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Introduction to 3D Printing
Introduction to 3D Printing
Definition: Additive manufacturing process where objects are built layer by layer from digital models.
FDM (Fused Deposition Modeling) *
SLA (Stereolithography)
DLP (Digital Light Processing)
SLS (Selective Laser Sintering)
MJ (Material Jetting)
DOD (Drop on Demand)
Sand Binder Jetting
Metal Binder Jetting
DMLS (Direct Metal Laser Sintering)
SLM (Selective Laser Melting)
EBM (Electron Beam Melting)
* All the 3D printers we use in class uses FDM technology
Strengths of 3d Printing
Strengths of 3d Printing
Rapid Prototyping
You can design a part in Onshape on day 1 and have a physical version to test the next day. This lets you "fail faster" to succeed sooner.
Example: You're designing a new phone stand. Your first print reveals the angle is too steep. You can quickly adjust the model in Onshape and print a new version in a few hours
Geometric Complexity at No Extra Cost:
In traditional manufacturing, complex shapes (like honeycombs, internal channels, or curved surfaces) are difficult and expensive to make. With 3D printing, the cost is based on material used and time taken, not complexity.
Example: Designing a lightweight drone frame with an internal lattice structure to save weight but maintain strength. This is nearly impossible to make any other way as a single piece.
Mass Customization:
Every single print can be different without any extra setup costs. You can easily personalize designs for a specific user or purpose.
Example: Creating custom ergonomic grips for a robotics team controller, tailored to each member's hands.
Part Consolidation:
You can combine multiple, simpler parts that would normally be bolted or glued together into a single, more robust printed part.
Example: Instead of designing a box with a separate lid and hinges, you can design a "print-in-place" hinge that is created fully assembled during the printing process.
Material Efficiency
Minimal waste compared to subtractive manufacturing.
Example: If you are cutting a piece of plywood to make a gear a significant percent of the material will be wasted. With 3D Printing, only the adhesion layer and supports are disposed of.
Limitations of 3d Printing
Limitations of 3d Printing
Slow for Mass Production:
Slower than most other manufacturing methods, especially for large quantities.
Example: Printing a 2 inch cube takes several hours depending on the infill density, versus a few minutes with a saw.
Anisotropic Properties (Strength Varies with Direction):
This is the most critical concept for engineering. FDM parts are like a stack of cooked spaghetti. They are strong along the length of the strands, but weak between the layers. A force that pulls the layers apart can easily break the part.
Analogy: It's easy to split a block of wood along the grain, but hard to break it across the grain. The layer lines in a 3D print are its "grain."
Lower Dimensional Accuracy:
The final part might not be exactly the size you designed it to be in Onshape. Dimensions can be off by a fraction of a millimeter due to plastic shrinking as it cools.
Example: A 10 mm peg you designed might print at 9.8 mm, and a 10 mm hole might print at 9.7 mm. They won't fit together without planning for this.
Surface Finish:
The layer lines are almost always visible, resulting in a ridged or rough surface texture. It won't be perfectly smooth like a molded plastic part.
Example: If you need a perfectly smooth surface for an aerodynamic test, a 3D print will likely require significant sanding and post-processing.
Size Constraints
Limited by the build volume of the printer.
Example: A MakerBot Sketch printer has a dimensional limitations of 5.9 inches, while a circular saw can cut a piece as long as you need it.
Key 3D Printing Design Tips
Key 3D Printing Design Tips
Part Orientation: Always orient your part so that the critical forces are applied along the layer lines, not pulling them apart.
The 45-Degree Rule for Overhangs: Most printers can handle overhangs up to about 45 from vertical without needing "support structures." Anything shallower will droop or fail.
Wall Thickness: A good rule of thumb is to make your walls at least two to three times your printer's nozzle diameter. For a standard 0.4 mm nozzle, this means a minimum wall thickness of 0.8 mm to 1.2 mm. Anything thinner may not print or will be extremely fragile.
Tolerance Planning: Due to plastic shrinkage, holes (especially small ones) tend to print slightly smaller than designed.
