Week 12
In today's lesson, we have learned the functions of a 3D printer. Here are some of the things we have learned.
What is Additive Manufacturing?
Additive Manufacturing (AM) is used to describe technologies that can build 3D objects by adding layer-upon-layer of materials. For example, 3D printing, Rapid Prototyping (RP), Direct Digital Manufacturing (DDM). The materials used includes plastic, metal and concrete.
AM will first read a Computer-Aided Design (CAD) which is produced using a 3D modelling software like Fusion 360. The AM equipment will then read the data from the CAD file and will start printing the object.
AM applications are limitless because of their flexibility. It is being used to fabricate end-use products in aircraft, dental restorations, medical implants, automobiles, and even fashion products.
FDM
Fused deposition modelling (best for simple prototyping)
- Melts and extrudes thermoplastic filament
- The lowest price of entry, material, resolution and accuracy
FDM is the most widely used 3D printer at the consumer level where standard thermoplastics such as ABS, PLA and a mix of both are commonly used to operate FDM. One downside of this machine is that it tends to have visible layer lines and might show inaccuracies around complex figures. Out of the 3 types of 3D printers, this has the lowest resolution and accuracy.
SLA
Stereolithography (best for functional prototyping, patterns moulds and tooling)
- Laser cures photopolymer resins.
- Highly versatile material selection.
- Highest resolution and accuracy (fine details).
SLA, unlike FDM, is very versatile. SLA parts can have sharp edges, a smooth surface finish and minimal visible lines. SLA is a great option for highly detailed prototypes requiring tight tolerances and smooth surfaces, such as moulds, patterns, and functional parts. SLA is widely used in a range of industries from engineering and product design to manufacturing, dentistry, jewellery, model making, and education.
SLS
Selective Laser Sintering (best for functional prototyping and end-use production)
- Laser fuses polymer powder
- Low cost per part, high productivity and no support structures
- Excellent mechanical properties resembling injection moulded parts.
Ideal for complex geometries, including interior features, undercuts, thin walls, and negative features. Parts produced with SLS printing have excellent mechanical characteristics, with strength resembling that of injection-moulded parts. The most common material for selective laser sintering is nylon.
Poly-Lactic Acid (PLA)
PLA is used very frequently because of its high versatility because it has a low chance of warping and has good reusability.
However, due to its low melting point at about 66°C, it cannot be used for high heat work. Moreover, the final product can be brittle, so it is not suitable for products that are supposed to be strong.
Acrylonitrile Butadiene Styrene (ABS)
ABS has a melting point of 105°C, which is higher than PLA. It is also a durable material where we can sand, paint, and polish it, and it will not crack or warp.
High Impact Polystyrene (HIPS)
HIPS is a rigid, water-resistant and lightweight plastic. It can be used to create support structures for large models. It can be used for replaceable parts.
However, it requires a heated printing bed so that it will not stick. It also has to be printed in a well-ventilated area because the buildup fumes can cause a headache.
Polyvinyl Alcohol (PVA)
PVA is soft, biodegradable, and is usually used as a support material. It is able to dissolve completely in warm water.
However, when using this material in a 3D printer, it tends to clog the nozzle if it is heated and not actually printing. Moreover, an airtight container is required so that it will prevent moisture from getting in.
Nylon
Nylon is a tough, abrasion-resistant and flexible material. However, nylon tends to absorb moisture from the surroundings, which can warp the finished product and compromise its structural integrity. Therefore, when it is not in use, it must be stored in an air-tight container.
Carbon Fiber
In order to enhance stability, carbon fiber is usually made by infusing PLA or ABS with tough fibers. It is light, stiff and rigid. Also, the required printing settings barely differ from PLA or ABS filament.
However, the filament makes brittle prints and tends to clog easily. The fibers may also scratch the nozzle. Therefore, a stronger nozzle is required when using carbon fiber.
Polycarbonate (PC)
PC is a transparent, flexible, tough and heat resistant (150°C) material, that can be used in a wide range of circumstances. However, just like nylon, it can also absorb moisture from the surroundings. Also, heat protection is required due to the high temperatures it is involved in.
Acrylic Styrene Acrylonitrile (ASA)
ASA is commonly used outdoors due to its high heat resistance. It is also a tough material. However, it is costly and also gives out fumes that are hazardous to our health.
Slicer settings
Temperature
The temperature must not be too high or too low. Too high temperatures will cause over-extrusion with blobs and zits all over the print. Too low temperatures will cause under-extrusion, where not all layers are fully printed.
Bed temperature is also important as if the temperature of the bed is too high, this may lead to deformation of the bed.
Layer height
The smaller the layer height, the more layers will be required in the overall print hence printer will have more room to generate finite detail on parts like miniatures. More layers also mean longer printing times and weaker parts. As such a suitable height is needed to be found before starting the 3D printer process.
Print speed
Speed will be chosen based on your chosen layer height and material. Too fast may cause nozzle run-ins where the printhead could knock over small structures while printing.
Retraction
Determines how much and how fast filament is sucked back into the nozzle to prevent material from oozing out when it’s not being extruded. Retraction is controlled by a few specific settings, chief among them being retraction distance and retraction speed. Too much retraction can cause nozzle jams, as the filament is more aggressively pushed in and out of the nozzle.
