Juan Carlos Miranda Castro

FabAcademy - 2017

Costa Rica - St. Jude School


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3D scanning and printing



Assignment
  • Test the design rules for your printer(s) (group project).
  • Design and 3D print an object (small, few cm) that could not be made subtractively.
  • 3D scan an object (and optionally print it).
Learning outcomes
  • Identify the advantages and limitations of 3D printing and scanning technology.
  • Apply design methods and production processes to show your understanding.
Have you
  • Described what you learned by testing the 3D printers.
  • Shown how you designed and made your object and explained why it could not be made subtractively.
  • Scanned an object.
  • Outlined problems and how you fixed them.
  • Included your design files and ‘hero shot’ photos of the scan and the final object.



Software


software

Artec studio (3d scanning software)

Sense (Sense 3d scanner software)

Cura (3d slicing software)

Tinkercad (online 3d cad design tool)

Inkscape (vector graphics)



Materials


materials

PLA filament



Test the design rules for your printer

  • The printer we have at the lab is the Printrbot 1405 simple maker's kit. This is a basic printer, it comes in parts, and the user must assemble it.

    This printer has some visible issues. Mainly the structure is no very stable, in some cases, it uses plastic ribbons to attach parts of the machine.

    Another visible issue is that the bed is not leveled. I used some paper pieces to level it.

    Also, when the head moves out in the Y axis, it is visibly lower on the furthest position because of the weight of the head.

    defectos de la máquina

    A part was designed in Tinkercad to test the design rules of the printer:

    parte de prueba

    This part has:

  • Walls of different thicknesses (from 0,5 mm to 4 mm)
  • Round holes with different diameters (from 1 mm to 3 mm)
  • Holes separated by different length spaces (0,1 mm to 2 mm).
  • Inclined and overhanging parts to test possible angles.
  • Pointy structure to test material bonding.
  • Cura setup for the printer:

    configuración de Cura

    This is the printed part:

    parte de prueba impresa
  • resultado de la parte de prueba impresa

    The resulting part came out better than I expected:

  • I had to clean the part of some residual PLA.
  • The horizontal holes on the side of the model revealed a disadjustment on the Y axis.
  • The vertical holes of 2 mm and 3 mm diameter were good, but the 1 mm hole had did not work.
  • Rhe overhanging part did not collapse, but the shape is not accurate.
  • The vertical holes with separation of 0 mm, 1 mm and 2 mm were good.
  • The walls came out fine. The 1 mm thick wall is acceptable. The 0,5 mm printed well but is too weak.
  • The inclined parts were very good. The steepest one (45°) did not collapse.
  • Using Inkscape, I imported the picture and drew paths over the picture to convert it to an svg file.


Design and print a 3d object

  • For another project, I needed a connector between a stepper motor, and a water tap, so I designed it for 3D printing.

    It is basically a hollow cylinder, but on one side, the hole shape is square and on the other is a truncated circle.

    pistola de silicón

    I started with the hollow shapes.

    One cube shape for the water tap.

    One truncated cylinder for the stepper motor.

    Four horizontal holes for secure screws.

    One big cylinder for the body of the part.

    This part cannot be made subtractively mainly because:

      The final part is too thick for the laser cutter.

      The horizontal holes for the screws cannot be done by a laser cutter or a milling machine.

      The angle for the square hole would not be 90° if the part is machined.

    This is the final part mounted:

    parte montada en el tubo
  • I also made another 3D design, it is a replacement part for a hot glue gun that was about to be thrown to the trash can.

    pistola de silicón

    The broken part was extracted.

    I drew the part on paper and took a picture of it (there is a hole where the axis is located).

    Using Inkscape, I imported the picture and drew paths over the picture to convert it to an svg file.

    Then, the svg file was imported into tinkercad, it was given the aproximate size to match the original, it was also extruded. The cylinder holes were used to correct the holes' radius. The axis was made with a simple cylinder.

    proceso de diseño

    The finished part was not suitable for 3D printing, because it has some overhanging sections. Several orientations were evaluated.

    partes sin soporte

    So the part was divided into the flat part with holes and the axis.

    parte dividida

    Then the part was printed and compared to the original. The printed model was not very smooth, but it seems to be strong enough to take the presion applied to the trigger of the glue gun.

    comparar partes parte terminada

    Finally, the part was installed on the hot glue gun.

    parte instalada

    The glue gun will be tested, and in case the printed part fails, I will try some of these changes:

    • Print the axis horizontally, to change the direction of the plastic thread.
    • Adjust the axis hole to fit tightly the axis piece.
    • Increase the thickness of the part to make it stronger.

3D scanning

  • We visited 3D Systems for a quick review and training of 3D scanners. We had an introduction to four types of scanners. They differ in resolution, objective properties (size, material, texture), scan file purpose, price.

    scanners de 3d systems

    We had the chance to scan an object using the Artec Spider, wich has a high resolution and can scan the color of the object. I practiced by scanning a Pisa tower miniature. Because the scanner is handheld, some practice is required to maintain a steady scan while rotating the object. The optimal scanning distance to the object for this model is about 20 to 30 cm. Also, while scanning, you must pay attention to the software on the computer screen, it tells you when the optimal distances is achieved, and when the system loses track of the scan, in wich case you have to stop and wait, or pause the scanning and resume.

    The limitations dor 3D scanners are:

    Shiny objects can cause problems.

    Hollow objects or inside details are not captured by these scanners.

    3D scanning is in general a slow process.

    Some scanners do not capture colors.

    High resolution 3D scanners are expensive.

    This is the practice we did at at 3D-Systems with the high resolution 3D scanner and the Projet CJP printer:

    At the Lab, we used the 3D Sense to scan each other.

    The main problem to solve when 3d scanning is the hollow parts of the objects. The software solves this by closing the shape, but this fix is not always elegant or useful.

    The 3D sense is an inexpensive scanner, but it has a low resolution.

    3D scanning requires long time to get a good file.

    When scanning, the software loses track of the objects very easily.


    The file created by the scanner software has .ply extension. Using Ubuntu, this tyoe of file can be opened with Blender or FreeCAD. The final mesh can be seen in the following pictures:

    modelo 3d 1 modelo 3d 2

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