Pro Tip: Use Onshape's Variables feature! Create a variable called #clearance = 0.3 and use it in your dimensions. If your test print is too tight or too loose, you only need to change the variable, and the whole model will update.
Use Fillets and Chamfers to Your Advantage: Add a small Fillet to inside corners to distribute stress and make the part stronger. Add them to bottom edges that touch the print bed to counteract warping.
Think in Assemblies Before You Print: Before printing multiple parts that need to fit together, put them into an Onshape Assembly. Use the Mate tools to see how they interact.
Pro Tip: Use the interference analysis tool to check for interference and ensure your clearances are correct before you waste hours printing parts that don't fit.
Designing for 3D Printing in Onshape
Designing for 3D Printing in Onshape
Part Orientation
Design with print orientation in mind to reduce supports and improve strength.
In Onshape:
While designing, think about which flat surface will be on the bottom. When you export, you will make the final orientation choice in the "slicer" software, but designing with an intended orientation in mind is key.
In Cura:
Always orient your part(s) so that critical forces are applied along the layer lines, not pulling them apart.
(Image suggestion: A diagram showing a simple hook. In the bad orientation, the layers are horizontal, and the weight on the hook pulls the layers apart. In the good orientation, the layers are vertical, and the force is applied along the strong continuous strands of plastic.)
Image Source: https://www.thingiverse.com/make:909264
The 45-Degree Rule for Overhangs
Use angles < 45° from vertical or add support structures.
The printer builds layer by layer. It can't print in mid-air. An overhang is a part of the model that juts out with no support underneath.
In Onshape:
Most printers can handle overhangs up to about 45 from vertical without needing "support structures." Anything shallower will droop or fail.
Use the Chamfer tool instead of a Fillet on downward-facing edges to create self-supporting 45° angles.
Design T-shaped holes as "teardrop" shapes to make them self-supporting.
Wall Thickness
The printer has a minimum thickness for the extruded material based on the nozzle diameter. You want to have at least a few layers for each wall to ensure the part slices successfully.
In Onshape:
A good rule of thumb is to make your walls at least two to three times your printer's nozzle diameter. For a standard 0.4 mm nozzle, this means a minimum wall thickness of 0.8 mm to 1.2 mm. Anything thinner may not print or will be extremely fragile.
Use the Measure tool to check the thickness of your walls. The Shell tool is great for creating parts with uniform wall thickness, but double-check that it's not too thin.
Tolerance Planning
Leave clearance between moving or interconnecting parts (e.g., 0.2–0.5 mm gap).
In Onshape:
For parts that need to fit together (like a pin in a hole), design the hole to be slightly larger. A good starting point for clearance is 0.2 mm to 0.4 mm.
For example, for a 5 mm screw, model the hole at 5.3 mm.
Use Onshape's Variables feature! Create a variable called #clearance = 0.3 and use it in your dimensions. If your test print is too tight or too loose, you only need to change the variable, and the whole model will update.
Use Fillets and Chamfers to Your Advantage
Sharp corners can create stress points and warp as they cool.
In Onshape:
Add a small Fillet to inside corners to distribute stress and make the part stronger. Add them to bottom edges that touch the print bed to counteract warping.
The Fillet and Chamfer tools are your best friends. Use them on the edges of your final part to improve both strength and printability.
Think in Assemblies Before You Print
You can break complex models into parts for better printing and use post-assembly techniques to put together your design.
In Onshape:
Before printing multiple parts that need to fit together, put them into an Onshape Assembly. Use the Mate tools to see how they interact.
Use the interference analysis tool to check for interference and ensure your clearances are correct before you waste hours printing parts that don't fit.
Consider breaking large parts into multiple smaller parts to increase iteration time.
Our Classroom 3D printers
Our Classroom 3D printers
Makerbot Sketch
Makerbot Sketch
Makerbot Sketch Standard - Product Data Sheet.pdfUltimaker S7
Ultimaker S7
UM-S7-Product-Data-Sheet.pdfPage updated
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