3. 3D printing#

This unit present the step of making a 3D printed object thought my own experimentation. It is presented more like a storyline than a documentation because there are so many parameters, that going through it all would be practically impossible.

Preparing the g-code#

gcode is the file format needed to print in 3D with Prusa printers. Here is the object to be printed:

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  • In the CAD software, extract a stl file from the object.
  • Install PrusaSlicer and import the stl file.
  • The most important part of printing a 3d object is to choose a good position for it on the plate. The catapult has to be positioned sideways because the spiral has to be printed horizontally to ensure maximum torsion resistance.

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  • The launcher (the spoon) is positioned so that the surface taken is the minimum possible. It reduces the support needed and the distances that the head has to make.
  • Go to print settings -> support material -> generate support material. Now the support will be generated when slicing the print. There are a lot of tweaks for 3D printing. Too much parameter to be listed here. This guide for Prusa slicer is a good starting point as well as this design rule guide.

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  • Export the g-code to a SD card and put it in a printer reserved with fabman.
  • Things to do before printing
    • The plate has to be cleaned with alcohol
    • Checking if there are knots in the filament.
    • If the filament has just been changed, verify if the color exiting the heating head is corresponding to the color of the filament.
  • Once the printing started, verify if the plastic adhere correctly to the plate.

first result#

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The first try was too fragile and broke when extracting the support. This is due to an attempt to reduce the printing time by making each part as thin as possible. Nonetheless, This first try showed that the mechanism is functional.

second result#

This model is directly based on the first try with some modification.

Modification#

Changing the scale of the object in PrusaSlice to increase the size is possible. I didn’t opt for this considering that it could take much more time to print and not be very efficient.

To make the object more resistant, the parts that broke easily have to be reinforced -> back to Fusion 360.

  • The first thing to realize is that printing the spring directly on the plate make it practically impossible to extract from the support. The solution is to place support between the spring and the plate.

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  • To no break the spring when removing support, the width of the spring has been increased, and it’s pitch too.
  • Added chamfer to body part under constraint.

(A chamfer remove the cutting part of an edge.)

Here is a comparison of before and after. Alt text

Pro and Cons#

The second version is better than the first, but it introduces some other problems.

Pros#

  • It is now simpler to extract the object from the support.
  • The object is more sturdy.

Cons#

  • Increasing the thickness of the spring put more torsion on the axe between them as the force to move it has increased.
    • The central axe is no longer sufficient to endure the new torsion.
    • The trebuchet is too powerful.

Demonstration#

Files#

STL file

F3D file (fusion 360 file)

reinforced_trebuchet by Milan on Sketchfab

What I learned#

I learned the following things:

  • Design
    • One of the principal consideration when designing an object to print is time.
    • To reduce the 2D area of the object to optimize printing time.
    • I didn’t know FlexLink were 3D printable (PLA plastic flexibility) and working.
  • Slicer
    • Tweaking around with parameter of PrusaSlicer
    • We can inspect layer by layer the slicing to verify if there is something that may pose problem during printing.
  • Printer
    • Changing filaments.
    • 3D printed objects are a lot sturdier than what I expected.
    • The printing position has a great impart on the resistance of the object. As the printer put plastic layer by layer, the fragile zone is the connection between these layers.