Introduction: Guide to 3D Printing
What is 3D Printing?
3D Printing is a process for making a physical object from a three-dimensional digital model, typically by laying down many successive thin layers of a material. An easy way to visualise this would be to think of cutting multiple sheets of paper and laying them successively on top of one another to create a 3d part. The difference here would be that 3d printed parts are not made of paper but rather more durable material such as plastic or composite materials.
What are the advantages to 3D printing?
Custom designs- 3d printing enables mass customisation. Every 3d printed object can be customised to one's needs and requirements.
Prototyping- With the help of 3d printing, prototyping is much simpler, effective, and more affordable. Without 3d printing, each prototype of an object would be either made out of weak materials such as wood or have to be expensively moulded. If the prototype would break, then making a new prototype would not only be expensive but also be hard to recreate with the exact tolerances.
3D printing alleviates those concerns. 3d printing allows for cheap, quick and consistent prototyping. 3d printed parts are also a lot lighter while still maintaining their strength.
Sustainable and environment friendly- Since there is so little waste involved created in 3d printing, it results in much less raw materials being used. Additionally, the materials used in 3d printing such as PLA, the most common material used in 3d printing, is made from a bio composite of corn. Similarly PET-G is a bio-degradable plastic also used in 3d printing.
How can I experience 3D Printing?
There are 2 ways of experiencing 3d printing.
Using a 3D Printing service: you can use 3d printing services such as shapeways or 3D matters. This method allows you to experience 3d printing without investing much time or money into 3d printing. They can also ensure optimum quality of parts without the hassle of learning how to optimize parts for printing.
Buying your own 3D Printer: This option is recommended for those who know the basics of 3D Printing and who want to fabricate their parts themselves rather than to use the 3d printing services. This method is also cheaper in the long run
What type of 3D Printing technologies exist?
FFF (Fused Filament Fabrication): This is a process to melt plastic and lay them out one layer at a time, with this comes a bit of restrictions in design and printing, but it is cost efficient to do quick prototyping or low cost production runs.
SLA (Stereo-lithography): This is a less common form of printing than FFF. It involves selective exposure of a photo sensitive material, such as special resin, to UV light. This creates a fused layer, and then the rest is similar to FFF. These resin layers are stacked on top of one another to create a 3d object.
SLS (Selective laser sintering): This is a more industrial grade and less common technology. This works by using a laser to selectively melt the material, in the form of a powder, to form 2d layers. Multiple of these 2d layers form a 3d object.
Step 1: Materials
Types of materials
PLA (Polylactic Acid) is a staple and one of the most popular choices for 3D printing with good reason. Aside from the fact that is a biodegradable thermoplastic derived from renewable resources such as corn starch, PLA is a very rigid material is easy to use for 3D printing and is able to withstand a good amount of impact and weight. It also has a glossier finish than ABS and in most scenarios PLA is our recommendation for 3D printing large objects with. The one disadvantage of PLA is it's heat resistance, it should not be placed in environments that exceed 60 degree celsius.
ABS (Acrylonitrile Butadiene Styrene) is another popular choice for 3D printing. A strong thermoplastic that is among one of the most widely used plastic in both consumer and manufacturing industries. It is tough with mild flexibility, making it more durable to stress and has a higher heat resistance of up to 100 degree celsius which is useful for. However, due to the materials tendency to shrink during printing, this material is not recommended for printing exceeding large objects with.
Flexible (Thermoplastic Elastomer) material is for applications that require incredible rubbery flex in their applications. Think about watch straps, shoes, tires.
PETG (Polyethylene Trephthalate) PETG is a material that is similar to PLA, with more attractive characteristics such as being generally a tougher and denser material good heat resistance of up to 88 degree celsius. PETG is so tough that it is used in police riot shields.
HIPS and PVA are relatively new materials that are qrowing in popularity for their dissolvable properties. They are used for creating support material. Their ability to dissolve under certain liquids means that they can be easily removed (support material is meant to be removed. I will talk more about it in the next step)
Step 2: What Is Infill Density
It would be incredibly inefficient to be printing objects that were fully solid. This would not only take a much longer time, but it would make the part heavier and consume more material to create which leads to higher costs. Therefore unless needed for strength, it is unnecessary to print at full 100% density. In most cases, you can create structural supports inside the 3d printed object to compensate for the fully solid infill and still maintain a high level of structural rigidity.
