The Basics of 3D Printing
Welcome
Welcome to Memorial University’s Student Design Hub! Here you have access to multiple 3D printers where can bring your digital designs to life!
Overview
3D printing or additive manufacturing is a process in which solid objects are made from a digital file. The most widely used technique is Fused Deposition Modeling (FDM).FDM is the process of feeding a polymer-based material through a nozzle in which the material melts and gets extruded in a distnict pattern onto a flat surface where it will harden again. 3D printers repeat this process with many distinct and thin layers to mold the material into the desired design. The relative speed of creating these parts (a couple of hoursdepending on size, design, and infill) allows for proof of concepts to be developed rapidly, moving past 3Dmodeling, a very powerful tool tied to 3D printing. The end results used to be used exclusively for prototyping, however, due to the advancements of 3D printing technology and materials, 3D prints are being used more frequently as end products and parts.
For more detailed information please visit the sources used under Reference List
Materials
The most common materials for 3D printing are Poly Lactic Acid (PLA) and Acrylonitrile Butadiene Styrene (ABS). PLA filament is a biodegradable material that is easy to print due to its low heating requirements, however it does not possess a very high resilience to UV rays, its more suitable for parts used indoors and at around room temperature. ABS filament in the other hand requires a higher temperature to be printed, but it offers UV resilience as well as better mechanical properties in high temperature environments. There are many other materials available to print as well, depending on the printer you use. Some materials are:
Polyethylene Terephthalate Glycol (PETG)
Thermoplastic Polyurethane (TPU)
High Impact Polystyrene (HIPS)
Polycarbonate (PC)
Thermoplastic Elastomer (TPE)
Nylon
Acrylonitrile Styrene Acrylate (ASA)
Polypropylene (PP)
Polyvinyl Alcohol (PVA)
Glass Fiber or Carbon Fiber Infused
Metal or Wood Fill
Etc.
Modelling
One of the advantages of 3D printing is that very complex models can be achieved. However, when crafting your 3D model in a computer-aided design (CAD) software, such as SolidWorks, some design considerations can help ensure better results.
Resoultion: Similar to image resolution, a 3D printer has a minimum feature, analogous to a pixel in a picture, this is the smallest “dot” a 3D printer can extrude accurately and consistently. This is called the printers resolution. Resolution is divided into XY-resolution, and is influenced by factors such as nozzle diameter and the smallest movement capable of the stepper motor on the printer. Because of this, each printer can have a different minimum layer height, but a general rule of thumb is a minimum layer height of 0.2mm. Anyhting less than 0.2mm may arise consistency and accuracy issues
Orientation: Printing orientation of the 3D model can greatly improve the surface quality of the print. The figure displays the same 3D model printed horizontally and vertically. The horizontal print on the left displays a “staircase” pattern finish, while the vertically prited part on the right has a much smoother finish due to it’s logical orientation. A logically oriented part accounts for minimal overhang areas and lofts the scale vertically. When printing parts that would undergo a mechanical load, the former would support more force applied to it at the peak of the semi-dome than the latter.
Size: Each printer has maximum length, width and height in which it can print. When considering the size of your design consider the size of the print bed and the orientation of your part. If the design cannot be scaled down and is simply too big for the printer, making the prototype is seperate prints the combining with post-processing may be a viable option.
Wall Thickness: A minimum wall thickness is required for the model to be able to print and be structurally sound. This dimension would be affected if the model needs to support any force, but as a rule of thumb for ABS it is recommended to use a minimum wall thickness of 1.2mm. Different materials and printers have their own configurations. If thin wall prints are required see Thin Wall Printing in Building the Supermarine Spitfire Mk IX Plane Case Study.
Shrinkage and Assembly: When printing parts that are design to be connected to each other, keep in mind the shrinkage that the prints will undergo. This deviation of the print from the model’s nominal size is also known as dimensional accuracy and is generally around 0.1% or ±0.2mm.
Embossed and Engraved Details: Engraving refers to details added into the print (inwards), a minimum line thickness of 1 mm and a depth of 0.3 mm is recommended. By contrast, embossing are details that protrude from the printed model, a line thickness of at minimum 2.5 mm and a depth of at least 0.5 mm is advice. Engravings are usually preferred as they require much lower tolerances than embossing details.
Support Material: To be able to achieve intricate designs most 3D printers employ support materials. The most popular support method is breakaway supports. Breakaway support materials are temporary beams that are printed around your model to support overhangs or ares where the melted plastic cannot support itself until hardened. These can be broken away as soon as the print has been finished, but in certain complex geometries they tend to leave residue behind and/or are difficult to completely remove without damaging the print. This is caused if the design possess deep channels/crevices in the inside faces of the model, where no exit hole is accounted for. With that being said the difference is minimal and breakaways are the best option for the majority of prints you will complete. This is very important to keep in mind when modeling your 3D design. Every printer in the Student Design Hub uses this method of support for 3D printing. Another method to create supports is through soluable supports. Soluble support materials work the same as breakaways but instead they leave a smoother finish and are easier to remove because they are able to be dissolved in water instead of having to be broken away. However this method of support material is only available through one printer located in the Digital Design and Prototyping Lab and is a quite longer process.
Moving Parts: Support material allows for the printing of preassembled models with moving parts, for these to successfully print a minimum clearance of 0.4mm is advised, the greater the space that can be afford, the better chance the model has to print properly.
STL Format
After you have finished your design, save the SolidWorks model in the native format SolidWorks Part File (SLDPRT) as well as the Standard Triangle/Tessellation Language file format (STL) [1]. To save your model in STL format go to File>>Save as, and change the file format from SolidWorks Part (.prt;.sldprt) to STL (*.stl) in the prompted window, as shown in the image below:
The SLDPRT file stores the part as a solid model, keeping the specified details of material, color, and texture. On the other hand, an STL file stores only the information of the 3D model surface, it represents this surface as small adjacent triangles.
Printing
Once you have the .STL file, it will be imported into a slicer, a software that produces a path for the 3D printer to follow to be able to print the model. This set path is known as G-code, and it tells the printer what movements to make from the begging to the end of the print. More on this in Generating the G-Code
