4. 3D scanning and printing

Group Assignment

The goal of this week group assignment was to test the strengths and weaknesses of the 3d printers we have available at Fab Lab Barcelona and characterize the design rules we need to follow moving forward.

First test - General design rules

The first test was done by Tue Ngo, David Prieto and Antoine Jaunard. They used the Creality CR-10 S5 printer to print this test file using 1.75mm PLA. The detailed specs of the machine:

  • Printing technology: FDM
  • Printing size: 500 x 500 x 500mm
  • Printing accuracy：± 0.1mm
  • Nozzle diameter：standard 0.4mm (can be changed to 0.3 or 0.2mm)
  • Printing speed：normal 80mm/s, max 200mm/s
  • Materials：PLA, Copper, Wood, Carbon Fiber, etc.
  • Printing method: SD card, USB

They used Ultimaker Cura in order to slice the model, to modify some important settings for the 3D printing process, and to generate a .gcode file. G-code is the language through which we can communicate with computer-controlled machine tools (in this case, the 3D printers) and give them instructions on what to do. The Cura apps installed in Fab Lab Barcelona's computers have the profiles of all available printers with tons of proper settings. However, we had to, and should only, modify some settings to manipulate the printing time:

  • Layer height: 0.2mm. The thinner the layer, the more detailed the result, and the longer the total printing time. They chose 0.2mm for the tests to get a more delicate result.
  • Wall thickness: 0.8mm - usually double the size of nozzle diameter because we generally print with two shells: one for inside and one for outside.
  • Infill density: 10% - Infill pattern: Grid. Infill is a repetitive structure used to fill the empty space in a print. A high infill density can make the printing time longer and the outcome heavier and more rigid. In the case of printing assembles, a higher infill density is recommended.
  • Print speed: 60mm/s. The lower the speed, the finer the outcome.
  • Support: not in this case, but we might need to generate a support structure under the model in order to prevent the material from falling down when it comes to large overhang angles.
  • Here you go the video recording the printing process:

The printing was done in 1 hour 27 minutes:

As per the images above, the quality of the print was quite good, many details were respected. Here are the detailed test results after I measured carefully the outcome with the caliper:

  • Quality of wave (rounded print), star (sharp edges), CtrlV (complex shapes): slightly acceptable
  • Dimension accuracy: +0.08mm (x,y) and +0.1mm (z)
  • Tolerance (by measuring holes' diameters): 0.3mm - 0.4mm
  • Minimum hole size: all passed, up to 0.6mm
  • Minimum wall thickness: 0.1mm
  • Minimum distance between walls: 0.6mm
  • Horizontal surface finish: quite smooth, all passed (both spheres and pyramides)
  • Overhang angles: perfectly nice at 35°, slightly acceptable up to 60°
  • Bridges: all passed, up to 16mm length

Second test - Testing tolerances

For the second test, I teamed up with Roger Anguera, Tue Ngo, David Prieto, and Lynn Dika. We used the Anycubic Kossel Delta printer, and our Fab Lab Manager Mikel Llobera guided us through the process. The detailed specs of the machine:

  • Printing technology: FDM
  • Printing size: 230 x 180 x 300mm
  • Nozzle diameter：0.4mm
  • Printing speed：20 - 80mm/s
  • Materials：PLA, ABS, HIPS, Wood, etc.
  • Printing method: SD card, USB

The estimated printing time was too long, hence, we had to scale-down the object to 70%. We then used the same settings as the first test. The printing was done in 1 hour 35 minutes:

Generally, the quality of the print was poorer compared to the one printed by the Creality printer. Here are the detailed test results measured by the caliper:

  • Dimension accuracy: +0.1mm (x,y,z)
  • Tolerance (by measuring holes' sizes): 0.5mm - 0.6mm
  • Minimum hole size: up to 0.7mm. Smaller than this, the printer ignored the walls and printed a big hole.
  • Minimum wall thickness: 0.1mm
  • Minimum distance between walls: 0.3mm
  • Horizontal surface finish: lower quality than the outcome of the Creality printer
  • None of the wheels could be able to move, and the reason might be because we scaled-down the object to 70%.