This means that there is less stringing and oozing that occurs because of worse retraction and leads to a higher quality print. 2. Smaller Motors In addition, the closeness of the extruder to the hot end means that less torque is required from the stepper motor than in a Bowden extruder. Because of this, the stepping motor does not need to be as large or as powerful as in a Bowden setup. However, a large motor can provide more power with a Direct extruder, which can be beneficial. 3.Wider Range of Filaments Direct extruders are also able to effectively print a wider range of filaments, most notably, Composite filiment. While flexible filaments can work with Bowden extruders, Direct extruders can print them more effectively. This is because a Direct extrusion system is more constrained. Disadvantages However, the location of the Direct extruder also leads to its main disadvantages. The weight of the extruder on the print head can lead to several problems. Since the print head is constantly moving, additional weight to move around could lead to backlash, banding, overshoot, or frame wobble. Additionally, the size of the extruder can be disadvantageous for some 3D printers, as it makes up a majority of the print head. Advantages of Bowden extruders Lighter, Faster, and More Accurate Like the Direct extruder, many of the advantages and disadvantages come from the location of the extruder in relation to the print head. The largest advantage is the reduced weight of the print head. Since the extruder is removed from the print head, there is less weight on the print carriage. Also, because the print head is lighter, a printer using a Bowden extruder can print faster, more accurately, and more precisely. This can result in either higher quality prints or quicker prints, as the print head can move at higher speeds. Additionally, Bowden extruders are more compact and take up less space than Direct extruders.   Disadvantages While Bowden extruders can increase print speed and reduce the print head weight, there are several disadvantages that make them less appealing than Direct extruders. For one, they cannot use as many filaments as effectively as Direct extruders. While they can print flexible filaments, these filaments tend to bind in the Bowden tubing. Additionally, Bowden extruders cannot use abrasive filaments because these filaments will wear away the inside of the Bowden tubing.
• #16: BENEFITS 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 (sometimes even cheaper since less material is used) Very low start-up costs In formative manufacturing (Injection Molding and Metal Casting) each part requires a unique mold. These custom tools come at a high price. 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 Customization of each and every part 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. LIMITATIONS Low-cost prototyping with very quick turnarounds 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) Large range of (specialty) 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 specialty 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. Lower strength & anisotropic material properties 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. 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. 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. Post-processing & support removal Printed parts are rarely ready to use off the printer. These 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.