Flow
Determines rate at which filament is extruded. adjusting flow affects how many steps the extruder’s motor turns per millimeter of material deposited. low can be used to account for over or under-extrusion on your printer without adjusting a printer’s E-step parameter, a value stored in firmware. While technically, flow and E-steps can both be used to solve the same problems, it’s best to tune the E-step value during printer calibration and adjust flow as required by particular print jobs.
Part orientation
3D printed parts are strongest in planes parallel to the printed beds so print orientation can literally make or break a part. Part orientation thus affects 3D prints in terms of quality, accuracy, strength and surface finish and manufacturing time.
Bed adhesion
Bed adhesion is the ability of 3D printed plastic to “stick” to the build plate while printing. When 3D prints don’t stay in place on the build plate, you can get curled, shifted, potentially disastrous results. Makers use varying types of 3D printing surfaces to help different materials stick to the plate while printing.
Factors that affect bed adhesion are how well the plastic “wets” the plates, thermal expansion and how to level the bed is.
Wetting refers to the ability of a liquid to conform and stick to a solid surface. When the filament is extruded onto a build plate, it tries to conform to the build surface during printing.
Thermal expansion describes the change in dimensions of an object at various temperatures. Temperature differences between the bottom of a print and the top can cause the edges of an object to peel up during 3D printing.
To adhere filament to the bed, it is important that the nozzle is a consistent and reasonable distance from the build plate. There is a distance where the filament is close enough to the build plate that it will stick to it. However, too close and the nozzle will rip previously printed materials off the build plate.
Supports
Support structures help to ensure the printability of a part during the 3D printing process. Supports can help to prevent part deformation, secure a part to the printing bed and ensure that parts are attached to the main body of the printed part.
Settings that affect print speed
Layer height
Layer height is the exact height of each layer of plastic extruded, cured, or sintered by a 3D printer.
In an FDM printer, A shorter vertical layer results in a thicker horizontal line, and a taller vertical layer results in a thinner horizontal line. This can throw off precision in the horizontal plane, especially in small moving parts sometimes used by print-in-place mechanisms.
SLA and laser-based printers typically have a much smaller minimum compared to FDM printers, which is what accounts for the incredibly detailed prints they typically create.
Print speed
Print speed is the main speed setting that will influence your 3D prints.
Too slow of a print speed may cause print deformation due to the nozzle sitting on the plastic for too long. Too fast and there may be other overheating artifacts caused by insufficient cooling, as well as ringing, under extrusion, and weak layer adhesion. The sweet spot should be as fast as your printer can get without sacrificing too much print quality. Decide how much print quality is appropriate for your use case.
Part orientation
3D printers extrude with higher speeds on the X and Y axes, as detailed by default printing speeds on slicers. The lower the 3D print’s height is, the faster it is going to be printed.
Infill density
Higher infill density will result in more printing time. A 3D model with 0 percent infill density is hollow from inside. Hence, taking less duration to print. Subsequently, resulting in high speed. On the other hand, the 100 percent infill density would mean a completely solid part. Most of the models with a balance of speed and infill density can be accomplished between 20% and 35% settings.
Supports
Adding support material to your part will increase its print time more than any other factor. Because support material consists of a long, slowly printed wall, the addition is akin to adding a massive amount of surface area. While support is necessary to print some parts, there are a few steps that you can take to limit the time added due to it.
Changing the orientation of parts can drastically change the overall print time.
3D Printing in the News
3D printing for Covid-19 Swab Test in SG
Local Company Structo, initially geared to produce surgical guides for patient's teeth.
Due to the shortage of swab tests last April, they quickly switched to producing swab tests. They are also capable of producing 4.5 million swabs in the span of 3 months.
Key challenge: Designing the tip as it is traditionally made using cotton, they had to replicate the design of the plastic such that it can serve the same function
3D printing of Human Organs
It works by scientists harvesting human cells from stem cells (or biopsies), these are allowed to multiply in a petri dish. This becomes a resulting mix like a biological printing ink that is fed into the 3D printer.
Hong Kong’s Fragile Coral Reefs Boasted by 3D Printing
Scientists printed tiles that works as an artificial bed for corals to latch onto and thrive.
Climate change has damaged coral reefs, causing them to lose their vibrant colour and die.
3D printing allows dead reefs to be repopulated by printing tiles suitable for coral larvae to latch onto.
Able to customized a tile or a solution for any type of environment.
3D Printed Food in SG
3D printed food is used to feed the elderly and those with chewing or swallowing difficulties
Problem: Most pureed food does not look appetizing and may be rejected by patients, resulting in malnutrition
Solution: 3D print food that is appealing, while being pureed and also contains necessary nutrients
5 Ways We Benefit from 3D Printing
Lower costs
Manufacturing flexibility
Medical advances
Sustainability
Economic growth
Learning Reflection
In this week's lesson, we were given topics to research about 3D printing. Then, we were asked to prepare some slides and present what we have researched. This gives us a new perspective on learning as the lecturer is usually the one teaching. Moreover, our group was in charge of researching the advancement in 3D printing. In the news, we have found many examples of how far 3D technology has advanced. What we have found is 3D printers can be made to make food, save coral reefs, be used for covid as well as replicating functioning organs. This news shocked us at how much potential 3D printing could impact us and nature. It has potential to change the world in terms of technological advancement.
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