Step 3: What Is Layer Height
Layer height is the thickness of each individual 2d layer. A thicker layer height will result in a less detailed print but will reduce cost, time, and increase strength.
What layer height should I print at?
3D printing is a layer by layer process and by adjusting the thickness of each layer of a 3D print, you can manipulate the surface of your model to show more or less details. I do not view layer resolution as a measure of quality, which is determinable by a combination of hardware implementation and good design.
Instead, when deciding which layer resolution you should consider if your model requires high detail e.g. the model represents a sculpture or dentures that has many fine features on the surface or your object is miniature in size and requires a high resolution to capture the features of the object. Speed and cost may also affect your decision as a higher resolution wll take a longer time to deliver and cost more due to additional machine time.
A model that has many straight walls will not benefit greatly from a higher resolution, apart from the layering being less obvious (layers being smaller).
Common layer resolution options start from 0.3mm (300 Microns), 0.2mm (200 Microns) and 0.1mm (100 Microns). The lower the numerical value the higher the resolution and ability to capture more detail during print.
Step 4: Where to Find Models to Print?
You should be able to print any .stl and also most .obj files as long as they can fit your 3D printer. A few good places to find 3d models is Thingiverse.com, Myminifactory.com, youmagine.com etc.
Step 5: How Do I Design My Own Models
You can use any cad program that can export .stl or .obj file types.
Here are a few recommendations based on difficulty for a beginner and price
Easy: Autodesk 123D (Free)
Medium: Autodesk Fusion 360 (Free, Paid for commercial applications)
Hard: Solidworks (Paid)
Step 6: Factors to Keep in Mind While Designing Parts
Similar to architecture in 3D printing nothing would float in the air, one would use scaffolding in architecture, while in 3D printing we utilize supports.
Similar to a process in construction of a building, we have to tear down the “scaffoldings” or supports after printing as part of post processing. The deeper the support is in a print the harder it would be to “tear down” the supports.
When you are designing parts, think about the over hangs that the parts contain. If the part does not require such a high resolution then the overhang should be under 45 degrees unless you expect to be printing with support. With higher resolution you can print with steeper overhang angles, up to 55 degrees, without overhangs. The reason for this is that the smaller z steps lead to a more gradual overhang and therefore you can print steeper overhang angles.
When choosing or designing 3D printed parts that are supposed to slot together or attach, design with 1mm tolerances in mind. Otherwise the part may be too big. This rule also applies to feature sizes, hence don't design parts with feature sizes under 1mm. Screw threads are similarly not advisable to 3d print. You can always tap the holes later or add threaded inserts to the plastic.
As a general rule of thumb, design any holes slightly smaller than you would like them to be. Once the part has been printed, you can drill the hole to be the exact size that you might want.
Do keep in mind, the tolerance mentioned above may vary slightly depending on the material that you request. For example, you may need larger tolerances with materials with ABS as it shrinks a lot, but you can get away with smaller tolerances on materials like PLA.
Lastly make sure not to use Loctite on any of your parts especially ABS parts. The Loctite will make the part crumble away rendering it useless.
It is always good to ensure that the design is a manifold or also known as “water-tight” most software's are not designed to ensure this process. Thus a certain amount of knowledge is required when addressing this issue. youc can utilize NetFabb to identify if the design is a manifold or if it has 'holes' in it.
Step 7: How Do I Check If My Part Is Printable/ Not Corrupt?
The easiest way to test your .stl file is using Netfabb. Download Netfabb from their website here.
First import your stl into Netfabb. If you see any red parts or a red exclamation sign at the bottom right of your screen, that means that the .stl may be corrupt or poorly formatted. If there are no such signs, then the part can be 3d printed.
To fix any issues, right click on the part and select the repair option. Then execute the automatic repair procedure. Remove the original stl from Netfabb and check to see if the repaired stl has any issues by looking for the same red exclamation triangle. If the issue persists then it is possible that the stl is not repairable and you may have to re-export it from the cad software that was used to design it.
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