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Additive Manufacturing (3D Printing) Processes Cheat Sheet
A printable reference covering FDM, SLA, SLS, layer height, infill, supports, tolerances, and post-processing for grades 8-12.
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Additive manufacturing, often called 3D printing, builds parts layer by layer from a digital model. This cheat sheet covers the main 3D printing processes used in engineering, including material extrusion, vat photopolymerization, and powder bed fusion. Students need these ideas to connect design choices with strength, accuracy, surface finish, cost, and printing time. It also helps students compare processes when choosing how to prototype or manufacture a part. The most important concepts are layer height, build orientation, infill, supports, tolerance, and post-processing. Print time often increases when layer height decreases because the machine must create more layers. Part strength depends on material, process, orientation, bonding between layers, and the amount and pattern of infill. Good engineering design for additive manufacturing uses the process limits, not just the shape of the final part.
Key Facts
- Additive manufacturing creates parts by adding material layer by layer, while subtractive manufacturing removes material from a solid block.
- For a simple estimate, number of layers = part height / layer height.
- Smaller layer height usually improves surface finish and detail but increases print time.
- FDM, or fused deposition modeling, melts and deposits thermoplastic filament through a heated nozzle.
- SLA, or stereolithography, cures liquid resin with light and usually produces smoother surfaces than FDM.
- SLS, or selective laser sintering, fuses powder with a laser and often does not need separate support structures because loose powder supports the part.
- Infill percentage = interior material volume / total interior volume x 100%, so higher infill usually increases mass, strength, and print time.
- Clearance is the intentional gap between moving or fitting parts, and required clearance must be larger than the printer tolerance.
Vocabulary
- Additive manufacturing
- A manufacturing method that builds an object by adding material in layers from a digital 3D model.
- FDM
- Fused deposition modeling is a 3D printing process that extrudes melted thermoplastic filament through a nozzle.
- SLA
- Stereolithography is a 3D printing process that uses light to harden liquid resin into solid layers.
- SLS
- Selective laser sintering is a 3D printing process that uses a laser to fuse powdered material into solid layers.
- Layer height
- Layer height is the thickness of each printed layer, which affects detail, surface finish, and print time.
- Build orientation
- Build orientation is the direction a part is positioned on the print bed, which affects strength, supports, accuracy, and surface quality.
Common Mistakes to Avoid
- Choosing the smallest layer height for every print is a mistake because it can greatly increase print time without improving a part that does not need fine detail.
- Ignoring build orientation is a mistake because many printed parts are weaker between layers than along continuous printed paths.
- Designing zero-clearance moving parts is a mistake because real printers have tolerance limits, so parts may fuse together or not fit.
- Forgetting supports for overhangs in FDM and SLA is a mistake because unsupported material can sag, fail, or cure in the wrong shape.
- Comparing print processes only by cost is a mistake because accuracy, material properties, surface finish, safety, and post-processing can be more important.
Practice Questions
- 1 A part is 60 mm tall and printed with a layer height of 0.20 mm. How many layers are needed?
- 2 A solid part would use 80 cm3 of plastic, but it is printed with 25% infill inside the interior. Estimate the interior plastic volume used if the whole part is treated as infill space.
- 3 A printer has a dimensional tolerance of plus or minus 0.20 mm. What minimum clearance would you recommend between two moving parts if the design should avoid sticking?
- 4 A student needs a smooth, detailed model for a small medical device prototype, while another student needs a strong nylon bracket with complex internal shapes. Which additive manufacturing processes are better choices for each case, and why?